Visual-motor response fields and spatial tuning in supplementary eye field (SEF) of the head unrestrained monkeys.

Abstract

We recently used an analytic technique involving statistical fits of different spatial models against neural response fields to show that visual response encodes target direction and motor response encodes planned gaze direction (both relative to initial eye orientation) in the superior colliculus (SC; Sadeh et al. European journal of Neuroscience.2015) and in the frontal eye fields (FEF; Sajad et al. Cerebral Cortex.2015). Here, we applied a similar methodology to investigate if similar spatial codes are employed in the supplementary eye field (SEF). Since the SEF and FEF have strong reciprocal connections, we hypothesized that they would show similar egocentric spatial codes. Monkeys were trained to make gaze shifts toward briefly presented targets distributed throughout the potential neuronal receptive fields. After a variable memory delay, a go signal was provided for a gaze saccade. Experiments were performed in head-unrestrained conditions with 3-D eye and head recordings to allow discrimination of all egocentric models of gaze coding. Until now, approximately 60 neurons in monkey have been recorded in relation to the above task, 20 with visual responses, 17 with motor responses, and 5 Visuomotor. These have been analyzed employing our previous methodology, including the use of non-parametric fits to response fields. Preliminary data show that both the visual and motor response fields of most SEF neurons show broad receptive fields with poorly defined spatial tuning, and considerable variability in activity for each target direction unrelated to any measured spatial parameter. To date (unlike the FEF), SEF visual population shows a slight (non-significant) bias toward a target within space (Ts) spatial model, but only one model (target relative to head) was statistically eliminated. These preliminary data suggest that the SEF plays a minor role in specifying the spatial direction of targets and gaze plans compared with the SC and FEF. Meeting abstract presented at VSS 2017