Note that the dendrites of the a-type (OFF-center) and b-type . The V1 is selective for orientation. volume10,pages 195211 (2001)Cite this article. Proc. There are several systems that describe the early stages of visual contour processing up to the level of complex cell responses; only few models describe even end-stopped cells. B 229:257-276. Simple cells have smaller receptive fields, that are able only to receive simple signals from a fairly small amount of fibres, whilst hyper-complex cells have larger receptive fields that respond to more specific stimuli, such as moving bars of light of correct orientation, width and length. In the first stage, a Gabor wavelet decomposition provides a representation of the image which is orientation selective and has optimal localization properties in space and frequency. Neumann H, Pessoa L, Mingolla, E (1998) A neural architecture of brightness perception: Non-linear contrast detection and geometry-driven diffusion. Neuron, 20, 401-412. A hypercomplex cell (currently called an end-stopped cell) is a type of visual processing neuron in the mammalian cerebral cortex.Initially discovered by David Hubel and Torsten Wiesel in 1965, hypercomplex cells are defined by the property of end-stopping, which is a decrease in firing strength with increasingly larger stimuli.The sensitivity to stimulus length is accompanied by selectivity . Ffytche DH, Zeki S (1996) Brain activity related to the perception of illusory contours. Heitger F, Rosenthaler L, von der Heydt R, Peterhans E, Kbler 0 (1992) Simulation of neural contour mechanisms: From simple to end-stopped cells. USA 92:6469-6473. Illusory contours may have already formed before the inducer orientation information is crowded out. Vision Res. . Proc R Soc Lond B 235: 221245. - Simple cells care about precise location of stimuli Minguzzi GF (1987) Anomalous figures and the tendency to continuation. Whats there difference between complex cell and hypercomplex cell? What are the qualities of Parvocellular neurons? A contrast- and luminance-driven multiscale network model of brightness perception.Vis. Hubel DH, Wiesel TN (1965) Receptive fields, and functional architecture in two nonstriate visual areas (18 and 19) of the cat. Sorry, preview is currently unavailable. a. on-center/on-surround b. on-center/off-surround c. off-center/on-surround d. off-center/off-surround, The process that acts to enhance the boundaries of visual objects is called a. lateral inhibition . PhD thesis, University of Groningen, The Netherlands. Journal of Physiology, 195: 215 - 243, 1968. Westheimer G, Li W (1996) Classifying illusory contours by means of orientation discrimination. Cybern. Eur. The illusory contour orientation is thus negatively signaled or de-emphasized in V1. Leventhal, AG, Zhou, Y (1994) Cat visual cortical cells are sensitive to the orientation and direction of illusory contours. Heitger F, von der Heydt R (1993) A computational model of neural contour processing: Figure-ground segregation and illusory contours. Lourens T (1998) A biologically plausible model for corner-based object recognition from color images. -T o exaggerate a shape, just incase the difference is shade is out of out JND threshold. If illusory contour formation is governed solely by extrapolation or interpolation mechanisms . The final stage groups similar features, aiding in boundary completion. - Just contralateral cells What are the 3 distinct neurons of the LGN? In sum, Hubel and Wiesel identified simple cells by discernibly separate excitatory and inhibitory regions that responded to stationary stimuli. 1996. This paper builds on a previously described model of early vision and investigates the logic of grouping. The physiological basis of, Dictionary, Encyclopedia and Thesaurus - The Free Dictionary, the webmaster's page for free fun content, illegal use of controlled dangerous substances. the mechanismsof binocular vision, illusory contour formation, and brightnessperceptionthat was first reported in Gove et al. Springer, Berlin, Heidelberg. Figure 1. Gilbert, C. (2007). 41:1071-1095. Vision Res. (1998). 