Limiting Factors for the Detection of Orientation

Perception ◽  
1998 ◽  
Vol 27 (2) ◽  
pp. 167-181
Author(s):  
Johannes M Zanker
Keyword(s):  
Visual Field ◽  
Visual Information ◽  
Receptive Fields ◽  
Limiting Factors ◽  
Visual Stream ◽  
Local Operation ◽  
Cortical Magnification ◽  
Orientation Detection ◽  
Cortical Magnification Factor ◽  
Cortical Receptive Fields

First steps of visual-information processing in primates are characterised by a highly ordered representation of the outside world on the cortex. Two prominent features of cortical organisation are the retinotopic mapping of position in the visual field on the first stages of the visual stream, and the systematic variation of orientation preference in the same areas. In an attempt to understand the relation of position and orientation representation, we need to know the minimum spatial requirements for orientation detection. In the present paper, the spatial limits for detecting orientation are analysed by simulating simple orientation filters and testing the ability of human observers to detect the orientation of small lines at various positions in the visual field. At sufficiently high contrast levels, the minimum physical length of a line to discriminate orientation differences of 45°–90° is not constant when presented at various eccentricities, but covaries inversely with the cortical magnification factor. In consequence, a line needs to correspond to about 0.2 mm of cortical surface, independently of the actual eccentricity at which the stimulus is presented, in order to allow observers to recognise its orientation. This has consequences for our understanding of orientation detection, (i) In combination with simulation experiments, it becomes clear that the elementary process underlying orientation detection is a local operation, which seems to focus on small regions compared with cortical receptive fields, (ii) With respect to the number of inputs to the visual cortex, the performance of this local operation approaches the physical limits, requiring hardly more than three-four input LGN axons to be activated for detecting the orientation of a highly visible line segment. Comparing these spatial characteristics with the receptive fields of orientation-sensitive neurons in the primate visual system could suggest new insights into the neuronal circuits underlying orientation mapping in the human cortex.

The Detection of Orientation of Small Objects

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 59-59
Author(s):  
J M Zanker ◽  
M P Davey
Keyword(s):  
Visual Field ◽  
Visual System ◽  
Computer Simulations ◽  
Visual Information ◽  
Human Performance ◽  
Receptive Fields ◽  
Experimental Result ◽  
Orientation Tuning ◽  
Basic Question ◽  
Visual Stream

Visual information processing in primate cortex is based on a highly ordered representation of the surrounding world. In addition to the retinotopic mapping of the visual field, systematic variations of the orientation tuning of neurons are described electrophysiologically for the first stages of the visual stream. On the way to understanding the relation of position and orientation representation, in order to give an adequate account of cortical architecture, it will be an essential step to define the minimum spatial requirements for detection of orientation. We addressed the basic question of spatial limits for detecting orientation by comparing computer simulations of simple orientation filters with psychophysical experiments in which the orientation of small lines had to be detected at various positions in the visual field. At sufficiently high contrast levels, the minimum physical length of a line whose orientation can just be resolved is not constant when presented at various eccentricities, but covaries inversely with the cortical magnification factor. A line needs to span less than 0.2 mm on the cortical surface in order to be recognised as oriented, independently of the actual eccentricity at which the stimulus is presented. This seems to indicate that human performance for this task approaches the physical limits, requiring hardly more than approximately three input elements to be activated, in order to detect the orientation of a highly visible line segment. Combined with the estimates for receptive field sizes of orientation-selective filters derived from computer simulations, this experimental result may nourish speculations of how the rather local elementary process underlying orientation detection in the human visual system can be assembled to form much larger receptive fields of the orientation-sensitive neurons known to exist in the primate visual system.

scholarly journals Picturing Peripheral Acuity

Perception ◽  
1998 ◽  
Vol 27 (7) ◽  
pp. 817-825 ◽  
Author(s):  
Stuart Anstis
Keyword(s):  
Visual Field ◽  
Receptive Fields ◽  
Magnification Factor ◽  
Cortical Magnification ◽  
Retinal Receptive Fields ◽  
Cortical Magnification Factor

The grain of the retina becomes progressively coarser from the fovea to the periphery. This is caused by the decreasing number of retinal receptive fields and decreasing amount of cortex devoted to each degree of visual field (= cortical magnification factor) as one goes into the periphery. We simulate this with a picture that is progressively blurred towards its edges; when strictly fixated at its centre it looks equally sharp all over.

