Local Field Potentials and Spiking Activity in the Primary Auditory Cortex in Response to Social Calls

Abstract

The mustached bat, Pteronotus parnellii, uses complex communication sounds ("calls") for social interactions. We recorded both event-related local field potentials (LFPs) and single/few-unit (SU) spike activity from the same electrode in the posterior region of the primary auditory cortex (AIp) during presentation of simple syllabic calls to awake bats. Temporal properties of the LFPs, which reflect activity within local neuronal clusters, and spike discharges from SUs were studied at 138 recording sites in six bats using seven variants each of 14 simple syllables presented at intensity levels of 40-90 dB SPL. There was no clear spatial selectivity to different call types within the AIp area. Rather, as shown previously, single units responded to multiple call types with similar values of the peak response rate in the peri-stimulus time histogram (PSTH). The LFPs and SUs, however, showed a rich temporal structure that was unique for each call type. Multidimensional scaling (MDS) of the averaged waveforms of call-evoked LFPs and PSTHs revealed that calls were better segregated in the two-dimensional space based on the LFP compared with the PSTH data. A representation within the "LFP-space" revealed that one of the dimensions correlated with the predominant and fundamental frequency of a call. The other dimension showed a high correlation with "harmonic complexity" ("fine" spectral structure of a call). We suggest that the temporal pattern of LFP and spiking activity reflects call-specific dynamics at any locus within the AIp area. This dynamic contributes to a distributed (population-based) representation of calls. Alternatively stated, the fundamental frequency and harmonic structure of calls, and not the recording location within the AIp, determines the temporal structure of the call-evoked LFP.

Sex-dependent hemispheric asymmetries for processing frequency-modulated sounds in the primary auditory cortex of the mustached bat

“…Surgical and recording methods were previously described Medvedev and Kanwal 2004;Washington and Kanwal 2008). We used 10 (6 male and 4 female) wild-caught mustached bats.…”

“…Studies of brain-damaged (Divenyi and Robinson 1989), learning-impaired (Merzenich et al 1996;Nagarajan et al 1999;Tallal et al 1993;Temple et al 2000), and healthy passive listeners (Belin et al 1998;Makela et al 2005;Schwartz and Tallal 1980) demonstrate high temporal precision of the left auditory cortex (AC) that enables it to process speech sounds that contain rapid formant transitions similar to linear frequency-modulated (FM) sweeps (Jamison et al 2006;Zatorre and Belin 2001). The low temporal precision of the right AC matches its inability to follow fast spectral changes that span a large frequency range within a given time window (Poeppel 2003;Zatorre et al 2002).…”

Auditory cortex of bats and primates: managing species-specific calls for social communication

“…Neurons in the FM-FM area compute inter-syllable intervals of silence and those in the DSCF area compute the direction and possibly the slope of FMs within social calls (20,95). Neurons with multipeaked frequency tuning in the AI-p area do not appear to be selective to FM direction, but are sensitive to the harmonic complexity in calls (21). Thus, combinations of temporal and spectral features within calls appear to be extracted and represented in different cortical areas (24).…”

“…We focus here in particular on two species, namely the mustached bat, Pteronotus parnellii, and the rhesus monkey, Macaca mulatta, that have been used for intense studies over the last decade (10)(11)(12)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29). New and interesting findings have also been made in the domestic cat, Felis domestica (16,(30)(31)(32)(33), the house mouse, Mus muscus (34,35), and the marmoset, Callithrix jacchus (36,37) and these contribute to our general perspective of how the mammalian cortex manages complex sounds within the neural domain so as to make the most direct and efficient use of the information present in the acoustic domain.…”

Time-varying covariance of neural activities recorded in striatum and frontal cortex as monkeys perform sequential-saccade tasks

“…Resolving this issue is at the limits of current technology, because both population-level analysis across multiple brain regions and high spatiotemporal resolution at a local level are required, together with large-scale identification of anatomically connected pairs of single neurons (6)(7)(8)(9). As a step toward analyzing corticostriatal dynamics, we identified striatal and cortical components of the oculomotor cortico-basal ganglia circuit in macaque monkeys and simultaneously recorded neural activity in these regions with multiple chronically implanted electrodes as the monkeys viewed a sequence of visual targets and made saccades to each in order to receive reward.…”