Lower Beta: A Central Coordinator of Temporal Prediction in Multimodal Speech

Abstract

How the brain decomposes and integrates information in multimodal speech perception is linked to oscillatory dynamics. However, how speech takes advantage of redundancy between different sensory modalities, and how this translates into specific oscillatory patterns remains unclear. We address the role of lower beta activity (~20 Hz), generally associated with motor functions, as an amodal central coordinator that receives bottom-up delta-theta copies from specific sensory areas and generate top-down temporal predictions for auditory entrainment. Dissociating temporal prediction from entrainment may explain how and why visual input benefits speech processing rather than adding cognitive load in multimodal speech perception. On the one hand, body movements convey prosodic and syllabic features at delta and theta rates (i.e., 1–3 Hz and 4–7 Hz). On the other hand, the natural precedence of visual input before auditory onsets may prepare the brain to anticipate and facilitate the integration of auditory delta-theta copies of the prosodic-syllabic structure. Here, we identify three fundamental criteria based on recent evidence and hypotheses, which support the notion that lower motor beta frequency may play a central and generic role in temporal prediction during speech perception. First, beta activity must respond to rhythmic stimulation across modalities. Second, beta power must respond to biological motion and speech-related movements conveying temporal information in multimodal speech processing. Third, temporal prediction may recruit a communication loop between motor and primary auditory cortices (PACs) via delta-to-beta cross-frequency coupling. We discuss evidence related to each criterion and extend these concepts to a beta-motivated framework of multimodal speech processing.

Individual neurophysiological signatures of spontaneous rhythm processing

“…To address this question, we focused on subject-level neurophysiological variability and modelled single-trial beta-band evoked activity (Fig.3A) to probe whether accentuation patterns mirror binary, triple, and other forms of grouping. Neural activity in the beta-range has been associated with rhythm (Arnal, 2012; Biau & Kotz, 2018; Fujioka et al, 2012; Fujioka et al, 2015; Morillon et al, 2016) and beat processing (Fujioka et al, 2012; Fujioka et al, 2010). The current findings confirm its prevalence in time-locked responses to STD tones (Fig.2D), corroborated by activity in the theta-band.…”

“…4A) to probe whether accentuation patterns mirror binary, ternary, and other forms of grouping. Neural activity in the beta range has been associated with rhythm (Arnal, 2012;Biau & Kotz, 2018;Fujioka et al, 2015;Morillon et al, 2016) and beat processing Fujioka et al, 2010).…”

“…Neural oscillatory dynamics in the beta (β; 12-25Hz) and delta (δ; 1-4Hz) frequency range have been associated with rhythm processing, temporal prediction, and attention (Arnal, 2012; Biau & Kotz, 2018; Colling et al, 2017; Fujioka et al, 2012, 2015; Morillon et al, 2016; Nozaradan et al, 2015, 2017a) and in non-human primates (Bartolo & Merchant, 2015; Merchant et al, 2015; Merchant & Bartolo, 2018; Patel & Iversen, 2014). However, the critical question of which neurophysiological signatures indicate how exactly individuals process the beat and rhythm has so far not been answered.…”

“…Particularly, delta- (δ; 1-4Hz) and beta- (β; 12-25Hz) frequency-band neural oscillations have been associated with rhythm processing, temporal prediction, and attention in humans (Arnal, 2012; Biau & Kotz, 2018; Colling et al, 2017; Fujioka et al, 2012, 2015; Morillon et al, 2016; Nozaradan et al, 2015, 2017a) and in non-human primates (Bartolo & Merchant, 2015; Merchant et al, 2015; Merchant & Bartolo, 2018; Patel & Iversen, 2014). However, prior behavioural studies reported large within-subject variability in individual beat preferences across trials (Baath, 2015; Poudrier, 2020).…”

Auditory detection is modulated by theta phase of silent lip movements

“…Assaneo & Poeppel (2018) demonstrated recently that activity in the motor and auditory cortices couple at theta rate during syllable perception, correlating with the strength of coupling between speech signal and EEG in the auditory cortex. On the other hand, motor areas play a role in temporal analysis of rhythmic sensory stimulation (Biau & Kotz, 2018;Arnal et al, 2015;Fujioka et al, 2015;Morillon et al, 2019). Entrainment to lip movements may provide the temporal theta structure of speech signal to motor cortex, which in turn adjusts downstream auditory excitability at critical windows containing the corresponding acoustic features in a top-down fashion (in line with Park et al 2015).…”