Effectiveness of blood pressure control in a small community

The aim of this study was to examine the degree of control of blood pressure with respect to individuals on anti-hypertensive drug therapy attending a Health Centre for repeat prescription. Despite their being on anti-hypertensive drug therapy, only 35% of the individuals were found to be normotensive, 27% were in the borderline range whereas 38% were found to be hypertensive. The relatively high prevalence of poorly controlled patients suffering from high blood pressure is partly a reflection of the degree of non-compliance by patients to prescribed drug regimens although this is difficult to either qualify or quantify. Education of the patient vis-à-vis his medical condition and its treatment is of great importance as is regular monitoring and effective control of raised blood pressure by the family physician.peer-reviewe

The dissociable effects of reward on sequential motor behavior

Reward has consistently been shown to enhance motor behavior; however, its beneficial effects appear to be largely unspecific. For example, reward is associated with both rapid and training-dependent improvements in performance, with a mechanistic account of these effects currently lacking. Here we tested the hypothesis that these distinct reward-based improvements are driven by dissociable reward types: monetary incentive and performance feedback. Whereas performance feedback provides information on how well a motor task has been completed (knowledge of performance), monetary incentive increases the motivation to perform optimally without providing a performance-based learning signal. Experiment 1 showed that groups who received monetary incentive rapidly improved movement times (MTs), using a novel sequential reaching task. In contrast, only groups with correct performance-based feedback showed learning-related improvements. Importantly, pairing both maximized MT performance gains and accelerated movement fusion. Fusion describes an optimization process during which neighboring sequential movements blend together to form singular actions. Results from experiment 2 served as a replication and showed that fusion led to enhanced performance speed while also improving movement efficiency through increased smoothness. Finally, experiment 3 showed that these improvements in performance persist for 24 h even without reward availability. This highlights the dissociable impact of monetary incentive and performance feedback, with their combination maximizing performance gains and leading to stable improvements in the speed and efficiency of sequential actions. NEW & NOTEWORTHY Our work provides a mechanistic framework for how reward influences motor behavior. Specifically, we show that rapid improvements in speed and accuracy are driven by reward presented in the form of money, whereas knowledge of performance through performance feedback leads to training-based improvements. Importantly, combining both maximized performance gains and led to improvements in movement quality through fusion, which describes an optimization process during which sequential movements blend into a single action

The dissociable effects of punishment and reward on motor learning

A common assumption regarding error-based motor learning (motor adaptation) in humans is that its underlying mechanism is automatic and insensitive to reward- or punishment-based feedback. Contrary to this hypothesis, we show in a double dissociation that the two have independent effects on the learning and retention components of motor adaptation. Negative feedback, whether graded or binary, accelerated learning. While it was not necessary for the negative feedback to be coupled to monetary loss, it had to be clearly related to the actual performance on the preceding movement. Positive feedback did not speed up learning, but it increased retention of the motor memory when performance feedback was withdrawn. These findings reinforce the view that independent mechanisms underpin learning and retention in motor adaptation, reject the assumption that motor adaptation is independent of motivational feedback, and raise new questions regarding the neural basis of negative and positive motivational feedback in motor learning

Reward-driven enhancements in motor control are robust to TMS manipulation

A wealth of evidence describes the strong positive impact that reward has on motor control at the behavioural level. However, surprisingly little is known regarding the neural mechanisms which underpin these effects, beyond a reliance on the dopaminergic system. In recent work, we developed a task that enabled the dissociation of the selection and execution components of an upper limb reaching movement. Our results demonstrated that both selection and execution are concommitently enhanced by immediate reward availability. Here, we investigate what the neural underpinnings of each component may be. To this end, we aimed to alter the cortical excitability of the ventromedial prefrontal cortex and supplementary motor area using continuous theta-burst transcranial magnetic stimulation (cTBS) in a within-participant design (N = 23). Both cortical areas are involved in determining an individual’s sensitivity to reward and physical effort, and we hypothesised that a change in excitability would result in the reward-driven effects on action selection and execution to be altered, respectively. To increase statistical power, participants were pre-selected based on their sensitivity to reward in the reaching task. While reward did lead to enhanced performance during the cTBS sessions and a control sham session, cTBS was ineffective in altering these effects. These results may provide evidence that other areas, such as the primary motor cortex or the premotor area, may drive the reward-based enhancements of motor performance

