Neural properties of fundamental function encoding of sound selectivity in the female avian auditory cortex

Abstract

Zebra finches (Taeniopygia guttata) use their voices for communication. Song structures in the songs of individual males are important for sound recognition in females.The caudomedial mesopallium (CMM) and nidopallium (NCM) are known to be essential higher auditory regions for sound recognition. These two regions have also been discussed with respect to their fundamental functions and song selectivity. To clarify their functions and selectivity, we investigated latencies and spiking patterns and also developed a novel correlation analysis to evaluate the relationship between neural activity and the characteristics of acoustic factors. We found that the latencies and spiking patterns in response to song stimuli differed between the CMM and NCM. In addition, our correlation analysis revealed that amplitude and frequency structures were important temporal acoustic factors for both regions. Although the CMM and NCM have different fundamental functions, they share similar encoding systems for acoustic factors. K E Y W O R D S auditory cortex, electrophysiology, songbird, sound selectivity | 1771 INDA et Al.

High responsiveness of auditory neurons to specific combination of acoustic features in female songbirds

“…Some neurons showed strong excitatory activity in response to natural song stimuli, whereas other neurons showed weak activity. Sound‐responsive (SR) neurons (Inda et al., 2019) were those in which firing rates were significantly higher in response to natural songs when compared to the spontaneous firing rate (CMM: 86 units from 14 birds, NCM: 95 units from 13 birds). To investigate important acoustic features inducing neural responsiveness, we applied multiple linear regression analysis between firing rates of SR neuron and the value of acoustic features at selected syllables (Table 1).…”

“…These identified neurons (CMM: 97 units from 14 birds, NCM: 149 units from 13 birds, four birds were duplicated) were sorted into SR neurons or non‐SR neurons (Inda et al., 2019). The average firing rate during natural song stimuli presentation was calculated from a peristimulus time histogram (PSTH) and was defined as the firing rate for natural songs.…”

“…We took the first spike time of all trials for each neuron and defined the median as its latency. This adjustment method has been also used in our previous study (Inda et al., 2019). Next, we manually selected all syllables from eight songs and classified syllable types.…”

“…Behavioural research has also revealed a changing spectral envelope of birdcalls influences the motivational state (Spierings et al., 2017). Temporal modulation of Wiener entropy and mean frequency is encoded in the CMM and NCM (Inda et al., 2019) and research suggests that the spectral envelope is important for vocal communication of songbirds. Our results actually reveal the contribution of specific parts of the spectral envelope to songbird's song cognition at a neural level.…”

Early Auditory Experience Modifies Neuronal Firing Properties in the Zebra Finch Auditory Cortex

“…While it is still controversial, isolation or altering auditory experiences cause abnormal song discrimination in males but have no effects on females (Campell and Hauber, 2009 ; Maul et al, 2010 ; reviewed Woolley, 2012 ). While the NCM is thought to be involved in song learning in males (Bolhuis et al, 2000 ; Terpstra et al, 2004 ; London and Clayton, 2008 ; Yanagihara and Yazaki-Sugiyama, 2016 ), it has also been reported as an auditory area in females, and auditory experiences alter the responsiveness of the female NCM as well (Yoder et al, 2015 ; Diez et al, 2019 ; Inda et al, 2020 ). Auditory experiences with tutors may also cause different neuronal circuit modifications in juvenile males and females.…”