COMPARISON OF FREQUENCY-SPECIFIC C-FOS EXPRESSION AND FLUORO-2-DEOXYGLUCOSE UPTAKE IN AUDITORY-CORTEX OF GERBILS (MERIONES-UNGUICULATUS)

Induction of c-Fos in the auditory cortex of gerbils was investigated immunocytochemically 1 h after single, triple or 1 h continuous stimul ation with a series of narrow band frequency-modulated tone bursts. Wi th single stimulation c-Fos immunoreactive neurons were chiefly found in the primary auditory field (Al), where they formed a narrow frequen cy-specific column across layers Il-VI. Side-hand-like patterns adjace nt to this column appeared characteristically with triple stimulation. Immunoreactive cell density in the anterior auditory field and the ca udal fields was sparse and location not frequency specific with single or triple stimulation. Spatial comparisons of c-Fos immunoreactive ne uron density with 2-deoxy-2-fluoro-D-glucose (FDG) autoradiography in the same animals after 1 h of stimulation revealed spreading of c-Fos expression in neurons across the tonotopic maps of the Al and in the r ostral and caudal fields of the auditory cortex. The pattern of the hi ghest density of c-Fos labelled cells in the Al still matched the peak labelling of FDG autoradiographs. The results show that the postsynap tic marker c-Fos reflects the frequency representation in the Al with single or triple stimulation yet with a higher spatial resolution than the deoxyglucose technique. Longer stimulation causes non-tonotopic i ntracortical spreading of the c-fos-inducing message, a phenomenon pot entially reflecting the effects of cooperativity in the maps.