Neuronal network model of saccadic eye movement control system

Abstract

In this study, we propose a mathematical model of the saccadic eye movement system based on the neuronal network characteristics of the substantia nigra pars reticulata (SNr), the intermediate layer of the superior colliculus (SC), and the brainstem neurons, all of which are deeply involved in the generation of saccades. The frontal eye field (FEF) is involved in the planning of the direction and amplitude of saccades, and the SC is involved in the generation of the commands for saccades and transmits them to the brainstem; subsequently, the ocular muscles contract to produce saccades. These cortices contain many functionally distinct cell types such as fixation neurons, buildup neurons, and burst neurons. The fixation neurons discharge while maintaining fixation. The buildup neurons become active during the preparatory stages of saccadic eye movements, and the burst neurons become active while executing the saccades. The firing properties of these types of cells have been well described. However, detailed information regarding their network, that is, how they communicate with each other through neural pulses, is not available. Our model can reproduce the properties of neural responses of saccade-related areas in express saccade tasks. In addition, the model can also reproduce the activity of the intermediate-layer neurons of the SC in antisaccade tasks. These results indicate the validity of the mathematical model for the mechanism underlying saccade generation.