Neural mechanisms of auditory categorization: from across brain areas to within local microcircuits

Abstract

Categorization enables listeners to efficiently encode and respond to auditory stimuli. Behavioral evidence for auditory categorization has been well documented across a broad range of human and non-human animal species. Moreover, neural correlates of auditory categorization have been documented in a variety of different brain regions in the ventral auditory pathway, which is thought to underlie auditory-object processing and auditory perception. Here, we review and discuss how neural representations of auditory categories are transformed across different scales of neural organization in the ventral auditory pathway: from across different brain areas to within local microcircuits. We propose different neural transformations across different scales of neural organization in auditory categorization. Along the ascending auditory system in the ventral pathway, there is a progression in the encoding of categories from simple acoustic categories to categories for abstract information. On the other hand, in local microcircuits, different classes of neurons differentially compute categorical information.

Meaning in the avian auditory cortex: neural representation of communication calls

“…To achieve categorization of meaningful stimuli, neural responses should not only be different between categories, but also be invariant with respect to the variations of the spectro‐temporal features that encode other information, such as the identity of the vocalizer (Tsunada & Cohen, ). In our study, we were able to measure the degree to which units discriminating a particular semantic category could be invariant with respect to the variations in production of that particular vocalization type.…”

“…The use of conspecific vocalizations in primate neurophysiological studies has shown that spatial and semantic information are processed by two different streams (respectively, the dorsal and ventral streams) in the auditory cortex of monkeys (Rauschecker & Tian, ; Tian et al ., ; Romanski et al ., ; Rauschecker & Scott, ; Romanski & Averbeck, ; Bizley & Cohen, ). This extensive work has begun to reveal the categorization properties at different stages of the ventral pathway: from the categorization of spectro‐temporal features in the core region of the auditory cortex, to the categorization of abstract features such as call semantics in the superior temporal gyrus and the ventro‐lateral prefrontal cortex (Gifford et al ., 2005b; Cohen et al ., , ; Tsunada et al ., ; Tsunada & Cohen, ). However, these studies have clear limitations.…”

“…Identifying the neural basis of the discrimination of acoustic communication signals and the tolerance or invariance of responses to vocalizations that share the same meaning but differ acoustically is challenging. To study such natural categorization, one must use a model species for which the semantics of vocalizations can be easily derived from the semantics in the superior temporal gyrus and the ventro-lateral prefrontal cortex (Gifford et al, 2005b;Cohen et al, 2006Cohen et al, , 2009Tsunada et al, 2012;Tsunada & Cohen, 2014). However, these studies have clear limitations.…”

A roadmap to integrate astrocytes into Systems Neuroscience

“…Their generation is caused by fine homeostatic adjustments of membrane voltage that per se may not qualify as a computation (Stuart, Spruston, Sakmann, & Hausser, ), but complex combinations of action potentials constitute the “symbols” of the “alphabet” used by the brain to compute. Examples of variables encoded by the brain are the position, color, and shape features of a given object (Seymour, Clifford, Logothetis, & Bartels, ), sound categories (Tsunada & Cohen, ), the distance between the eyes in face recognition (Chang & Tsao, ), and the reward value of a choice during decision making (Saez et al, ). The information embedded in neural biophysical substrates can be decoded and transferred (rerouted), possibly transformed into different formats and neural substrates.…”

Source localization of event-related brain activity elicited by food and nonfood odors

“…This ability of the brain to coherently produce meaningful categories is a research topic of high interest studied in various sensory modalities, like the visual (Rosch, 2003), auditory (Miller et al, 2003;Tsunada and Cohen, 2014) or olfactory systems (Howard et al, 2009). Food-related odors are of interest not only for food-and cosmetics-related industries, but also in terms of the study of odor-related behavior, social interaction, or individual well-being.…”