scholarly journals SUVOKIAMO ATKARPOS ILGIO PRIKLAUSOMYBĖ NUO JOS ATVAIZDO VIETOS AKIES TINKLAINĖJE

Psichologija ◽  
2011 ◽  
Vol 43 ◽  
pp. 78-91
Author(s):  
A. Dzekevičiūtė ◽  
A. Daugirdienė ◽  
A. Švegžda ◽  
R. Stanikūnas ◽  
H. Vaitkevičius
Keyword(s):  
Visual Field ◽  
Line Length ◽  
The Other ◽  
Size Perception ◽  
Normal Vision ◽  
Magnification Factor ◽  
Extremum Point ◽  
Cortical Magnification ◽  
Cortical Magnification Factor ◽  
The Given

Tyrimo tikslas yra patikrinti, kaip keičiasi objekto dydžio suvokimas, kintant jo projekcijos padėčiai akies tinklainėje, ir kaip objekto dydžio suvokimas priklauso nuo akies tinklainės receptorių (kūgelių ir lazdelių) tankio. Tiriamieji, žiūrėdami viena akimi ir fiksuodami žvilgsnį, dalijo skirtingų ilgių atkarpas – nustatydavo suvokiamą vidurį. Atkarpos dalių santykio nuo atkarpos ilgio funkcija turėjo lūžio tašką (66,7 proc. tiriamiesiems, kai atkarpos ilgis 7 laipsniai, 23,33 proc. – 13 laipsnių, kiti neturėjo). Rezultatai aiškinami skirtingu kūgelių ir lazdelių tankiu akies tinklainėje ir skirtinga kūgelių ir lazdelių įtaka.Pagrindiniai žodžiai: dydžio suvokimas, žievinis didinimo veiksnys, fotoreceptorių tankis.Perceived Size of a Line Depending on Its Projection Place on the RetinaDzekevičiūtė A., Daugirdienė A., Švegžda A., Stanikūnas R., Vaitkevičius H. SummaryIt is known that objects located in the centre of the visual field are perceived as larger than the objects located in the periphery (Пиаже, 1978). The image of an object differs from its perception object. The perceived size of an object depends on the size of its image in the visual cortex. This stems from the so-called cortical magnification factor. It is assumed that the same quantity of receptors sends information to the same area of the cortex. But photoreceptors are different – rods and the cones. It is not clear whether the different type of receptors make a different influence on the above-mentioned distortion of mapping. Also, the image of the object on the retina is perceived differently, depending on its location on the retina. Our goal was to explore how this subjective expansion changes while moving away from the centre of the retina, because there are no data on this, phenomenon.Method. Thirty normal or corrected to normal vision adults participated in the study. Five different length lines (5, 7, 10, 13, 15 degrees) were represented on the computer’s monitor one line at a time. Participants had monoculary bisected lines into two subjectively equal parts fixating sight on a cross located at the given end of the line.Results. The ratio ρ (length of the line near the cross / length of the other part) was calculated. This ratio as a function of the length of the whole line was not monotonic: when the line was short, ρ decreased, but then it began to increase. Three groups of results were formed considering the ratio of the line length (where the function had the extremum point). The largest group (66.67%) had the extremum point when the line length was 7 deg. The second group (23.33%) had the extremum point when the line length was 13 deg. The last group (10%) had not clear extremum point and was excluded from the calculation. Changes of the ρ value cannot be explained by the perceptual instability of the length of the line (Brown, 1953). There could be a correlation between the value of ρ and the density of all receptors in the retina where the line was projected.Conclusions. Humans make a bias while monocular by bisecting a line: the part near the point of fixation is perceived as bigger than the other part. The function of the line size ratio changes not monotonically – it has an extremum point. Most often, the extremum point is observed when the line size is 7 deg. This point is near the point where the density of rods exceeds that of cones. Other subjects show the extremum point when line size is 13 deg., but the reasons for such a point shift remain unclear. Some subjects have no extremum point.Key words: size perception, cortical magnification factor, density of photoreceptors.

scholarly journals Spatiotemporal adaptation through corticothalamic loops: A hypothesis

2000 ◽  
Vol 17 (1) ◽  
pp. 107-118 ◽  
Author(s):  
ULRICH HILLENBRAND ◽  
J. LEO van HEMMEN
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Lateral Geniculate Nucleus ◽  
Sensory Processing ◽  
Object Segmentation ◽  
Receptive Fields ◽  
The Novel ◽  
Spatiotemporal Structure ◽  
Cortical Responses ◽  
Cortical Receptive Fields

The thalamus is the major gate to the cortex and its control over cortical responses is well established. Cortical feedback to the thalamus is, in turn, the anatomically dominant input to relay cells, yet its influence on thalamic processing has been difficult to interpret. For an understanding of complex sensory processing, detailed concepts of the corticothalamic interplay need yet to be established. Drawing on various physiological and anatomical data, we elaborate the novel hypothesis that the visual cortex controls the spatiotemporal structure of cortical receptive fields via feedback to the lateral geniculate nucleus. Furthermore, we present and analyze a model of corticogeniculate loops that implements this control, and exhibit its ability of object segmentation by statistical motion analysis in the visual field.

