Tectal Control of Vertical Eye Movements: A Search for Underlying Neuronal Circuits in the Mesencephalon

Abstract

Studies of connectivity patterns underlying input from the superior colliculus (CS) to the horizontal burst generator in cats and monkeys led to a conclusion that the link is established through direct or oligosynaptic connections of collicular projection neurons with the PPRF (Precht et al., 1974, Grantyn, Grantyn, 1976, Raybourn, Keller, 1977). As concerns contribution of the CS to the control of vertical saccadic eye movements, there exists only one report (King et al., 1980) indicating the absence of any synaptic effects from the CS on neurons in the interstitial nucleus of Cajal (NIC), including burst and burst-tonic units discharging in relation to vertical saccades. In the present communication we shall briefly summarize our material bearing on the problem of synaptic connections between the CS and preoculomotor regions of the midbrain related to the generation of vertical components of saccadic eye movements.