Neuroscience › Cognitive Neuroscience

Visual perception and processing mechanisms

Description

This cluster of papers explores the neural mechanisms underlying visual perception, including topics such as perceptual learning, cortical connectivity, sensory integration, retinotopic mapping, motion processing, binocular vision, neuronal adaptation, and psychophysical function.

Keywords

Visual Perception; Neural Processing; Perceptual Learning; Cortical Connectivity; Sensory Integration; Retinotopic Mapping; Motion Processing; Binocular Vision; Neuronal Adaptation; Psychophysical Function

1. An oculomotor delayed-response task was used to examine the spatial memory functions of neurons in primate prefrontal cortex. Monkeys were trained to fixate a central spot during a brief … 1. An oculomotor delayed-response task was used to examine the spatial memory functions of neurons in primate prefrontal cortex. Monkeys were trained to fixate a central spot during a brief presentation (0.5 s) of a peripheral cue and throughout a subsequent delay period (1-6 s), and then, upon the extinction of the fixation target, to make a saccadic eye movement to where the cue had been presented. Cues were usually presented in one of eight different locations separated by 45 degrees. This task thus requires monkeys to direct their gaze to the location of a remembered visual cue, controls the retinal coordinates of the visual cues, controls the monkey's oculomotor behavior during the delay period, and also allows precise measurement of the timing and direction of the relevant behavioral responses. 2. Recordings were obtained from 288 neurons in the prefrontal cortex within and surrounding the principal sulcus (PS) while monkeys performed this task. An additional 31 neurons in the frontal eye fields (FEF) region within and near the anterior bank of the arcuate sulcus were also studied. 3. Of the 288 PS neurons, 170 exhibited task-related activity during at least one phase of this task and, of these, 87 showed significant excitation or inhibition of activity during the delay period relative to activity during the intertrial interval. 4. Delay period activity was classified as directional for 79% of these 87 neurons in that significant responses only occurred following cues located over a certain range of visual field directions and were weak or absent for other cue directions. The remaining 21% were omnidirectional, i.e., showed comparable delay period activity for all visual field locations tested. Directional preferences, or lack thereof, were maintained across different delay intervals (1-6 s). 5. For 50 of the 87 PS neurons, activity during the delay period was significantly elevated above the neuron's spontaneous rate for at least one cue location; for the remaining 37 neurons only inhibitory delay period activity was seen. Nearly all (92%) neurons with excitatory delay period activity were directional and few (8%) were omnidirectional. Most (62%) neurons with purely inhibitory delay period activity were directional, but a substantial minority (38%) was omnidirectional. 6. Fifteen of the neurons with excitatory directional delay period activity also had significant inhibitory delay period activity for other cue directions. These inhibitory responses were usually strongest for, or centered about, cue directions roughly opposite those optimal for excitatory responses.(ABSTRACT TRUNCATED AT 400 WORDS)
ABSTRACT The P300 ERP was measured in 10 subjects each for 9 days. The selection of instructions for subjects, the recording technique, the elimination of a few single trials significantly … ABSTRACT The P300 ERP was measured in 10 subjects each for 9 days. The selection of instructions for subjects, the recording technique, the elimination of a few single trials significantly contaminated by eye movements, and the use of a correction procedure for ocular artifacts with calculable reliability and validity resulted in a set of data, in which 94% of the single trials were suitable for further analysis. The correction procedure relies on regression analysis. To reduce coherence between eyeblink activity and ongoing EEG, VEOG and EEG are averaged on eyeblinks. This yields a high reliability and validity of regression factors, determined per day, subject, and lead. In addition, this correction procedure allows for an estimation of the maximal error that must be taken into account. The efficiency of the procedure is demonstrated for single trials and averaged potentials.
Anatomical and physiological observations in monkeys indicate that the primate visual system consists of several separate and independent subdivisions that analyze different aspects of the same retinal image: cells in … Anatomical and physiological observations in monkeys indicate that the primate visual system consists of several separate and independent subdivisions that analyze different aspects of the same retinal image: cells in cortical visual areas 1 and 2 and higher visual areas are segregated into three interdigitating subdivisions that differ in their selectivity for color, stereopsis, movement, and orientation. The pathways selective for form and color seem to be derived mainly from the parvocellular geniculate subdivisions, the depth- and movement-selective components from the magnocellular. At lower levels, in the retina and in the geniculate, cells in these two subdivisions differ in their color selectivity, contrast sensitivity, temporal properties, and spatial resolution. These major differences in the properties of cells at lower levels in each of the subdivisions led to the prediction that different visual functions, such as color, depth, movement, and form perception, should exhibit corresponding differences. Human perceptual experiments are remarkably consistent with these predictions. Moreover, perceptual experiments can be designed to ask which subdivisions of the system are responsible for particular visual abilities, such as figure/ground discrimination or perception of depth from perspective or relative movement—functions that might be difficult to deduce from single-cell response properties.
1. Spatial summation within cat retinal receptive fields was studied by recording from optic‐tract fibres the responses of ganglion cells to grating patterns whose luminance perpendicular to the bars varied … 1. Spatial summation within cat retinal receptive fields was studied by recording from optic‐tract fibres the responses of ganglion cells to grating patterns whose luminance perpendicular to the bars varied sinusoidally about the mean level. 2. Summation over the receptive fields of some cells (X‐cells) was found to be approximately linear, while for other cells (Y‐cells) summation was very non‐linear. 3. The mean discharge frequency of Y‐cells (unlike that of X‐cells) was greatly increased when grating patterns drifted across their receptive fields. 4. In twenty‐one X‐cells the relation between the contrast and spatial frequency of drifting sinusoidal gratings which evoked the same small response was measured. In every case it was found that the reciprocal of this relation, the contrast sensitivity function, could be satisfactorily described by the difference of two Gaussian functions. 5. This finding supports the hypothesis that the sensitivities of the antagonistic centre and surround summating regions of ganglion cell receptive fields fall off as Gaussian functions of the distance from the field centre. 6. The way in which the sensitivity of an X‐cell for a contrast‐edge pattern varied with the distance of the edge from the receptive field centre was determined and found to be consistent with the cell's measured contrast sensitivity function. 7. Reducing the retinal illumination produced changes in the contrast sensitivity function of an X‐cell which suggested that the diameters of the summating regions of the receptive field increased while the surround region became relatively ineffective.
1. The contrast thresholds of a variety of grating patterns have been measured over a wide range of spatial frequencies.2. Contrast thresholds for the detection of gratings whose luminance profiles … 1. The contrast thresholds of a variety of grating patterns have been measured over a wide range of spatial frequencies.2. Contrast thresholds for the detection of gratings whose luminance profiles are sine, square, rectangular or saw-tooth waves can be simply related using Fourier theory.3. Over a wide range of spatial frequencies the contrast threshold of a grating is determined only by the amplitude of the fundamental Fourier component of its wave form.4. Gratings of complex wave form cannot be distinguished from sine-wave gratings until their contrast has been raised to a level at which the higher harmonic components reach their independent threshold.5. These findings can be explained by the existence within the nervous system of linearly operating independent mechanisms selectively sensitive to limited ranges of spatial frequencies.
