Communication sound recognition and response modification in the secondary auditory cortex of female mice

OBJECTIVE To study the response characteristics of the secondary auditory cortex (A2) to wriggling calls (WC) and the mechanism of response modulation in female mice. METHODS We used patch-clamp and immunofluorescence labeling technique to mark and record the action potential and cell type of A2 neurons. Female C57 mice were stimulated with pure tone and white noise (control), 4.5 kHz, 9 kHz, or 13.5 kHz sound waves extracted from WC (single-frequency simulation group), the combinations of every two of the 3 single-frequency sound waves (two-tone frequency simulation group), or the combinations of 4.5 kHz+7.7 kHz+13.5 kHz and 4.5 kHz+9 kHz+13.5 kHz sound waves (three-frequency simulation group). The firing pattern, firing number, threshold, and latency of the action potential of the A2 neurons were recorded in response to the stimulations. RESULTS By comparison of the spikes elicited by different sound stimulations, we identified 3 types of neurons with different sensitivities to WC. The WC-sensitive neurons had a significantly greater number of spikes in response to WC than to other sounds and noise (P < 0.001). Comparison of the latency and threshold revealed significantly longer latencies of the WC-sensitive neurons and WC-insensitive neurons in response to WC stimulation than to pure tone stimulation (P=0.002), but their latencies to WC and noise stimulation were similar (P=0.093). The WC-sensitive neurons also had lower threshold to WC than to pure tone and noise stimulations (P=0.02). Analysis of the firing patterns of action potentials showed that the WCsensitive neurons consisted mainly of parvalbumin interneurons. The results of immunofluorescence labeling indicated that inhibitory interneurons were present in the A2 neurons that responded to WC. CONCLUSION A2 contains 3 types of neurons with different sensitivities to WC. Among them, the WC-sensitive neurons is mainly PV neurons, whose response characteristics to different types of sounds can help to explain the mechanism of communication sound recognition and response modification in A2.