ALTERATION OF AUDITORY-CORTEX ACTIVITY WITH A VISUAL STIMULUS THROUGHCONDITIONING - A 2-DEOXYGLUCOSE ANALYSIS

In two experiments, the 2-deoxyglucose metabolic mapping technique was used to examine the hypothesis that a stimulus of one modality (a lig ht) will begin to activate the sensory cortex of a stimulus of another modality (a tone) with which it has been repeatedly paired. Adult ger bils received repeated presentations of either a light or the light pa ired with a tone known to affect 2DG labeling patterns in the auditory cortex. Intermittent footshock was included on a pseudo-random basis to maintain arousal in the subjects. One day after training, each gerb il was injected with 2DG and either received repeated presentations of the light only or was simply exposed to the training context. Analysi s of the auditory cortex revealed no differences in overall metabolic activity of the auditory cortex between the groups. However, in both e xperiments, the light that was previously paired with the tone changed the relative activity of the cortical subfields compared to the light not previously paired with the tone. Specifically, the results indica te greater activity in the anterior auditory field (AAF-Experiments 1 and 2) and the posterior fields (DPVP-Experiment 2) relative to the pr imary field AI in response to the light that was previously paired wit h the tone during training. Gerbils either only placed in the context during the 2DG session or that received unpaired presentations of the light and tone during training did not show this shift in relative lab eling between the subfields. Because no differences in overall activit y of the auditory cortex were found, we conclude that the shift in rel ative labeling between the subfields reflects, on average, both an inc rease in activity of fields AAF and DPVP and a concomitant decrease in AI activity in response to the light stimulus. The results have impli cations for our understanding both of brain learning mechanisms in gen eral and the potential functions of auditory cortex subfields in parti cular. (C) 1996 Academic Press, Inc.