Ocular Motor Anatomy in Interrupted Saccades

Saccades normally place the eye on target with one smooth movement. In late-onset Tay Sachs (LOTS), there is a distinctive saccadic abnormality with abrupt, premature transient decelerations. This presents a unique opportunity to refine understanding of brainstem and cerebellar circuitry involved in saccade termination. Initial saccadic peak velocities were normal, suggesting integrity of saccadic excitatory burst neurons (EBNs). Transient inuasaccadic decelerations or interruptions may result from two mechanisms: 1) premature omnipause neuron (OPN) reactivation due to malfunction of a latch circuit that inhibits OPNs for the saccade duration or 2) premature inhibitory burst neuron (IBN) activation due to fastigial nucleus (FN) dysregulation by the dorsal cerebellar vermis.