Stereotyped Head Movements Research Articles

Patterns of reticular unit activity observed during the performance of a discriminative task

Abstract The firing patterns of reticular neurons were monitored during the performance of a behavioral task, using a chronic single unit recording technique. The spontaneous activity of 95 of 134 midbrain reticular units was noticeably modified by the presentation of visual discrimination trials. Four major response profiles emerged from these responsive units. The response of Type I units was closely related to stereotyped head, neck, and eye movements. The auditory cue occurring when the bar became available, and the onset of the light evoked transient increases in the discharge rate of Type II units. Type III units displayed a brief increase in firing rate associated with either the onset of the light or the initiation of a bar press response. Type IV units responded to the auditory and visual stimuli with sustained increases in firing rate. These findings illustrate, at a cellular level, the modulatory influences conditioned stimuli exert upon the level of reticular activity.

Head, eye, body and limb movements from semicircular canal nerves

Electric stimulation of single ampullary nerves in alert cats and monkeys produced rapid stereotyped head movements. These head movements were similar in the cat and monkey and appeared to be in a plane parallel to the plane of the canal whose nerve was stimulated. Body and limb responses also were evoked. They were more pronounced in the cat than in the monkey and consisted of varying degrees of ipsilateral forelimb extension, contralateral forelimb flexion, curvature of the trunk, and contralateral circling. By stimulating canals singly or in combination head movements could be produced in any spatial plane. These findings demonstrate the specific nature of the reflex head and postural movements produced by the semicircular canals in these animals.