Decoding Target Distance and Saccade Amplitude from Population Activity in the Macaque Lateral Intraparietal Area (LIP).

Frank Bremmer,Steffen Klingenhoefer,Andre Kaminiarz,Jan Churan

doi:10.3389/fnint.2016.00030

Frank Bremmer, Steffen Klingenhoefer + Show 2 more

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https://doi.org/10.3389/fnint.2016.00030

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Abstract

Primates perform saccadic eye movements in order to bring the image of an interesting target onto the fovea. Compared to stationary targets, saccades toward moving targets are computationally more demanding since the oculomotor system must use speed and direction information about the target as well as knowledge about its own processing latency to program an adequate, predictive saccade vector. In monkeys, different brain regions have been implicated in the control of voluntary saccades, among them the lateral intraparietal area (LIP). Here we asked, if activity in area LIP reflects the distance between fovea and saccade target, or the amplitude of an upcoming saccade, or both. We recorded single unit activity in area LIP of two macaque monkeys. First, we determined for each neuron its preferred saccade direction. Then, monkeys performed visually guided saccades along the preferred direction toward either stationary or moving targets in pseudo-randomized order. LIP population activity allowed to decode both, the distance between fovea and saccade target as well as the size of an upcoming saccade. Previous work has shown comparable results for saccade direction (Graf and Andersen, 2014a,b). Hence, LIP population activity allows to predict any two-dimensional saccade vector. Functional equivalents of macaque area LIP have been identified in humans. Accordingly, our results provide further support for the concept of activity from area LIP as neural basis for the control of an oculomotor brain-machine interface.

Highlights

Primates perform saccadic eye movements in order to bring the image of an interesting target onto the fovea
Given that neurons in area lateral intraparietal area (LIP) receive strong input from area medio-temporal area (MT) (Blatt et al, 1990), we considered it likely that area LIP is involved in the programming of saccades toward moving targets
We recorded from 131 neurons in area LIP of two macaque monkeys: 99 from monkey K and 32 from monkey C

Summary

Introduction

Primates perform saccadic eye movements in order to bring the image of an interesting target onto the fovea. In everyday life, it is often a moving target which attracts our interest. It has been suggested that the oculomotor system uses speed and direction information about the visual target as well as knowledge about its own processing latency to program an adequate, predictive saccade. This hypothesis is supported by the finding that after lesions in the medio-temporal area (MT) of the macaque, which is known to be one of the key-areas for the processing of visual motion, the accuracy of saccades toward moving targets is reduced (Newsome et al, 1985; Schiller and Lee, 1994).

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