Coupling between beta band and high frequency oscillations as a clinically useful biomarker for DBS.

Beta hypersynchrony was recently introduced into clinical practice in Parkinson's disease (PD) to identify the best stimulation contacts and for adaptive deep brain stimulation (aDBS) sensing. However, many other oscillopathies accompany the disease, and beta power sensing may not be optimal for all patients. The aim of this work was to study the potential clinical usefulness of beta power phase-amplitude coupling (PAC) with high frequency oscillations (HFOs). Subthalamic nucleus (STN) local field potentials (LFPs) from externalized DBS electrodes were recorded and analyzed in PD patients (n = 19). Beta power and HFOs were evaluated in a resting-state condition; PAC was then studied and compared with the electrode contact positions, structural connectivity, and medication state. Beta-HFO PAC (mainly in the 200-500 Hz range) was observed in all subjects. PAC was detectable more specifically in the motor part of the STN compared to beta power and HFOs. Moreover, the presence of PAC better corresponds to the stimulation setup based on the clinical effect. PAC is also sensitive to the laterality of symptoms and dopaminergic therapy, where the greater PAC cluster reflects the more affected side and medication "off" state. Coupling between beta power and HFOs is known to be a correlate of the PD "off" state. Beta-HFO PAC seems to be more sensitive than beta power itself and could be more helpful in the selection of the best clinical stimulation contact and probably also as a potential future input signal for aDBS.

Parkinson´s disease cardiovascular symptoms: A new complex functional and structural insight.

BACKGROUND: The known impairments of the cardiovascular system in Parkinson´s disease (PD) are caused by autonomic dysfunction and manifested mainly in postural hypotension, chronotropic insufficiency, and reduced heart rate variability. Other dysfunctions, mainly stress response, arrhythmia occurrence, and heart morphology changes, are still the subject of research. OBJECTIVES: To assess the heart rate and blood pressure reaction during exercise, advanced measurements of heart volumes and mass using cardiac magnetic resonance (CMR), and occurrence of arrhythmias in PD patients. METHODS: Thirty PD patients (19 men, mean age 57.5 years) without known cardiac comorbidities underwent bicycle ergometry, electrocardiogram Holter monitoring and CMR. Exercise and CMR parameters were compared with controls (24 subjects for ergometry, 20 for CMR). RESULTS: PD patients had lower baseline systolic blood pressure (SBP) (117.8 vs. 128.3 mmHg, p < 0.01), peak SBP (155.8 vs. 170.8 mmHg, p < 0.05), and lower heart rate increase (49.7 vs. 64.3 beats per minute, p < 0.01). PD patients had higher indexed left and right ventricular end-diastolic volumes (68.5 vs. 57.3, p = 0.003 and 73.5 vs. 61.0 mL/m2 , respectively) and also indexed left and right ventricular end-systolic volumes (44.1 vs. 39.0, p = 0.013 and 29.0 vs. 22.0 mL/m2 , p = 0.013, respectively). A high prevalence of atrial fibrillation (8 subjects, 26.7%) was found. CONCLUSIONS: This novel study combining functional and structural approaches showed that PD is linked with weaker blood pressure and heart rate reaction during exercise, increased myocardial mass and heart volumes compared to controls, and a high prevalence of atrial fibrillation.

The effect of deep brain stimulation in Parkinson's disease reflected in EEG microstates.

Mechanisms of deep brain stimulation (DBS) on cortical networks were explored mainly by fMRI. Advanced analysis of high-density EEG is a source of additional information and may provide clinically useful biomarkers. The presented study evaluates EEG microstates in Parkinson's disease and the effect of DBS of the subthalamic nucleus (STN). The association between revealed spatiotemporal dynamics of brain networks and changes in oscillatory activity and clinical examination were assessed. Thirty-seven patients with Parkinson's disease treated by STN-DBS underwent two sessions (OFF and ON stimulation conditions) of resting-state EEG. EEG microstates were analyzed in patient recordings and in a matched healthy control dataset. Microstate parameters were then compared across groups and were correlated with clinical and neuropsychological scores. Of the five revealed microstates, two differed between Parkinson's disease patients and healthy controls. Another microstate differed between ON and OFF stimulation conditions in the patient group and restored parameters in the ON stimulation state toward to healthy values. The mean beta power of that microstate was the highest in patients during the OFF stimulation condition and the lowest in healthy controls; sources were localized mainly in the supplementary motor area. Changes in microstate parameters correlated with UPDRS and neuropsychological scores. Disease specific alterations in the spatiotemporal dynamics of large-scale brain networks can be described by EEG microstates. The approach can reveal changes reflecting the effect of DBS on PD motor symptoms as well as changes probably related to non-motor symptoms not influenced by DBS.

