Neuroscience 2003 Abstract
| Presentation Number: | 910.9 |
|---|---|
| Abstract Title: | Two kinds of illusory contour responses in visual cortex neurons: a filtering model. |
| Authors: |
Baker, C. L.*1
; Song, Y.1
1Dept. Ophthalmol, McGill Univ, Montreal, Canada |
| Primary Theme and Topics |
Sensory Systems - Vision -- Visual cortex: Orientation, form and color |
| Secondary Theme and Topics | Sensory Systems<br />- Vision<br />-- Visual cortex: Neural coding |
| Session: |
910. Striate Cortex: Neuronal Properties Poster |
| Presentation Time: | Wednesday, November 12, 2003 1:00 PM-2:00 PM |
| Location: | Morial Convention Center - Hall F-I, Board # E62 |
| Keywords: | second-order, texture, spatial frequency, non-Fourier |
Many mammalian visual cortex neurons show orientation selective responses to “illusory contours” formed by abutting gratings. Our recent results demonstrate two distinct modes of neuronal response to these stimuli (Song and Baker, SFN 2003). Here we demonstrate how spatial filtering models of receptive fields, like those previously proposed for responses to other kinds of second-order stimuli, can predict both these modes of response. The model sums two parallel pathways. One path is a simple linear filter (F0), whose parameters determine the selectivity to first-order stimuli such as sinewave gratings. The other path is a filter-rectify-filter (F1-R-F2) cascade, in which F1 is tuned to much higher spatial frequencies than F2. Responses of this model were simulated and compared to single neuron responses in cat area 18. Illusory contour stimuli consisted of abutting (inducing) gratings whose relative spatial phase periodically reverses. If the inducing grating’s spatial frequency is relatively low, then the abrupt luminance edges along the contour can drive the first-order path (F0). In this mode the model shows a low-pass dependence on spatial frequency of the inducing grating. On the other hand, the model can also show true second-order responses to illusory contours when the inducing grating has a much higher spatial frequency, matched to the first filter of the F1-R-F2 cascade; in this mode the inducing grating has bars much too small to be resolved by the linear path (F0) filter. In this case the model shows tuning to the spatial frequency of the inducing grating (determined by the early filter, F1), and also tuning to the periodic phase reversal (determined by the late filter, F2). The model shows very specific agreement with our neurophysiological data, and demonstrates how a neuron can exhibit illusory contour responses that are either luminance-based (Peirce and Lennie, SFN 2002) or due to specialized nonlinear mechanisms.
Supported by Canadian CIHR grant MOP 9685
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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