Distinct spatial and non-spatial response properties of excitatory narrow-spike and burst-firing neurons in the marmoset auditory cortex

Cell types are the basic units of the cerebral cortex. Broad and narrow spike waveforms (BW and NW) are the primary criteria for classifying putative excitatory and inhibitory cortical neurons, particularly in non-human primates where genetic accessibility is limited. We have classified cell types in the auditory cortex of marmosets using spike waveforms and firing patterns and identified a new type of neuron: the NW-burst neuron. NW-burst neurons are excitatory, as they drive but do not suppress the firing of connected neurons. Furthermore, NW-burst neurons displayed shorter response latencies, lower response variability, smaller receptive fields, stronger correlations between spatial and non-spatial selectivity, and higher decoding accuracy than other neurons. Together, these findings suggest that cortical NW-burst neurons in non-human primates represent a distinct excitatory cell type. Significance StatementClassifying cell types in non-human primates is challenging due to limited genetic tools. Traditionally, neurons with narrow spikes are assumed to be inhibitory. Challenging this view, we analyzed 1,816 high-quality single units in the marmoset auditory cortex and discovered that narrow-spike burst-firing neurons were excitatory. These neurons exhibited shorter response latencies, smaller receptive fields, and higher decoding accuracy. Crucially, they showed a positive correlation between "where" and "what" selectivity, defying the standard trade-off between spatial and non-spatial response properties. These findings reveal a specific excitatory cell type in the auditory cortex of a non-human primate species that integrates sound information with high temporal fidelity and feature selectivity.