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People with methamphetamine use disorder (MUD) struggle to shift their behaviour from methamphetamine‐orientated habits to goal‐oriented choices. The model‐based/model‐free framework is well suited to understand this difficulty by unpacking the computational mechanisms that support experienced‐based (model‐free) and goal‐directed (model‐based) choices. We aimed to examine whether 1) participants with MUD differed from controls on behavioural proxies and/or computational mechanisms of model‐based/model‐free choices; 2) model‐based/model‐free decision‐making correlated with MUD symptoms; and 3) model‐based/model‐free deficits improved over six weeks in the group with MUD. Participants with MUD and controls with similar age, IQ and socioeconomic status completed the Two‐Step Task at treatment commencement (MUD n = 30, Controls n = 31) and six weeks later (MUD n = 23, Controls n = 26). We examined behavioural proxies of model‐based/model‐free decisions using mixed logistic regression, and their underlying mechanisms using computational modelling. At a behavioural level, participants with MUD were more likely to switch their choices following rewarded actions, although this pattern improved at follow up. At a computational level, groups were similar in their use of model‐based mechanisms, but participants with MUD were less likely to apply model‐free mechanisms and less likely to repeat rewarded actions. We did not find evidence that individual differences in model‐based or model‐free parameters were associated with greater severity of methamphetamine dependence, nor did we find that group differences in computational parameters changed between baseline and follow‐up assessment. Decision‐making challenges in people with MUD are likely related to difficulties in pursuing choices previously associated with positive outcomes. [ABSTRACT FROM AUTHOR]

Cardiorespiratory exercise is known to modulate motor cortical plasticity in young adults, but the influence of ageing on this relationship is unknown. Here, we compared the effects of a single session of cardiorespiratory exercise on motor cortical plasticity in young and older adults. We acquired measures of cortical excitatory and inhibitory activity of the primary motor cortex using transcranial magnetic stimulation (TMS) from 20 young (mean ± SD = 25.30 ± 4.00 years, 14 females) and 20 older (mean ± SD = 64.10 ± 6.50 years, 11 females) healthy adults. Single‐ and paired‐pulse TMS measurements were collected before and after a 20 min bout of high‐intensity interval cycling exercise or an equivalent period of rest, and again after intermittent theta burst stimulation (iTBS). In both young (P = 0.027, Cohen's d = 0.87) and older adults (P = 0.006, Cohen's d = 0.85), there was an increase in glutamatergic excitation and a reduction in GABAergic inhibition from pre‐ to postexercise. However, in contrast to younger adults, older adults showed an attenuated plasticity response to iTBS following exercise (P = 0.011, Cohen's d = 0.85). These results demonstrate an age‐dependent decline in cortical plasticity and indicate that a preceding bout of high‐intensity interval exercise might be less effective for enhancing primary motor cortex plasticity in older adults. Our findings align with the hypothesis that the capacity for cortical plasticity is altered in older age. Key points: Exercise enhances motor cortical plasticity in young adults, but how ageing influences this effect is unknown.Here, we compared primary motor cortical plasticity responses in young and older adults before and after a bout of high‐intensity interval exercise and again after a plasticity‐inducing protocol, intermittent theta burst stimulation.In both young and older adults, exercise led to an increase in glutamatergic excitation and a reduction in GABAergic inhibition.Our key result was that older adults showed an attenuated plasticity response to theta burst stimulation following exercise, relative to younger adults.Our findings demonstrate an age‐dependent decline in exercise‐enhanced cortical plasticity and indicate that a preceding bout of high‐intensity interval exercise might be less effective for enhancing primary motor cortex plasticity in older adults. [ABSTRACT FROM AUTHOR]

Psychological stress is a potential modifiable risk factor for cognitive decline. However, the extent to which self-reported psychological stress is differentially associated with decline in specific cognitive domains remains unclear. Differences may be due to heterogeneity in the aspects of psychological stress investigated, for example, neuroticism (which is linked to vulnerability to stress), perceived stress, or exposure to stressful life events. This review aims to establish the associations between these aspects of self-reported psychological stress and cognitive decline. PsychINFO, Embase and MEDLINE were searched from database inception to September 2021. Studies were included if they were observational, prospective, and if they investigated the association between self-reported psychological stress and cognitive decline in adults with a minimum mean age of 40 years at baseline. Thirty studies satisfied the inclusion criteria, with most examining neuroticism (n = 17) as a predictor of cognitive decline. Fewer examined perceived stress (n = 7) or stressful life events (n = 6). There was evidence of an association between neuroticism and cognitive decline, particularly in the domain of memory. Similarly, across studies, perceived stress was also associated with memory decline. Research investigating the relationship between stressful life events and cognitive decline had fewer outcomes to interpret. Overall, the findings highlight that memory may be particularly susceptible to high levels of neuroticism and perceived stress. We identified a lack of research into some cognitive domains, such as executive function, which should be addressed by future studies. [ABSTRACT FROM AUTHOR]

