The relative importance of local contingencies and global biases for statistical learning.

Effective behavior requires adapting to the changing regularities evident in the world. Analogous to the global and local processing distinction for perception, these statistical regularities may be evident in global biases (i.e., some events are more likely) or local contingencies (i.e., subsequent events depend on preceding events). To explore whether mental model updating unfolds in distinct ways according to global and local statistical properties, we had healthy individuals perform two variations of an updating task in which both global and local statistical properties changed over time. Participants predicted whether the next triangle in a sequence of triangles would point up or down. The probability of pointing up or down was fixed for epochs of trials (i.e., global probability) and correlated with the colors of elements in the display. In addition, we made the triangle's apex direction on trial n+1 depend on the pointing direction of the prior trial (i.e., local probability). For both experiments, it was the local contingencies that dominated participant choices. When global and local statistical cues of equal magnitude are available, we conclude that healthy individuals are biased towards using the local statistical properties.

Trends in health service use among persons with Parkinson's disease by rurality: A population-based repeated cross-sectional study.

BACKGROUND: The global burden of Parkinson's disease (PD) has more than doubled over the past three decades, and this trend is expected to continue. Despite generally poorer access to health care services in rural areas, little previous work has examined health system use in persons with PD by rurality. We examined trends in the prevalence of PD and health service use among persons with PD by rurality in Ontario, Canada. METHODS: We conducted a repeated, cross-sectional analysis of persons with prevalent PD aged 40+ years on April 1st of each year from 2000 to 2018 using health administrative databases and calculated the age-sex standardized prevalence of PD. Prevalence of PD was also stratified by rurality and sex. Negative binomial models were used to calculate rate ratios with 95% confidence intervals comparing rates of health service use in rural compared to urban residents in 2018. RESULTS: The age-sex standardized prevalence of PD in Ontario increased by 0.34% per year (p<0.0001) and was 459 per 100,000 in 2018 (n = 33,479), with a lower prevalence in rural compared to urban residents (401 vs. 467 per 100,000). Rates of hospitalizations and family physician visits declined over time in both men and women with PD in rural and urban areas, while rates of emergency department, neurologist, and other specialist visits increased. Adjusted rates of hospitalizations were similar between rural and urban residents (RR = 1.04, 95% CI [0.96, 1.12]), while rates of emergency department visits were higher among rural residents (RR = 1.35, 95% CI [1.27, 1.42]). Rural residents had lower rates of family physician (adjusted RR = 0.82, (95% CI [0.79, 0.84]) and neurologist visits (RR = 0.74, 95% CI [0.72, 0.77]). INTERPRETATION: Lower rates of outpatient health service use among persons residing in rural regions, contrasting with higher rates of emergency department visits suggest inequities in access. Efforts to improve access to primary and specialist care for persons with PD in rural regions are needed.

Cognitive effects of unilateral thalamotomy for tremor: a meta-analysis.

Tremor is a debilitating symptom that can lead to functional impairment. Pharmacotherapy is often successful, but up to 50% of patients are resistant to medications or cannot tolerate side effects. Thalamotomy to the ventral intermediate nucleus of the thalamus is a surgical intervention for refractory tremor. Thalamotomy surgeries include radiofrequency and incisionless procedures, such as Gamma Knife radiosurgery and magnetic resonance-guided focused ultrasound. Cognitive changes following thalamotomy have been inconsistently reported across studies. We performed a meta-analysis to summarize the impact of unilateral thalamotomy to the ventral intermediate nucleus of the thalamus across multiple cognitive domains. We searched MEDLINE, Embase Classic, Embase and EBM Reviews for relevant studies. Neuropsychological tests were categorized into seven cognitive domains: global cognition, verbal memory, non-verbal memory, executive function, phonemic fluency, semantic fluency and visuospatial processing. We calculated standardized mean differences as Hedges' g and 95% confidence intervals of the change between pre- and postoperative cognitive scores. Pooling of standardized mean differences across studies was performed using random-effects models. Risk of bias across studies and quality of evidence for each cognitive domain were assessed with the National Institute of Health quality assessment tool and the GRADEpro Guideline Development Tool, respectively. Of the 1251 records reviewed, eight studies met inclusion criteria. We included 193 patients with essential tremor, Parkinson's disease, or multiple sclerosis in the meta-analysis. There was a small significant decline in phonemic fluency [standardized mean difference = -0.29, 95% confidence interval: (-0.52, -0.05), P = 0.017] and a trend towards a decline in semantic fluency [standardized mean difference = -0.19, 95% confidence interval: (-0.40, 0.01), P = 0.056]. No postoperative changes were observed in the other cognitive domains (P values >0.14). In secondary analyses, we restricted the analyses to studies using magnetic resonance-guided focused ultrasound given its growing popularity and more precise targeting. In those analyses, there was no evidence of cognitive decline across any domain (P values >0.37). In terms of risk of bias, five studies were rated as 'good' and three studies were rated as 'fair'. According to GRADEpro guidelines, the certainty of the effect for all cognitive domains was low. This study provides evidence that unilateral thalamotomy to the ventral intermediate nucleus of the thalamus is relatively safe from a cognitive standpoint, however, there may be a small decline in verbal fluency. Magnetic resonance-guided focused ultrasound might have a more favourable postoperative cognitive profile compared with other thalamotomy techniques.