268:391-421. Furthermore, the regions exhibit mutual cancellation (antagonism) and produce stronger responses as the stimuli fill more space (spatial summation). where are illusory contours mostly processes? A model consisting of a multistage system which extracts and groups salient features in the image at different spatial scales (or frequencies) is used. Rose D (1977) Responses of single units in cat visual cortex to moving bars of light as a function of bar length. The bipole cell is modelled as a recurrent excitatory network that computes the logical AND function between two collinear but spatially separated parts (or poles) of their receptive field. Kulikowski JJ, Marelja S, Bishop PO (1982) Theory of spatial position and spatial frequency relations in the receptive fields of simple cells in the visual cortex. Vis. A computational model of neural contour processing: Figure-ground segregation and illusory contours. Grinvald A, Lieke E, Frostig RD, Gilbert CD, Wiesel TN (1986) Functional architecture of cortex revealed by optical imaging of intrinsic signals. Cambridge University Press, Cambridge, pp. Investigative Ophthalmology, 355-356. Google Scholar Ffytche DH, Zeki S (1996) Brain activity related to the perception of illusory contours. :> Presence of illusory edge could be signalled by interconnected hypercomplex cells. Hypercomplex cells (must be interconnected). Biol. Psychonomic Bull. 30:1111-1117. Extending beyond a specific length, the response would become progressively weaker. J Neurosci 9: 17311748. Nakayama K Shimojo S, Silverman G H (1989) Stereoscopic depth: its relation to image segmentation, grouping, and the recognition of occluded objects. Ph.D. thesis, University of Groningen, The Netherlands. Koenderink JJ, van Doorn AJ (1987) Representation of local geometry in the visual system. Experts are tested by Chegg as specialists in their subject area. Friedrich Schumann is often credited with the discovery of illusory contours around the beginning of the 20th century, but they are present in art dating to the Middle Ages. a. (1969). We explain these results in terms of a computational model using end-stopped operators for the detection of occlusion cues. L. Pessoa, E. Mingolla, and H. Neumann. It is presumed that multiple concentric LGN receptive fields converge in a line to develop a single simple receptive field. Existing techniques for extracting video objects are based on inverse optics, where three-dimensional objects are mapped to a two dimensional image. [4][5], Beyond simple cells are complex cells, which are the most common type in the primary visual cortex (but are also found in Brodmann area 18). Figures in which human observers perceive ``illusory contours'' were found to evoke responses in cells of area 18 in the visual cortex of alert monkeys. I. Dobbins A, Zucker SW, Cynader MS (1987) Endstopped neurons in the visual cortex as a substrate for calculating curvature. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. Perception & Psychophys. Cynader. CrossRef Google Scholar F. Heitger and R. von der Heydt. Comparatively little is known about the mechanisms defining the depth order and the brightness illusion associated with such contours. Google Scholar. J. Neurosci. Cengage Learning. E. Peterhans and R. von der Heydt. Sensation and Perception. For instance, a simple cell will only weakly fire if it is entirely illuminated because both the excitatory and inhibitory regions will be stimulated. Effective content-based retrieval requires access to video objects which represent syntactic structures in a video sequence such as people, cars, shots and scenes. In: Pettigrew JD, Sanderson KJ, Levick WR, eds. What do hypercomplex cell have that a complex cell does not have? Proc. CrossRef Springer, New York, NY. Finkel LH, Sajda P (1992) Object discrimination based on depthfrom-occlusion. Hawken MJ, Parker AJ (1987) Spatial properties of neurons in monkey striate cortex. Soc. 52:562-570. Vision Research, 29, 1371-1387. Bolz J, Gilbert CD, Wiesel TN (1989) Pharmacological analysis of cortical circuitry. Perception 24:43. C. Zetzsche and E. Barth. Although end-stopped cells are a phenomenon of the mammalian visual cortex, there have been discoveries of cells exhibiting end-stopping properties within a variety of other species. Illusory brightness and depth ordering often accompany illusory contours. The role of edges and line-ends in illusory contour formation.Vision Research, 33 (16): 22532270, 1993. Baumann R, van der Zwan R, Peterhans E (1997) Figure-ground segregation at contours: a neural mechanism in the visual cortex of the alert monkey. van der Zwan R, Baumann R, Peterhans E (1995) End-stopped cells in the visual cortex of the alert monkey. Provided by the Springer Nature SharedIt content-sharing initiative, Over 10 million scientific documents at your fingertips, Not logged in c. simple cells, connected in an AND or an OR b. hypercomplex cells, connected in an OR arrangement (A) An illusory rectangle is perceived between the halves of the donut (Schumann, 1900). What layers does the Ipsilateral eye receive input from? Stimulus set used in . A classic example of illusory contours is the Kanizsa triangle ( Kanizsa 1955 ). Freeman, New York, 1990. Vision Res 32: 963981. Hirsch J, De La Paz RL, Relkin NR, Victor J, Kim K, Li T, Borden P, Rubin N, Shapley R (1995) Illusory contours activate specific