RESPONSIVENESS OF UNITS IN THE AUDITORY NEOSTRIATUM OF THE GUINEA FOWL (NUMIDA-MELEAGRIS) TO SPECIES-SPECIFIC CALLS AND SYNTHETIC STIMULI .1. TONOTOPY AND FUNCTIONAL ZONES OF FIELD-L

1. One auditory area of the neostriatum (field L) in the guinea fowl is defined both by autoradiography of terminal labelling after injection of tritiated amino acids into the nucleus ovoidalis and by systematic mapping of the activity of small ensembles of units in the frontal and horizontal plane. 2. Anatomical and physiological maps are congruent and show three zones in dorso ventral sequence L1, L2, L3, which together constitute the neostriatal field L (Fig. 2). L2 receives most of the input fibers from the nucleus ovoidalis and shows high activity of units with sharply peaked responses to tones (best frequencies). It probably corresponds to the former field L of Rose. 3. L1 and L2 show less terminal labelling and lower activity of units. Peak responses to tones are present but weaker (Fig. 2). 4. Field L of the neostriatum shows a tonotopic organization with peak frequencies between 300 Hz caudally and 6 kHz rostrally and isofrequency contours running from rostral-lateral to medial-caudal (Fig. 3). Continuous isofrequencies are also present in the vertical plane, i.e. across the boundaries between L1, L2 and L3 (Fig. 2). 5. The area of CFs between 1 and 2 kHz reveals a high proportion of units which respond to Iambus-like calls and distinguish these calls from other calls of the guinea fowl. Systematic penetrations with single unit recording confirm the subdivision of neostriatal field L into three zones. In addition to the different tone responsiveness, selectivity for calls provides a criterion for the subdivision (Fig. 5). 6. Units in L2 are responsive but do not distinguish Iambus-like calls from other calls. Units in L1 and L3 are highly selective. Some respond only to natural variations of the Iambus call (Figs. 6, 7, 8). © 1979 Springer-Verlag.