This scientific commentary discusses the topic of apathy in Parkinson's disease and its impact on patients' quality of life. The article explores the concept of goal-directed behavior and how it is affected by apathy. The authors present the results of a study that investigated whether people with apathy in Parkinson's disease learn differently from their experiences. The study used a combination of behavioral experiments and brain imaging to examine the learning processes in individuals with apathy. The findings suggest that there are differences in how people with apathy learn about the outcomes of their choices, which may contribute to their reduced motivation. However, further research is needed to fully understand the underlying mechanisms. [Extracted from the article]

Substantial evidence suggests that observed actions can engage their corresponding motor representations within the observer. It is currently believed that this process of observation-execution matching occurs relatively automatically, without the need for top-down control. In this study we tested the susceptibility of the observation-execution matching process to selective attention. We used a Go/NoGo paradigm to investigate the phenomenon of "automatic imitation", in which participants are faster to initiate a hand movement that is congruent with a concurrently observed action, relative to one that is incongruent. First, we replicated previous findings of automatic imitation, and excluded the possibility that spatial compatibility effects might explain these results (Experiment 1). We then presented participants with the same goal-directed actions while directing their attention to an imperative stimulus that spatially overlapped, but was distinct from, the observed actions (Experiment 2). Crucially, automatic imitation no longer occurred when participants directed their attention away from the displayed actions and towards the spatially overlapping stimulus. In a final experiment, we examined whether the automatic imitation of grasp persists when participants attend to an irrelevant feature of the observed action, such as whether it is performed by a left or right hand (Experiment 3). Here we found that automatic imitation is contingent on participants attending to the feature of the observed hand that was relevant to their responses. Together these findings demonstrate the importance of selective mechanisms in the filtering of task-irrelevant actions, and indicate a role for top-down control in limiting the motoric simulation of observed actions. (Contains 5 figures.)

People with Methamphetamine Use Disorder (PwMUD) spend substantial time and resources on substance use, which hinders their ability to explore alternate reinforcers. Gold-standard behavioural treatments attempt to remedy this by encouraging action towards non-drug reinforcers, but substance use often persists. We aimed to unravel the mechanistic drivers of this behaviour by applying a computational model of explore/exploit behaviour to decision-making data (Iowa Gambling Task) from 106 PwMUD and 48 controls. We then examined the longitudinal link between explore/exploit mechanisms and changes in methamphetamine use 6 weeks later. Exploitation parameters included reinforcement sensitivity and inverse decay (i.e., number of past outcomes used to guide choices). Exploration parameters included maximum directed exploration value (i.e., value of trying novel actions). The Timeline Follow Back measured changes in methamphetamine use. Compared to controls, PwMUD showed deficits in exploitative decision-making, characterised by reduced reinforcement sensitivity, U = 3065, p = 0.009, and less use of previous choice outcomes, U = 3062, p = 0.010. This was accompanied by a behavioural pattern of frequent shifting between choices, which appeared consistent with random exploration. Furthermore, PwMUD with greater reductions of methamphetamine use at 6 weeks had increased directed exploration (β = 0.22, p = 0.045); greater use of past choice outcomes (β = -0.39, p = 0.002) and greater choice consistency (β = -0.39, p = 0.002). Therefore, limited computational exploitation and increased behavioural exploration characterise PwMUD's presentation to treatment, while increased directed exploration, use of past choice outcomes and choice consistency predict greater reductions of methamphetamine use. [ABSTRACT FROM AUTHOR]

Objective: There is variability across individuals in cognitive aging. To investigate the associations of several modifiable factors with high and low cognitive performance. Methods: Data came from 17,724 community-dwelling individuals aged 65–98 years. Global cognition, verbal fluency, episodic memory, and psychomotor speed were assessed over up to seven years. Group-based multi-trajectory modeling identified distinct cognitive trajectories. Structural equation modeling examined the direct/indirect associations of social/behavioral factors and several chronic conditions with cognitive trajectories. Results: Seven trajectory subgroups were identified. In the structural equation modeling we compared two subgroups-participants with the highest (14.2%) and lowest (4.1%) cognitive performance with the average subgroup. Lower education, never alcohol intake, and frailty directly predicted increased risk of low performance, and decreased likelihood of high performance. Hypertension (RR: 0.69, 95%CI: 0.60–0.80), obesity (RR: 0.84, 95%CI: 0.73–0.97), diabetes (RR: 0.69, 95%CI: 0.56–0.86) and depression (RR: 0.68, 95%CI: 0.54–0.85) only predicted lower likelihood of high cognitive performance, while dyslipidemia was only associated with low performance (RR: 1.30, 95%CI: 1.07–1.57). Living alone predicted increased risk of low cognitive performance and several comorbidities. Smoking did not predict cognitive trajectories but was associated with increased risk of diabetes, obesity and frailty. Findings were similar when examining the direct associations between modifiable risk factors and all seven cognitive subgroups. Conclusions: Although several modifiable factors were associated with high performance, and reversely with low performance, this was not observed for obesity, hypertension and dyslipidemia. Further, health behaviors may affect cognitive function indirectly, via geriatric conditions. This indicates that strategies to promote healthy cognitive aging, may be distinct from those targeting dementia prevention. [ABSTRACT FROM AUTHOR]

