Demonstration of Saccade-Related Single-Unit Activity in the Dorsolateral Pontine Nucleus (DLPN) of the Rhesus Monkey

Thier, P., Dicke, P.W., Barash, S., Ilg, U., Sektion Visuelle Sensomotorik, Neurologische UniversitΣtsklinik, 72076 Tⁿbingen, Germany and The Weizmann Institute, 76100 Rehovot, Israel

The DLPN is connected to saccade-related regions, but saccade-related neuronal activity has not been reported in the DLPN. The DLPN receives strong input from cortical area LIP and the FEF, and it projects to vermal lobules VI, VII. The involvement of all these areas in saccades is well established. Nevertheless, only pursuit-related activity, not saccade-related activity, has been reported in the DLPN. The question, whether saccade-related activity exists in the DLPN is particularly interesting in view of current thinking about cortical contributions to goal-directed eye movements, which favors the dichotomy of a cortico- pontine pathway for smooth-pursuit eye movements and a cortico-tectal pathway for saccades . We have started to record single-units from the DLPN of a rhesus monkey trained to execute saccades to remembered locations ("memory saccade task"). So far, we have recorded from 50 single-units, we would provisionally assign to the DLPN, based on their locations relative to conspicuous electrophysiological landmarks such as the oculomotor nuclei and additional information derived from MRI scans. Out of these, 8 exhibited clearcut directionally selective saccade-related responses, characterized by strong pre- or perisaccadic bursts of discharge. In several cases, these bursts were preceded by a tonic increase of activity in the "memory period", in which the monkey was required to memorize the spatial location of the peripheral target in the absence of visual information . These preliminary electrophysiological observations strengthen the hypothesis of a cortico-pontine pathway for saccades, which involves the DLPN, and bypasses the classical cortico-tectal pathway for saccades. Supported by the German-Israeli-Foundation.
page created by peter.dicke@uni-tuebingen.de(peter.dicke@uni-tuebingen.de) and Friedemann Bunjes(fried@lgn.neurologie.uni-tuebingen.de) - Stand: 18. Juli 1996