Prevalence of Abnormal Systemic Hemodynamics in Veterans with and without Spinal Cord Injury

Advances in the clinical management of patients with acute and chronic spinal cord injury (SCI) have contributed to extended life expectancies; however longevity in those with SCI remains below that of the general population.(1) Reduced longevity in the SCI population has been attributed to increased incidence of age-associated chronic illnesses,(2) premature cardiovascular aging,(3) and increased prevalence of heart disease, stroke (4) and diabetes mellitus, (5) compared to the general population. In fact, cardiovascular disease (CVD) is now a leading cause of morbidity and mortality in the SCI population, which may be amplified due to increased risk factors such as inactivity, chronic inflammation, and impairment in autonomic cardiovascular control.(6) The American Spinal Injury Association (ASIA) impairment scale (AIS) is used to document remaining motor and sensory function following SCI; (7, 8) however, the degree of autonomic nervous system impairment is not considered within this classification schema.(9, 10) That said, impaired autonomic control of the cardiovascular system after SCI results in measurable changes in heart rate (HR) and blood pressure (BP) that loosely reflect the level and completeness of SCI documented using the AIS classification, (11, 12) but may also reflect orthostatic positioning.(6, 12, 13) The impact of these changes in HR and BP on cardiovascular health and longevity is not fully appreciated in the SCI population; however, prior to identifying the consequences of these cardiovascular abnormalities, prevalence rates of HR and BP values which fall outside the expected normal range should be documented. The International Standards to Document Autonomic Function (post-SCI) initially established guidelines for the assessment of HR and BP abnormalities in 2009, (10) which was updated in 2012, but the thresholds remained consistent. (14) Specifically, bradycardia is defined as a HR ≤ 60 beats/minute (bpm) and tachycardia as a HR ≥ 100 bpm. (14) Hypotension is defined as a systolic BP (SBP) ≤ 90 mmHg and a diastolic BP (DBP) ≤ 60 mmHg; hypertension is SBP ≥ 140 and/or DBP ≥ 90 mmHg. (14) While these definitions comply with standards established in the non-SCI population, due to decentralized cardiovascular control, they may not be appropriate for use in the SCI population. In addition, relatively recent evidence has emerged which associates adverse outcomes in the general population using other HR (15, 16) and BP (17-21) thresholds. Beyond the clinical consequences of alterations in HR and BP, persons with SCI may experience loss of independence and life quality related to the inability to adequately maintain cardiovascular homeostasis; however, until we gain a better understanding of the prevalence of these abnormalities, the development and testing of effective treatment strategies will not be a priority. Therefore, the goal of this investigation was to assess HR and BP in veterans with (SCI) and without SCI (non SCI). Similar to a recent report, (6) we hypothesized that level of SCI (i.e., the higher the lesion level the greater the prevalence of abnormal HR and BP recordings) and orthostatic positioning (i.e., increased prevalence of abnormal HR and BP recordings in the seated versus the supine position) would influence the prevalence of HR and BP abnormalities. In addition, we hypothesized that the prevalence of comorbid cardiovascular medical conditions, current smoking status, age and use of prescription anti-hypertensive (anti-HTN) medications would influence the prevalence of HR and BP abnormalities in veterans with and without SCI

The contribution of explicit processes to reinforcement-based motor learning

Despite increasing interest in the role of reward in motor learning, the underlying mechanisms remain ill defined. In particular, the contribution of explicit processes to reward-based motor learning is unclear. To address this, we examined subjects’ ( n = 30) ability to learn to compensate for a gradually introduced 25° visuomotor rotation with only reward-based feedback (binary success/failure). Only two-thirds of subjects ( n = 20) were successful at the maximum angle. The remaining subjects initially followed the rotation but after a variable number of trials began to reach at an insufficiently large angle and subsequently returned to near-baseline performance ( n = 10). Furthermore, those who were successful accomplished this via a large explicit component, evidenced by a reduction in reach angle when they were asked to remove any strategy they employed. However, both groups displayed a small degree of remaining retention even after the removal of this explicit component. All subjects made greater and more variable changes in reach angle after incorrect (unrewarded) trials. However, subjects who failed to learn showed decreased sensitivity to errors, even in the initial period in which they followed the rotation, a pattern previously found in parkinsonian patients. In a second experiment, the addition of a secondary mental rotation task completely abolished learning ( n = 10), while a control group replicated the results of the first experiment ( n = 10). These results emphasize a pivotal role of explicit processes during reinforcement-based motor learning, and the susceptibility of this form of learning to disruption has important implications for its potential therapeutic benefits. NEW &amp; NOTEWORTHY We demonstrate that learning a visuomotor rotation with only reward-based feedback is principally accomplished via the development of a large explicit component. Furthermore, this form of learning is susceptible to disruption with a secondary task. The results suggest that future experiments utilizing reward-based feedback should aim to dissect the roles of implicit and explicit reinforcement learning systems. Therapeutic motor learning approaches based on reward should be aware of the sensitivity to disruption. </jats:p

