Distinct natural syllable-selective neuronal ensembles in the primary auditory cortex of awake marmosets

Marmosets are highly social non-human primates living in families. They exhibit rich vocalization, but neural basis underlying complex vocal communication is largely unknown. Here we report the existence of specific neuronal ensembles in marmoset A1 that respond selectively to distinct monosyllable or disyllable calls made by conspecific marmosets. These neurons were spatially dispersed within A1 but distinct from those responsive to pure tones. Syllable-selective responses were markedly diminished when individual domains of the syllable were deleted or the domain sequence was altered, indicating the importance of global rather than local spectral-temporal properties of the sound. Disyllable-selective responses also disappeared when the sequence of the two monosyllable components was reversed or their interval was extended beyond 1 second. Light anesthesia largely abolished disyllable-selective responses. Our findings demonstrate extensive inhibitory and facilitory interactions among syllable-evoked responses, and provide the basis for further study of circuit mechanisms underlying vocal communication in awake non-human primates.