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Measuring response saturation in human MT and MST as a function of motion density
Szonya Durant1, Michele Furlan1
1Department of Psychology, Royal Holloway, University of London, Egham, UK.
Journal of Vision
|July 25, 2014
Summary
Human brain areas MT and MST show a saturated response to motion density, unlike some single-cell data. This suggests population responses in these visual areas may not linearly increase with motion coherence.
Area of Science:
- Neuroscience
- Visual Perception
- fMRI Studies
Background:
- Human brain areas MT and MST are crucial for motion processing.
- Previous studies using fMRI and single-cell recordings show varying responses to motion coherence and density.
- The relationship between population-level fMRI responses and single-cell activity in these areas requires further clarification.
Purpose of the Study:
- To investigate the blood oxygen level dependent (BOLD) response function of human MT and MST to motion density.
- To compare the responses of MT and MST with area V1.
- To determine how population responses in MT and MST reflect the combination of linear and saturating responses observed in single-cell data.
Main Methods:
- Measured BOLD responses in MT and MST using a motion density signal.
- Utilized spatially fixed apertures with motion stimuli to control the area covered by motion.
- Compared responses across different motion densities and types (coherent vs. random).
Main Results:
- MT and MST responded above baseline even with minimal motion.
- Both areas exhibited a relatively flat response to increasing motion density, indicating saturation.
- No significant difference in response was found between coherent and random motion at any density.
Conclusions:
- The population response in MT and MST saturates with increasing motion density.
- This saturation may be influenced by receptive field size and inhibitory interactions.
- The linear relationship between MT/MST population response and motion coherence may not hold when responses are averaged over larger visual field areas.