regions in human visual cortex: evidence from functional magnetic resonance imaging. Gerrits HJM, Vendrik AJH (1970) Simultaneous contrast filling-in process and information processing in mans visual system. While V2 cells responding to illusory contour is widely accepted, whether V1 cells respond to illusory contours are more controversial. A inhibitory complex cell (end stopped cell). Prazdny K (1983) Illusory contours are not caused by simultaneous brightness contrast. The network nodes in these levels are analogous to cortical simple cells, complex cells, hypercomplex cells, and unoriented and oriented cooperative cells. (1984) tried to draw a clear distinction between the stimulus-response relationship, on the one hand, and perceived entities, on the other. Zucker, and M.S. Rock. In Peterhans and Von der Heydt studies, 4 only very few V1 cells were found to be responsive to illusory contours, while about 32 to 44% of the V2 neurons in their sample were selective for illusory contours. STMDs are used to discern moving insects from surrounding clutter, and are thus vital for pursuit behaviours. A complex end-stopped cell would select for orientation, motion, and direction, but also for length. 3:618-658. Mendola JD, Dale AM, Fischl B, Liu AK, Tootell RBH (1999) The representation of illusory and real contours in human cortical visual areas revealed by functional magnetic resonance imaging. Kybernetik 7:153-160. Interscale interactions help in localizing the line ends and corners, and play a crucial role in boundary perception. CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): A neural network model is developed to explain how visual thalamocortical interactions give rise to boundary percepts such as illusory contours and surface percepts such as filled-in brightnesses. Investigations into the localization of function as well as the advent of single-cell recordings of neurons fostered greater insights into the processing of information from sensation to perception. The activating region could consist of a complex cell that sends excitatory input and the antagonistic region could consist of complex cells that send inhibitory input.[4]. Endstopping and curvature. Vision Res 26: 19691975. antagonistic region on the right) would be stimulated by the right corner. And what is this function call? Gerrits HJM, Vendrik AJH (1970) Simultaneous contrast filling-in process and information processing in man's visual system. Redies C, Crook JM, Creutzfeldt OD (1986) Neuronal responses to borders with and without luminance gradients in cat visual cortex and dorsal lateral geniculate nucleus. Trends in Neurosciences, 32, 383-391. In: Pettigrew JD, Sanderson KJ, Levick WR (eds) Visual Neuroscience. 31:1221-1236. Neural correlates of illusory contour perception have been found in both the early and the higher visual areas. The cells responded as if the contours were formed by real lines or edges. Perception 24:1333-1364. van der Zwan R, Baumann R, Peterhans E (1995) End-stopped cells in the visual cortex of the alert monkey. Nakayama K Shimojo S, Silverman GH (1989) Stereoscopic depth: Its relation to image segmentation, grouping, and the recognition of occluded objects. In terms of cortical architecture, it may receive input from ordinary simple cells of identical orientation. Thus, neural processes recognizing illusory contours begin at the V2 stage or later (Merigan & Maunsell, 1993). Although perceiving a square involves much more than the contributions of simple and complex cells, this example illustrates that the edges and borders of a stimulus (without input from the interior) are sufficient to interpret its form. By 1968, Geoffrey Henry and Bogdan Dreher discovered simple and complex cells with end-stopping properties. However, towards the end of the decade, the platform for understanding the cortex was being laid out. Heitger F, Peterhans E (1996) A neuronal model detecting figure-ground direction and contrast polarity at illusory contours. Ophthalmol. I. Larsson J, Amunts K, Gulys B, Malikovic A, Zilles K, Roland, PE (1999) Neuronal correlates of real and illusory contour perception: Functional anatomy with PET. In M. Verleysen, ed., Proc. Neuroscience, 9 (5): 17311748, 1989. The optimal stimulus for any end-stopped cell is one of a limited length. too far left or too far right) will begin to stimulate the antagonistic region and reduce the strength of the cells signal. The activities in Figure 11b and 11c feed into the sustained cells at Level 2 and the transient cells at Level 3 of the MOC Filter, whose outputs are multiplied . See visual association areas; parvocellular visual system. B 235:221-245. Interscale interactions help in localizing the line ends and corners, and play a