Eye position effects on pursuit related responses in area lip of macaque monkey

Abstract

Abstract Pursuit related activity is a well described neuronal phenomenon for monkey visual cortical areas MT and MST in the superior temporal sulcus (STS). For the posterior parietal cortex (PPC) pursuit related activity has been shown for neurons in areas 7A and VIP, which both receive cortico-cortical projections from area MST. Pursuit related activity has yet not been shown for the Lateral Intra Parietal area (LIP), which is reciprocally connected to areas MT and MST. In an accompanying study we could show that pursuit related responses of neurons in areas MT and MST are modulated by eye position. In the actual experiments we tried to reveal whether also in area LIP neurons pursuit related activity if present is modulated by eye-position. Single unit recordings were made from 2 hemispheres of two monkeys (Macaca mulatta). In a first step neurons were tested for pursuit related activity while the monkey pursued a target which moved randomly into one out of four directions on a translucent screen. For 107 of 269LIP neurons tested a direction specific pursuit related activity could be found. In order to test whether responsiveness of these neurons was modulated by the position of the eye in the orbit the monkey had to pursue a target which started moving with the same speed into the same direction from different locations on the screen. The majority of cells showed a significant effect of the starting position of pursuit on the mean neuronal response. This response varied mostly linearly with both horizontal and vertical eye position. It is suggested that the observed modulatory effect of eye position on visual neuronal responses in area LIP might be a common phenomenon and that it might be used for the generation of a representation of the visual environment in a non-retinocentric frame of reference.