Unit Activity in the Hypothalamus and Striatum of the Rat During Learning

Year: 1973

DOI: 10.7907/9BAS-1713

Unit activity was recorded from the hypothalamus and striatum
of 80 freely moving rats during an appetitive classical conditioning
situation. Responses to auditory stimuli were observed from 118
units before and during a conditioning procedure in which presentation
of food occurred one second after the onset of an auditory stimulus.
A large proportion of units (111) showed changed responses to the CS
during conditioning. Only 8 of these, however, showed new conditioned
responses of the very shortest latency measured, 20 msec. after CS
onset. These were interpreted as likely sites of rerouting of the stimulus
information within the brain as a result of learning. They
were located largely near the intersection of hypothalamic and striatal
structures. A transient increase in rate of background firing over
trials was recorded following the onset of conditioning among hypothalamic
units, suggesting they may temporarily represent a dynamic trace of the
new learning. No significant differences were found between areas
studied in order of appearance over trials of the conditioned responses.
However, as a group, the conditioned responses studied here, appeared
significantly earlier than a group of cortical neurons studied under
similar conditions. There was greater generalization of response
to the CS- by units of the basal ganglia than other areas, suggesting
they may be of importance in inhibition of response to the CS-.