Date of Award


Document Type


Degree Name

Master of Arts (MA)




Multiple unit recording is a relatively new electrophysiological recording technique which records spike potentials from many neurons. In several laboratories, systematic changes have been observed during classical and instrumental conditioning but none under other conditioning procedures. The present study attempts to extend the method of multiple unit recording to discrimination learning using rats as experimental animals.

Five permanent electrodes were implanted in each of six rats. The sites implanted were the dorsal medial hypothalamus, the amygdaloid complex, the reticular formation, the medial geniculate, and the inferior colliculus. The animals were subjected to discrimination training which utilized tone as the auditory stimulus and water as the reinforcement.

Neuronal activity from the electrodes was recorded on tape and then transferred to computer cards for statistical analysis. Basically, the number of neuronal spikes for the pre-tone, tone, and post-tone periods were compared in order to judge the effects of reinforcement or non-reinforcement on brain activity.

Generally, there was inhibition of neuronal activity when tones were presented during habituation sessions. However, by the last day of conditioning, four of the five electrode sites were demonstrating significantly greater neuronal activity after the presentation of a previously reinforced tone. This was not the case upon presentation of a previously non-reinforced tone. Extinction generally resulted in inhibition of activity.

No significant differences were obtained between the reinforced and non--reinforced trials on the last day of conditioning. However, behavioral curves appeared closely associated with neuronal activity.