Hemispheric and Sex Differences in Mustached Bat Primary Auditory Cortex Revealed by Neural Responses to Slow Frequency Modulations

The mustached bat (Pteronotus parnellii) is a mammalian model of cortical hemispheric asymmetry. In this species, complex social vocalizations are processed preferentially in the left Doppler-shifted constant frequency (DSCF) subregion of primary auditory cortex. Like hemispheric specializations for speech and music, this bat brain asymmetry differs between sexes (i.e., males>females) and is linked to spectrotemporal processing based on selectivities to frequency modulations (FMs) with rapid rates (>0.5 kHz/ms). Analyzing responses to the long-duration (>10 ms), slow-rate (<0.5 kHz/ms) FMs to which most DSCF neurons respond may reveal additional neural substrates underlying this asymmetry. Here, we bilaterally recorded responses from 176 DSCF neurons in male and female bats that were elicited by upward and downward FMs fixed at 0.04 kHz/ms and presented at 0–90 dB SPL. In females, we found inter-hemispheric latency differences consistent with applying different temporal windows to precisely integrate spectrotemporal information. In males, we found a substrate for asymmetry less related to spectrotemporal processing than to acoustic energy (i.e., amplitude). These results suggest that in the DSCF area, (1) hemispheric differences in spectrotemporal processing manifest differently between sexes, and (2) cortical asymmetry for social communication is driven by spectrotemporal processing differences and neural selectivities for amplitude.

Bat species richness in the region of the Central Valleys of Oaxaca, Mexico

We present a revised checklist of bat species occurring in the semi–urbanized region of the Central Valleys of Oaxaca, Mexico. The checklist is based on surveys using mist nets, recordings of echolocation calls, data from literature, and museum databases. Results show that the Central Valleys of Oaxaca have a species richness of 33 bat species belonging to 22 genera and five families. Species like the Mustached bat Pteronotus parnellii, the Western Red bat Lasiurus blossevillii and the Free–tailed bat Promops centralis were recorded after 32, 30 and 19 years respectively according to the records of the literature. We also recorded four species classified in some risk category according to either the Mexican government’s red list (NOM–059) or the IUCN red list. The recordings of the echolocation calls are the first from the region of Central Valleys of Oaxaca. Bat diversity in the Central Valleys of Oaxaca was underestimated and emphasizes the need for further research