Effects of unpaired footshock on rabbit limbic and auditory neuronal responses to tone stimuli

Multiple unit activity was recorded from the anterior cingulate cortical area (AC), anteroventral nucleus of the thalamus (AV), and medial geniculate nucleus (MGN) in rabbits during presentations of pure tone stimuli. In one experimental session (S) the tones were presented with unpaired footshock, and in a different session (NS) tones alone, without footshock, were presented. The order of the sessions was counterbalanced, and they were separated by 24 hr. The response of AC neurons to the tones was greater in the S treatment, relative to NS, and the S-related enhancement carried over to the NS session when the latter followed S. The response of AV neurons was also greater in the S treatment, relative to NS, but the enhancement did not carry over to NS. The response of MGN neurons showed different relationships to the experimental variables in different animals. This suggested that the effect of the treatments depended on the specific recording site in MGN.