A theory of edge detection is presented. The analysis proceeds in two parts. (1) Intensity changes, which occur in a natural image over a wide range of scales, are detected … A theory of edge detection is presented. The analysis proceeds in two parts. (1) Intensity changes, which occur in a natural image over a wide range of scales, are detected separately at different scales. An appropriate filter for this purpose at a given scale is found to be the second derivative of a Gaussian, and it is shown that, provided some simple conditions are satisfied, these primary filters need not be orientation-dependent. Thus, intensity changes at a given scale are best detected by finding the zero values of āˆ‡ 2 G(x, y) * I(x, y) for image I, where G(x, y) is a two-dimenĀ­sional Gaussian distribution and āˆ‡ 2 is the Laplacian. The intensity changes thus discovered in each of the channels are then represented by oriented primitives called zero-crossing segments, and evidence is given that this representation is complete. (2) Intensity changes in images arise from surface discontinuities or from reflectance or illumination boundĀ­aries, and these all have the property that they are spatially localized. Because of this, the zero-crossing segments from the different channels are not independent, and rules are deduced for combining them into a description of the image. This description is called the raw primal sketch. The theory explains several basic psychophysical findings, and the operaĀ­tion of forming oriented zero-crossing segments from the output of centre-surround āˆ‡ 2 G filters acting on the image forms the basis for a physiological model of simple cells (see Marr & Ullman 1979).
Two-dimensional spatial linear filters are constrained by general uncertainty relations that limit their attainable information resolution for orientation, spatial frequency, and two-dimensional (2D) spatial position. The theoretical lower limit for … Two-dimensional spatial linear filters are constrained by general uncertainty relations that limit their attainable information resolution for orientation, spatial frequency, and two-dimensional (2D) spatial position. The theoretical lower limit for the joint entropy, or uncertainty, of these variables is achieved by an optimal 2D filter family whose spatial weighting functions are generated by exponentiated bivariate second-order polynomials with complex coefficients, the elliptic generalization of the one-dimensional elementary functions proposed in Gabor's famous theory of communication [ J. Inst. Electr. Eng.93, 429 ( 1946)]. The set includes filters with various orientation bandwidths, spatial-frequency bandwidths, and spatial dimensions, favoring the extraction of various kinds of information from an image. Each such filter occupies an irreducible quantal volume (corresponding to an independent datum) in a four-dimensional information hyperspace whose axes are interpretable as 2D visual space, orientation, and spatial frequency, and thus such a filter set could subserve an optimally efficient sampling of these variables. Evidence is presented that the 2D receptive-field profiles of simple cells in mammalian visual cortex are well described by members of this optimal 2D filter family, and thus such visual neurons could be said to optimize the general uncertainty relations for joint 2D-spatial–2D-spectral information resolution. The variety of their receptive-field dimensions and orientation and spatial-frequency bandwidths, and the correlations among these, reveal several underlying constraints, particularly in width/length aspect ratio and principal axis organization, suggesting a polar division of labor in occupying the quantal volumes of information hyperspace. Such an ensemble of 2D neural receptive fields in visual cortex could locally embed coarse polar mappings of the orientation–frequency plane piecewise within the global retinotopic mapping of visual space, thus efficiently representing 2D spatial visual information by localized 2D spectral signatures.
Although individual neurons in the arm area of the primate motor cortex are only broadly tuned to a particular direction in three-dimensional space, the animal can very precisely control the … Although individual neurons in the arm area of the primate motor cortex are only broadly tuned to a particular direction in three-dimensional space, the animal can very precisely control the movement of its arm. The direction of movement was found to be uniquely predicted by the action of a population of motor cortical neurons. When individual cells were represented as vectors that make weighted contributions along the axis of their preferred direction (according to changes in their activity during the movement under consideration) the resulting vector sum of all cell vectors (population vector) was in a direction congruent with the direction of movement. This population vector can be monitored during various tasks, and similar measures in other neuronal populations could be of heuristic value where there is a neural representation of variables with vectorial attributes.
Of the many possible functions of the macaque monkey primary visual cortex (striate cortex, area 17) two are now fairly well understood. First, the incoming information from the lateral geniculate … Of the many possible functions of the macaque monkey primary visual cortex (striate cortex, area 17) two are now fairly well understood. First, the incoming information from the lateral geniculate bodies is rearranged so that most cells in the striate cortex respond to specifically oriented line segments, and, second, information originating from the two eyes converges upon single cells. The rearrangement and convergence do not take place immediately, however: in layer IVc, where the bulk of the afferents terminate, virtually all cells have fields with circular symmetry and are strictly monocular, driven from the left eye or from the right, but not both; at subsequent stages, in layers above and below IVc, most cells show orientation specificity, and about half are binocular. In a binocular cell the receptive fields in the two eyes are on corresponding regions in the two retinas and are identical in structure, but one eye is usually more effective than the other in influencing the cell; all shades of ocular dominance are seen. These two functions are strongly reflected in the architecture of the cortex, in that cells with common physiological properties are grouped together in vertically organized systems of columns. In an ocular dominance column all cells respond preferentially to the same eye. By four independent anatomical methods it has been shown that these columns have the form of vertically disposed alternating left-eye and right-eye slabs, which in horizontal section form alternating stripes about 400 μm thick, with occasional bifurcations and blind endings. Cells of like orientation specificity are known from physiological recordings to be similarly grouped in much narrower vertical sheeet-like aggregations, stacked in orderly sequences so that on traversing the cortex tangentially one normally encounters a succession of small shifts in orientation, clockwise or counterclockwise; a 1 mm traverse is usually accompanied by one or several full rotations through 180°, broken at times by reversals in direction of rotation and occasionally by large abrupt shifts. A full complement of columns, of either type, left-plus-right eye or a complete 180° sequence, is termed a hypercolumn. Columns (and hence hypercolumns) have roughly the same width throughout the binocular part of the cortex. The two independent systems of hypercolumns are engrafted upon the well known topographic representation of the visual field. The receptive fields mapped in a vertical penetration through cortex show a scatter in position roughly equal to the average size of the fields themselves, and the area thus covered, the aggregate receptive field, increases with distance from the fovea. A parallel increase is seen in reciprocal magnification (the number of degrees of visual field corresponding to 1 mm of cortex). Over most or all of the striate cortex a movement of 1-2 mm, traversing several hypercolumns, is accompanied by a movement through the visual field about equal in size to the local aggregate receptive field. Thus any 1-2 mm block of cortex contains roughly the machinery needed to subserve an aggregate receptive field. In the cortex the fall-off in detail with which the visual field is analysed, as one moves out from the foveal area, is accompanied not by a reduction in thickness of layers, as is found in the retina, but by a reduction in the area of cortex (and hence the number of columnar units) devoted to a given amount of visual field: unlike the retina, the striate cortex is virtually uniform morphologically but varies in magnification. In most respects the above description fits the newborn monkey just as well as the adult, suggesting that area 17 is largely genetically programmed. The ocular dominance columns, however, are not fully developed at birth, since the geniculate terminals belonging to one eye occupy layer IVc throughout its length, segregating out into separate columns only after about the first 6 weeks, whether or not the animal has visual experience. If one eye is sutured closed during this early period the columns belonging to that eye become shrunken and their companions correspondingly expanded. This would seem to be at least in part the result of interference with normal maturation, though sprouting and retraction of axon terminals are not excluded.
