The columnar organisation of the human motion complex hMT+ allows fMRI studies to decode the direction of visual motion from the multivoxel pattern responses in that region. While previous studies have shown that directional information is present in hMT+, a more precise characterisation of its functional properties is needed if we are to understand the computational mechanisms underlying cortical motion processing. In the present study, we sought to address this problem by characterising the response profiles of individual voxels to a visual stimulus, moving in four possible directions. In addition to more voxels preferring vertical over horizontal dot motion, we observed a correlation of directional preferences: a voxel which prefers dot motion in one direction will be more likely to prefer dot motion in the opposing direction, too. Several hypotheses exist which could explain this result. The first is that any particular column preferring a particular direction functions through the interaction of opposing inhibitory interneurons (1). The second possible cause is due to the organisation of columns found in electrophysiological experiments in primates, in which columns of opposing direction lie next to each other in stripes (2). The final possible hypothesis is based on the finding that a small proportion of neurons in MT (again in primates) were found to prefer two, opposing, directions (2). To test which of the above hypotheses was correct, we built a computational model of part of hMT+, in which neurons were given specific 3d locations and orientation preferences, based on electrophysiological data. Each voxel within the model had its own particular preference correlation, and these were compared with the results from the fMRI study. The model suggests that the correlations seen in the fMRI data appear to be due to both the columnar organisation and the effect of bidirectional neurons.
|Publication status||Published - 2011|
|Event||The British Neuroscience Association Meeting 2011 - Harrogate International Conference Centre, Harrogate, United Kingdom|
Duration: 17 Apr 2011 → 20 Apr 2011
|Conference||The British Neuroscience Association Meeting 2011|
|Period||17/04/11 → 20/04/11|