Abstract
For humans and animals, the ability to discriminate speech and conspecific vocalizations is an important physiological assignment of the auditory system. To reveal the underlying neural mechanism, many electrophysiological studies have investigated the neural responses of the auditory cortex to conspecific vocalizations in monkeys. The data suggest that vocalizations may be hierarchically processed along an anterior/ventral stream from the primary auditory cortex (A1) to the ventral prefrontal cortex. To date, the organization of vocalization processing has not been well investigated in the auditory cortex of other mammals. In this study, we examined the spike activities of single neurons in two early auditory cortical regions with different anteroposterior locations: anterior auditory field (AAF) and posterior auditory field (PAF) in awake cats, as the animals were passively listening to forward and backward conspecific calls (meows) and human vowels. We found that the neural response patterns in PAF were more complex and had longer latency than those in AAF. The selectivity for different vocalizations based on the mean firing rate was low in both AAF and PAF, and not significantly different between them; however, more vocalization information was transmitted when the temporal response profiles were considered, and the maximum transmitted information by PAF neurons was higher than that by AAF neurons. Discrimination accuracy based on the activities of an ensemble of PAF neurons was also better than that of AAF neurons. Our results suggest that AAF and PAF are similar with regard to which vocalizations they represent but differ in the way they represent these vocalizations, and there may be a complex processing stream between them.
Highlights
One of the important physiological roles of the auditory system is to discriminate the communication sounds generated by conspecies
Information being transferred from the primary visual cortex to extrastriated visual cortex constitutes two processing streams: a ventral or ‘what’ processing stream and a dorsal or ‘where’ processing stream, which is involved in the object vision and spatial vision, respectively [9,10,11]
According to the histological reconstruction of recording sites, 92 units were identified in anterior auditory field (AAF) and the remaining 102 units were in posterior auditory field (PAF)
Summary
One of the important physiological roles of the auditory system is to discriminate the communication sounds generated by conspecies. The ‘‘what’’ stream originates in A1 and includes a series of projections through the antero-lateral belt auditory cortex (AL), the dorsal bank of the superior temporal sulcus (STS), and to the ventro-lateral prefrontal cortex (vPFC). Inspired by this concept, various studies have been conducted on monkeys to investigate conspecific vocalizationevoked responses in AL, STS and vPFC [16,17,18,19,20,21]. There is some controversy about call selectivity in the neurons of different regions [16,17,18,19,20], these studies suggest the existence of a vocalization-processing hierarchy in the non-human primate cortex
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