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Abstract: Action representations can interact with object recognition processes. For example, so-called mirror neurons respond both when performing an action and when seeing or hearing such actions. Investigations of auditory object processing have largely focused on categorical discrimination, which begins within the initial 100 ms post-stimulus onset and subsequently engages distinct cortical networks. Whether action representations themselves contribute to auditory object recognition and the precise kinds of actions recruiting the auditory–visual mirror neuron system remain poorly understood. We applied electrical neuroimaging analyses to auditory evoked potentials (AEPs) in response to sounds of man-made objects that were further subdivided between sounds conveying a socio-functional context and typically cuing a responsive action by the listener (e.g. a ringing telephone) and those that are not linked to such a context and do not typically elicit responsive actions (e.g. notes on a piano). This distinction was validated psychophysically by a separate cohort of listeners. Beginning ~300 ms, responses to such context-related sounds significantly differed from context-free sounds both in the strength and topography of the electric field. This latency is >200 ms subsequent to general categorical discrimination. Additionally, such topographic differences indicate that sounds of different action sub-types engage distinct configurations of intracranial generators. Statistical analysis of source estimations identified differential activity within premotor and inferior (pre)frontal regions (Brodmann''s areas (BA) 6, BA8, and BA45/46/47) in response to sounds of actions typically cuing a responsive action. We discuss our results in terms of a spatio-temporal model of auditory object processing and the interplay between semantic and action representations. [Copyright &y& Elsevier]

Abstract: The rapid and precise processing of environmental sounds contributes to communication functions as well as both object recognition and localization. Plasticity in (accessing) the neural representations of environmental sounds is likewise essential for an adaptive organism, in particular humans, and can be indexed by repetition priming. How the brain achieves such plasticity with representations of environmental sounds is presently unresolved. Electrical neuroimaging of 64-channel auditory evoked potentials (AEPs) in humans identified the spatio-temporal brain mechanisms of repetition priming involving sounds of environmental objects. Subjects performed an ‘oddball’ target detection task, based on the semantic category of stimuli (living vs. man-made objects). Repetition priming effects were observed behaviorally as a speeding of reaction times and electrophysiologically as a suppression of the strength of responses to repeated sound presentations over the 156–215 ms post-stimulus period. These effects of plasticity were furthermore localized, using statistical analyses of a distributed linear inverse solution, to the left middle temporal gyrus and superior temporal sulcus (BA22), which have been implicated in associating sounds with their abstract representations and actions. These effects are subsequent to and occur in different brain regions from what has been previously identified as the earliest discrimination of auditory object categories. Plasticity in associative-semantic, rather than perceptual-discriminative functions, may underlie repetition priming of sounds of objects. We present a multi-stage mechanism of auditory object processing akin to what has been described for visual object processing and which also provides a framework for accessing multisensory object representations. [Copyright &y& Elsevier]