ASA 126th Meeting Denver 1993 October 4-8

5aSP6. Development of the song selectivity by nonlinear neural response interactions in the zebra finch.

Dukhwan Lim

Div. of Biol., California Inst. of Technol., Pasadena, CA 91125

The zebra finch's song control system contains song-selective neurons. One of the song nuclei, hyperstriatum ventral, caudal (HVc) receives auditory inputs from the forebrain auditory area, field L, which is subdivided into L1, L2, and L3. Where and how this selectivity is formed has not been studied quantitatively in this forebrain area. The song of the zebra finch consists of simultaneous and sequential arrangements of acoustic elements. Neuronal responses to individual song elements and to syllables composed of harmonic frequencies were studied in each subdivision of field L and HVc. The responses to pairwise sequences or harmonic syllables differed from their responses to an individual element or a tone presented in isolation. These nonlinear responses were evaluated by a matrix-based analysis method. Results showed a hierarchical increase of nonlinear interactions as a recording site moved from field L to HVc. Both sequential and simultaneous nonlinear interactions were enhanced from field L to HVc. These interactions involved either inhibitory or facilitatory effects. Although, in theory, this selectivity could be formed by a linear way, the song selectivity proved to be achieved dominantly by these nonlinear interactions. [Work supported by IHFSPO.]