Altered Spatiotemporal Dynamics of the Resting Brain in Mild Cognitive Impairment with Lewy Bodies.

BACKGROUND: Electrophysiological markers of prodromal dementia with Lewy bodies were described in the spectral domain. The sub-second temporal resolution may provide additional information. OBJECTIVE: To evaluate electroencephalography (EEG) microstates in patients with mild cognitive impairment with Lewy bodies and to assess the association between their temporal dynamics and the spectral marker. METHODS: Temporal parameters of microstates were compared between 21 patients with mild cognitive impairment with Lewy bodies and 21 healthy controls. The dominant alpha frequency was correlated with microstate parameters. RESULTS: Microstates A-D showed higher occurrence in the patient group. Microstate B additionally revealed shorter mean duration and increased time coverage; its occurrence correlated with the dominant alpha frequency in the patient group. CONCLUSIONS: Temporal dynamics of all EEG microstates were altered in medication-naïve subjects with prodromal dementia with Lewy bodies. Longitudinal follow-up may reveal how EEG microstates reflect progression of brain function deficits and effects of treatment manipulations. © 2021 International Parkinson and Movement Disorder Society.

Cortical network organization reflects clinical response to subthalamic nucleus deep brain stimulation in Parkinson's disease.

The degree of response to subthalamic nucleus deep brain stimulation (STN-DBS) is individual and hardly predictable. We hypothesized that DBS-related changes in cortical network organization are related to the clinical effect. Network analysis based on graph theory was used to evaluate the high-density electroencephalography (HDEEG) recorded during a visual three-stimuli paradigm in 32 Parkinson's disease (PD) patients treated by STN-DBS in stimulation "off" and "on" states. Preprocessed scalp data were reconstructed into the source space and correlated to the behavioral parameters. In the majority of patients (n = 26), STN-DBS did not lead to changes in global network organization in large-scale brain networks. In a subgroup of suboptimal responders (n = 6), identified according to reaction times (RT) and clinical parameters (lower Unified Parkinson's Disease Rating Scale [UPDRS] score improvement after DBS and worse performance in memory tests), decreased global connectivity in the 1-8 Hz frequency range and regional node strength in frontal areas were detected. The important role of the supplementary motor area for the optimal DBS response was demonstrated by the increased node strength and eigenvector centrality in good responders. This response was missing in the suboptimal responders. Cortical topologic architecture is modified by the response to STN-DBS leading to a dysfunction of the large-scale networks in suboptimal responders.

Electrophysiological biomarkers for deep brain stimulation outcomes in movement disorders: state of the art and future challenges.

Several neurological diseases are accompanied by rhythmic oscillatory dysfunctions in various frequency ranges and disturbed cross-frequency relationships on regional, interregional, and whole brain levels. Knowledge of these disease-specific oscillopathies is important mainly in the context of deep brain stimulation (DBS) therapy. Electrophysiological biomarkers have been used as input signals for adaptive DBS (aDBS) as well as preoperative outcome predictors. As movement disorders, particularly Parkinson's disease (PD), are among the most frequent DBS indications, the current research of DBS is the most advanced in the movement disorders field. We reviewed the literature published mainly between 2010 and 2020 to identify the most important findings concerning the current evolution of electrophysiological biomarkers in DBS and to address future challenges for prospective research.

Resting-State Phase-Amplitude Coupling Between the Human Subthalamic Nucleus and Cortical Activity: A Simultaneous Intracranial and Scalp EEG Study.

