Changes in canine postural control after injury to anterior vermal cerebellum.

For a preliminary exploration of cerebellar influences on postural control, dogs were trained to stand quietly erect. Posture was perturbed by sinusoidal movement of the supporting table while the dogs were sighted and while they were blindfolded or stimulated by sinusoidal optokinetic stimuli. Postural responses were evaluated by measuring the relative amplitude of pelvis movement over a series of perturbing frequencies; frequency response descriptions were derived. Lesions of the cerebellar vermis in 3 dogs involved the cortex of lobules V and VI, of lobules IV, V and VI, and of lobules IV--VII plus damage to the medial portion of nucleus fastigius. The two smaller lesions degraded the animal's tracking ability under all three conditions temporarily with extensive but incomplete compensation in 14--21 days. The larger lesion effectively and permanently eliminated the animal's ability to track table or visual field motion. Elimination of visual cues by blindfolding or perturbing the posture with optokinetic stimuli significantly exaggerated the control deficiencies produced by the lesions. It is concluded that the visual input to the cerebellar vermis finds expression through postural control channels.