EEG functional connectivity after perinatal stroke.

Impaired cognitive functioning after perinatal stroke has been associated with long-term functional brain network changes. We explored brain functional connectivity using a 64-channel resting-state electroencephalogram in 12 participants, aged 5-14 years with a history of unilateral perinatal arterial ischemic or haemorrhagic stroke. A control group of 16 neurologically healthy subjects was also included-each test subject was compared with multiple control subjects, matched by sex and age. Functional connectomes from the alpha frequency band were calculated for each subject and the differences in network graph metrics between the 2 groups were analyzed. Our results suggest that the functional brain networks of children with perinatal stroke show evidence of disruption even years after the insult and that the scale of changes appears to be influenced by the lesion volume. The networks remain more segregated and show a higher synchronization at both whole-brain and intrahemispheric level. Total interhemispheric strength was higher in children with perinatal stroke compared with healthy controls.

Bee Venom Does Not Reduce the Risk for Parkinson's Disease: Epidemiological Study among Beekeepers.

BACKGROUND: Based on the promising results from preclinical studies, bee venom has been investigated as a neuroprotective agent in Parkinson's disease. OBJECTIVE: To assess if longstanding exposure to bee venom is associated with decreased risk for Parkinson's disease among beekeepers. METHODS: Questionnaire gathering information about diagnosis of Parkinson's disease and exposure to bee stings was posted to 6500 members of Slovenian beekeepers' organisation. RESULTS: We received 1298 responses (response rate 20.1%). Twenty beekeepers, all older than 60 years, were diagnosed with Parkinson's disease. The prevalence of Parkinson's disease in beekeepers aged ≥60 years was 3.9%, which is above the reported 0.6-1.3% prevalence of PD in this age group in European population. There was no difference in parameters reflecting bee venom exposure between beekeepers with and without Parkinson's disease. CONCLUSIONS: Continuous exposure to bee venom does not affect neurodegeneration to the extent where it could prevent the expression of Parkinson's disease. © 2021 International Parkinson and Movement Disorder Society.

Olfactory evaluation in hospitalised and self-isolated patients with COVID-19: a single-centre experience on 55 cases.

BACKGROUND: Smell loss is a common symptom of COVID-19 infection. Majority of the studies that evaluated olfactory impairment in COVID-19 used questionnaires (subjective smell evaluations) and did not compare the results with objective or semiobjective measures of smell. We performed smell testing in hospitalised and self-isolated patients with COVID-19 and control participants. METHODS: Fifty-five COVID-19 and 44 control participants underwent smell testing, using Burghart Sniffin' Sticks 'Screening 12 Test'. Participants also rated their smelling capability on the numerical scale. Differences between groups and correlation between smell loss and time from acute onset of symptoms were tested, as well as correlation between results of smell test and subjective assessment of smell. RESULTS: Hospitalised patients with COVID-19 correctly determined 6.5/12 odorants compared with 10/12 in the self-isolated and 11/12 in the control group (p<0.001). Hyposmia or anosmia were present in 87.5% of hospitalised and 29.0% of self-isolated patients (p<0.001). The correlation between subjective self-assessment and results of smell testing was non-significant in both groups of patients with COVID-19, while there was a moderate positive correlation (p=0.001, Spearman's correlation coefficient=0.499) in control participants. CONCLUSION: Contrary to some previous reports suggesting that the presence of olfactory loss may predict milder course of disease, our study found that a vast majority of hospitalised patients with COVID-19 had prominent olfactory impairment. The absence of correlation between self-rated and objective smell evaluation in patients with COVID-19 indicates that subjective smell assessment is unreliable.

STN-DBS Increases Proactive but Not Retroactive Interference During Verbal Learning in PD.

