Neurophysiology of the saccadic system: The reticular formation

This chapter discusses the neurophysiology and function of subcortical circuits and cortical areas involved in saccade generation. While cells within the different nuclei of the brainstem reticular formation shape the temporal details of ipsiversive horizontal and vertical/cyclotorsional saccade components, the cerebellar flocculus, vermis and fastigial nucleus are thought to modulate these saccadic waveforms. Burst neurons in the deep layers of the superior colliculus encode the saccade vector in the contralateral field by a localized population in a motor-error map. The complexity of the saccadic system is evident in the different subclasses of SC cells, ranging from purely visual, to visual-motor, purely motor, and quasi-visual cells. Movement-related activity in all SC cells is dissociated from the retinotopic visual activity. The chapter further discusses neurophysiological findings obtained from the substantia nigra (pars reticulata), the medial thalamus, the frontal eye fields, the supplementary motor area and the parietal lobes, discussing the ever more complex response patterns of their neurons in relation to saccades.