Selectivity for Animal Vocalizations in the Human Auditory Cortex

Abstract

We aimed at testing the cortical representation of complex natural sounds within auditory cortex using human functional magnetic resonance imaging (fMRI). To this end, we employed 2 different paradigms in the same subjects: a block-design experiment was to provide a localization of areas involved in the processing of animal vocalizations, whereas an event-related fMRI adaptation experiment was to characterize the representation of animal vocalizations in the auditory cortex. During the first experiment, we presented subjects with recognizable and degraded animal vocalizations. We observed significantly stronger fMRI responses for animal vocalizations compared with the degraded stimuli along the bilateral superior temporal gyrus (STG). In the second experiment, we employed an event-related fMRI adaptation paradigm in which pairs of auditory stimuli were presented in 4 different conditions: 1) 2 identical animal vocalizations, 2) 2 different animal vocalizations, 3) an animal vocalization and its degraded control, and 4) an animal vocalization and a degraded control of a different sound. We observed significant fMRI adaptation effects within the left STG. Our data thus suggest that complex sounds such as animal vocalizations are represented in putatively nonprimary auditory cortex in the left STG. Their representation is probably based on their spectrotemporal dynamics rather than simple spectral features.

Familiarity affects environmental sound processing outside the focus of attention: An event-related potential study

“…the supratemporal N1 generator), which should cause frontocentrally maximal effects. This is in line with Altmann et al (2007) who proposed a processing of animal vocalizations in putatively nonprimary auditory areas of the superior temporal gyrus (cf. also Lewis et al, 2004).…”

“…also Lewis et al, 2004). Whereas Altmann et al (2007) as well as Lewis et al (2004) further reported a left-hemispheric predominance in the processing of animal sounds or familiar environmental sounds in fMRI data, no lateralization effects were observed in the present study. The posterior distribution of the N1 familiarity effect could reflect the activation of additional cortical generator structures for a familiar environmental sound (for example, the anterior-temporal cortex that has been proposed to be critical for the activation of semantic knowledge representations; cf.…”

“…The unfamiliar stimulus was synthesized from the familiar stimulus using a multi-stage stimulus manipulation algorithm [data processing via Matlab 7.1 (MathWorks GmbH, 2005); for similar algorithms of stimulus manipulation cf. Lenz et al, 2007;Altmann et al, 2007]. After extracting the frequency spectrum of the familiar sound via a Fast-Fourier-Transformation (FFT), the obtained phase information, characterizing the temporal relationships between the frequencies contained in the sound, was randomly jumbled between the frequencies.…”

The animal nature of spontaneous human laughter

“…Participants were then asked to identify these vocalizations as being either from a human or from a nonhuman animal. No previous research to our knowledge has examined judgments of whether stimuli were produced by human or nonhuman animals, but neuroimaging work has examined cerebral responses to nonhuman animal vocalizations relative to a variety of other stimuli including human voices (e.g., Lewis, Brefczynski, Phinney, Janik, & DeYoe, 2005;Altmann, Doehrmann, & Kaiser, 2007;Belin et al, 2008). De Lucia, Clarke, andMurray (2010) found that human and nonhuman animal vocalizations elicited early responses in statistically indistinguishable brain networks.…”

Environmental sound research as it stands today

“…On the other hand highly periodic sounds with inharmonic spectra generally reflect machinery [32] and water sounds are characterized by slowly modulated broadband noises, often saturated with transient components [27]. There is neurophysiological evidence that sounds generated by tools are processed by distinct cortical pathways from animal vocalizations, which excited similar pathways to human speech [33,34], implying this important distinction in source properties is preserved well into the cortex.…”