Spatiotemporal Receptive Feld Structure of Macaque MT Neurons Mapped by Reverse Correlation

Abstract

Abstract: : Purpose:We mapped the spatiotemporal receptive fields (RFs) of motion sensitive neurons in area MT of the macaque monkey. Methods:We presented patches of random pixel arrays with short motion impulses at a number of different locations. The random pixel array within a patch was pseudo-randomly moving in either the cell's preferred or null direction, chosen independently for each patch at each motion impulse (8-13 msec). All the patches were presented simultaneously. Spike trains of the neurons were recorded and reverse-correlated to the stimulus sequence. This allowed us to reconstruct the time course of the spatial RF structure. For each neuron we also determined direction and speed tuning by reverse correlating neural response with one large patch of a random pixel array moving pseudo-randomly in 8 different directions and 9 different speeds. Results:The results show that temporal response profiles are biphasic and that the positions of the RF can change in time. Furthermore, the inhibitory surround is not evenly distributed and the response in the inhibitory surround is delayed to that of the RF centre (in the range of 5-20 ms). Conclusion:The delayed response in the RF surround versus the RF center suggests an extra processing stage for inhibitory input to the MT surround.

Keywords: 621 visual cortex • 540 receptive fields • 394 electrophysiology: non-clinical