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Disparity Processing in Human Visual Cortex using High-Density EEG| old_uid | 9118 |
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| title | Disparity Processing in Human Visual Cortex using High-Density EEG |
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| start_date | 2010/10/05 |
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| schedule | 11h |
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| online | no |
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| summary | In frontal-eyed animals, a percept of depth can be produced from the small
horizontal disparities between the monocular half-images. Single-neuron recording
studies have demonstrated that neurons in primate striate cortex (V1) respond only to the absolute disparity of the stimulus. However, responses in extra-striate visual areas can be altered by the addition of another different disparity in the image, and are therefore involved in encoding relative disparity. Extra-cellular recordings can precisely describe the activity of individual neurons, but they cannot characterize population-level disparity responses that may be distributed over large cortical networks.
In this talk, I’ll present new techniques that combine high-density EEG with
functional and anatomical MRI to characterize the spatio-temporal properties of the
neural population-responses to the stimulation of the disparity system.
In a first experiment, we measured disparity tuning over a wide range of
horizontal disparities in different areas under two different spatial configurations: one
where only the absolute disparity of the stimulus was detectable and the other where a static reference permitted the extraction of relative disparity. The associated tuning functions peaked between 2-16 arcmin in each region-of-interest (ROI) for the two conditions. The responses of the striate cortex remained unchanged, but the amplitudes and/or phases of the responses in higher visual areas were affected by the presence of the surround, indicating their sensitivity to the disparity context, i.e., relative disparity.
In another study, we examined the cortical mechanisms underlying the
discrimination of relative disparity. The subjects were asked to detect small depth
increments during a steady-state protocol. We contrasted responses from trials
containing a change that was correctly identified (‘hits’) with responses from trials in
which no change occurred, again correctly identified (correct rejects). We found that
the activities preceding the subjects’ response were distributed among many areas, including the sensory visual system and more frontal regions in a complex cortical network. |
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| responsibles | Rämä |
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