Modulation of cerebellar excitability by polarity-specific noninvasive direct current stimulation

The cerebellum is a crucial structure involved in movement control and cognitive processing. Non-invasive stimulation of the cerebellum results in neurophysiological and behavioral changes, an effect that has been attributed to modulation of cerebello–brain connectivity. At rest, the cerebellum exerts an overall inhibitory tone over the primary motor cortex (M1), cerebello-brain inhibition (CBI), likely through dentate-thalamo-cortical connections. The level of excitability of this pathway before and after stimulation of the cerebellum, however, has not been directly investigated. In this study we used transcranial magnetic stimulation (TMS) to determine changes in M1, brainstem and CBI before and after 25 minutes of anodal, cathodal or sham transcranial direct current stimulation (tDCS) applied over the right cerebellar cortex. We hypothesized that anodal tDCS would result in an enhancement of CBI and cathodal would decrease it, relative to sham stimulation. We found that cathodal tDCS resulted in a clear decrease of CBI, whereas anodal tDCS increased it, in the absence of changes after sham stimulation. These effects were specific to the cerebello-cortical connections with no changes in other M1 or brainstem excitability measures. The cathodal effect on CBI was found to be dependent on stimulation intensity and lasted up to 30 minutes after the cessation of tDCS. These results suggest that tDCS can modulate in a focal and polarity-specific manner cerebellar excitability, likely through changes in Purkinje cell activity. Therefore, direct current stimulation of the cerebellum may have significant potential implications for patients with cerebellar dysfunction as well as to motor control studies

Dynamic modulation of cerebellar excitability for abrupt, but not gradual, visuomotor adaptation

The cerebellum is critically important for error driven adaptive motor learning, as evidenced by the fact that cerebellar patients do not adapt well to sudden predictable perturbations. However, recent work has shown that cerebellar patients adapt much better if the perturbation is gradually introduced. Here we explore physiological mechanisms that underlie this distinction between abrupt and gradual motor adaptation in humans. We used Transcranial Magnetic Stimulation (TMS) to evaluate whether neural mechanisms within the cerebellum contribute to either process during a visuomotor reach adaptation. When a visuomotor rotation was introduced abruptly, cerebellar excitability changed early in learning, and approached baseline levels near the end of the adaptation block. However, we observed no modulation of cerebellar excitability when we presented the visuomotor rotation gradually during learning. Similarly, we did not observe cerebellar modulation during trial-by-trial adaptation to random visuomotor displacements or during reaches without perturbations. This suggests that the cerebellum is most active during the early-phases of adaptation when large perturbations are successfully compensated

Dopaminergic manipulations affect the modulation and meta-modulation of movement speed:Evidence from two pharmacological interventions

A body of research implicates dopamine in the average speed of simple movements. However, naturalistic movements span a range of different shaped trajectories and rarely proceed at a single constant speed. Instead, speed is reduced when drawing “corners” compared to “straights” (i.e., speed modulation), and the extent of this slowing down is dependent upon the global shape of the movement trajectory (i.e., speed meta-modulation) – for example whether the shape is an ellipse or a rounded square. At present, it is not known how (or whether) dopaminergic function controls continuous changes in speed during movement execution. The current paper reports effects on these kinematic features of movement following two forms of dopamine manipulation: Study One highlights movement differences in individuals with PD both ON and OFF their dopaminergic medication (N = 32); Study Two highlights movement differences in individuals from the general population on haloperidol (a dopamine receptor blocker, or “antagonist”) and placebo (N = 43). Evidence is presented implicating dopamine in speed, speed modulation and speed meta-modulation, whereby low dopamine conditions are associated with reductions in these variables. These findings move beyond vigour models implicating dopamine in average movement speed, and towards a conceptualisation that involves the modulation of speed as a function of contextual information