Abstract
Deep brain stimulation (DBS) has significant effects on motor symptoms in Parkinson's disease (PD), but existing studies on the effect of DBS on speech are rather inconclusive. It is assumed that deficits in auditory-motor integration strongly contribute to Parkinsonian speech pathology. The aim of the present study was to assess whether subthalamic DBS can modulate these deficits. Twenty PD patients (15 male, 5 female; 62.4 ± 6.7 years) with subthalamic DBS were exposed to pitch-shifted acoustic feedback during vowel vocalization and subsequent listening. Voice and brain activity were measured ON and OFF stimulation using magnetoencephalography (MEG). Vocal responses and auditory evoked responses time locked to the onset of pitch-shifted feedback were examined. A positive correlation between vocal response magnitude and pitch variability was observed for both, stimulation ON and OFF (ON: r = 0.722, p < 0.001, OFF: r = 0.746, p < 0.001). However, no differences of vocal responses to pitch-shifted feedback between the stimulation conditions were found [t(19) = −0.245, p = 0.809, d = −0.055]. P200m amplitudes of event related fields (ERF) of left and right auditory cortex (AC) and superior temporal gyrus (STG) were significantly larger during listening [left AC P200m: F(1, 19) = 10.241, p = 0.005, f = 0.734; right STG P200m: F(1, 19) = 8.393, p = 0.009, f = 0.664]. Subthalamic DBS appears to have no substantial effect on vocal compensations, although it has been suggested that auditory-motor integration deficits contribute to higher vocal response magnitudes in pitch perturbation experiments with PD patients. Thus, DBS seems to be limited in modulating auditory-motor integration of speech in PD.
Highlights
Deep brain stimulation (DBS) is known to have strong beneficial effects on motor symptoms in Parkinson’s disease (PD) [1, 2]
The analysis focused on four regions of interest in the right and left hemisphere, previously described to relate to P200 changes in PD [13]: (i) auditory cortex, (ii) superior temporal gyrus, (iii) inferior parietal lobe, and (iv) premotor cortex
Post-hoc paired t-tests revealed a significant difference between tasks for P200m amplitudes over right and left superior temporal gyrus (STG) and auditory cortex (AC), when the stimulation was ON [left AC: t(19) = 2.66, p = 0.015, d = 0.597; right STG t(19) = 6.47, p = 0.006, d = 0.689]
Summary
Deep brain stimulation (DBS) is known to have strong beneficial effects on motor symptoms in Parkinson’s disease (PD) [1, 2]. Reduced voice volume (hypophonia) and monopitch (hypoprosodia) are typically part of speech characteristics in PD [6]. Sensorimotor deficits are thought to contribute to speech symptoms in PD like hypophonia and hypoprosodia [7]. When changing auditory feedback in loudness, PD patients compensate the amplitude of their voices substantially stronger than healthy individuals [10]. The reduced ability in modulation of pitch represents a significant component of dysprosody and may be at least partly explained by sensorimotor deficits in auditory-motor integration as well [6, 11]
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