Related Experiment Videos
Cortical evoked potentials due to motion contrast in the blind hemifield
P J Benson1, K Guo, M J Hardiman
1University Laboratory of Physiology, Oxford, UK.
Neuroreport
|January 5, 2000
Summary
Subcortical visual pathways to motion cortex persist after primary visual cortex damage. These pathways contribute to visual experience but not conscious perception, as shown by visual evoked potentials.
Area of Science:
- Neuroscience
- Visual Neuroscience
- Primate Vision
Background:
- Primary visual cortex (V1) damage can impair vision.
- Subcortical visual pathways may compensate for V1 damage.
- Motion-selective cortex processes visual motion information.
Purpose of the Study:
- To investigate subcortical visual inputs to motion cortex in primates after V1 damage.
- To examine motion-onset visual evoked potentials (VEPs) in V1-damaged individuals.
- To determine the role of these pathways in visual experience versus conscious perception.
Main Methods:
- Utilized scalp electrodes to record VEPs in a human hemianope with V1 damage.
- Analyzed motion-onset VEPs in the blind visual field.
- Assessed VEP characteristics in relation to stimulus contrast.
Main Results:
- Motion-onset VEPs in the blind field showed characteristics of sighted vision but with reduced amplitude and longer latency.
- VEP amplitude and peak latency were contrast-dependent, indicating detection difficulty.
- VEPs were detectable at low contrasts where motion was imperceptible, yet direction guessing was accurate.
Conclusions:
- Subcortical inputs to motion cortex remain functional after V1 damage.
- These inputs contribute to visual experience, enabling some level of visual processing.
- Conscious visual perception, however, may rely on additional cortical processing not fully restored by subcortical pathways.