RELATIONSHIP OF PRESACCADIC ACTIVITY IN FRONTAL EYE FIELD AND SUPPLEMENTARY EYE FIELD TO SACCADE INITIATION IN MACAQUE - POISSON SPIKE TRAIN ANALYSIS

The purpose of this study was to investigate the temporal relationship between presaccadic neuronal discharges in the frontal eye fields (FE F) and supplementary eye fields (SEF) and the initiation of saccadic e ye movements in macaque. We utilized an analytical technique that coul d reliably identify periods of neuronal modulation in individual spike trains. By comparing the observed activity of neurons with the random Poisson distribution generated from the mean discharge rate during th e trial period, the period during which neural activity was significan tly elevated with a predetermined confidence level was identified in e ach spike train. In certain neurons, bursts of action potentials were identified by determining the period in each spike train in which the activation deviated most from the expected Poisson distribution. Using this method, we related these defined periods of modulation to saccad e initiation in specific cell types recorded in FEF and SEE Cells were recorded in SEF while monkeys made saccades to targets presented alon e. Cells were recorded in FEF while monkeys made saccades to targets p resented alone or with surrounding distracters. There were no signific ant differences in the timecourse of activity of the population of FEF presaccadic movement cells prior to saccades generated to singly pres ented or distractor-embedded targets. The discharge of presaccadic mov ement cells in FEF and SEF could be subdivided quantitatively into an early prelude followed by a high-rate burst of activity that occurred at a consistent interval before saccade initiation. The time of burst onset relative to saccade onset in SEF presaccadic movement cells was earlier and more variable than in FEF presaccadic movement cells. The termination of activity of another population of SEF neurons, known as preparatory set cells, was time-locked to saccade initiation. In addi tion, the cessation of SEF preparatory set cell activity coincided pre cisely with the beginning of the burst of SEF presaccadic movement cel ls. This finding raises the possibility that SEF preparatory set cells may be involved in saccade initiation by regulating the activation of SEF presaccadic movement cells. These results demonstrate the utility of the Poisson spike train analysis to relate periods of neuronal mod ulation to behavior.