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In the symphony of human communication, speech is the principal instrument. Behind every uttered word lies a complex interplay of physiological and psychological signals, each telling a unique story about the speaker’s state of mind and physical well-being. The critical data provided by these signals has become a pivotal focus in both speech research and therapy, offering useful insights into the mechanisms of verbal communication and its disorders while enhancing speech ability and overall health.

Electromyography (EMG), a technique used to measure muscle activity, plays an invaluable role in speech research by revealing the interaction of facial muscles involved in articulation. By monitoring EMG signals from muscles such as the lips, tongue, and jaw, researchers can elucidate the precise movements and coordination required for speech production, shedding light on the underlying mechanisms of speech disorders like dysarthria or apraxia.

A French study published in the 2024 edition of Science Reports used EMG to establish the role tongue reflex plays in speech posture control. The presence of a tongue reflex in maintaining tongue posture, the proper positioning of the tongue in the mouth, has been a matter of debate among speech researchers. The study team employed an unorthodox recording technique that involved attaching EMG electrodes to the base of the tongue “to record activation of the anterior genioglossus, which is responsible for the control of the anterior part of the tongue.” A robotic arm was used to rapidly stretch the tongue while researchers measured muscular reflex EMG data during the formation of various vowel sounds, which were fed to a BIOPAC EMG amplifier for signal amplification and filtering. According to the research team, the study results “represent the first physiological demonstration in humans that the tongue is driven by reflex in response to a sudden stretch.”

Electrocardiography (ECG), which measures the electrical activity of the heart, offers insights into the intricate relationship between emotion and speech. Research has shown that changes in heart rate variability (HRV) correlate with emotional arousal and cognitive load during speech tasks. By integrating ECG data with speech analysis, researchers can explore the complex connection between emotional states and linguistic expression, paving the way for emotion-aware speech synthesis systems or interventions for social communication disorders.microphone

A 2023 study by researchers at Vanderbilt University used ECG to examine the relationship between respiratory sinus arrhythmia (RSA) on the persistence of stuttering and, specifically, the role emotional regulation plays in stuttering. Researchers measured potential differences in RSA in preschool-age children with persistent stuttering, children who recovered from stuttering, and children who do not stutter. RSA, an index of parasympathetic nervous system activity, was measured during the viewing of both neutral (baseline) and emotionally stimulating video clips and during subsequent speaking tasks. To obtain RSA for each study participant, ECG data was gathered via a BIOPAC data collection and analysis system running AcqKnowledge. A low RSA baseline is often associated with difficulty regulating emotion and, according to the study’s main hypothesis, plays a role in speech disorders like stuttering. The study’s findings supported this hypothesis, with some caveats, but the overall result demonstrated that emotional regulation could provide a promising avenue for speech therapy.

Electroencephalography (EEG), a noninvasive method for recording brain activity, offers insight into neural underpinnings of speech processing and comprehension. By analyzing EEG signals, researchers can map the spatiotemporal dynamics of neural networks involved in language processing, from phonological encoding to semantic integration. EEG-based studies offer insights into the neural signatures of speech disorders like aphasia or developmental language disorders, informing targeted therapeutic interventions and neurorehabilitation strategies. EEG has presented challenges with regard to artifacts created by participant movement during speech, but recent studies have shown promise in EEG as a speech research tool.

This is just an introduction to the signals that are being used to provide researchers with a better understanding of speech and speech pathology. For additional information on how BIOPAC products are being integrated into the study of speech, see our application note on Speech Motor Control.

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