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Gain control in the response of human visual cortex to plaids
J Scott McDonald1, Damien J Mannion, Colin W G Clifford
1School of Psychology, The University of New South Wales, Sydney, Australia.
Journal of Neurophysiology
|March 2, 2012
Summary
Human visual cortex responses to plaid patterns differ from predictions based on individual grating components. Functional MRI data show significantly higher responses to plaids, challenging existing models.
Area of Science:
- Neuroscience
- Visual Perception
- Computational Neuroscience
Background:
- Previous research in tree shrews suggested V1 population responses to plaid patterns could be predicted by averaging responses to individual components.
- This finding prompted further investigation into human visual cortex responses.
Purpose of the Study:
- To compare human visual cortex responses to plaid patterns versus individual grating components.
- To investigate the influence of contrast and orientation on these responses.
- To evaluate the validity of the averaging model for human fMRI BOLD responses.
Main Methods:
- Functional Magnetic Resonance Imaging (fMRI) was used to measure blood oxygenation level-dependent (BOLD) responses in human visual areas V1-V3.
- Participants viewed plaid patterns (superposed gratings of equal contrast) and individual grating components.
Main Results:
- BOLD responses in V1-V3 were significantly higher for plaid patterns compared to single grating components.
- The orientation response profile of plaid patterns was poorly predicted by a linear combination of responses to its components.
Conclusions:
- The simple averaging model proposed by MacEvoy et al. (2009) does not fully explain fMRI BOLD responses to plaid patterns in human visual cortex.
- Human visual cortex exhibits complex responses to plaid stimuli that deviate from predictions based on component analysis.
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