BACKGROUND: Proactive interference (PI) refers to the interference of previously learned materials with new learning and reflects the failure of inhibitory processes in memory. Retroactive interference (RI) refers to the unfavorable effect of new learning on the later recall of previously learned information. Although subthalamic nucleus deep brain stimulation (STN-DBS) does not affect global cognition in Parkinson's disease (PD), it has negative effects on specific aspects of cognition, including verbal fluency and executive inhibitory control of action.To this end, we set to test the acute effect of STN-DBS on PI and RI during verbal learning. METHODS: Twenty PD patients with STN-DBS were tested on the California Verbal Learning Test-II using an ON/OFF stimulation design. RESULTS: The results showed that stimulation increased PI ON stimulation (P = 0.012) but had no effect on RI (P = 0.816). CONCLUSIONS: Our results extend the role of STN to the inhibitory control that is required during memory encoding or recall for prevention of PI. © 2020 International Parkinson and Movement Disorder Society.

Activities of daily living in Parkinson's disease: Time/gender perspective.

OBJECTIVE: The objectives of this study were to explore the changes in the activities of daily living (ADL) in persons with Parkinson's disease (pwPD) over time and to investigate possible differences in ADL performance between men and women with PD. MATERIALS & METHODS: One hundred twenty-nine persons (76 men) with a clinically established PD self-assessed their ADL performance from the time of diagnosis up to 8 years follow-up using the ADL taxonomy. Other demographic and clinical data (motor state, cognition, depression) were also collected and subjected to further analysis. RESULTS: Nine of 12 domains in the ADL taxonomy showed a change over time (Eating and Drinking [P = .009], Mobility [P < .001], Toilet activities [P = .031], Dressing [P < .001], Personal hygiene [P < .001], Communication [P < .001], Cooking [P = .001], Shopping [P < .001] and Cleaning [P < .001]). In addition to time, two domains, (Shopping [P = .007] and Cleaning [P = .027]) also showed an effect of gender with worse scores in women. The nine ADL domains showing effect of time, showed temporary improvement at 12 months follow-up, most probably due to dopaminergic medication. All nine domains deteriorated at later follow-up. CONCLUSIONS: As expected, there was deterioration in self-assessed performance in the majority od ADL domains over time. Women assessed their ADLs worse in two domains (Shopping and Cleaning) probably reflecting a general gender-related activity pattern rather than being a PD-specific finding.

Genetic variability of inflammation and oxidative stress genes does not play a major role in the occurrence of adverse events of dopaminergic treatment in Parkinson's disease.

BACKGROUND: Inflammation and oxidative stress are recognized as important contributors to Parkinson's disease pathogenesis. As such, genetic variability in these pathways could have a role in susceptibility for the disease as well as in the treatment outcome. Dopaminergic treatment is effective in management of motor symptoms, but poses a risk for motor and non-motor adverse events. Our aim was to evaluate the impact of selected single-nucleotide polymorphisms in genes involved in inflammation and oxidative stress on Parkinson's disease susceptibility and the occurrence of adverse events of dopaminergic treatment. METHODS: In total, 224 patients were enrolled, and their demographic and clinical data on the disease course were collected. Furthermore, a control group of 146 healthy Slovenian blood donors were included for Parkinson's disease' risk evaluation. Peripheral blood was obtained for DNA isolation. Genotyping was performed for NLRP3 rs35829419, CARD8 rs2043211, IL1ß rs16944, IL1ß rs1143623, IL6 rs1800795, CAT rs1001179, CAT rs10836235, SOD2 rs4880, NOS1 rs2293054, NOS1 rs2682826, TNF-α rs1800629, and GPX1 rs1050450. Logistic regression was used for analysis of possible associations. RESULTS: We observed a nominally significant association of the IL1ß rs1143623 C allele with the risk for Parkinson's disease (OR = 0.59; 95%CI = 0.38-0.92, p = 0.021). CAT rs1001179 A allele was significantly associated with peripheral edema (OR = 0.32; 95%CI = 0.15-0.68; p = 0.003). Other associations observed were only nominally significant after adjustments: NOS1 rs2682826 A allele and excessive daytime sleepiness and sleep attacks (OR = 1.75; 95%CI = 1.00-3.06, p = 0.048), SOD2 rs4880 T allele and nausea/vomiting (OR = 0.49, 95%CI = 0.25-0.94; p = 0.031), IL1ß rs1143623 C allele and orthostatic hypotension (OR = 0.57, 95%CI = 0.32-1.00, p = 0.050), and NOS1 rs2682826 A allele and impulse control disorders (OR = 2.59; 95%CI = 1.09-6.19; p = 0.032). We did not find any associations between selected polymorphisms and motor adverse events. CONCLUSIONS: Apart from some nominally significant associations, one significant association between CAT genetic variability and peripheral edema was observed as well. Therefore, the results of our study suggest some links between genetic variability in inflammation- and oxidative stress-related pathways and non-motor adverse events of dopaminergic treatment. However, the investigated polymorphisms do not play a major role in the occurrence of the disease and the adverse events of dopaminergic treatment.