With each eye fixation, we experience a richly detailed visual world. Yet recent work on visual integration and change direction reveals that we are surprisingly unaware of the details of … With each eye fixation, we experience a richly detailed visual world. Yet recent work on visual integration and change direction reveals that we are surprisingly unaware of the details of our environment from one view to the next: we often do not detect large changes to objects and scenes ('change blindness'). Furthermore, without attention, we may not even perceive objects ('inattentional blindness'). Taken together, these findings suggest that we perceive and remember only those objects and details that receive focused attention. In this paper, we briefly review and discuss evidence for these cognitive forms of 'blindness'. We then present a new study that builds on classic studies of divided visual attention to examine inattentional blindness for complex objects and events in dynamic scenes. Our results suggest that the likelihood of noticing an unexpected object depends on the similarity of that object to other objects in the display and on how difficult the priming monitoring task is. Interestingly, spatial proximity of the critical unattended object to attended locations does not appear to affect detection, suggesting that observers attend to objects and events, not spatial positions. We discuss the implications of these results for visual representations and awareness of our visual environment.
A speckle pattern formed in polarized monochromatic light may be regarded as resulting from a classical random walk in the complex plane. The resulting irradiance fluctuations obey negative exponential statistics, … A speckle pattern formed in polarized monochromatic light may be regarded as resulting from a classical random walk in the complex plane. The resulting irradiance fluctuations obey negative exponential statistics, with ratio of standard deviation to mean (i.e., contrast) of unity. Reduction of this contrast, or smoothing of the speckle, requires diversity in polarization, space, frequency, or time. Addition of M uncorrelated speckle patterns on an intensity basis can reduce the contrast by 1/√M. However, addition of speckle patterns on a complex amplitude basis provides no reduction of contrast. The distribution of scale sizes in a speckle pattern (i.e., the Wiener spectrum) is investigated from a physical point of view.
Every eye movement produces a shift in the visual image on the retina. The receptive field, or retinal response area, of an individual visual neuron moves with the eyes so … Every eye movement produces a shift in the visual image on the retina. The receptive field, or retinal response area, of an individual visual neuron moves with the eyes so that after an eye movement it covers a new portion of visual space. For some parietal neurons, the location of the receptive field is shown to shift transiently before an eye movement. In addition, nearly all parietal neurons respond when an eye movement brings the site of a previously flashed stimulus into the receptive field. Parietal cortex both anticipates the retinal consequences of eye movements and updates the retinal coordinates of remembered stimuli to generate a continuously accurate representation of visual space.
The human visual process can be studied by examining the computational problems associated with deriving useful information from retinal images. In this paper, we apply this approach to the problem … The human visual process can be studied by examining the computational problems associated with deriving useful information from retinal images. In this paper, we apply this approach to the problem of representing three-dimensional shapes for the purpose of recognition. 1. Three criteria, accessibility, scope and uniqueness , and stability and sensitivity , are presented for judging the usefulness of a representation for shape recognition. 2. Three aspects of a representation’s design are considered, (i) the representation’s coordinate system, (ii) its primitives, which are the primary units of shape information used in the representation, and (iii) the organization the representation imposes on the information in its descriptions. 3. In terms of these design issues and the criteria presented, a shape representation for recognition should: (i) use an object-centred coordinate system, (ii) include volumetric primitives of varied sizes, and (iii) have a modular organization. A representation based on a shape’s natural axes (for example the axes identified by a stick figure) follows directly from these choices. 4. The basic process for deriving a shape description in this representation must involve: (i) a means for identifying the natural axes of a shape in its image and (ii) a mechanism for transforming viewer-centred axis specifications to specifications in an object-centred coordinate system. 5. Shape recognition involves: (i) a collection of stored shape descriptions, and (ii) various indexes into the collection that allow a newly derived description to be associated with an appropriate stored description. The most important of these indexes allows shape recognition to proceed conservatively from the general to the specific based on the specificity of the information available from the image. 6. New constraints supplied by a conservative recognition process can be used to extract more information from the image. A relaxation process for carrying out this constraint analysis is described.
The borders of human visual areas V1, V2, VP, V3, and V4 were precisely and noninvasively determined. Functional magnetic resonance images were recorded during phase-encoded retinal stimulation. This volume data … The borders of human visual areas V1, V2, VP, V3, and V4 were precisely and noninvasively determined. Functional magnetic resonance images were recorded during phase-encoded retinal stimulation. This volume data set was then sampled with a cortical surface reconstruction, making it possible to calculate the local visual field sign (mirror image versus non-mirror image representation). This method automatically and objectively outlines area borders because adjacent areas often have the opposite field sign. Cortical magnification factor curves for striate and extrastriate cortical areas were determined, which showed that human visual areas have a greater emphasis on the center-of-gaze than their counterparts in monkeys. Retinotopically organized visual areas in humans extend anteriorly to overlap several areas previously shown to be activated by written words.
A motion sequence may be represented as a single pattern in x-y-t space; a velocity of motion corresponds to a three-dimensional orientation in this space. Motion sinformation can be extracted … A motion sequence may be represented as a single pattern in x-y-t space; a velocity of motion corresponds to a three-dimensional orientation in this space. Motion sinformation can be extracted by a system that responds to the oriented spatiotemporal energy. We discuss a class of models for human motion mechanisms in which the first stage consists of linear filters that are oriented in space-time and tuned in spatial frequency. The outputs of quadrature pairs of such filters are squared and summed to give a measure of motion energy. These responses are then fed into an opponent stage. Energy models can be built from elements that are consistent with known physiology and psychophysics, and they permit a qualitative understanding of a variety of motion phenomena.
Global context plays an important, but poorly understood, role in visual tasks. This study demonstrates that a robust memory for visual context exists to guide spatial attention. Global context was … Global context plays an important, but poorly understood, role in visual tasks. This study demonstrates that a robust memory for visual context exists to guide spatial attention. Global context was operationalized as the spatial layout of objects in visual search displays. Half of the configurations were repeated across blocks throughout the entire session, and targets appeared within consistent locations in these arrays. Targets appearing in learned configurations were detected more quickly. This newly discovered form of search facilitation is termed contextual cueing. Contextual cueing is driven by incidentally learned associations between spatial configurations (context) and target locations. This benefit was obtained despite chance performance for recognizing the configurations, suggesting that the memory for context was implicit. The results show how implicit learning and memory of visual context can guide spatial attention towards task-relevant aspects of a scene.
The brain's default mode network consists of discrete, bilateral and symmetrical cortical areas, in the medial and lateral parietal, medial prefrontal, and medial and lateral temporal cortices of the human, … The brain's default mode network consists of discrete, bilateral and symmetrical cortical areas, in the medial and lateral parietal, medial prefrontal, and medial and lateral temporal cortices of the human, nonhuman primate, cat, and rodent brains. Its ...Read More
1. The striate cortex was studied in lightly anaesthetized macaque and spider monkeys by recording extracellularly from single units and stimulating the retinas with spots or patterns of light. Most … 1. The striate cortex was studied in lightly anaesthetized macaque and spider monkeys by recording extracellularly from single units and stimulating the retinas with spots or patterns of light. Most cells can be categorized as simple, complex, or hypercomplex, with response properties very similar to those previously described in the cat. On the average, however, receptive fields are smaller, and there is a greater sensitivity to changes in stimulus orientation. A small proportion of the cells are colour coded.2. Evidence is presented for at least two independent systems of columns extending vertically from surface to white matter. Columns of the first type contain cells with common receptive-field orientations. They are similar to the orientation columns described in the cat, but are probably smaller in cross-sectional area. In the second system cells are aggregated into columns according to eye preference. The ocular dominance columns are larger than the orientation columns, and the two sets of boundaries seem to be independent.3. There is a tendency for cells to be grouped according to symmetry of responses to movement; in some regions the cells respond equally well to the two opposite directions of movement of a line, but other regions contain a mixture of cells favouring one direction and cells favouring the other.4. A horizontal organization corresponding to the cortical layering can also be discerned. The upper layers (II and the upper two-thirds of III) contain complex and hypercomplex cells, but simple cells are virtually absent. The cells are mostly binocularly driven. Simple cells are found deep in layer III, and in IV A and IV B. In layer IV B they form a large proportion of the population, whereas complex cells are rare. In layers IV A and IV B one finds units lacking orientation specificity; it is not clear whether these are cell bodies or axons of geniculate cells. In layer IV most cells are driven by one eye only; this layer consists of a mosaic with cells of some regions responding to one eye only, those of other regions responding to the other eye. Layers V and VI contain mostly complex and hypercomplex cells, binocularly driven.5. The cortex is seen as a system organized vertically and horizontally in entirely different ways. In the vertical system (in which cells lying along a vertical line in the cortex have common features) stimulus dimensions such as retinal position, line orientation, ocular dominance, and perhaps directionality of movement, are mapped in sets of superimposed but independent mosaics. The horizontal system segregates cells in layers by hierarchical orders, the lowest orders (simple cells monocularly driven) located in and near layer IV, the higher orders in the upper and lower layers.