It has been suggested that slow oscillations in the subthalamic nucleus (STN) reflect top-down inputs from the medial prefrontal cortex, thus implementing behavior control. It is unclear, however, whether the STN oscillations are related to cortical activity in a bottom-up manner. To assess resting-state subcortico-cortical interactions, we recorded simultaneous scalp electroencephalographic activity and local field potentials in the STN (LFP-STN) in 11 patients with Parkinson's disease implanted with deep brain stimulation electrodes in the on-medication state during rest. We assessed the cross-structural phase-amplitude coupling (PAC) between the STN and cortical activity within a wide frequency range of 1 to 100 Hz. The PAC was dominant between the δ/θ STN phase and ß/γ cortical amplitude in most investigated scalp regions and between the δ cortical phase and θ/α STN amplitude in the frontal and temporal regions. The cross-frequency linkage between the slow oscillations of the LFP-STN activity and the amplitude of the scalp-recorded cortical activity at rest was demonstrated, and similar involvement of the left and right STNs in the coupling was observed. Our results suggest that the STN plays a role in both bottom-up and top-down processes within the subcortico-cortical circuitries of the human brain during the resting state. A relative left-right symmetry in the STN-cortex functional linkage was suggested. Practical treatment studies would be necessary to assess whether unilateral stimulation of the STN might be sufficient for treatment of Parkinson's disease.

Successful asymmetrical deep brain stimulation using right subthalamic and left pallidal electrodes in a patient with Parkinson's disease.

PURPOSE: Despite the best efforts of neurologists, the results of pharmacotherapy in the late stages of Parkinson's disease are often disappointing and accompanied by debilitating side effects. Under these circumstances, deep brain stimulation is a viable treatment option. The aim of the meticulous pre-surgical planning is not only precise electrode implantation, but also the avoidance of intraoperative vascular conflicts potentially causing intracerebral bleeding. MATERIAL AND METHODS: In this report, we present a patient with early-onset Parkinson's disease whose cerebral vascular anatomy precluded standard bilateral subthalamic nucleus electrode implantation. Initially, right subthalamic stimulation alone provided a very mild clinical benefit that was not reflected in the patient's quality of life. In this patient, an unusual configuration of intracerebral electrodes with right subthalamic and left pallidal stimulation electrodes was applied 15 months after the initial subthalamic electrode implantation. RESULTS: The procedure has had a highly beneficial long-term effect without any significant complications. The greatest improvement was noted using the setting 1.8 V, 130 Hz, 90 µs at the right side (STN) and 3.7 V, 130 Hz, 120 µs at the left side (GPi). This allowed the patient to return to his daily life activities. CONCLUSIONS: The reported case provides a new perspective of treatment possibilities in complex functional neurosurgical cases requiring exceptional individualisation of the treatment approach.

Suboptimal response to STN-DBS in Parkinson's disease can be identified via reaction times in a motor cognitive paradigm.

Although deep brain stimulation of the subthalamic nucleus (STN-DBS) in Parkinson's disease (PD) is generally a successful therapy, adverse events and insufficient clinical effect can complicate the treatment in some patients. We studied clinical parameters and cortical oscillations related to STN-DBS to identify patients with suboptimal responses. High-density EEG was recorded during a visual oddball three-stimuli paradigm in DBS "off" and "on" conditions in 32 PD patients with STN-DBS. Pre-processed data were reconstructed into the source space and the time-frequency analysis was evaluated. We identified a subgroup of six patients with longer reaction times (RT) during the DBS "on" state than in the DBS "off" state after target stimuli. These subjects had lower motor responsiveness to DBS and decreased memory test results compared to the other subjects. Moreover, the alpha and beta power decrease (event-related desynchronizations, ERD), known as an activation correlate linked to motor and cognitive processing, was also reduced in the DBS "on" condition in these patients. A subgroup of PD patients with a suboptimal response to STN-DBS was identified. Evaluation of RT could potentially serve as a biomarker for responsiveness to STN-DBS.

Impairment of brain functions in Parkinson's disease reflected by alterations in neural connectivity in EEG studies: A viewpoint.

Clinical symptoms of Parkinson's disease (PD) are accompanied by pathological phenomena detected locally in the basal ganglia (BG) as changes in local field potentials (LFPs) and also in cortical regions by electroencephalography (EEG). The literature published mainly between 2000 and 2017 was reviewed with an emphasis on approaches emerging after 2000, in particular on oscillatory dynamics, connectivity studies, and deep brain stimulation. Eighty-five articles were reviewed. The main observations were a general slowing of background activity, excessive synchronization of beta activity, and disturbed movement-related gamma oscillations in the BG and in the cortico-subcortical and cortico-cortical motor loops, suppressible by dopaminergic medication as well as by high-frequency deep brain stimulation (DBS). Non-motor symptoms are related mainly to changes in the alpha frequency range. EEG parameters can be useful in defining the risk of dementia in PD. Further progress was reported recently using advanced analytical technologies and high-performance computing (graph theory). Detailed knowledge of LFPs in PD enabled progress particularly in DBS therapy, which requires optimizing the clinical effect and minimizing adverse side effects. The neurocognitive networks and their dysfunction in PD and DBS therapy are promising targets for future research.

