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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.

The cat's pons was isolated by two brainstem transections, at the junction of medulla and pons and at the junction of pons and midbrain. In the deafferented pons the EEG activity was virtually absent, whereas the spatial density of active units and the rate of their spontaneous spike activity were at a high level. In the pons of control preparations with brainstem transected only at the ponto-midbrain junction the EEG activity was present, while the single-unit activity was such as in the isolated pons. The electrical activity of the isolated pons was similar to that previously described in the cat's isolated midbrain. The discrepancy between EEG and single-unit activity suggests that in the deafferented pons or midbrain many neurones are asynchronously autoactive. Also, these results show that a flat EEG record is not necessarily a sign of absence of the neural activity and neural death.

Discrimination learning of instrumental responses to auditory compound stimuli was investigated in opossums using the R-no R (go-no go) differentiation. Each compound stimulus consisted of two factors: quality and location. Each correct response performed to the conditioned positive, or "safe" stimulus, was rewarded by food and never punished. Each incorrect response performed to the conditioned negative, or "warning" stimulus, was punished by an electric shock. In subsequent testing, each opossum proved to use only the quality cues to solve the task even though later testing showed them capable of using the location cues. Thus, the rule discovered in higher mammals, that the efficacy of auditory stimuli in differentiation depends on the perceptual ability of the animal as well as the type of the behavioral response with which the animal is confronted, may be extended to neurologically primitive mammals and also to a joint conditioned approach-avoidance method.

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.

A differentiation of instrumental responses to auditory location stimuli using the Konorski Test was investigated. Each stimulus consisted of two components separated by intrastimulus interval. The components were click series presented from four loudspeakers situated in front of the animal, on horizontal and vertical axes. Each correct response, performed to the second component of positive stimulus, was rewarded by food. Responses to negative stimuli were not reinforced. Solving the test was possible by comparing the memory trace of the first component location, with location of actually presented second component. Two groups of dogs were trained. In one group positive and negative stimuli were presented, in which intrastimulus interval lasted 1 s. In the other group, differentiation training included stimuli with intrastimulus interval lasting 3 s. Unexpectedly, the first group was unable to reach differentiation criterion, whereas the second group reached criterion without difficulty. The effect of reaching the criterion with longer and not shorter interval between stimulus components, may be specifically related to location cues as opposed to reported earlier auditory quality stimuli.

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.

Two groups of naive dogs were trained on a spatial variant of the Konorski Test, in which pairs of successively presented auditory location cues were differentiated in a conditioning procedure. Instrumental leg flexion to positive stimuli was reinforced by food. Combinations of four different location cues were used as compound conditioned stimuli (CS). In group AA a positive CS involved two identical, successively presented location cues, Sx-Sx, separated by an interval of 5 s, whereas the negative CS was formed by two different successive location, cues, Sx-Sy, with the same intercomponent interval. In group AB positive and negative combinations of location cues were reversed: Sx-Sy combinations were positive, while Sx-Sx were negative. Solving the task required a comparison of the second CS component with the memory trace left by the first component of CS. The two groups did not differ in reaching the preoperative criterion, but the response time was significantly shorter in the AA group. Prefrontal proreal lesion produced a significant but transient impairment of performance in both groups. The third group, trained on a simple differentiation task with single location cues, was completely unimpaired.