Abstract
Multiunit activity represents the average spiking of a neuronal population recorded within the vicinity of a microelectrode. There is increasing consensus that the multiunit activity contains information about the spatial structure of the stimulus or the task involved. Indeed, recently, using single neuron electrophysiology and a unique toolbox developed in our laboratory, we have shown that the frontal eye field (FEF) and the superior colliculus (SC) visual neurons encode the target in eye coordinates (Te) and the motor response describes the gaze in eye coordinates (Ge). Here, we sought to examine the spatial structure embedded in the multiunit activity of the FEF neurons which are central to visual-motor transformation in the 3-D gaze system. Neuronal recordings with tungsten microelectrodes were performed in the FEF of two rhesus monkeys which were trained to make centrifugal gaze shifts (to the remembered target) in a delayed memory task, either in the presence or absence of an allocentric landmark. Using the same model-fitting approach as for the single neurons, we fitted and distinguished different egocentric models embedded in the multiunit activity of the FEF neurons. The preliminary analyses show that the visual burst of the multiunit response (n=11) also encodes the target relative to the eye (Te), whereas the multiunit motor responses (n=8) encode the gaze in the eye coordinates (Ge). This suggests that 1) the receptive fields of neurons comprising the multiunit are overlapped and 2) the multiunit activity can also be used as a reliable marker of the visual-motor transformations in the FEF, if one is unable to sort the single units from it. Further analysis is targeted on analyzing more multiunit sites and the same analysis in the SC and supplementary eye fields (SEF).
Meeting abstract presented at VSS 2018