Device-based non-invasive brain stimulation (NIBS) techniques show promise for the treatment of neurological and psychiatric disorders, although inconsistencies in protocol designs and study findings can make the field difficult to navigate. In this Review, we discuss applications of NIBS for enhancing cognitive and motor function in people with various neurological diseases that are characterized by disruption of large-scale brain networks, including neurodegenerative diseases and brain lesion disorders such as stroke and traumatic brain injury. In particular, we focus on repetitive transcranial magnetic stimulation and transcranial electrical stimulation, as these techniques have been widely used in clinical settings and randomized controlled trials. We summarize and synthesize current knowledge, and highlight gaps and shortcomings in the existing research that make it difficult to draw firm conclusions, including small sample sizes, heterogeneous patient populations and variations in stimulation protocols. We believe that a rapid evolution of NIBS techniques from state-dependent, network-informed, multifocal and subcortical paradigms to individualized electric field modelling and accelerated NIBS protocols will improve the management of neurological disorders. However, realizing this potential will require us to address crucial challenges and acquire deeper mechanistic insights, with the aim of developing adaptive, biomarker-driven protocols to optimize target engagement, dosing and timing for each patient.

• Publication type
• Journal Article MeSH
• Review MeSH

INTRODUCTION: Hypokinetic dysarthria (HD) is a common motor speech symptom of Parkinson's disease (PD) which does not respond well to PD treatments. We investigated short-term effects of transcranial direct current stimulation (tDCS) on HD in PD using acoustic analysis of speech. Based on our previous studies we focused on stimulation of the right superior temporal gyrus (STG) - an auditory feedback area. METHODS: In 14 PD patients with HD, we applied anodal, cathodal and sham tDCS to the right STG using a cross-over design. A protocol consisting of speech tasks was performed prior to and immediately after each stimulation session. Linear mixed models were used for the evaluation of the effects of each stimulation condition on the relative change of acoustic parameters. We also performed a simulation of the mean electric field induced by tDCS. RESULTS: Linear mixed model showed a statistically significant effect of the stimulation condition on the relative change of median duration of silences longer than 50 ms (p = 0.015). The relative change after the anodal stimulation (mean = -5.9) was significantly lower as compared to the relative change after the sham stimulation (mean = 12.8), p = 0.014. We also found a correlation between the mean electric field magnitude in the right STG and improvement of articulation precision after anodal tDCS (R = 0.637; p = 0.019). CONCLUSIONS: The exploratory study showed that anodal tDCS applied over the auditory feedback area may lead to shorter pauses in a speech of PD patients.

• Keywords
• Acoustic analysis, Hypokinetic dysarthria, Parkinson’s disease, Superior temporal gyrus, Transcranial electric stimulation,
• MeSH
• Dysarthria etiology   therapy   physiopathology   MeSH
• Cross-Over Studies MeSH
• Middle Aged MeSH
• Humans MeSH
• Parkinson Disease * therapy   complications   physiopathology   MeSH
• Pilot Projects MeSH
• Transcranial Direct Current Stimulation * MeSH
• Speech physiology   MeSH
• Aged MeSH
• Temporal Lobe physiopathology   MeSH
• Treatment Outcome MeSH
• Check Tag
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Hypokinetic dysarthria (HD) is a difficult-to-treat symptom affecting quality of life in patients with Parkinson's disease (PD). Levodopa may partially alleviate some symptoms of HD in PD, but the neural correlates of these effects are not fully understood. The aim of our study was to identify neural mechanisms by which levodopa affects articulation and prosody in patients with PD. Altogether 20 PD patients participated in a task fMRI study (overt sentence reading). Using a single dose of levodopa after an overnight withdrawal of dopaminergic medication, levodopa-induced BOLD signal changes within the articulatory pathway (in regions of interest; ROIs) were studied. We also correlated levodopa-induced BOLD signal changes with the changes in acoustic parameters of speech. We observed no significant changes in acoustic parameters due to acute levodopa administration. After levodopa administration as compared to the OFF dopaminergic condition, patients showed task-induced BOLD signal decreases in the left ventral thalamus (p = 0.0033). The changes in thalamic activation were associated with changes in pitch variation (R = 0.67, p = 0.006), while the changes in caudate nucleus activation were related to changes in the second formant variability which evaluates precise articulation (R = 0.70, p = 0.003). The results are in line with the notion that levodopa does not have a major impact on HD in PD, but it may induce neural changes within the basal ganglia circuitries that are related to changes in speech prosody and articulation.

• Keywords
• Hypokinetic dysarthria, Levodopa, Parkinson’s disease, Task fMRI,
• MeSH
• Antiparkinson Agents adverse effects   MeSH
• Dysarthria etiology   complications   MeSH
• Quality of Life MeSH
• Levodopa * adverse effects   MeSH
• Humans MeSH
• Magnetic Resonance Imaging methods   MeSH
• Parkinson Disease * complications   diagnostic imaging   drug therapy   MeSH
• Speech Disorders diagnostic imaging   etiology   MeSH
• Speech physiology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Antiparkinson Agents MeSH
• Levodopa * MeSH

Parkinson's disease (PD) affects the language processes, with a significant impact on the patients' daily communication. We aimed to describe specific alterations in the comprehension of syntactically complex sentences in patients with PD (PwPD) as compared to healthy controls (HC) and to identify the neural underpinnings of these deficits using a functional connectivity analysis of the striatum. A total of 20 patients PwPD and 15 HC participated in the fMRI study. We analyzed their performance of a Test of sentence comprehension (ToSC) adjusted for fMRI. A task-dependent functional connectivity analysis of the striatum was conducted using the psychophysiological interaction method (PPI). On the behavioral level, the PwPD scored significantly lower (mean ± sd: 77.3 ± 12.6) in the total ToSC score than the HC did (mean ± sd: 86.6 ± 8.0), p = 0.02, and the difference was also significant specifically for sentences with a non-canonical word order (PD-mean ± sd: 69.9 ± 14.1, HC-mean ± sd: 80.2 ± 11.5, p = 0.04). Using PPI, we found a statistically significant difference between the PwPD and the HC in connectivity from the right striatum to the supplementary motor area [SMA, (4 8 53)] for non-canonical sentences. This PPI connectivity was negatively correlated with the ToSC accuracy of non-canonical sentences in the PwPD. Our results showed disturbed sentence reading comprehension in the PwPD with altered task-dependent functional connectivity from the right striatum to the SMA, which supports the synchronization of the temporal and sequential aspects of language processing. The study revealed that subcortical-cortical networks (striatal-frontal loop) in PwPD are compromised, leading to impaired comprehension of syntactically complex sentences.

• Keywords
• Parkinson’s disease, functional connectivity, language impairment, sentence reading comprehension, striatum, task fMRI,
• Publication type
• Journal Article MeSH