Effect of allocentric cues on primate gaze behaviour in a cue conflict task

Abstract

The visual system can remember the location of a peripheral target relative to the self (egocentric coordinates) or to an external landmark (allocentric coordinates). The relative influence of each reference frame have been examined for reach (Byrne & Crawford, J. Neurophysiol. 2010), but have not been systematically explored in the gaze control system. Here, we utilized a cue conflict paradigm to assess the effect of allocentric cues on gaze behaviour in the rhesus monkey. One monkey was trained to maintain central fixation while a target was presented for 100ms in one of eight radial directions, along with an allocentric cue presented at one of four oblique directions 11° from the target. This cue was the intersection of two horizontal/vertical lines spanning the visual field. After a 100ms delay, a mask was shown for 100ms during which the allocentric cue was displaced by 8° in one of eight radial directions. After a second delay of 300-700ms, the fixation point extinguished, acting as a 'go' signal for a head-unrestrained saccade towards the remembered target. The monkey did not look toward the original target or the cue location, but rather toward a point shifted partially toward a virtual target defined relative to final cue location (i.e., in allocentric coordinates). Overall, there was a significant (P< 0.01) allocentric shift in gaze endpoints relative to controls (with no cue shift), with a mean gain of 0.27 (where 0 = no shift and 1.0 = complete shift). In addition, the cue had a significantly greater effect when it shifted away from centre in the direction of the saccade (P< 0.01) and when it shifted towards the original target (P< 0.01). These preliminary findings suggest that internal representations of gaze targets are weighted between egocentric and allocentric cues, and this weighting is further modulated by specific gaze parameters.

Meeting abstract presented at VSS 2016