The middle temporal (MT) area has traditionally been thought to be a retinotopic area. However, recent functional magnetic resonance imaging and psychophysical evidence have suggested that human MT may have some spatiotopic processing. To gain an understanding of the neural mechanisms underlying this process, we recorded neurons from area MT in awake behaving animals performing a simple saccade task in which a spatially stable moving dot stimulus was presented for 500 ms in one of two locations: the presaccadic receptive field or the postsaccadic receptive field. MT neurons responded as if their receptive fields were purely retinotopic. When the stimulus was placed in the presaccadic receptive field, the response was elevated until the saccade took the stimulus out of the receptive field. When the stimulus was placed in the postsaccadic receptive field, the neuron only began its response after the end of the saccade. No evidence of presaccadic or anticipatory remapping was found. We conclude that gain fields are most likely to be responsible for the spatiotopic signal seen in area MT.
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