Negative Blood Oxygen Level Dependent Signals During Speech Comprehension

Abstract

Speech comprehension studies have generally focused on the isolation and function of regions with positive blood oxygen level dependent (BOLD) signals with respect to a resting baseline. Although regions with negative BOLD signals in comparison to a resting baseline have been reported in language-related tasks, their relationship to regions of positive signals is not fully appreciated. Based on the emerging notion that the negative signals may represent an active function in language tasks, the authors test the hypothesis that negative BOLD signals during receptive language are more associated with comprehension than content-free versions of the same stimuli. Regions associated with comprehension of speech were isolated by comparing responses to passive listening to natural speech to two incomprehensible versions of the same speech: one that was digitally time reversed and one that was muffled by removal of high frequencies. The signal polarity was determined by comparing the BOLD signal during each speech condition to the BOLD signal during a resting baseline. As expected, stimulation-induced positive signals relative to resting baseline were observed in the canonical language areas with varying signal amplitudes for each condition. Negative BOLD responses relative to resting baseline were observed primarily in frontoparietal regions and were specific to the natural speech condition. However, the BOLD signal remained indistinguishable from baseline for the unintelligible speech conditions. Variations in connectivity between brain regions with positive and negative signals were also specifically related to the comprehension of natural speech. These observations of anticorrelated signals related to speech comprehension are consistent with emerging models of cooperative roles represented by BOLD signals of opposite polarity.

The “two-brain” approach reveals the active role of task-deactivated default mode network in speech comprehension

“…In this study, we investigated the functional properties of DMN during natural verbal communication and examined both within-brain response profiles and between-brain interactions. Replicating previous findings (Wirth et al, 2011; Rodriguez Moreno et al, 2014; Humphreys et al, 2015; Jackson et al, 2019), most DMN areas in the listener’s brain exhibited reduced activities during speech comprehension relative to the low-level baseline, and the network dynamics of DMN were anticorrelated with the task-positive pLN. Dynamic Causal Modeling showed the pLN had inhibitory influence on the DMN, whereas the DMN had excitatory influence on the pLN.…”

“…Despite the theoretical expectation, direct and convincing evidence for an active role of the DMN in auditory language comprehension is still lacking. Instead, as auditory language processing requires the participants to keep tracking external audio streams, the DMN has been repeatedly found to be deactivated relative to low-level baselines (Wilson et al, 2007; Szaflarski et al, 2012; Rodriguez Moreno et al, 2014; Horowitz-Kraus et al, 2017; Cuevas et al, 2019), and anticorrelated with networks dedicated to externally-oriented processes (including the pLN and attention network) (Fox et al, 2005; Uddin et al, 2009; Smith et al, 2012). The task-induced deactivation and network anticorrelation seem to imply that the DMN was “suppressed” to support externally-oriented cognitive activities (Anticevic et al, 2012; Gauffin et al, 2013; Zhou et al, 2016).…”

Brain Cortex Activity in Children With Anterior Open Bite: A Pilot Study

“…It is well established that the central sulcus area, in which the ventral half of the sensorimotor cortex is located, is related to the tongue’s functions of deglutition, movement, and coordinated movements of phonation ( Breshears et al, 2015 ). These processes are influenced by cognitive performance ( Burgaleta et al, 2014 ) and oxygen saturation ( Rodriguez Moreno et al, 2015 ).…”