Indirect, across-the-midline retinotectal projections and representation of ipsilateral visual field in superior colliculus of the cat

1978 ◽  
Vol 41 (2) ◽  
pp. 285-304 ◽  
Author(s):  
A. Antonini ◽  
G. Berlucchi ◽  
J. M. Sprague
Keyword(s):  
Visual Field ◽  
Receptive Field ◽  
Superior Colliculus ◽  
Visual Information ◽  
Receptive Fields ◽  
Optic Chiasm ◽  
Anterior Portion ◽  
Vertical Meridian ◽  
Contralateral Eye ◽  
Rostral Portion

1. In agreement with previous work, we have found that the ipsilateral visual field is represented in an extensive rostral portion--from one-third to one-half--of the superior colliculus (SC) of the cat. This representation is binocular. The SC representation of the ipsilateral visual field can be mediated both directly, by crossed retinotectal connections originating from temporal hemiretina, and indirectly, by across-the-midline connections relaying visual information from one-half of the brain to contralateral SC. 2. In order to study the indirect, across-the-midline visual input to the SC, we have recorded responses of SC neurons to visual stimuli presented to either the ipsilateral or the contralateral eye of cats with a midsagittal splitting of the optic chiasm. Units driven by the ipsilateral eye, presumably through the direct retinotectal input and/or corticotectal connections from ipsilateral visual cortex, were found throughout the SC, except at its caudal pole, which normally receives fibers from the extreme periphery of the contralateral nasal hemiretina. Units driven by the contralateral eye, undoubtedly through an indirect across-the-midline connection, were found only in the anterior portion of the SC, in which is normally represented the ipsilateral visual field. Receptive fields in both ipsilateral and contralateral eye had properties typical of SC receptive fields in cats with intact optic pathways. 3. All units having a receptive field in the contralateral eye had also a receptive field in the ipsilateral eye; for each of these units, the receptive fields in both eyes invariably abutted the vertical meridian of the visual field. The receptive field in one eye had about the same elevation relative to the horizontal meridian and the same vertical extension as the receptive field in the other eye; the two receptive fields of each binocular unit matched each other at the vertical meridian and formed a combined receptive field straddling the vertical midline of the horopter...

Importance of corpus callosum for visual receptive fields of single neurons in cat superior colliculus

1979 ◽  
Vol 42 (1) ◽  
pp. 137-152 ◽  
Author(s):  
A. Antonini ◽  
G. Berlucchi ◽  
C. A. Marzi ◽  
J. M. Sprague
Keyword(s):  
Visual Field ◽  
Corpus Callosum ◽  
Superior Colliculus ◽  
Visual Information ◽  
Visual Learning ◽  
Receptive Fields ◽  
Vertical Meridian ◽  
Retinotectal Projections ◽  
Contralateral Eye ◽  
Stimulation Of

1. Section of the posterior two-thirds of the corpus callosum eliminates almost completely the response of superior colliculus (SC) neurons to stimulation of the contralateral eye in split-chiasm cats. On the contrary, the responsiveness of SC neurons to stimulation of the contralateral eye is not abolished by a transection of the posterior and tectal commissures leaving the corpus callosum intact. The callosal section also reduces the number of SC receptive fields abutting the vertical meridian in the ipsilateral eye of split-chiasm cats. 2. In cats with intact optic pathways, a similar callosal section abolishes the SC representation of the ipsilateral visual field in the ipsilateral eye and also reduces the number of receptive fields adjoining the vertical meridian in the same eye. In the contralateral eye, the SC representation of the ipsilateral visual field is reduced in extension to about one-fifth of that seen in cats with intact commissures. 3. The results suggest that the corpus callosum is the main pathway for cross-midline communication of visual information at not only the cortical, but also the midbrain level. The corpus callosum may subserve this function because it contains uninterrupted crossed corticotectal projections or because it transmits visual information from one hemisphere to contralateral cortical areas projecting ipsilaterally to SC. The latter hypothesis is more likely but, in any case, the findings imply that the lack of interhemispheric transfer of visual learning in cats with a chiasmatic and callosal section may depend on a midline disconnection of both subcortical and cortical visual centers. 4. The corpus callosum is also responsible for the representation of the ipsilateral visual field of the ipsilateral eye in the cat SC. The SC representation of the ipsilateral visual field in the contralateral eye is due, in minimal part, to direct retinotectal connections from temporal retina and, for the largest part, to the corpus callosum. 5. Finally, the corpus callosum contributes to the representation of the contralateral visual field near the vertical meridian of the temporal retina in both split-chiasm and normal cats. This is probably due to the scarcity of direct retinotectal projections from this part of the retina and to their supplementation by corticotectal neurons influenced by the callosal afferents.

