Motor responses to localized electrical stimulation of the tectum in the freshwater perch (Perca fluviatilis)

The results of localized electrical stimulation of the teleostean tectum indicate the presence within each tectal lobe of separate motor areas mediating ipsilateral turning, contralateral turning, and rolling movements. Stimulation of caudal regions produced larger turning circles than stimulation of rostral sites. Both these sets of observations conflict with the retinotopic map. Stimulation sites connected with turning and rolling movements were mostly located in the upper layer of the tectum. Other kinds of movement including aggressive behaviour, escape movements, head dipping, and forward swimming were obtained by stimulating the deeper tectal sites and subtectal areas. These results suggest that the tectum may be differentiated into areas with specific motor functions and afferent connections. This has important consequences for studies on optic nerve regeneration and neuronal specificity.