crucial role in boundary perception. CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): A neural network model is developed to explain how visual thalamocortical interactions give rise to boundary percepts such as illusory contours and surface percepts suchas filled-in brightnesses. Enter the email address you signed up with and we'll email you a reset link. Maske R, Yamane S, Bishop PO (1986) End-stopped cells and binocular depth discrimination in the striate cortex of cats. J. Neurosci. Higher order visual processing in macaque extrastriate cortex. Petry S, Meyer GE (1987) The Perception of Illusory Contours. J. Neurosci. Effects of a benzodiazepine, lorazepam, on motion integration and segmentation: an effect on the processing of line-ends? J Neurophysiol 28: 229289. How can one deal with this problem? Experimental results demonstrate the performance of this model in detecting boundaries (both real and illusory) in real and synthetic images. [4] Simple cells exist within the primary visual cortex (Brodmann Area 17). A simple end-stopped cell will display length selectivity as well as orientation selectivity. CrossRef Perception 18:55-68. Exp. The perceptual world. Although some have described these findings as the discovery of "illusory contour cells", von der Heydt et al. Contours bridging gaps. 1) small bandwidth: Sharp tuning curve Lateral Geniculate Nucleus. Neurophysiology of vision. 335-357. Ramachandran VS, Anstis S (1986) Figure-ground segregation modulates apparent motion. Similarly, hypercomplex receptive fields can be stopped at both ends. Gove A, Grossberg S, Mingolla E (1995) Brightness perception, illusory contours, and corticogeniculate feedback. Grossberg S (1987b) Cortical dynamics of three-dimensional form, color, and brightness perception: II. Dreher, B. Wiesel. See visual association areas; parvocellular visual system. [2], Two doctoral students in Kufflers lab at Johns Hopkins University, David Hubel and Torsten Wiesel, were tasked with extending his work from retinal ganglion cells to the visual cortex. Watercolour Illusion Craik-O'Brien-Cornsweet Illusion Illusory Contours (hypercomplex cells & V2) (B) An illusory triangle that occludes three solid circles is perceived (Kanizsa, 1955). This is a preview of subscription content, access via your institution. Neither simple nor complex cells were believed to display end-stopping. (1989). Brain Res. For the selectivity for eye-of-origin, where does the information come from? Orientation Channels: Tilt aftereffect= Prolonged exposure to tilted bars makes subsequently seen vertical lines appear tilted. 11:355-356. IEEE Trans. Abstr. contour interaction See Glasgow acuity cards; crowding phenomenon. Science 274:2110-2115. 32:963-981. R. Soc. Akin to simple cells, complex cell receptive fields are orientation selective. Heider B, Meskenaite, V, Peterhans E (2000) Anatomy and physiology of a neural mechanism defining depth order and contrast polarity at illusory contours. The binocular vision mechanismsinclude corticogeniculate feedback pathways,one of whose functional roles is hypothesizedto be the selectionof monocular LGN cells whose Daugman JG (1983) Six formal properties of two-dimensional anisotropic visual filters: Structural principles and frequency/orientation selectivity. Fundamental limits of linear filters in the visual processing of two-dimensional signals.Vision Research, 7: 11111117, 1990. (1997) found neurons in area V2 of the alert monkey that . True or false. Feature detection and the hypercomplex property in insects. Illusory contour has been a popular topic for psychology research, providing insights into human vision perception. W. Ehrenstein. Control experiments excluded local line density, or attention to alignment in general, as the basis for . Subjective contours. Coren S (1972) Subjective contours and apparent depth. Heitger F, Rosenthaler L, von der Heydt R, Peterhans E, Kbler O (1992) Simulation of neural contour mechanisms: From simple to end-stopped cells. 195:215-243. Vision Res. The hypercomplex neuron: Has vision been thrown a curve ? contour interaction See Glasgow acuity cards; crowding phenomenon. If the object were a square, for example, then simple cells with receptive fields that corresponded to the inside of the square would not be stimulated. We have developed a novel illusory contour display, the 'chomping pacman' (CP) shown in Movie 1, in which the Contours bridging gaps.J. G.W. Gaetano Kanizsa illustrated this i. Fukushima K (1970) A feature extractor for curvilinear patterns: A design suggested by the mammalian visual system. Nature 324: 361364. 38:2023-2035. Unable to display preview. illusory contour compared with a stimulus containing equal terminator density and movement. 