Estimating visual motion in space during smooth pursuit by MST neurons

Abstract

Our eyes are in constant motion, but we are usually unaware of retinal image motions resulting from our own eye movements. This perceptual stability is assumed by an internal estimation of the external visual world derived from two signals, the retinal and extra-retinal signals. While we are tracking a moving object, this internal estimation of visual motion in space is known to work fairly well although not perfectly. Here we show the neuronal correlates of the estimated visual motion in space in the cortical area MST of macaque monkeys. We studied responses of MST and MT neurons to a visual stimulus moving at a series of constant speeds during smooth pursuit and stationary fixation. Most of the MST neurons responded in relation to the stimulus speed in space, although MT neurons responded in relation to the stimulus speed on the retina. The results are consistent with the idea of the internal estimation of the external visual world and suggest that the visual motion in space is served by the MST neurons through the information processing from the MT to MST. [Jpn J Physiol 55 Suppl:S158 (2005)]