Methamphetamine use disorder involves continued use of the drug despite negative consequences. Such 'compulsivity' can be measured by reversal learning tasks, which involve participants learning action-outcome task contingencies (acquisition-contingency) and then updating their behaviour when the contingencies change (reversal). Using these paradigms, animal models suggest that people with methamphetamine use disorder (PwMUD) may struggle to avoid repeating actions that were previously rewarded but are now punished (inflexibility). However, difficulties in learning task contingencies (reinforcement learning) may offer an alternative explanation, with meaningful treatment implications. We aimed to disentangle inflexibility and reinforcement learning deficits in 35 PwMUD and 32 controls with similar sociodemographic characteristics, using novel trial-by-trial analyses on a probabilistic reversal learning task. Inflexibility was defined as (a) weaker reversal phase performance, compared with the acquisition-contingency phases, and (b) persistence with the same choice despite repeated punishments. Conversely, reinforcement learning deficits were defined as (a) poor performance across both acquisition-contingency and reversal phases and (b) inconsistent postfeedback behaviour (i.e., switching after reward). Compared with controls, PwMUD exhibited weaker learning (odds ratio [OR] = 0.69, 95% confidence interval [CI] [0.63-0.77], p < .001), though no greater accuracy reduction during reversal. Furthermore, PwMUD were more likely to switch responses after one reward/punishment (OR = 0.83, 95% CI [0.77-0.89], p < .001; OR = 0.82, 95% CI [0.72-0.93], p = .002) but just as likely to switch after repeated punishments (OR = 1.03, 95% CI [0.73-1.45], p = .853). These results indicate that PwMUD's reversal learning deficits are driven by weaker reinforcement learning, not inflexibility. [ABSTRACT FROM AUTHOR]

Introduction: To determine whether slowed gait and weakened grip strength independently, or together, better identify risk of cognitive decline or dementia. Methods: Time to walk 3 meters and grip strength were measured in a randomized placebo‐controlled clinical trial involving community‐dwelling, initially cognitively healthy older adults (N = 19,114). Results: Over a median 4.7 years follow‐up, slow gait and weak grip strength at baseline were independently associated with risk of incident dementia (hazard ratio [HR] = 1.44, 95% confidence interval [CI]: 1.19–1.73; and 1.24, 95% CI: 1.04–1.50, respectively) and cognitive decline (HR = 1.38, 95% CI: 1.26–1.51; and 1.04, 95% CI: 0.95–1.14, respectively) and when combined, were associated with 79% and 43% increase in risk of dementia and cognitive decline, respectively. Annual declines in gait and in grip over time showed similar results. Discussion: Gait speed and grip strength are low‐cost markers that may be useful in the clinical setting to help identify and manage individuals at greater risk, or with early signs, of dementia, particularly when measured together. Highlights: Grip strength and gait speed are effective predictors and markers of dementia.Dementia risk is greater than cognitive decline risk with declines in gait or grip.Decline in gait speed, more so than in grip strength, predicts greater dementia risk.Greater risk prediction results from combining grip strength and gait speed. [ABSTRACT FROM AUTHOR]

Introduction: This study aimed to investigate cognitive aging trajectories, the associated sociodemographic characteristics, and the association of these trajectories with dementia. Methods: Generally healthy older adults (n = 19,114) were followed for up to 7 years, with regular cognitive assessments. Group‐based trajectory modeling identified distinct cognitive trajectories. Results: Four to seven trajectories were identified per cognitive domain. Stable trajectories were observed across domains. Improvement in verbal fluency and minor psychomotor slowing were common. Substantial decline in global cognition and episodic memory were observed in a small proportion of individuals. Older, less educated participants and men were more common in lower‐functioning trajectories (p < .001). The highest proportions of dementia cases were in trajectories with major decline in global cognition (56.9%) and memory (33.2%). Discussion: Inter‐individual variability in cognitive trajectories was observed across all domains. Some individuals appear resilient to cognitive decline even with advancing age. Further research into factors promoting cognitive resilience is needed. [ABSTRACT FROM AUTHOR]