Learning Curve in Anatomo-Electrophysiological Correlations in Subthalamic Nucleus Stimulation.

AIM: Advances in neuroradiological planning techniques in deep brain stimulation have put the need for intraoperative electrophysiological monitoring into doubt. Moreover intraoperative monitoring prolongs surgical time and there is potential association between the use of microelectrodes and increased incidence of hemorrhagic complications. The aim of this study was to analyze the correlation between the anatomically planned trajectory and the final subthalamic electrode placement after electrophysiological monitoring in patients with Parkinson"s disease and its change with the increasing experience of the surgical team. MATERIAL AND METHODS: The trajectories of right (first implanted) and left electrodes were compared in the first 50 patients operated on (Group 1) and the next 50 patients (Group 2). RESULTS: In Group 1, 52% of central trajectories were on the right and 38% on the left; in Group 2, the percentage of central trajectories was 76% on the right and 78% on the left; the difference was statistically significant (p=0.021 and 0.001). The difference in the percentage of posterior trajectories reflecting brain shift between the right and left sides was statistically insignificant in Groups 1 (26% and 28%, p=0.999) and 2 (18% and 12%, p=0.549). The percentage of bilateral central electrodes was 14% and 62% in Groups 1 and 2, respectively. CONCLUSION: The correlation between anatomically planned trajectory and final electrode placement markedly improves with the number of patients. However the significant percentage of patients with final electrode trajectory differing from anatomically planned target supports the use of intraoperative monitoring.

Oscillatory reactivity to effortful cognitive processing in the subthalamic nucleus and internal pallidum: a depth electrode EEG study.

This study investigates how complex motor-cognitive activities are processed in the subthalamic nucleus (STN) and internal globus pallidum (GPi), as adverse neuropsychiatric effects may accompany deep brain stimulation (DBS), mainly in Parkinson's disease (PD) and STN-DBS. Dystonia patients with GPi-DBS electrodes (n = 5) and PD subjects (n = 5) with STN-DBS electrodes performed two tasks: (1) copying letters; and (2) writing any letter other than that appearing on the monitor. The cognitive load of the second task was greater than that of the first. Intracranial local field potentials (LFPs) were analysed. A beta power decrease was the main correlate of the enhanced cognitive load during the second task in both structures, with a lateralization to the left side, mainly in the GPi. A gamma power increase linked with the increased cognitive activity was observed only in the STN. Differences were also observed in the theta and alpha bandpasses. Beta ERD reactivity seems to be essential during the processing of complex motor-cognitive tasks, increases with enhanced cognitive effort, and was observed in both the STN and GPi. Oscillatory reactivity to effortful cognitive processing in other frequency bands was less consistent, with differences between the studied nuclei. Lateralization of activity related to cognitive factors was observed mainly in the GPi.

The Role of Anterior Nuclei of the Thalamus: A Subcortical Gate in Memory Processing: An Intracerebral Recording Study.

OBJECTIVE: To study the involvement of the anterior nuclei of the thalamus (ANT) as compared to the involvement of the hippocampus in the processes of encoding and recognition during visual and verbal memory tasks. METHODS: We studied intracerebral recordings in patients with pharmacoresistent epilepsy who underwent deep brain stimulation (DBS) of the ANT with depth electrodes implanted bilaterally in the ANT and compared the results with epilepsy surgery candidates with depth electrodes implanted bilaterally in the hippocampus. We recorded the event-related potentials (ERPs) elicited by the visual and verbal memory encoding and recognition tasks. RESULTS: P300-like potentials were recorded in the hippocampus by visual and verbal memory encoding and recognition tasks and in the ANT by the visual encoding and visual and verbal recognition tasks. No significant ERPs were recorded during the verbal encoding task in the ANT. In the visual and verbal recognition tasks, the P300-like potentials in the ANT preceded the P300-like potentials in the hippocampus. CONCLUSIONS: The ANT is a structure in the memory pathway that processes memory information before the hippocampus. We suggest that the ANT has a specific role in memory processes, especially memory recognition, and that memory disturbance should be considered in patients with ANT-DBS and in patients with ANT lesions. ANT is well positioned to serve as a subcortical gate for memory processing in cortical structures.

