Neuroscience 2003 Abstract
| Presentation Number: | 439.8 |
|---|---|
| Abstract Title: | The role of early visual receptive fields in processing junctions and corners. |
| Authors: |
Troncoso, X. G.*1,2
; Macknik, S. L.1
; Martinez-Conde, S.1
1Inst. of Ophthalmology, Univ. Col. London, London, United Kingdom 2Gatsby Computational Neurosci. Unit, Univ. Col. London, London, United Kingdom |
| Primary Theme and Topics |
Sensory Systems - Vision -- Visual cortex: Orientation, form and color |
| Session: |
439. Visual Cortex: Shape & Color Slide |
| Presentation Time: | Monday, November 10, 2003 2:45 PM-2:45 PM |
| Location: | Morial Convention Center - Room 262 |
| Keywords: | VISUAL CORTEX, LGN , RHESUS MACAQUE, BRIGHTNESS |
Neurons in the early visual system are often considered “edge detectors”. However, we previously showed (Martinez-Conde & Macknik, SFN’01) that single cells in area V1 of the awake monkey respond more strongly to junctions than to edges. Therefore, junction processing may not be a subsequent stage to edge processing, but junctions may instead be a more optimal stimulus than edges for early receptive fields. We have now recorded from 110 neurons in the LGN and area V1, confirming our preliminary conclusions. We have also developed computational models of receptive fields in the retina/LGN and area V1, which make quantifiable and principled predictions of how early neurons of the visual system should respond to junctions versus edges. By measuring the response from these models to visual scenes containing edges and junctions we have discovered that early visual receptive fields (i.e. those from center-surround cells, simple cells, and complex cells) are shaped so as to respond more strongly to junctions than to edges. This is the first time that the salience of junctions has been quantified against the salience of edges, either physiologically or computationally. Both approaches match our qualitative perception of visual illusions in which junctions are more salient than edges. We have also found that, whereas responses to bars and spots are dependent on specific receptive field sizes, neuronal responses to junctions and edges are not dependent on the specific receptive field size of neurons processing them. This may provide a mechanism for shape constancy in foveal and peripheral vision. Finally, our data are compatible with the idea that junctions are processed very early in the visual system (i.e. starting in the retina, with center-surround receptive fields), without the implication of high-level mechanisms, such as feedback loops or intracortical circuits.
Supported by NEI, Fight for Sight, MRC (UK).
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2003 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2003. Online.
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