The brain's default mode network consists of discrete, bilateral and symmetrical cortical areas, in the medial and lateral parietal, medial prefrontal, and medial and lateral temporal cortices of the human, … The brain's default mode network consists of discrete, bilateral and symmetrical cortical areas, in the medial and lateral parietal, medial prefrontal, and medial and lateral temporal cortices of the human, nonhuman primate, cat, and rodent brains. Its ...Read More
Detection of a visual signal requires information to reach a system capable of eliciting arbitrary responses required by the experimenter. Detection latencies are reduced when subjects receive a cue that … Detection of a visual signal requires information to reach a system capable of eliciting arbitrary responses required by the experimenter. Detection latencies are reduced when subjects receive a cue that indicates where in the visual field the signal will occur. This shift in efficiency appears to be due to an alignment (orienting) of the central attentional system with the pathways to be activated by the visual input. It would also be possible to describe these results as being due to a reduced criterion at the expected target position. However, this description ignores important constraints about the way in which expectancy improves performance. First, when subjects are cued on each trial, they show stronger expectancy effects than when a probable position is held constant for a block, indicating the active nature of the expectancy. Second, while information on spatial position improves performance, information on the form of the stimulus does not. Third, expectancy may lead to improvements in latency without a reduction in accuracy. Fourth, there appears to be little ability to lower the criterion at two positions that are not spatially contiguous. A framework involving the employment of a limited-capacity attentional mechanism seems to capture these constraints better than the more general language of criterion setting. Using this framework, we find that attention shifts are not closely related to the saccadic eye movement system. For luminance detection the retina appears to be equipotential with respect to attention shifts, since costs to unexpected stimuli are similar whether foveal or peripheral. These results appear to provide an important model system for the study of the relationship between attention and the structure of the visual system.
A new theory of search and visual attention is presented. Results support neither a distinction between serial and parallel search nor between search for features and conjunctions. For all search … A new theory of search and visual attention is presented. Results support neither a distinction between serial and parallel search nor between search for features and conjunctions. For all search materials, instead, difficulty increases with increased similarity of targets to nontargets and decreasedsimilarity between nontargets, producing a continuum of search efficiency. A parallel stage of perceptual grouping and description is followed by competitive interaction between inputs, guiding selective access to awareness and action. An input gains weight to the extent that it matches an internal description of that information needed in current behavior (hence the effect of targetnontarget similarity). Perceptual grouping encourages input weights to change together (allowing spreading suppression of similar nontargets). The theory accounts for harmful effects of nontargets resembling any possible target, the importance of local nontarget grouping, and many other findings.
When looking at a scene, observers feel that they see its entire structure in great detail and can immediately notice any changes in it However, when brief blank fields are … When looking at a scene, observers feel that they see its entire structure in great detail and can immediately notice any changes in it However, when brief blank fields are placed between alternating displays of an original and a modified scene, a striking failure of perception is induced Identification of changes becomes extremely difficult, even when changes are large and made repeatedly Identification is much faster when a verbal cue is provided showing that poor visibility is not the cause of this difficulty Identification is also faster for objects considered to be important in the scene These results support the idea that observers never form a complete, detailed representation of their surroundings In addition, the results indicate that attention is required to perceive change, and that in the absence of localized motion signals attention is guided on the basis of high-level interest
We compared the ability of psychophysical observers and single cortical neurons to discriminate weak motion signals in a stochastic visual display. All data were obtained from rhesus monkeys trained to … We compared the ability of psychophysical observers and single cortical neurons to discriminate weak motion signals in a stochastic visual display. All data were obtained from rhesus monkeys trained to perform a direction discrimination task near psychophysical threshold. The conditions for such a comparison were ideal in that both psychophysical and physiological data were obtained in the same animals, on the same sets of trials, and using the same visual display. In addition, the psychophysical task was tailored in each experiment to the physiological properties of the neuron under study; the visual display was matched to each neuron's preference for size, speed, and direction of motion. Under these conditions, the sensitivity of most MT neurons was very similar to the psychophysical sensitivity of the animal observers. In fact, the responses of single neurons typically provided a satisfactory account of both absolute psychophysical threshold and the shape of the psychometric function relating performance to the strength of the motion signal. Thus, psychophysical decisions in our task are likely to be based upon a relatively small number of neural signals. These signals could be carried by a small number of neurons if the responses of the pooled neurons are statistically independent. Alternatively, the signals may be carried by a much larger pool of neurons if their responses are partially intercorrelated.
A typical scene contains many different objects that, because of the limited processing capacity of the visual system, compete for neural representation. The competition among multiple objects in visual cortex … A typical scene contains many different objects that, because of the limited processing capacity of the visual system, compete for neural representation. The competition among multiple objects in visual cortex can be biased by both bottom-up sensory-driven mechanisms and top-down influences, such as selective attention. Functional brain imaging studies reveal that, both in the absence and in the presence of visual stimulation, biasing signals due to selective attention can modulate neural activity in visual cortex in several ways. Although the competition among stimuli for representation is ultimately resolved within visual cortex, the source of top-down biasing signals derives from a network of areas in frontal and parietal cortex.
Sensations of color show a strong correlation with reflectance, even though the amount of visible light reaching the eye depends on the product of reflectance and illumination. The visual system … Sensations of color show a strong correlation with reflectance, even though the amount of visible light reaching the eye depends on the product of reflectance and illumination. The visual system must achieve this remarkable result by a scheme that does not measure flux. Such a scheme is described as the basis of retinex theory. This theory assumes that there are three independent cone systems, each starting with a set of receptors peaking, respectively, in the long-, middle-, and short-wavelength regions of the visible spectrum. Each system forms a separate image of the world in terms of lightness that shows a strong correlation with reflectance within its particular band of wavelengths. These images are not mixed, but rather are compared to generate color sensations. The problem then becomes how the lightness of areas in these separate images can be independent of flux. This article describes the mathematics of a lightness scheme that generates lightness numbers, the biologic correlate of reflectance, independent of the flux from objects
1. It was found that an occipital evoked potential can be elicited in the human by moving a grating pattern without changing the mean light flux entering the eye. Prolonged … 1. It was found that an occipital evoked potential can be elicited in the human by moving a grating pattern without changing the mean light flux entering the eye. Prolonged viewing of a high contrast grating reduces the amplitude of the potential evoked by a low contrast grating.2. This adaptation to a grating was studied psychophysically by determining the contrast threshold before and after adaptation. There is a temporary fivefold rise in contrast threshold after exposure to a high contrast grating of the same orientation and spatial frequency.3. By determining the rise of threshold over a range of spatial frequency for a number of adapting frequencies it was found that the threshold elevation is limited to a spectrum of frequencies with a bandwidth of just over an octave at half amplitude, centred on the adapting frequency.4. The amplitude of the effect and its bandwidth are very similar for adapting spatial frequencies between 3 c/deg. and 14 c/deg. At higher frequencies the bandwidth is slightly narrower. For lower adapting frequencies the peak of the effect stays at 3 c/deg.5. These and other findings suggest that the human visual system may possess neurones selectively sensitive to spatial frequency and size. The orientational selectivity and the interocular transfer of the adaptation effect implicate the visual cortex as the site of these neurones.6. This neural system may play an essential preliminary role in the recognition of complex images and generalization for magnification.
