Eye Movements and Related Behavioral Responses Evoked by Electrical Stimulation of the Brain in Free-Swimming Sunfish, Lepomis cyanellus

Abstract

Areas of the sunfish brain from which eye movements related to rolling about the longitudinal and interpupillary axes were elicited by electrical stimulation in anesthetized animals (acute preparation) were also tested in free-swimming fish (chronic preparation). Stimulation in the oculomotor complex resulted primarily in bilateral backward rotation of the eyes (acute preparation), and backward looping of the whole animal (chronic preparation). Stimulation near the trochlear nerves and nuclei evoked mostly bilateral forward rotation of the eyes (acute preparation), and downward pitching of the head (chronic preparation). Testing the cerebellum in the molecular area adjacent to the eminentia granulans resulted in conjugate lateral rolling of the eyes (acute preparation), and side-to-side tilts or wobbles (chronic preparation). Stimulation in the presumed vestibular area of the medulla triggered mainly conjugate lateral rolling of the eyes (acute preparation), and lateral rolling about the fish's long axis (chronic preparation). The results are discussed with respect to possible functional pathways involved in the mediation of behavioral responses to inputs from the otolith organs.