Presaccadic spike potential with congenital lateral rectus palsy

Abstract

Presaccadic spike potentials were recorded with 20° horizontal eye movements in a subject with a congenital left lateral rectus palsy. Electrodes at the inner and outer canthi recorded the eye movements and an electrode below the eye recorded the presaccadic spikes. The responses to 20 abducting and 20 adducting saccades were back-averaged from the onset of the eye movement with the wave forms for abduction and adduction averaged separately. Recordings were made from each eye under 2 conditions: firstly with the eye from which the spikes were being recorded fixating and secondly with the eye from which the spikes were not being recorded fixating. In each case the non-fixating eye was occluded throughout. Recordings were made with eye position monitored initially in the eye from which the spikes were recorded and repeated with eye position monitored in the other eye. Results show that spikes could be recorded during abduction and adduction movements of both eyes but only if eye position was monitored in the right eye. Using the left eye as position monitor gave very broad low amplitude spikes. When eye position was monitored in the right eye the spikes recorded during abduction of the left eye had a low amplitude compared to those recorded during right eye abduction; right eye adduction spikes were also of low amplitude. A possible explanation for these findings and their implications on future recordings in pathological cases are discussed.