Complex motor-cognitive factors processed in the anterior nucleus of the thalamus: an intracerebral recording study.

Cognitive adverse effects were reported after the deep brain stimulation (DBS) of the anterior nucleus of the thalamus (AN) in epilepsy. As the AN may have an influence on widespread neocortical networks, we hypothesized that the AN, in addition to its participation in memory processing, may also participate in cognitive activities linked with the frontal neocortical structures. The aim of this study was to investigate whether the AN might participate in complex motor-cognitive activities. Three pharmacoresistant epilepsy patients implanted with AN-DBS electrodes performed two tasks involving the writing of single letters: (1) copying letters from a monitor; and (2) writing of any letter other than that appearing on the monitor. The cognitive load of the second task was increased. The task-related oscillatory changes and evoked potentials were assessed. Local event-related alpha and beta desynchronization were more expressed during the second task while the lower gamma synchronization decreased. The local field event-related potentials were elicited by the two tasks without any specific differences. The AN participates in cognitive networks processing complex motor-cognitive tasks. Attention should be paid to executive functions in subjects undergoing AN-DBS.

The modulatory role of subthalamic nucleus in cognitive functions - a viewpoint.

The modifications of electrophysiological activities of subthalamic nucleus (STN) by non-motor tasks, i.e. movement observation, emotional stimuli and impulse control, were reported repeatedly. Despite being a small structure, STN is apparently involved in a variety of functions. Based on our own electrophysiological recordings and results of other groups we believe that it acts as an indirect modulator which may be involved in tuning the functional systems. STN may modulate specific cognitive activities via contextual modulation of certain cortical areas. Our findings support the hypothesis of a cortical-STN bypass (via hyperdirect pathway) of "classical" basal ganglia-thalamocortical circuitry, at least during the processing of certain cognitive functions. The modulation of cognitive functions appears to be selective, probably determined by the involvement of cortical neuronal populations interconnected with STN. There could also exist a spatial overlap of areas within STN regulating various functions. That may explain the fact that some non-motor symptoms of Parkinson's disease may improve after deep brain stimulation of STN. These improvements are likely caused by combination of direct stimulation effect on non-motor function and overall beneficial effect of motor improvement on quality of life.

Subthalamic nucleus involvement in executive functions with increased cognitive load: a subthalamic nucleus and anterior cingulate cortex depth recording study.

We studied the appearance of broadband oscillatory changes (ranging 2-45 Hz) induced by a cognitive task with two levels of complexity. The event-related de/synchronizations (ERD/S) in the subthalamic nucleus (STN) and in the anterior cingulate cortex (ACC) were evaluated in an executive function test. Four epilepsy surgery candidates with intracerebral electrodes implanted in the ACC and three Parkinson's disease patients with externalized deep brain stimulation electrodes implanted in the STN participated in the study. A Flanker test (FT) with visual stimuli (arrows) was performed. Subjects reacted to four types of stimuli presented on the monitor by pushing the right or left button: congruent arrows to the right or left side (simple task) and incongruent arrows to the right or left side (more difficult complex task). We explored the activation of STN and the activation of the ACC while processing the FT. Both conditions, i.e. congruent and incongruent, induced oscillatory changes in the ACC and also STN with significantly higher activation during incongruent trial. At variance with the ACC, in the STN not only the ERD beta but also the ERD alpha activity was significantly more activated by the incongruent condition. In line with our earlier studies, the STN appears to be involved in activities linked with increased cognitive load. The specificity and complexity of task-related activation of the STN might indicate the involvement of the STN in processes controlling human behaviour, e.g. in the selection and inhibition of competing alternatives.

DBS amplitude setting can improve aspects of quality of life in patients with Parkinson's disease.

The DBS STN is a non-curative treatment; its effect on the patient's quality of life (QoL) determines the therapeutic success of this procedure. We aimed to assess whether stimulation parameters setting may influence also some of the non-motor aspects of QoL. The QoL was assessed by PDQ-39 questionnaire. The questionnaire was administered to patients before and after the DBS surgery. A sham change of stimulation amplitude was performed before the actual increase. After the further amplitude increase in subgroup of patients (mean increase of amplitude of 0.35 V), there was a statistically significant additional improvement of total PDQ-39 score by another 22.9 %. In this group the emotions, stigma and communication subscales improved after the stimulation increase, without further change of UPDRS III. We were able to demonstrate that the increase of stimulation parameters (amplitude) has a potential to improve some non-motor functions and aspects of QoL and thus has an additional effect on quality of life in certain subset of PD patients. The meticulous observation of QoL should be a routine part of assessments before and after the DBS STN surgery, and can even aid during the parameter setting.