scholarly journals Development differentially sculpts receptive fields across human visual cortex

2017 ◽  
Author(s):  
Jesse Gomez ◽  
Vaidehi Natu ◽  
Brianna Jeska ◽  
Michael Barnett ◽  
Kalanit Grill-Spector
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Right Hemisphere ◽  
Receptive Fields ◽  
Visual Stream ◽  
Differential Development ◽  
Processing Information ◽  
Ventral Visual Stream ◽  
Visual Field Maps ◽  
The Right

ABSTRACTReceptive fields (RFs) processing information in restricted parts of the visual field are a key property of neurons in the visual system. However, how RFs develop in humans is unknown. Using fMRI and population receptive field (pRF) modeling in children and adults, we determined where and how pRFs develop across the ventral visual stream. We find that pRF properties in visual field maps, V1 through VO1, are adult-like by age 5. However, pRF properties in face- and word-selective regions develop into adulthood, increasing the foveal representation and the visual field coverage for faces in the right hemisphere and words in the left hemisphere. Eye-tracking indicates that pRF changes are related to changing fixation patterns on words and faces across development. These findings suggest a link between viewing behavior of faces and words and the differential development of pRFs across visual cortex, potentially due to competition on foveal coverage.

Binocular neurons in the nucleus of the basal optic root (nBOR) of the pigeon are selective for either translational or rotational visual flow

1990 ◽  
Vol 5 (5) ◽  
pp. 489-495 ◽  
Author(s):  
Douglas R. Wylie ◽  
Barrie J. Frost
Keyword(s):  
Visual Field ◽  
Visual Information ◽  
Visual Motion ◽  
Visual Fields ◽  
Receptive Fields ◽  
Locomotor Behavior ◽  
Visual Flow ◽  
Electrophysiological Studies ◽  
Crucial Part ◽  
Stimulation Of

AbstractPrevious electrophysiological studies have shown that neurons in the nucleus of the basal optic root (nBOR) of the pigeon respond best to wholefield stimuli moving slowly in a particular direction in the contralateral visual field. In this study, we have found that some nBOR neurons respond to wholefield stimulation of both eyes. These binocular neurons have spatially separate receptive fields in both visual fields. Some binocular neurons prefer the same direction of wholefield motion in both eyes, and thus respond best to wholefield visual motion which would result from translation movements of the bird, either ascent, descent, or forward and backward motion. Other neurons prefer opposite directions of wholefield motion in each eye and therefore respond optimally to wholefield visual motion simulating rotational movements of the bird, either roll or yaw. These binocular neurons may play a crucial part in the locomotor behavior of the pigeon by providing visual information distinguishing translational and rotational movements.

scholarly journals Thalamocortical processing in vision

2017 ◽  
Vol 34 ◽  
Author(s):  
REECE MAZADE ◽  
JOSE MANUEL ALONSO
Keyword(s):  
Visual Field ◽  
Cortical Neurons ◽  
Visual Information ◽  
Receptive Fields ◽  
Visual Space ◽  
Spatial Position ◽  
Strongly Correlated ◽  
Cortex Area ◽  
Multiple Copies ◽  
Efficient Processing

AbstractVisual information reaches the cerebral cortex through a major thalamocortical pathway that connects the lateral geniculate nucleus (LGN) of the thalamus with the primary visual area of the cortex (area V1). In humans, ∼3.4 million afferents from the LGN are distributed within a V1 surface of ∼2400 mm2, an afferent number that is reduced by half in the macaque and by more than two orders of magnitude in the mouse. Thalamocortical afferents are sorted in visual cortex based on the spatial position of their receptive fields to form a map of visual space. The visual resolution within this map is strongly correlated with total number of thalamic afferents that V1 receives and the area available to sort them. The ∼20,000 afferents of the mouse are only sorted by spatial position because they have to cover a large visual field (∼300 deg) within just 4 mm2 of V1 area. By contrast, the ∼500,000 afferents of the cat are also sorted by eye input and light/dark polarity because they cover a smaller visual field (∼200 deg) within a much larger V1 area (∼400 mm2), a sorting principle that is likely to apply also to macaques and humans. The increased precision of thalamic sorting allows building multiple copies of the V1 visual map for left/right eyes and light/dark polarities, which become interlaced to keep neurons representing the same visual point close together. In turn, this interlaced arrangement makes cortical neurons with different preferences for stimulus orientation to rotate around single cortical points forming a pinwheel pattern that allows more efficient processing of objects and visual textures.

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