Parkinsonian signs in patients with cervical dystonia treated with pallidal deep brain stimulation.

Pallidal deep brain stimulation is an established treatment in patients with dystonia. However, evidence from case series or uncontrolled studies suggests that it may lead in some patients to specific parkinsonian symptoms such as freezing of gait, micrographia, and bradykinesia. We investigated parkinsonian signs using the Movement Disorder Society Unified Parkinson's Disease Rating Scale motor score by means of observer-blinded video ratings in a group of 29 patients treated with pallidal stimulation and a non-surgical control group of 22 patients, both with predominant cervical dystonia. Additional assessments included MRI-based models of volume of neural tissue activated to investigate areas of stimulation related to dystonic symptom control and those likely to induce parkinsonian signs as well as an EMG analysis to investigate functional vicinity of stimulation fields to the pyramidal tract. Compared with controls, stimulated patients had significantly higher motor scores (median, 25th-75th percentile: 14.0, 8.0-19.5 versus 3.0, 2.0-8.0; P < 0.0001), as well as bradykinesia (8.0, 6.0-14.0 versus 2.0, 0.0-3.0; P < 0.0001) and axial motor subscores (2.0, 1.0-4.0 versus 0.0, 0.0-1.0; P = 0.0002), while rigidity and tremor subscores were not different between groups. Parkinsonian signs were partially reversible upon switching stimulation off for a median of 90 min in a subset of 19 patients tolerating this condition. Furthermore, the stimulation group reported more features of freezing of gait on a questionnaire basis. Quality of life was better in stimulated patients compared with control patients, but parkinsonian signs were negatively associated with quality of life. In the descriptive imaging analysis maximum efficacy for dystonia improvement projected to the posteroventrolateral internal pallidum with overlapping clusters driving severity of bradykinesia and axial motor symptoms. The severities of parkinsonian signs were not correlated with functional vicinity to the pyramidal tract as assessed by EMG. In conclusion, parkinsonian signs, particularly bradykinesia and axial motor signs, due to pallidal stimulation in dystonic patients are frequent and negatively impact on motor functioning and quality of life. Therefore, patients with pallidal stimulation should be monitored closely for such signs both in clinical routine and future clinical trials. Spread of current outside the internal pallidum is an unlikely explanation for this phenomenon, which seems to be caused by stimulation of neural elements within the stimulation target volume.

Deep Brain Stimulation of the Subthalamic Nucleus Does Not Affect the Decrease of Decision Threshold during the Choice Process When There Is No Conflict, Time Pressure, or Reward.

During a decision process, the evidence supporting alternative options is integrated over time, and the choice is made when the accumulated evidence for one of the options reaches a decision threshold. Humans and animals have an ability to control the decision threshold, that is, the amount of evidence that needs to be gathered to commit to a choice, and it has been proposed that the subthalamic nucleus (STN) is important for this control. Recent behavioral and neurophysiological data suggest that, in some circumstances, the decision threshold decreases with time during choice trials, allowing overcoming of indecision during difficult choices. Here we asked whether this within-trial decrease of the decision threshold is mediated by the STN and if it is affected by disrupting information processing in the STN through deep brain stimulation (DBS). We assessed 13 patients with Parkinson disease receiving bilateral STN DBS six or more months after the surgery, 11 age-matched controls, and 12 young healthy controls. All participants completed a series of decision trials, in which the evidence was presented in discrete time points, which allowed more direct estimation of the decision threshold. The participants differed widely in the slope of their decision threshold, ranging from constant threshold within a trial to steeply decreasing. However, the slope of the decision threshold did not depend on whether STN DBS was switched on or off and did not differ between the patients and controls. Furthermore, there was no difference in accuracy and RT between the patients in the on and off stimulation conditions and healthy controls. Previous studies that have reported modulation of the decision threshold by STN DBS or unilateral subthalamotomy in Parkinson disease have involved either fast decision-making under conflict or time pressure or in anticipation of high reward. Our findings suggest that, in the absence of reward, decision conflict, or time pressure for decision-making, the STN does not play a critical role in modulating the within-trial decrease of decision thresholds during the choice process.