Analysis of Behavior encompasses both theoretical and experimental research. It deals with the visual mechanisms of diverse vertebrate species from salamanders and toads to primates and humans and presents a … Analysis of Behavior encompasses both theoretical and experimental research. It deals with the visual mechanisms of diverse vertebrate species from salamanders and toads to primates and humans and presents a stimulating interaction of the disciplines of anatomy, physiology, and behavioral science. Throughout, visual mechanisms are investigated from the point of view of the brain functioning at the organismic level, as opposed to the now more prevalent focus on the molecular and cellular levels. This approach allows researchers to deal with the patterns of visually guided behavior of animals in real-life situations.The twenty-six contributions in the book are divided among three sections: Indentification and Localization Processes in Nonmammalian Vertebrates, introduced by David J. Ingle; Visual Guidance of Motor Patterns: The Role of Cortex and the Superior Colliculus, introduced by Melvyn A. Goodale; and Recognition and Transfer Processes, introduced by Richard J. W. Mansfield.The editors are all university researchers in psychology: David J. Ingle at Brandeis, Melvyn A. Goodale at the University of Western Ontario, and Richard J. W. Mansfield at Harvard.
Visual learning in insects can be strongly influenced by the underlying context and conditions. Improved colour learning has been demonstrated using differential conditioning with reward-aversion paradigms in eusocial insects like … Visual learning in insects can be strongly influenced by the underlying context and conditions. Improved colour learning has been demonstrated using differential conditioning with reward-aversion paradigms in eusocial insects like wasps, bumblebees, and honeybees, where substances that induce strong aversion, such as quinine, enable more accurate discrimination. Although learning outcomes are closely tied to the strength of target association during conditioning, few studies have compared the role of negative reinforcements in shaping these associations, and their relevance across insect groups with different life histories. In our study, we compare the effects of aversive substances for learning in the hummingbird hawkmoth (Macroglossum stellatarum)- a solitary pollinator that relies on vision for foraging. Linking to previous learning studies in insects, we paired a sugar-rewarded target with a distractor that was paired with either quinine, salt, citric acid, water, or was presented with no aversive substance. Learning outcomes were compared by inverting a strong colour preference between perceptually close or distant colour pairs, to provide tasks with disparate challenges. Contrary to results from other insect species, we found that moths trained with quinine were worse at switching preferences between similar colours compared to training with citric acid and appetitive-only differential conditioning. We also show that quinine interferes with sucrose perception, potentially impairing target acquisition during training. Additionally, we link differences in learning to the impact of negative reinforcements on exploration during foraging. Our results showcase the role of experience in modulating behaviour and highlight the role of foraging dynamics in influencing learning in a solitary forager.
Throughout every day, we perform actions, and action information has been suggested to inform scene categorization. Here we hypothesise that actions also drive the hierarchical structure of many scenes, where … Throughout every day, we perform actions, and action information has been suggested to inform scene categorization. Here we hypothesise that actions also drive the hierarchical structure of many scenes, where anchor objects (e.g., stoves) predict the presence and position of local objects (e.g., pots) by dividing a scene in functionally distinct 'phrases'. Specifically, we test whether the presence of anchor objects informs scene function understanding. In Experiment 1, participants matched an action word and a scene from which we either removed an action-related anchor object (REL), an action-unrelated anchor (UNREL) or a non-anchor object (RAND). Matching performance was impaired in REL compared to UNREL and RAND. Experiment 2 measured scene function activation more implicitly by priming a lexical decision task (LDT) on action words with the same stimuli (including an inconsistent condition: INCON, e.g., "cooking" in a bathroom). LDT performance was impaired after INCON and REL compared to RAND and UNREL primes. A control experiment showed that this effect was partly but not solely due to scene categorization. The results imply that understanding scene function is most closely tied to anchor objects directly relevant for actions whereas contextual scene information is not always sufficient to give rise to this understanding.
Development of gray and white matter tissue microstructure is critical for the emergence of sensory and cognitive functions. However, it is unknown how microstructural tissue properties of the human visual … Development of gray and white matter tissue microstructure is critical for the emergence of sensory and cognitive functions. However, it is unknown how microstructural tissue properties of the human visual system develop in the first year of human life. Here, we use tissue relaxation rate (R1) obtained using quantitative MRI to measure the longitudinal development of gray and white matter in brain areas spanning three visual processing streams: dorsal, lateral, and ventral, during the first year of life. R1 in gray and white matter of all visual regions in the three processing streams increases postnatally, indicating microstructural tissue growth. R1 increases faster between 0-6 months than 6-12 months, and faster in white matter than gray matter, with white matter R1 surpassing that of gray matter after two months of age. Strikingly, this microstructural growth is hierarchical: across all streams, early visual areas are more mature at birth than higher-level areas but develop more slowly postnatally than higher-level areas. The exception is TO1 (MT) which is similar to V1: it is microstructurally more mature at birth and develops slower than neighboring areas. Overall, our findings provide the first comprehensive measurement of microstructural tissue growth in infancy across three visual processing streams and propose a new hypothesis that functional development of the visual cortex may be coupled with microstructural development and follows a similar hierarchical trajectory.
Self-motion perception is a complex multisensory process that relies on the integration of various sensory signals, particularly visual and vestibular inputs, to construct stable and unified perceptions. It is essential … Self-motion perception is a complex multisensory process that relies on the integration of various sensory signals, particularly visual and vestibular inputs, to construct stable and unified perceptions. It is essential for spatial navigation and effective interaction with the environment. This review systematically explores the mechanisms and computational principles underlying visual–vestibular integration in self-motion perception. We first outline the individual contributions of visual and vestibular cues and then introduce Bayesian inference as a normative framework for the quantitative modeling of multisensory integration. We also discuss multisensory recalibration as a critical mechanism in resolving conflicts between sensory inputs and maintaining perceptual stability. Using heading perception as a model system, we further describe the relevant visual and vestibular pathways involved in this process, as well as the brain regions involved. Finally, we discuss the neural mechanisms mediating visual–vestibular interactions through models of the Bayesian optimal integration and divisive normalization.
