Deep Brain Stimulation Does Not Modulate Auditory-Motor Integration of Speech in Parkinson's Disease

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.

Deep brain stimulation device-specific artefacts in MEG recordings

“…The aforementioned movement artefacts relate to the ferromagnetic properties of the DBS hardware components (Bahners et al, 2020; Kandemir et al, 2020). In comparison to ABT and MDT devices, the BSC hardware induced the weakest movement-related artefacts.…”

“…The DBS parameters were kept constant across recordings, when switched on, with a stimulation amplitude of 4.0 mA, a pulse width of 60μs, and a stimulation frequency of 130 Hz. Due to the fact, that the size of the electrical stimulation artefact is about 25 times stronger when using monopolar compared to bipolar stimulation settings, we used a bipolar stimulation montage as typically applied in MEG-DBS studies (Bahners et al, 2020; Oswal et al, 2016b).…”

“…However, MEG is prone to artefacts induced by electrical stimulation and movement of ferromagnetic DBS hardware components (Bahners et al, 2020;Kandemir et al, 2020;Litvak et al, 2010;Oswal et al, 2016b).…”

“…Using magnetoencephalography (MEG), noninvasive recordings of cortical neural activity can be performed during active DBS. However, MEG is prone to artefacts induced by electrical stimulation and movement of ferromagnetic DBS hardware components (Bahners et al, 2020; Kandemir et al, 2020; Litvak et al, 2010; Oswal et al, 2016b).…”

“…Artefacts induced by the movement of ferromagnetic DBS hardware, i.e. the impulse generator (IPG), extension cables, and connectors contaminate the recording at lower frequencies (Bahners et al, 2020; Kandemir et al, 2020). These components move due to the arterial pulsation and breathing and create artefacts on channels on the side of IPG implantation (Bahners et al, 2020; Litvak et al, 2010).…”