The Lateralization of Speech-Brain Coupling Is Differentially Modulated by Intrinsic Auditory and Top-Down Mechanisms

Abstract

The lateralization of neuronal processing underpinning hearing, speech, language, and music is widely studied, vigorously debated, and still not understood in a satisfactory manner. One set of hypotheses focuses on the temporal structure of perceptual experience and links auditory cortex asymmetries to underlying differences in neural populations with differential temporal sensitivity (e.g., ideas advanced by Zatorre et al. (2002) and Poeppel (2003) . The Asymmetric Sampling in Time theory (AST) ( Poeppel, 2003 ), builds on cytoarchitectonic differences between auditory cortices and predicts that modulation frequencies within the range of, roughly, the syllable rate, are more accurately tracked by the right hemisphere. To date, this conjecture is reasonably well supported, since – while there is some heterogeneity in the reported findings – the predicted asymmetrical entrainment has been observed in various experimental protocols. Here, we show that under specific processing demands, the rightward dominance disappears. We propose an enriched and modified version of the asymmetric sampling hypothesis in the context of speech. Recent work ( Rimmele et al., 2018b ) proposes two different mechanisms to underlie the auditory tracking of the speech envelope: one derived from the intrinsic oscillatory properties of auditory regions; the other induced by top-down signals coming from other non-auditory regions of the brain. We propose that under non-speech listening conditions, the intrinsic auditory mechanism dominates and thus, in line with AST, entrainment is rightward lateralized, as is widely observed. However, (i) depending on individual brain structural/functional differences, and/or (ii) in the context of specific speech listening conditions, the relative weight of the top-down mechanism can increase. In this scenario, the typically observed auditory sampling asymmetry (and its rightward dominance) diminishes or vanishes.

Post-training Load-Related Changes of Auditory Working Memory – An EEG Study

“…These group-specific differences in beta-band power were right-lateralized, thus being in accordance with literature on voice-selective regions (Belin et al, 2000, and more general, in accordance with literature on hemispheric lateralization of the auditory cortex. There is a higher selectivity of the right auditory cortex for the processing of slow spectral aspects of auditory input, such as speech prosody or pitch variations, over fast temporal aspects, along with a complementary specialization of the left auditory cortex (for review : Poeppel, 2001;Zatorre et al, 2002;Assaneo et al, 2019). The right lateralization of the observed effect corresponds to this functional differentiation, as in our study voices, i.e., sounds' spectral resolution, had to be maintained and discriminated.…”

Acoustically driven cortical delta oscillations underpin perceptual chunking

“…Periodicities in these brain areas were present even for acoustic chunk rates at the edge of the delta range, albeit considerably weaker. Note that the observed lack of hemispheric lateralization in auditory cortex in our study is in line with previous reports on bilateral theta/delta activity elicited to more complex speech stimuli (Assaneo et al, 2019;Flinker et al, 2019). Interestingly, in contrast to the ventral stream, in the dorsal stream speech-motor integration areas more divergence between the left and right hemisphere was observed, whereas the left hemisphere more tightly followed the chunking rate compared to the right.…”

Asymmetry of Auditory-Motor Speech Processing is Determined by Language Experience

“…Our findings lead us to suggest that the asymmetry in the auditory system during speech perception is modulated by the motor system. Recently, a modified version of the asymmetric-sampling-in-time hypothesis was proposed, in which auditory processing is thought to be modulated by two different types of mechanism ( Rimmele et al, 2018 ; Assaneo et al, 2019 ): (1) intrinsic auditory mechanisms, which support auditory processing in non-speech listening conditions in line with acoustic hypotheses; and (2) top-down mechanisms, which might affect the lateralization of auditory processing, and the relative weight of which can increase depending on individual brain differences or specific speech-listening conditions or both. During continuous speech perception, the speech-coupled oscillations in auditory cortex are significantly modulated by top-down signals from the frontal and motor cortex ( Park et al, 2015 ).…”