Intracortical Responses in Human and Monkey Primary Auditory Cortex Support a Temporal Processing Mechanism for Encoding of the Voice Onset Time Phonetic Parameter

Abstract

This study tests the hypothesis that temporal response patterns in primary auditory cortex are potentially relevant for voice onset time (VOT) encoding in two related experiments. The first experiment investigates whether temporal responses reflecting VOT are modulated in a way that can account for boundary shifts that occur with changes in first formant (F1) frequency, and by extension, consonant place of articulation. Evoked potentials recorded from Heschl's gyrus in a patient undergoing epilepsy surgery evaluation are examined. Representation of VOT varies in a manner that reflects the spectral composition of the syllables and the underlying tonotopic organization. Activity patterns averaged across extended regions of Heschl's gyrus parallel changes in the subject's perceptual boundaries. The second experiment investigates whether the physiological boundary for detecting the sequence of two acoustic elements parallels the psychoacoustic result of approximately 20 ms. Population responses evoked by two-tone complexes with variable tone onset times (TOTs) in primary auditory cortex of the monkey are examined. Onset responses evoked by both the first and second tones are detected at a TOT separation as short as 20 ms. Overall, parallels between perceptual and physiological results support the relevance of a population-based temporal processing mechanism for VOT encoding.

Neural and Behavioral Discrimination of Sound Duration by Cats

“…In humans, identifying a separation of two acoustic events requires stimulus onset asynchrony of ϳ20 ms (Pisoni, 1977;Pastore, 1983;Stevens and Weaver, 2005). Auditory cortical neurons were also found to have a similar limitation in representing two separated sounds (Eggermont, 1995;Steinschneider et al, 2003Steinschneider et al, , 2005. Moreover, the spike timing of A1 neurons has been proved to convey sufficient information to discriminate slow changes (Ͻ50 Hz) in the envelopes of complex sounds, if the spike information is read at temporal resolutions of 20 ms or better (Walker et al, 2008).…”

Neurophysiological evidence for context-dependent encoding of sensory input in human auditory cortex

“…The context, or environment surrounding a probe tone, modulates the amplitude of both single-and multi-unit neural activity. Contextual factors such as temporal sound density (Blake and Merzinich, 2002;Brosch and Schreiner, 2000), temporal onset time (Steinschneider et al, 2005), interaural phase disparity (Malone et al, 2002), or forward (Brosch and Schreiner, 1997;Fishman et al, 2004) and backward (Brosch et al, 1998) masking, arising from properties of adjacent sounds, have been shown to influence the way that auditory cortical neurons respond to the probe tone. What is unique in the current study is that the cortically generated response to the probe tone was modified by sounds not in its immediate proximity.…”

Signal quality of simultaneously recorded invasive and non-invasive EEG

“…Next to their clinical importance, invasive recordings offer unique opportunities for electrophysiological investigations of human brain function with high spatial and temporal accuracy. An increasing number of studies have recently investigated motor Brovelli et al, 2005;Crone et al, 1998;Rektor, 2000;Szurhaj et al, 2006), sensory (Crone et al, 2001a;Edwards et al, 2005;Steinschneider et al, 2005), and cognitive (Canolty et al, 2006;Crone et al, 2001b;Ray et al, 2008;Sederberg et al, 2007;Sinai et al, 2005) systems using invasive EEG data. Furthermore, ECoG recordings have been proposed as a technology for brain-machine interfaces (BMIs) for neuronal motor prostheses in paralyzed patients (Ball et al, 2009;Leuthardt et al, 2004;Mehring et al, 2004;Pistohl et al, 2008;Schalk et al, 2007).…”