Physiological aspects of visual perception. II. The subcortical visual direction of behavior.

The second part of the Bennett Lecture for 1975 by Denny-Brown examined the subcortical representation of the dissociation of function described by Denny-Brown and Chambers. Complete removal in the macaque monkey of the corticomesencephalic fibers where they pass from pulvinar to colliculus, and of the colliculus, resulted in the same loss of visual object identification, binocular fixation, and visuosocial behavior that followed removal of area 17. Vision for peripheral movement and spatial orientation ("panoramic vision") remained excellent, with release of catatonia. Conversely, unilateral electrolytic lesions of the mesencephalic tegmentum produced visuospatial distortion, asymmetry of optic righting, and directional difficulties in eye movement (Parinaud syndrome and skew deviation). When bilateral, tegmental lesions produced great constriction of visual field with release of convergence and fixation spasm. Suppression of peripheral attention resulted from perceptual rivalry.