Presaccadic spike potential. Relation to eye movement direction.

The spike potential (SP) which precedes horizontal saccadic eye movement has been shown to arise in the agonist lateral and medial rectus muscles of the two eyes. To determine whether other extra-ocular muscles also generate an SP, recordings were carried out in normal subjects performing vertical and oblique as well as horizontal saccades. An SP was recorded before saccades in all directions. The potential was highest in amplitude with horizontal or oblique abducting saccades and was higher in amplitude with vertical upgoing than downgoing saccades.