Abstract
Previous studies have shown that sustained-response neurons in the primary auditory cortex (A1) of awake animals have sensitivities to the spectral-edge and fundamental frequency (F0) and that the sensitivity originates from the specific inhibition pattern of frequency receptive field (FRF). This study investigated cell-type correspondence between the different experiments by estimating the excitatory and inhibitory summation patterns for harmonic components with a given F0. The findings show that there are, at least, four types of sustained-response neurons sensitive to specific spectral features of the complex tone: energy-integrator cells integrate sound energy on the excitatory FRF; high-edge-sensitive cells are sensitive to the spectral high edge on the best frequency (BF); low-edge sensitive cells detect the spectral low edge on BF; F0-sensitive cells are sensitive to two F0s of harmonics corresponding to BF and an octave below, but not to noise with a similar spectral location. The spectral-cue sensitivity originates from specific inhibitory FRF: less dominant inhibition for energy-integrator cells, asymmetric inhibition for high- and low-edge-sensitive cells, and selective inhibition of non-preferred harmonics for F0-sensitive cells. A1 operates as filters with pass bands and reject bands, which correspond to the peak and trough in FRF. The filter specification is well organized for decoding three acoustic features: sound energy in a given spectral region, spectral edges, and F0 of harmonics. [J Physiol Sci. 2006;56 Suppl:S92]
