Neuroscience 2005 Abstract
| Presentation Number: | 136.12 |
|---|---|
| Abstract Title: | Neural decoding of motion direction from activity patterns in human visual cortex. |
| Authors: |
Tong, F.*1
; Kamitani, Y.2
1Dept Psychology, Vanderbilt Univ., Nashville, TN 2Japan, 301 WILSON HALL, 37203, |
| Primary Theme and Topics |
Sensory and Motor Systems - Vision -- Processing of visual motion |
| Session: |
136. Motion Processing I Slide |
| Presentation Time: | Sunday, November 13, 2005 10:45 AM-11:00 AM |
| Location: | Washington Convention Center - Room 201 |
| Keywords: | MOTION PERCEPTION, FUNCTIONAL MRI, VISUAL CORTEX, NEURAL CODING |
In recent fMRI studies, we have shown that activity patterns in early human visual areas contain robust orientation information that allows for accurate decoding of which of eight orientations is seen on a trial-by-trial basis (Kamitani & Tong, VSS/SFN 2004, Nat Neurosci, 2005). Our findings suggest that random variations in local feature preference across cortex can produce robust ensemble feature selectivity, when the information from many independent cortical regions is pooled in an optimized fashion. Here we investigated if ensemble patterns of fMRI activity in human visual areas contain robust information about motion direction. We performed conventional fMRI scans (3T scanner, voxel size 3x3x3mm) while subjects viewed random dots moving in 1 of 8 directions in each 16s stimulus trial. A linear decoder was trained to classify fMRI activity patterns induced by different motion directions by optimizing the voxel weights using linear support vector machines. Then, the decoder was evaluated with independent test data. Ensemble activity patterns from areas V1-V4 allowed for accurate prediction of the correct motion direction, with errors occurring primarily at neighboring motion directions (RMSE of 4 subjects, 64 deg). Area MT+, in which fewer voxels were available (~100 voxels), showed similar direction-selective performance as individual areas V1-V4. In contrast, orientation-selective performance was best in areas V1 and V2, modest in V3, V3A and V4v, and at chance levels in area MT+, indicating that MT+ is selective for motion direction rather than visual form. Tests of rotational motion led to similar direction-selective performance. These findings demonstrate that human visual areas are indeed selective for motion direction. More generally, our multi-voxel decoding analysis provides a powerful new method to characterize the feature selectivity of individual areas of the human brain, and can provide an important bridge between animal and human neurophysiology.
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2005 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2005. Online.
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