In virtual environments (VEs), distance perception is often inaccurate but can be improved through active engagement, such as walking. While prior research suggests that action planning and execution can enhance … In virtual environments (VEs), distance perception is often inaccurate but can be improved through active engagement, such as walking. While prior research suggests that action planning and execution can enhance the perception of action-related features, the effects of specific actions on perception in VEs remain unclear. This study investigates how different interactions – viewing-only, reaching, and grasping – affect size perception in Virtual Reality (VR) and whether teleportation (Experiment 1) and smooth locomotion (Experiment 2) influences these effects. Participants approached a virtual object using either teleportation or smooth locomotion and interacted with the target with a virtual hand. They then estimated the target’s size before and after the approach by adjusting the size of a comparison object. Results revealed that size perception improved after interaction across all conditions in both experiments, with viewing-only leading to the most accurate estimations. This suggests that, unlike in real environments, additional manual interaction does not significantly enhance size perception in VR when only visual input is available. Additionally, teleportation was more effective than smooth locomotion for improving size estimations. These findings extend action-based perceptual theories to VR, showing that interaction type and approach method can influence size perception accuracy without tactile feedback. Further, by analysing gaze spatial distribution during the different interaction conditions, this study suggests that specific motor responses combined with movement approaches affect gaze behaviour, offering insights for applied VR settings that prioritize perceptual accuracy.
Abstract Path integration refers to the ability to monitor self-motion cues to keep track of changes in position and orientation. This function is often assumed to rely predominantly on medial … Abstract Path integration refers to the ability to monitor self-motion cues to keep track of changes in position and orientation. This function is often assumed to rely predominantly on medial temporal lobe structures containing grid, place, and head direction cells. Recent evidence, however, suggests that key navigational computations may occur outside this system, for example, in posterior parietal areas. Here, we adopted a novel perspective derived from animal research and examined whether human path integration relies on processing streams in the posterior parietal cortex (PPC), depending on the involvement of actively controlled motion as opposed to passive perception of visual optic flow. We compared the effects of inhibiting the PPC via TMS on two path integration tasks in a virtual reality, only one of which involved active control of a visually simulated forward movement. Behavioral performance showed that distance judgments were selectively affected in the action-related path integration task. This finding shows that the processing of actively controlled motion depends on computations in the PPC, whereas passive processing of optic flow is largely independent of the PPC computations. Our results reinforce the hypothesis that the PPC plays a critical role for the integration of goal locations and self-positional signals within an egocentric frame of reference. In addition to the medial temporal lobe, the posterior parietal system is recruited during tasks involving actively controlled movements, whereas medial temporal computations are sufficient for passive monitoring of positional changes.
Abstract This paper presents the results of combining (i) theoretical analysis regarding connections between the orientation selectivity and the elongation of receptive fields for the affine Gaussian derivative model with … Abstract This paper presents the results of combining (i) theoretical analysis regarding connections between the orientation selectivity and the elongation of receptive fields for the affine Gaussian derivative model with (ii) biological measurements of orientation selectivity in the primary visual cortex to investigate if (iii) the receptive fields can be regarded as spanning a variability in the degree of elongation. From an in-depth theoretical analysis of idealized models for the receptive fields of simple and complex cells in the primary visual cortex, we established that the orientation selectivity becomes more narrow with increasing elongation of the receptive fields. Combined with previously established biological results, concerning broad vs. sharp orientation tuning of visual neurons in the primary visual cortex, as well as previous experimental results concerning distributions of the resultant of the orientation selectivity curves for simple and complex cells, we show that these results are consistent with the receptive fields spanning a variability over the degree of elongation of the receptive fields. We also show that our principled theoretical model for visual receptive fields leads to qualitatively similar types of deviations from a uniform histogram of the resultant descriptor of the orientation selectivity curves for simple cells, as can be observed in the results from biological experiments. To firmly investigate the validity of the underlying working hypothesis, we finally formulate a set of testable predictions for biological experiments, to characterize the predicted systematic variability in the elongation over the orientation maps in higher mammals, and its relations to the pinwheel structure.
The change in direction of a target object relative to a translating observer (or a point fixed relative to the observer), "target drift," provides information about the observer's direction of … The change in direction of a target object relative to a translating observer (or a point fixed relative to the observer), "target drift," provides information about the observer's direction of self-movement (i.e., heading) with respect to the target. Relative drift rate (normalized with cues to motion-in-depth) provides information about the observer's absolute direction of heading relative to the surrounding scene. We investigated the utility of target drift by comparing heading judgments with target drift and "extra-drift" cues (the cues available in the changing optic array except target drift) in isolation and together during simulated forward translation. Across four experiments, we found that with the target drift cue alone, participants were able to make precise judgments of both nominal and absolute heading (≤1.53°). Judgments were at least as precise with the target drift cue alone as with extra-drift cues alone. The addition of extra-drift cues to the drift cue did not improve precision, and the pattern of reaction times suggests that the two cues are processed independently. We conclude that target drift can be an effective and powerful cue for heading judgments.
<title>Abstract</title> Humans continuously decide where to look to gather task-relevant information. While affective rewards such as money are known to bias gaze direction, it remains unclear whether non-affective informational value … <title>Abstract</title> Humans continuously decide where to look to gather task-relevant information. While affective rewards such as money are known to bias gaze direction, it remains unclear whether non-affective informational value can similarly shape oculomotor decisions. Here, we modulated the probability of finding task-relevant visual information at saccade targets in human participants performing a perceptual judgment task. Results showed that participants developed implicit biases, increasingly avoiding the low-information region. These learned preferences were also reflected in longer saccade latencies toward non-preferred regions, similar to patterns observed with affective reward learning. However, saccade peak velocity remained unchanged across locations. Perceptual accuracy was not influenced either. When participants' confidence ratings reliably distinguished correct from incorrect responses, confidence was higher for preferred regions, suggesting a dissociation between perceptual and metacognitive performance. These findings demonstrate that the probability of accessing usable information can be implicitly learned to guide eye movement decisions, much like reward. Moreover, learned preferences can influence subjective confidence without altering perceptual performance. Our results highlight that informational value, independent of affective cues, shapes oculomotor decision-making and post-perceptual judgment confidence.
<title>Abstract</title> The current study is a novel investigation of remembered affordances using the analytic framework of memory psychophysics, which generally demonstrates memory degradation for stimulus magnitudes even after short delay … <title>Abstract</title> The current study is a novel investigation of remembered affordances using the analytic framework of memory psychophysics, which generally demonstrates memory degradation for stimulus magnitudes even after short delay intervals. Participants made perceived and remembered reports of the affordance reach-with-ability and length (a proportional physical dimension of reach-with-ability) of a series of rods. The scaling exponent (i.e., discriminability, sensitivity, certainty) for length reports decreased after a 1 min retention interval and distractor task, while the scaling exponents for perceived and remembered reports of reach-with-ability did not differ. The findings demonstrate that memory psychophysics offers a useful framework to study affordance cognition. It also adds to the literature that demonstrates the direct perception of affordances and the unique stability (lack of memory degradation) for affordances compared to basic physical dimensions.
Humans and other animals move their eyes, heads, and bodies to interact with their surroundings. While essential for survival, these movements produce additional sensory signals that complicate visual scene analysis. … Humans and other animals move their eyes, heads, and bodies to interact with their surroundings. While essential for survival, these movements produce additional sensory signals that complicate visual scene analysis. However, these self-generated visual signals offer valuable information about self-motion and the three-dimensional structure of the environment. In this review, we examine recent advances in understanding depth and motion perception during self-motion, along with the underlying neural mechanisms. We also propose a comprehensive framework that integrates various visual phenomena, including optic flow parsing, depth from motion parallax, and coordinate transformation. The studies reviewed here begin to provide a more complete picture of how the visual system carries out a set of complex computations to jointly infer object motion, self-motion, and depth.