The role of brain shift, patient age, and Parkinson's disease duration in the difference between anatomical and electrophysiological targets for subthalamic stimulation.

INTRODUCTION: Although microrecording is common in subthalamic stimulation, microelectrode monitoring prolongs surgical time and may increase the risk of haemorrhagic complications. The main reason for electrophysiological mapping is the discrepancy between the calculated anatomical and final electrophysiological targets. The aim of this paper is to describe the relationship between anatomical and electrophysiological targets defined as the best electrophysiological recordings from multiple parallel electrode tracts, explaining the target discrepancy with attention paid to the role of brain shift and patient- and disease-related factors. MATERIALS AND METHODS: Subthalamic electrodes were stereotactically implanted in 58 patients using microrecording by means of parallel electrodes at defined distances. The relationship between the final electrode placement to its anatomical trajectory and the relationship between the definitive electrodes implanted on the right and left sides were analysed, as was the influence of patient age, Parkinson's disease duration, and late motor complications duration. RESULTS: Final electrode placement matched the anatomical trajectory in 53.4% of patients on the right side and 43.1% of patients on the left side. Electrode positions were symmetrical in 38.3% of patients. The analysis of left and right electrode positions does not prove a statistically significant prevalence of lateral and posterior final electrode trajectories as could be expected from lateral and posterior movements of the brain caused by brain shift, although there was some tendency for a larger percentage of lateral electrodes on the left side. Age, Parkinson's disease duration, and L-DOPA effect duration were not confirmed as responsible factors. CONCLUSIONS: The difference between anatomical trajectory and final electrode placement supports the use of functional microelectrode monitoring in subthalamic deep brain stimulation. Brain shift is not the only causative factor of the difference. The possible roles of age, Parkinson's disease duration, and late motor complications duration were also not confirmed by study results.

Involvement of the subthalamic nucleus in cognitive functions -- a concept.

The involvement of the subthalamic nucleus (STN) in a broad spectrum of various non-motor functions - attention, executive functions, verbal learning and memory, verbal abstract reasoning, conflict resolution, and emotions - has been reported. The STN has an anatomically central position within the basal ganglia(BG)-thalamocortical motor, associative and limbic circuits. The STN might interfere with non-motor functions as an indirect modulator rather than a regulator. Mechanisms modulating the motor and non-motor functions might differ. The STN has been implicated in control of non-motor behaviors via the tuning of specific circuits depending on the task. The STN might modulate selected non-motor functions via contextual modulation of certain cortical areas. Based on intracerebral recordings, we proposed that the non-motor activities in the BG are organized in some way other than the well-known organization of the cortico-BG-thalamocortical circuits. These findings support the hypothesis of a cortico-STN bypass of the BG-thalamocortical circuitry under some circumstances. The exact role of the STN and the BG in non-motor functions remains an important and interesting challenge for future research.

Cognitive event-related potentials and oscillations in the subthalamic nucleus.

BACKGROUND: The cognitive role of the subthalamic nucleus (STN) remains largely unknown. METHODS/RESULTS: A modified protocol with a dual task elicited local field event-related potentials (ERPs) within the STN. No generators of ERPs were elicited by the standard oddball protocol in the STN (at variance with recordings from the putamen, caudate and pallidum). Repetitive transcranial magnetic stimulation (rTMS) over the right inferior frontal cortex caused a shortening of latencies of ERPs in standard and dual protocols. No changes were observable after the rTMS over the dorsolateral prefrontal cortex and sham stimulation. In the STN, only the tasks with an increased demand on executive functions produced the alpha-/beta-event-related desynchronization/synchronization in visuomotor tasks with single letters writing. CONCLUSION: Our results indicate a specific, task-related involvement of the STN in the cognitive activities. Cognitive processing in the STN is possibly processed via hyperdirect cortico-STN pathway. Certain effects of deep brain stimulation surgery on cognitive performance could be explained by a direct effect on 'cognitive' parts of the STN.