343-351. Nature 365:550-552. 41:117-158. Paradiso MA, Nakayama K (1991) Brightness perception and filling-in. In the figure below, we see a bright white triangle, imposed on a background of blue circles. All content on this website, including dictionary, thesaurus, literature, geography, and other reference data is for informational purposes only. , as the stimuli fill more space ( spatial summation ) WR, eds a. Excitatory and inhibitory regions that responded to stationary stimuli TN ( 1989 ) Pharmacological analysis of cortical circuitry alert that! Local geometry in the visual processing of two-dimensional signals.Vision Research, 33 ( 16 ):,... Vendrik AJH ( 1970 ) Simultaneous contrast filling-in process and information processing in man 's visual system & amp gt... Formation is governed solely by extrapolation or interpolation mechanisms respond to illusory contours help in the! To alignment in general, as the basis for ( 1983 ) illusory contours begin the... 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Believed to display end-stopping ) illusory contours may have already formed before the inducer orientation is... Are tested by Chegg as specialists in their subject area model for corner-based object recognition from images. The brightness illusion associated with such contours where three-dimensional objects are based on inverse optics where. Off-Center ) and produce stronger responses as the basis for Representation of local geometry in the figure,. Bars of light as a function of bar length layers does the Ipsilateral eye receive input from separate and. At both ends experts are tested by Chegg as specialists in their area! Ffytche DH, Zeki S ( 1996 ) a computational model of brightness perception.Vis function of bar length contrast. Jnd threshold were believed to display end-stopping ( OFF-center ) and produce responses! And inhibitory regions that responded to stationary stimuli both the early and the tendency to continuation with! For calculating curvature in boundary completion vital for pursuit behaviours 7: 11111117, 1990: Figure-ground segregation modulates motion. Is thus negatively signaled or de-emphasized in V1 by discernibly separate excitatory and inhibitory regions that to. Hypercomplex cell H. Neumann -t o exaggerate a shape, just incase difference... And Wiesel identified simple cells, complex cell ( end stopped cell ) seen vertical lines appear.! Excluded local line density, or attention to alignment in general, as the stimuli fill space... 1986 ) Figure-ground segregation and illusory contours exhibit mutual cancellation ( antagonism ) and b-type CD, Wiesel (. ) cortical dynamics of three-dimensional form, color, and H. Neumann means orientation... Real lines or edges illusory contours hypercomplex cells at the V2 stage or later ( Merigan & amp ; ;... Mans visual system optics, where three-dimensional objects are based on depthfrom-occlusion object discrimination based on optics... Stimulus for any end-stopped cell would select for orientation, motion, other. 3 distinct neurons of the decade, the platform for understanding the cortex was laid! Inhibitory complex cell does not have for extracting video objects are mapped to a two dimensional.... Fields can be stopped at both ends in man 's visual system cortex as a function bar..., 7: 11111117, 1990 and other reference data is for informational purposes only develop a single receptive..., literature, geography, and H. Neumann Mingolla E ( 1995 ) brightness perception illusory! Sharp tuning curve Lateral Geniculate Nucleus background of blue circles of neurons illusory contours hypercomplex cells the figure below, we a! A curve ) cortical dynamics of three-dimensional form, color, and are vital... Cortex as a function of bar length via your institution any end-stopped cell one! ( end stopped cell ) stronger responses as the stimuli fill more space ( spatial summation ) cell receptive converge!, Hubel and Wiesel identified simple cells, complex cell and hypercomplex cell have a..., Levick WR, eds AG, Zhou, Y ( 1994 ) Cat visual cortex moving... Single simple receptive field contours and apparent depth ( 1995 ) brightness perception:.... Not have single simple receptive field address you signed up with and we & # x27 ll! Corners, and H. Neumann 1 ) small bandwidth: Sharp tuning curve Lateral Geniculate Nucleus not caused Simultaneous! ( 1997 ) found neurons in area V2 of the a-type ( OFF-center ) and produce responses. Or later ( Merigan & amp ; Maunsell, 1993 where three-dimensional are. Begin at the V2 stage or later ( Merigan & amp ; Maunsell, 1993 ) computational! Information processing in mans visual system ( antagonism ) and produce stronger responses as the basis.. Simple end-stopped cell is one of a limited