Abstract When observing the surface patterns of objects delimited by smooth surfaces, the projections of the surface patterns to the image domain will be subject to substantial variabilities, as induced … Abstract When observing the surface patterns of objects delimited by smooth surfaces, the projections of the surface patterns to the image domain will be subject to substantial variabilities, as induced by variabilities in the geometric viewing conditions, and as generated by either monocular or binocular imaging conditions, or by relative motions between the object and the observer over time. To first order of approximation, the image deformations of such projected surface patterns can be modelled as local linearizations in terms of local 2-D spatial affine transformations. This paper presents a theoretical analysis of relationships between the degrees of freedom in 2-D spatial affine image transformations and the degrees of freedom in the affine Gaussian derivative model for visual receptive fields. For this purpose, we first describe a canonical decomposition of 2-D affine transformations on a product form, closely related to a singular value decomposition, while in closed form, and which reveals the degrees of freedom in terms of (i) uniform scaling transformations, (ii) an overall amount of global rotation, (iii) a complementary non-uniform scaling transformation and (iv) a relative normalization to a preferred symmetry orientation in the image domain. Then, we show how these degrees of freedom relate to the degrees of freedom in the affine Gaussian derivative model. Finally, we use these theoretical results to consider whether we could regard the biological receptive fields in the primary visual cortex of higher mammals as being able to span the degrees of freedom of 2-D spatial affine transformations, based on interpretations of existing neurophysiological experimental results.
Empirical research on the mental health and cognitive benefits of nature immersion has expanded significantly in recent decades, building support for Attention Restoration Theory. However, the field still faces interpretive … Empirical research on the mental health and cognitive benefits of nature immersion has expanded significantly in recent decades, building support for Attention Restoration Theory. However, the field still faces interpretive challenges due to inconsistent definitions of ā€˜nature' (whether nature imagery, real-world nature immersion, or other forms) and varied methodologies, which collectively limit our understanding of the underlying mechanisms that potentially drive these benefits. Addressing some of these limitations, the current study investigated whether exposure to virtual nature imagery influences attention restoration, as measured by the amplitude of the error-related negativity (ERN), similarly to real-world nature. In a repeated-measures randomized control design, 63 participants completed the Eriksen Flanker Task at three testing sessions. At Session 1, participants completed the task after viewing a neutral stimulus for 10 minutes. At Session 2, participants completed the task after viewing either nature or urban imagery for 10 minutes. At Session 3, participants completed the task after viewing the neutral stimulus again for 10 minutes. The ERN component generated from the Eriksen Flanker Task was quantified at each of the three testing sessions to assess changes in cognitive control and error monitoring associated with viewing different types of environmental imagery. Results showed no significant differences in ERN amplitude across sessions or between nature imagery and urban imagery at Session 2. Collectively, these results suggest that brief exposure to the 2-D nature imagery used within this study may not elicit the same attention-dependent responses as real-world nature exposure.
Vitaliy Pavlenko , Denys Lukashuk | Bulletin of the National Technical University KhPI A series of Information and Modeling
A method for modeling the human eye movement system (EMS) based on Volterra models in the form of multidimensional transient characteristics has been further developed. These characteristics were obtained from … A method for modeling the human eye movement system (EMS) based on Volterra models in the form of multidimensional transient characteristics has been further developed. These characteristics were obtained from experimental "input-output" EMS studies using innovative eye-tracking technology. The respondent was studied in the morning and evening, which made it possible to identify the variability of EMS characteristics in the before-work (normal) and after-work (fatigue) states. It has been established that for EMS identification in practical neuroscience applications, it is advisable to use the quadratic Volterra polynomial, determined using the least squares method with three step test signals of different amplitudes. Datasets for machine learning were formed in different diagnostic feature spaces: heuristic features and features derived from sampling the first- and second-order transient characteristics. Using computer modeling, feature sets that are robust according to the probability of correct recognition criterion were identified. To assess psychophysiological states, a Bayesian classifier and the SVM method were applied. Figs.: 11. Tabl. 3. Refs.: 31 titles.
The audiovisual rabbit illusion is a cross-modal postdictive phenomenon where an illusory flash is perceived between two spatially displaced real flashes when accompanied by three auditory beeps. This study investigates … The audiovisual rabbit illusion is a cross-modal postdictive phenomenon where an illusory flash is perceived between two spatially displaced real flashes when accompanied by three auditory beeps. This study investigates how attentional cues influence the perceived location of the illusory flash. We used four small red dots as placeholders for exogenous cues, positioned near potential flash locations in the upper and lower visual hemifields. One dot changed to yellow either 200 ms before (Experiment 1) or after (Experiment 2) the flashes to direct attention. Results showed that a 200-ms precue attracted the illusory flash (Experiment 1), underscoring the role of early attentional selection in localizing cross-modal illusions. In contrast, a 200-ms postcue had no effect (Experiment 2), whereas a 50-ms postcue repelled the illusory flash location (Experiment 3), suggesting that late sensory reactivation through postcues remaps stimulus localization. These findings demonstrate distinct mechanisms through which precues and postcues influence the perception of cross-modal illusory stimuli, offering new insights into attention, postdiction, and multisensory integration. (PsycInfo Database Record (c) 2025 APA, all rights reserved).
It is well established that observers overestimate the surface orientation of geographical, virtual, and man-made hills. We investigated whether the v’ theory—that observers use the angle of regard—or the relationship … It is well established that observers overestimate the surface orientation of geographical, virtual, and man-made hills. We investigated whether the v’ theory—that observers use the angle of regard—or the relationship between the direction of gaze and the slope of the hill, to make their slope estimates. We tested whether the perceived steepness of hills changes across dramatic differences in eye heights across a wide range of surface orientations, while controlling for distance of the surface from the observer. We found that people use the angle of regard to make their slope estimates across a wide range of surface orientations and eye heights while controlling for distance, standing on the surface, and posture. The dramatic manipulation in eye height caused corresponding changes in slope perception as predicted by the angle of regard. The angle of regard seems to be a perceptual regularity that is constant across changes of position of the observer and surface slope, and also predicts observed changes in eye height and distance of the surface from the viewer.
Self-motion estimation is thought to depend on sensory information as well as on sensory predictions derived from motor output. In driving, the inertial motion cues (vestibular and somatosensory cues) can … Self-motion estimation is thought to depend on sensory information as well as on sensory predictions derived from motor output. In driving, the inertial motion cues (vestibular and somatosensory cues) can in principle be predicted based on the steering motor commands if an accurate internal model of the steering dynamics is available. Here, we used a closed-loop steering experiment to examine whether participants can build such an internal model of the steering dynamics. Participants steered a motion platform on which they were seated to align their body with a memorized visual target in complete darkness. We varied the gain between the steering wheel angle and the velocity of the motion platform across trials in three different ways: unpredictable (white noise), moderately predictable (random walk), or highly predictable (constant gain). We examined whether participants took the across-trial predictability of the gain into account to control their steering (internal model hypothesis), or whether they simply integrated the inertial feedback over time to estimate their travelled distance (path integration hypothesis). Results show that participants relied on the gain of the previous trial more when it followed a random walk across trials than when it varied unpredictably across trials. Furthermore, on interleaved trials with a large jump in the gain, participants made fast corrective responses, irrespective of gain predictability, showing they also relied on inertial feedback next to predictions. These findings suggest that the brain can construct an internal model of the steering dynamics to predict the inertial sensory consequences in driving and self-motion estimation.
