The path of voices in our brain

Sensory Feedback in Parkinson Disease Voice Production: A Systematic Review

BACKGROUND

Understanding voice and speech impairments in Parkinson's disease (PD) is essential for developing effective interventions and ensuring efficient social communication.

OBJECTIVE

This review reports findings on voice perception and production in PD with a specific focus on sensory feedback (auditory and somatosensory) of the self-voice, neural correlates of the voice, and voice quality parameters such as pitch, loudness, and emotion modulation.

METHODS

A combined bibliometric analysis and a systematic review should identify key trends and knowledge gaps in the neuroimaging (functional magnetic resonance imaging (fMRI)/EEG) literature on PD self-voice processing.

RESULTS

EEG studies focusing on pitch revealed significant differences in the P200 event-related potential, but no differences in the N100, between healthy controls and individuals with PD. fMRI studies showed reduced activation in the motor cortex and basal ganglia during speech production in PD, accompanied by increased activation in other brain regions, such as the auditory cortex, which was associated with pitch variability and loudness control. A decrease in right dorsal premotor cortex activation was linked to impaired voice control, particularly regarding loudness modulation. Additionally, the review identified missing research on the emotion modulation of the voice, despite its critical role in social communication. Altered sensory feedback plays a significant role in compensatory cortical responses during vocalization, underscoring the importance of sensory feedback in maintaining normal voice production in PD.

CONCLUSIONS

This review identified missing research on voice loudness perception and the potential impact of emotion perception deficits regarding voice modulation in persons with PD.

rTMS of the auditory association cortex improves speech intelligibility in patients with sensorineural hearing loss

OBJECTIVE

Sensorineural hearing-loss (SHL) is accompanied by changes in the entire ear-brain pathway and its connected regions. While hearing-aid (HA) partially compensates for SHL, speech perception abilities often continue to remain poor, resulting in consequences in everyday activities. Repetitive transcranial magnetic stimulation (rTMS) promotes cortical network plasticity and may enhance language comprehension in SHL patients.

METHODS

27 patients using HA and with SHL were randomly assigned to a treatment protocol consisting of five consecutive days of either real (Active group: 13 patients) or placebo rTMS (Sham group: 14 patients). The stimulation parameters were as follows: 2-second trains at 10 Hz, 4-second inter-train-interval, and 1800 pulses. Neuronavigated rTMS was applied over the left superior temporal sulcus. Audiological tests were administered before (T0), immediately after (T1), and one week following treatment completion (T2) to evaluate the speech reception threshold (SRT) and the Pure Tone Average (PTA).

RESULTS

In the context of a general improvement likely due to learning, the treatment with real rTMS induced significant reduction of the SRT and PTA at T1 and T2 versus placebo.

CONCLUSIONS

The long-lasting effects on SRT and PTA observed in the Active group indicates that rTMS administered over the auditory cortex could promote sustained neuromodulatory-induced changes in the brain, improving the perception of complex sentences and pure tones reception skills.

SIGNIFICANCE

Five days of rTMS treatment enhances overall speech intelligibility and PTA in SHL patients.

Spectrotemporal cues and attention jointly modulate fMRI network topology for sentence and melody perception

Speech and music are two fundamental modes of human communication. Lateralisation of key processes underlying their perception has been related both to the distinct sensitivity to low-level spectrotemporal acoustic features and to top-down attention. However, the interplay between bottom-up and top-down processes needs to be clarified. In the present study, we investigated the contribution of acoustics and attention to melodies or sentences to lateralisation in fMRI functional network topology. We used sung speech stimuli selectively filtered in temporal or spectral modulation domains with crossed and balanced verbal and melodic content. Perception of speech decreased with degradation of temporal information, whereas perception of melodies decreased with spectral degradation. Applying graph theoretical metrics on fMRI connectivity matrices, we found that local clustering, reflecting functional specialisation, linearly increased when spectral or temporal cues crucial for the task goal were incrementally degraded. These effects occurred in a bilateral fronto-temporo-parietal network for processing temporally degraded sentences and in right auditory regions for processing spectrally degraded melodies. In contrast, global topology remained stable across conditions. These findings suggest that lateralisation for speech and music partially depends on an interplay of acoustic cues and task goals under increased attentional demands.