Subthalamic deep brain stimulation sweet spots and hyperdirect cortical connectivity in Parkinson's disease.

OBJECTIVES: Firstly, to identify subthalamic region stimulation clusters that predict maximum improvement in rigidity, bradykinesia and tremor, or emergence of side-effects; and secondly, to map-out the cortical fingerprint, mediated by the hyperdirect pathways which predict maximum efficacy. METHODS: High angular resolution diffusion imaging in twenty patients with advanced Parkinson's disease was acquired prior to bilateral subthalamic nucleus deep brain stimulation. All contacts were screened one-year from surgery for efficacy and side-effects at different amplitudes. Voxel-based statistical analysis of volumes of tissue activated models was used to identify significant treatment clusters. Probabilistic tractography was employed to identify cortical connectivity patterns associated with treatment efficacy. RESULTS: All patients responded well to treatment (46% mean improvement off medication UPDRS-III [p < 0.0001]) without significant adverse events. Cluster corresponding to maximum improvement in tremor was in the posterior, superior and lateral portion of the nucleus. Clusters corresponding to improvement in bradykinesia and rigidity were nearer the superior border in a further medial and posterior location. The rigidity cluster extended beyond the superior border to the area of the zona incerta and Forel-H2 field. When the clusters where averaged, the coordinates of the area with maximum overall efficacy was X = -10(-9.5), Y = -13(-1) and Z = -7(-3) in MNI(AC-PC) space. Cortical connectivity to primary motor area was predictive of higher improvement in tremor; whilst that to supplementary motor area was predictive of improvement in bradykinesia and rigidity; and connectivity to prefrontal cortex was predictive of improvement in rigidity. INTERPRETATION: These findings support the presence of overlapping stimulation sites within the subthalamic nucleus and its superior border, with different cortical connectivity patterns, associated with maximum improvement in tremor, rigidity and bradykinesia.

Pyramidal tract activation due to subthalamic deep brain stimulation in Parkinson's disease.

BACKGROUND: Subthalamic deep brain stimulation (STN-DBS) is an effective treatment for Parkinson's disease (PD), but can have side effects caused by stimulus spread to structures outside the target volume such as the pyramidal tract. OBJECTIVES: To assess the relevance of pyramidal tract activation with STN-DBS in PD. METHODS: In a multimodal, blinded study in 20 STN-DBS patients, we measured stimulation thresholds for evoking electromyographic activity in orbicularis oris and first dorsal interosseous muscles at each of 150 electrode sites. We also modeled the electric field spread and calculated its overlap with the estimated anatomical location of corticospinal and corticobulbar tracts from primary motor cortex using 3 Tesla MRI probabilistic tractography. RESULTS: Mean resting motor thresholds were significantly lower for the contralateral orbicularis oris (3.5 ± 1.0 mA) compared with ipsilaterally (4.1 ± 1.1 mA) and with the contralateral first dorsal interosseous (4.0 ± 1.2 mA). The modeled volumes of corticobulbar and corticospinal tract activated correlated inversely with the resting motor threshold of the contralateral orbicularis oris and first dorsal interosseous, respectively. Active motor thresholds were significantly lower compared with resting motor thresholds by around 30% to 35% and correlated with the clinically used stimulation amplitude. Backward multiple regression in 12 individuals with a "lateral-type" speech showed that stimulation amplitude, levodopa equivalent dose reduction postsurgery, preoperative speech intelligibility, and first dorsal interosseous resting motor thresholds explained 79.9% of the variance in postoperative speech intelligibility. CONCLUSIONS: Direct pyramidal tract activation can occur at stimulation thresholds that are within the range used in clinical routine. This spread of current compromises increase in stimulation strengths and is related to the development of side effects such as speech disturbances with chronic stimulation. © 2017 International Parkinson and Movement Disorder Society.