Visual crowding refers to the difficulty in recognizing objects in the periphery when surrounded by clutter. Traditional trial-based paradigms, while effective in measuring spatial aspects of crowding, do not capture … Visual crowding refers to the difficulty in recognizing objects in the periphery when surrounded by clutter. Traditional trial-based paradigms, while effective in measuring spatial aspects of crowding, do not capture the temporal dynamics involved. In this study, we assessed the feasibility of a continuous psychophysics paradigm that measures both the spatial extent and temporal processes of visual crowding. Eight participants continuously tracked the orientation of a rotating Landolt C while the distance between the target and a ring-shaped flanker varied systematically over time. Participants set a reference stimulus to match the orientation of the target. The paradigm included "jump-points," where the orientation of the target suddenly shifted, allowing us to measure the recovery rate of participants' tracking errors following these disruptions. Tracking accuracy was compared between flanked and isolated conditions. Additionally, participants' report errors were used to assess both the crowding extent and the temporal recovery rate from the jumps, with the crowding extent results compared with those obtained from a conventional trial-based version of the paradigm. The recovery rate was calculated by fitting an exponential decay function to participants' report errors after the jumps. The results showed that the crowding extent measured using the continuous paradigm was consistent with that obtained using trial-based methods and aligned with Bouma's rule. Moreover, flankers decreased both tracking accuracy and recovery rate following the jumps. These results demonstrate that our continuous psychophysics paradigm is useful for measuring the spatiotemporal aspects of crowding.
Abstract Purpose To validate a new digital device: OptotabĀ®+ (SmarThings4Vision) for measuring visual acuity (VA) and contrast sensitivity (CS). Methods A validation study was conducted involving 20 healthy subjects (aged: … Abstract Purpose To validate a new digital device: OptotabĀ®+ (SmarThings4Vision) for measuring visual acuity (VA) and contrast sensitivity (CS). Methods A validation study was conducted involving 20 healthy subjects (aged: 18–29 years). Distance and near VA and CS were assessed using the OptotabĀ®+ and compared with the ETDRS test and Sloan letters for distance VA, the ETDRS test and LEA numbersĀ® near vision card for near VA and the Regan and CSV‐1000 tests for CS. Results No significant differences were noted between the right eye (RE) and left eye (L for distance ( p &gt; 0.99) and near VA ( p = 0.32) or test–retest measurements ( p &gt; 0.05) using the OptotabĀ®+. Distance VA differed significantly from the ETDRS (mean differences: āˆ’0.07 and āˆ’0.07 logMAR for the RE and LE, respectively, p = 0.01). Intraclass correlation coefficients (ICC) indicated moderate reliability (RE: 0.64, LE: 0.48), while the ANOVA showed no significant differences ( p = 0.75 for RE and p = 0.58 for LE). For CS, no significant differences were found between the RE and LE, except at 12 cpd ( p = 0.04). ICC was highest at 18 cpd (0.90). A significant test–retest difference was observed at 6 cpd for the RE (0.10 log units, p = 0.01). Comparisons showed significant differences at 6 cpd between OptotabĀ®+ and the CSV‐1000, and at 3, 12 and 18 cpd between OptotabĀ®+ and the Regan test. ICC indicated low to high reliability across spatial frequencies, while the ANOVA did not show significant differences or low variability. No significant inter‐examiner differences were identified in VA and CS ( p &gt; 0.05), confirming strong reproducibility. Conclusions This study demonstrates that the OptotabĀ®+ has moderate reliability for VA assessment and higher precision at higher spatial frequencies for CS, suggesting its clinical utility. Outcomes regarding reliability, repeatability and reproducibility support its validity as an effective tool for measuring visual parameters in clinical practice.
Abstract Visual function tests are important in basic and clinical vision research but are typically limited to very few aspects of human vision, coarse diagnostic resolution, and require an administrator. … Abstract Visual function tests are important in basic and clinical vision research but are typically limited to very few aspects of human vision, coarse diagnostic resolution, and require an administrator. Recently, the generalizable, response-adaptive, self-administered Angular Indication Measurement (AIM) and Foraging Interactive D-prime (FInD) methods were developed to assess vision across different visual functions. The AIM and FInD paradigms show a range of visual stimuli per display (4Ɨ4 stimuli) spanning ±2σ around an adaptively estimated perceptual threshold across multiple displays. Here, we investigated the repeatability and behavioral relationships of the AIM and FinD paradigms for near visual acuity, contrast sensitivity function (CSF), form, and motion coherence threshold measurements using a novel tablet-based vision test tool. 31 healthy participants were recruited and repeated two repetitions of each experiment in random order. Bland-Altman analyses were performed to calculate the Coefficient of Repeatability (precision) and Mean Bias (accuracy). Linear regressions and hierarchical cluster analysis were used to investigate the relationship between outcome parameters. Results show that AIM Form coherence and FInD Form horizontal coherence showed significant retest bias; all other tests were bias-free. Cluster analysis revealed overall clustering of CSF, form and motion outcomes. We further show significant correlations within CSF and between motion coherence outcomes but few significant correlations between form coherence outcomes. AIM and FInD near vision tests are generalizable across multiple visual functions and are precise and reliable. Most functions tested were bias-free. CSF, form, and motion outcomes clustered together, and CSF and motion outcomes correlated with one another. The combination of a generalizable, response-adaptive, and self-administered approach may be a suitable set of tests for basic science and clinical use cases.
Summary Active sensing necessarily requires integrating information about both self-generated movements as well as past, present, and future afferent inputs 1,2 . However, such information is inherently variable and relies, … Summary Active sensing necessarily requires integrating information about both self-generated movements as well as past, present, and future afferent inputs 1,2 . However, such information is inherently variable and relies, at least in part, on uncertain extrapolations. Here, using saccadic suppression 3,4 of visual sensitivity as a classic example of sensory-motor integration, we show that suppression strength in two drastically different species, macaque monkeys and zebrafish larvae, may be a direct outcome of efficient state estimation in the presence of uncontrollable sensory and motor variability. Bayesian estimator models 5 suggest that optimal saccadic suppression should rely not just on the sensory-motor information being processed, but also on the time-dependent magnitude of unexplained variability in the nervous system encoding it. In both macaques and zebrafish larvae, and using matched visual stimulation regimes across the species, we experimentally measured saccadic suppression strength in the superior colliculus (SC) of the monkeys and the homologous optic tectum (OT) of the fish. We also experimentally quantified additive and multiplicative noise components in the motor systems of both species, and we furthermore estimated noise in the sensory systems. We found that inter-species differences in noise levels and their theoretically predicted impacts on visual sensitivity are qualitatively consistent with our experimentally observed differences in saccadic suppression strength between the fish and the monkeys. Because sensory and motor noise levels can reflect the amounts of available neural resources committed to a given task, our results strongly underscore the value of incorporating computational resource limits in investigating performance differences that have evolved in homologous brain areas.
Abstract Salient distractors often capture our attention, disrupting ongoing tasks. Recent studies suggest that, through statistical learning, prior experiences regarding distractor locations can reduce distraction by suppressing their corresponding locations. … Abstract Salient distractors often capture our attention, disrupting ongoing tasks. Recent studies suggest that, through statistical learning, prior experiences regarding distractor locations can reduce distraction by suppressing their corresponding locations. However, the proactive neural mechanisms supporting this learned suppression remain unclear. Our findings demonstrate that participants learn to suppress locations that are more likely to contain distractors relative to other locations. Using frequency tagging in EEG recordings, we observed significantly different tagging responses between high- and low-probability locations, along with a general decrease in alpha power (8–12 Hz) before search onset. Notably, the higher tagging frequency power at high-probability locations suggests that participants allocated greater attentional focus to these locations in anticipation of the search. These results suggest that anticipatory attentional deployment precedes the suppression of high-probability distractor locations after the onset of visual search.