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In cats, unanesthetized following transection of the brainstem at a level precluding painful sensation, and limiting ocular motility to a vertically oriented course (the pretrigeminal preparation), habituation of the orienting reflex, consisting of ocular fixation and smooth pursuit, readily transferred between moving visual stimuli directed first at one and then the other cerebral hemisphere. Under the same conditions, when the corpus callosum had been transected 2 weeks prior to the habituation, interhemispheric transfer was absent. Thus, despite substantial brainstem involvement and bilateral coordination of ocular motility the neocortex plays an essential role in this habituation, just as it does in the interhemispheric transfer of visual discrimination learning. This suggests that habituation is a fundamental form of learning in the mammalian forebrain.

Four normal and eight cage-reared cats were used. Four of the cage-reared cats were visually deprived in the first 6 months of life. The cats were trained on a three-choice delayed response task to auditory stimuli. All normal cats mastered a 1-min delay and two cats even a 6-min delay. In contrast, two cage-reared cats failed to cope even with a 5-s delay, four cats with a 15-s delay and the remaining two cats with a 1-min delay. No significant difference was found between the non-deprived and the deprived cage-reared cats. The deficits was analogous to that shown by cage-reared cats during delayed response, visual learning. Thus, cage-rearing strongly impairs delayed responding to at least two different sensory modalities.

Because both electrophysiological and behavioral methods have implicated the suprasylvian cortex of cat in audition, its afferents were studied using retrograde transport of horseradish peroxidase. The bulk-filling method was used to maximize the likelihood that virtually all afferents to the area would be labeled. Despite the vivid retrograde labeling of many thalamic cells with this procedure, no direct auditory projections to the suprasylvian cortex could be found in the thalamus (i.e. in medial geniculate body or in the dorsolateral part of the posterior nucleus). Furthermore, very few cells were labeled in the primary auditory cortex of the nearby ectosylvian gyrus. The source of afferents to the suprasylvian cortex originate mostly from the pulvinar-lateral posterior complex and to a lesser extent from ventral lateral and ventral anterior nuclei of the thalamus.

Eleven cats with brain stem transected at the pretrigeminal level were used. The cortex of the middle suprasylvian sulcus was removed on the left side. The vertical following reflex was evoked by a slit of light (1 degree x 4 degrees) or a black bar (1 degree x 1 degree x 4 degrees) moving along the vertical meridian or parallel to it out to 40 degrees in the left or right hemifield. In all cats the following reflexes to the contralesional hemifield were low or absent. A corresponding suprasylvian lesion was made subsequently on the right side. In 6 cats the reflexes to both hemifields were absent or low. In contrast, surprisingly in 5 cats the reflexes were large, much higher than those evoked previously from the contralateral hemifield after the first lesion. This might be due to a process of disinhibition occurring in the superior colliculi.

The cortex of the middle suprasylvian sulcus was removed unilaterally in cats with brain stem transected at the pretrigeminal level. The vertical following reflex was evoked by a slit of light (1 degree x 4 degrees) moving along the vertical meridian or parallel to it up to 40 degrees in the left or right hemifield. The reflexes from the contralateral hemified were greatly reduced. This contrasts with previous reports with perimetry test where authors made smaller lesions.

Six normally reared cats were trained on a three-choice delayed response task to visual stimuli. All cats mastered 1 min delay, three cats 2 min delay and one cat 6 min delay. Learning was much better than in previously studied cats reared in laboratory cages. It was comparable to that known for auditory stimuli in normally reared cats.