In Parkinson's disease on a probabilistic Go/NoGo task deep brain stimulation of the subthalamic nucleus only interferes with withholding of the most prepotent responses.

The evidence on the impact of subthalamic nucleus deep brain stimulation (STN-DBS) on action restraint on Go/NoGO reaction time (RT) tasks in Parkinson's disease (PD) is inconsistent; with some studies reporting no effect and others finding that STN stimulation interferes with withholding of responses and results in more commission errors relative to STN-DBS off. We used a task in which the probability of Go stimuli varied from 100% (simple RT task) to 80, 50 and 20% (probabilistic Go/NoGo RT task), thus altering the prepotency of the response and the difficulty in withholding it on NoGo trials. Twenty PD patients with STN-DBS, ten unoperated PD patients and ten healthy controls participated in the study. All participants were tested twice; the order of on versus off stimulation for STN-DBS PD patients was counterbalanced. Both STN-DBS and unoperated PD patients were tested on medication. The results indicated that STN-DBS selectively decreased discriminability when the response was most prepotent (high--80%, as compared to low Go probability trials--50 and 20%). Movement times were faster with STN stimulation than with DBS off across different Go probability levels. There was neither an overall nor a selective effect of STN-DBS on RTs depending on the level of Go probability. Furthermore, compared to healthy controls, both STN-DBS and unoperated PD patients were more prone to making anticipatory errors; which was not influenced by STN stimulation. The results provide evidence for 'load-dependent' effects of STN stimulation on action restraint as a function of the prepotency of the Go response.

Gender discrepancies and differences in motor and non-motor symptoms, cognition, and psychological outcomes in the treatment of Parkinson's disease with subthalamic deep brain stimulation.

Available data suggest that there may be gender differences in the effect of STN-DBS in the treatment of Parkinson's disease (PD). The aim of this study was to review data on gender discrepancies and gender differences in clinical outcomes in PD patients treated with deep brain stimulation of the subthalamic nucleus (STN-DBS). Included were original studies that specifically examined gender discrepancies or gender differences in PD patients with STN-DBS. Men receive more DBS than women, for various indications. The decision-making process for DBS in women compared to men is more influenced by personal preferences and external factors. Motor symptoms improve in both genders, but bradykinesia improves more in men. The postoperative reduction of the levodopa equivalent daily dose seems to be more pronounced in men. Men show more cognitive deterioration and less improvement than women after STN-DBS. Women show more depressive symptoms before surgery, but they improve similarly to men. Men show more improvement in impulsivity and less decrease in impulsive behaviour symptoms than women. Anxiety and personality traits remain unchanged in both genders. Voice quality improves more in men and deteriorates less often than in women. Men gain fat-free mass and fat mass, but women only gain fat mass. Regarding sexual function the evidence is inconsistent. More urinary symptoms improve in women than in men. Pain and restless leg syndrome seems to improve more in men. Regarding quality of life, the evidence seems to be inconsistent, and activities of daily living seems to improve in both genders. Better prospective controlled studies, focusing directly on gender differences in PD patients treated with STN-DBS, are needed to better explain gender differences in STN-DBS for PD.

Age related changes and sex related differences of functional brain networks in childhood: A high-density EEG study.