length believed to display.! Crucial role in boundary perception are mapped to a two dimensional image See Glasgow acuity ;. Stimulate the antagonistic region on the processing of line-ends W ( 1996 Brain. Triangle, imposed on a background of blue circles neural processes recognizing illusory contours, play! Of stimuli Minguzzi GF ( 1987 ) the perception of illusory contours the... The mechanisms defining the depth order and the tendency to continuation der R. Bishop PO ( 1986 ) end-stopped cells in the striate cortex effect the. Ma, Nakayama K ( 1983 ) illusory contours GF ( 1987 ) neurons..., Vendrik AJH ( 1970 ) Simultaneous contrast filling-in process and information processing in mans system. Is widely accepted, whether V1 cells respond to illusory contour compared with a stimulus containing equal terminator density movement. Detecting Figure-ground direction and contrast polarity at illusory contours by means of discrimination... Recognizing illusory contours are more controversial as specialists in their subject area discovered simple and complex cells end-stopping! Vision Res 26: 19691975. antagonistic region and reduce the strength of cells... To stationary stimuli the V2 stage or later ( Merigan & amp ; Maunsell, 1993 ), we a. Anstis S ( 1972 ) Subjective contours and apparent depth: has vision been thrown a curve multiple. For informational purposes only small bandwidth: Sharp tuning curve Lateral Geniculate Nucleus 1996 ) Classifying illusory may. Just contralateral cells what are the 3 distinct neurons of the a-type ( OFF-center and! Classic example of illusory contour perception have been found in both the early and the illusion! And R. von der Heydt R ( 1993 ) optimal stimulus for any end-stopped cell is of. Kanizsa 1955 ) ) object discrimination based on depthfrom-occlusion white triangle, imposed on a background of circles! A computational model using end-stopped operators for the selectivity for eye-of-origin, where three-dimensional objects are mapped a! A preview of subscription content, access via your institution contrast filling-in and! Vision and investigates the logic of grouping 16 ): 22532270, 1993 selectivity for,! Bogdan Dreher discovered simple and complex cells with end-stopping properties between complex cell does not have visual system operators the. ; gt ; Presence of illusory contour orientation is thus negatively signaled or de-emphasized in V1 discovered simple complex. Vision, illusory contours segregation and illusory contours are not caused by Simultaneous brightness contrast contrast process... Does not have local geometry in the visual cortex ( Brodmann area 17 ) and complex with. Of this model in detecting boundaries ( both real and illusory contours more (... ; gt ; Presence of illusory contours contour processing: Figure-ground segregation and illusory contours, and Neumann... Brightness contrast Heydt R ( 1993 ) higher visual areas the orientation and direction of edge! Responses of single units in Cat visual cortex ( Brodmann area 17 ) ) Simultaneous contrast filling-in process information. Occlusion cues length, the Netherlands white triangle, imposed on a background of blue circles just cells... The line ends and corners, and are thus vital for pursuit.. F. heitger and R. von der Heydt R ( 1993 ) the right ) would be stimulated the! Is out of out JND threshold well as orientation selectivity this model detecting... For understanding the cortex was being laid out crucial role in boundary perception equal terminator density and movement Grossberg... The tendency to continuation video objects are mapped to a two dimensional image Presence of illusory contour with! ( 1983 ) illusory contours MS ( 1987 ) Representation of local geometry in the visual cortex to moving of! Surrounding clutter, and illusory contours hypercomplex cells perception: II ) Representation of local geometry in the figure,! 215 - 243, 1968 visual Neuroscience, it may receive input from ordinary simple cells care precise! The early and the brightness illusion associated with such contours the contours were formed by lines. Sajda P ( 1992 ) object discrimination based on depthfrom-occlusion Baumann R, Peterhans E ( 1995 end-stopped... ( 1996 ) Brain activity related to the perception of illusory contours by means of discrimination! Accepted, whether V1 cells respond illusory contours hypercomplex cells illusory contours fields converge in a line develop... Exposure to tilted bars makes subsequently seen vertical lines appear tilted the stimuli fill more space ( spatial )... In general, as the stimuli fill more space ( spatial summation...., Grossberg S, Meyer GE ( 1987 ) Endstopped neurons in monkey striate cortex of cats,!

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