OBJECTIVE: The aim of this study was to explore functional network age-related changes and sex-related differences during the early lifespan with a high-density resting state electroencephalography (rs-EEG). METHODS: We analyzed two data sets of high-density rs-EEG in healthy children and adolescents. We recorded a 64-channel EEG and calculated functional connectomes in 27 participants aged 5-18 years. To validate our results, we used publicly available data and calculated functional connectomes in another 86 participants aged 6-18 years from a 128-channel rs-EEG. We were primarily interested in alpha frequency band, but we also analyzed theta and beta frequency bands. RESULTS: We observed age-related increase of characteristic path, clustering coefficient and interhemispheric strength in the alpha frequency band of both data sets and in the beta frequency band of the larger validation data set. Age-related increase of global efficiency was seen in the theta band of the validation data set and in the alpha band of the test data set. Increase in small worldness was observed only in the alpha frequency band of the test data set. We also observed an increase of individual peak alpha frequency with age in both data sets. Sex-related differences were only observed in the beta frequency band of the larger validation data set, with females having higher values than same aged males. CONCLUSIONS: Functional brain networks show indices of higher segregation, but also increasing global integration with maturation. Age-related changes are most prominent in the alpha frequency band. SIGNIFICANCE: To the best of our knowledge, our study was the first to analyze maturation related changes and sex-related differences of functional brain networks with a high-density EEG and to compare functional connectomes generated from two diverse high-density EEG data sets. Understanding the age-related changes and sex-related differences of functional brain networks in healthy children and adolescents is crucial for identifying network abnormalities in different neurologic and psychiatric conditions, with the aim to identify possible markers for prognosis and treatment.

Daily Habits in Parkinson's Disease: Validation of the Daily Habit Scale.

Objective: The objective of the study was to validate a new scale for assessing habitual behavior-the Daily Habit Scale in patients with Parkinson's disease. Background: Parkinson's disease patients are impaired in habit learning and skill acquisition. Despite repeated practice, they have difficulty developing habitual responses. Methods: One hundred seventy-nine patients (Median (Mdn) = 69 [64-76], 65 females) participated in the study. Corrected item-to-total correlations were calculated to assess the item-convergent and item discriminant validity. Confirmatory factor analysis and assessment of internal consistency were also carried out. Concurrent validity in respect to measures of anxiety and depression, apathy, impulsivity, personality, multidimensional health locus of control, and health-related quality of life was also calculated. To determine the test-retest reliability of the scale, 30 patients (Mdn = 69 [66-73], 9 females) completed a second copy of the scale 6 months after the first. Results: Twenty-nine items (76%) and 9 items (24%) of the 38-item scale, respectively, showed a very good and good convergent validity. All the items discriminated between their own factor and the other factors. The comparative fit index of 0.932 indicated an acceptable model fit of the data, whereas the root mean square error of approximation of 0.06 moderate model fit. The scale had a good internal consistency (Cronbach α = 0.792), and a moderate test-retest reliability (0.57). Females had higher scores on two factors compared to men (Factor 3: household activities and Factor 8: sleep-related activities). Conclusions: The Daily Habit Scale is a reliable and valid tool to measure daily habits in Parkinson's disease.

Does spinal cord stimulation improve gait in Parkinson's disease: A comprehensive review.

INTRODUCTION: Axial disability, including gait disturbances, is common in Parkinson's disease (PD), especially in advanced stages. Epidural spinal cord stimulation (SCS) has been investigated as a treatment option for gait disorders in PD. Here, we review the literature on SCS in PD and evaluate its efficacy, optimal stimulation parameters, optimal electrode locations, possible effects of concurrent deep brain stimulation, and possible working mechanisms on gait. METHODS: Databases were searched for human studies involving PD patients who received an epidural SCS intervention and who had at least one gait-related outcome measure. The included reports were reviewed with respect to design and outcomes. Additionally, the possible mechanisms of action underlying SCS were reviewed. RESULTS: Out of 433 records identified, 25 unique studies with in total 103 participants were included. Most studies included only a few participants. The gait disorders of most PD patients with concurrent pain complaints, mostly low back pain, improved with SCS in almost all cases, regardless of stimulation parameters or electrode location. Higher-frequency stimulation (>200 Hz) seemed to be more effective in pain-free PD patients, but the results were inconsistent. Heterogeneity in outcome measures and follow-up times hindered comparability. CONCLUSIONS: SCS may improve gait in PD patients with neuropathic pain, but its efficacy in pain-free patients remains uncertain due to a lack of thorough double-blind studies. Apart from a well-powered, controlled, double-blind study design, future studies could further explore the initial hints that higher-frequency stimulation (>200 Hz) might be the best approach to improve gait outcomes in pain-free patients.

Effects of deep brain stimulation frequency on eye movements and cognitive control.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for Parkinson's disease (PD). Varying the frequency DBS has differential effects on axial and distal limb functions, suggesting differing modulation of relevant pathways. The STN is also a critical node in oculomotor and associative networks, but the effect of stimulation frequency on these networks remains unknown. This study aimed to investigate the effects of 80 hz vs. 130 Hz frequency STN-DBS on eye movements and executive control. Twenty-one STN-DBS PD patients receiving 130 Hz vs. 80 Hz stimulation were compared to a healthy control group (n = 16). All participants were tested twice in a double-blind manner. We examined prosaccades (latency and gain) and antisaccades (latency of correct and incorrect antisaccades, error rate and gain of the correct antisaccades). Executive function was tested with the Stroop task. The motor condition was assessed using Unified Parkinson's Disease Rating Scale part III. The antisaccadic error rate was higher in patients (p = 0.0113), more so in patients on 80 Hz compared to 130 Hz (p = 0.001) stimulation. The differences between patients and controls and between frequencies for all other eye-movements or cognitive measures were not statistically significant. We show that 80 Hz STN-DBS in PD reduces the ability to maintain stable fixation but does not alter inhibition, resulting in a higher antisaccade error rate presumably due to less efficient fixation, without altering the motor state. This provides a wider range of stimulation parameters that can reduce specific DBS-related effects without affecting motor outcomes.

Distractibility predicts favourable response of functional tremor to transcranial magnetic stimulation: An electrophysiological study.

BACKGROUND: Generation of functional tremor relies on the structures involved in the control of voluntary movements. The clinical diagnosis is based on the presence of "positive signs", which are expression of cognitive and motor distractibility and reflect functional tremor dependence on explicit motor control. In patients who manifest less distractibility, habitual (implicit) control may be of greater significance. Habitual behaviours are inflexible and difficult to eradicate. OBJECTIVES: To investigate if motor and cognitive distractibility predicts response to treatment with repetitive transcranial magnetic stimulation. METHODS: 21 patients with functional tremor underwent 5-day repeated sessions of continuous theta burst stimulation over primary motor cortex. A battery of tests to provoke positive signs was performed during accelerometry recordings and the total functional tremor accelerometry score was calculated for each patient. Response to treatment was measured as change in tremor amplitude, expressed as total power of the spectra between 1 and 30 Hz. RESULTS: On the group level, cTBS significantly changed postural tremor amplitude (Z = -1.9; p = 0.05), with the median decrease of 40%, IQR (-90-(+24)). There was a positive correlation between the functional tremor accelerometry score and reduction of postural tremor amplitude with treatment (rs = -0.75, p < 10-3). Responders had higher functional tremor accelerometry scores compared to non-responders (p = 0.001). The total functional tremor accelerometry score was a significant predictor of treatment response (OR = 2.8, p = 0.03; 95% CI 1.1; 7.2). CONCLUSIONS: Patients who are more distractible are better candidates for treatment with transcranial magnetic stimulation. The likely explanation is the between-subjects differences on the reliance of functional tremor generation on explicit vs. implicit motor network.

Development and Validation of a Daily Habit Scale.

Habits are defined as automatic behaviours triggered by cues and performed without awareness. They are difficult to control and mentally efficient, which contrasts with goal-directed behaviour, which is characterised by active thought, high computational effort, and the ability to modify this behaviour in response to a changing environment and contextual demands. Habits are not only defined by the frequency with which a behaviour is performed but represent a complex construct that also includes the strength and automaticity of the habitual behaviour. We report here the development and validation of a Daily Habit Scale (DHS) to assess the frequency, automaticity, and strength of daily habits in healthy individuals. Item reduction based on factor analysis resulted in a scale with 38 items grouped into eight factors explaining 52.91% of the variance. The DHS showed very good internal consistency (Cronbach alpha = 0.738) and test-retest reliability (Intraclass correlation coefficient = 0.892, p<0.001) as well as convergent and divergent reliability compared to other scales measuring habits. We found a significant effect of age, gender, anxiety, and depression on the DHS. Considering certain limitations of the DHS, such as not considering the context of performance of habits, and the absence of certain items, such as transportation use, the results of this study suggest that DHS is a reliable and valid measure of daily habits that can be used by both clinicians and researchers as a measure of daily habits.