The effect of aging and contextual information on manual asymmetry in tool use.

Healthy aging affects manual asymmetries in simple motor tasks, such as unilateral reaching and aiming. The effects of aging on manual asymmetries in the performance of a complex, naturalistic task are unknown, but are relevant for investigating the praxis system. This study examined how aging influences manual asymmetry in different contexts in a tool manipulation task. Fifty healthy, right-hand-dominant young (N = 29; 21.41 ± 2.87 years), and elderly (N = 21; mean: 74.14 ± 6.64 years) participants performed a 'slicing' gesture in response to a verbal command in two contexts: with (tool) and without the tool (pantomime). For interjoint relationships between shoulder plane of elevation and elbow flexion, a HAND × AGE × CONTEXT interaction existed (F1,43 = 4.746, p = 0.035). In pantomime, interjoint control deviated more in the left (non-dominant) than the right (dominant) limb in the elderly adult group (Wilcoxon, p = 0.010). No such differences existed in the young adult group (Wilcoxon, p = 0.471). Furthermore, contextual information reduced interjoint deviation in young adults when the task was performed with the right (dominant) hand (Wilcoxon, p = 0.001) and in the elderly adults when the task was performed with the left (non-dominant) hand (Wilcoxon, p = 0.012). The presence of the tool did not reduce interjoint deviation for the right hand in the elderly group (Wilcoxon, p = 0.064) or the left hand in the young group (Wilcoxon, p = 0.044). Deviation within trials (i.e., intrasubject deviation) in elbow flexion was higher in the elderly relative to the young adult group (p = 0.003). Finally, resultant peak velocities were smaller (p = 0.002) and cycle duration longer (p < 0.0001) in the elderly adult group. This study provides novel evidence that aging affects manual asymmetries and sensorimotor control in a naturalistic task and warrants that aging research considers the context in which the task is performed.

Aerobic exercise is more effective than goal-based exercise for the treatment of cognition in Parkinson's disease.

BACKGROUND: Little is known about how different exercise modalities influence cognition in Parkinson's disease (PD). Moreover, the focus of previous investigations on examining the effects of exercise mainly on executive functions and the exclusion of individuals with cognitive impairment may limit the potential to define exercise as a treatment for cognitive decline in PD. OBJECTIVE: The aim of this study was to compare the effects of aerobic and goal-based exercise on five cognitive domains in cognitively normal and impaired individuals with PD. METHODS: Seventy-six individuals with PD were randomly allocated into three groups: Aerobic, Goal-based, and Control. Participants in the exercise groups attended 1-h sessions 3x/week for 12 weeks, while those in the Control group carried on with their regular activities. Changes in cognitive domains were assessed using paper-based neuropsychological tests. RESULTS: Inhibitory control improved only in the Aerobic group (p = .04), irrespective of participants cognitive status at baseline. Moreover, participants with cognitive impairment in Aerobic group maintained their set-shifting ability, whereas those in the Control group were worse at post-test (p = .014). CONCLUSION: This is the first study to show that aerobic exercise is more effective than goal-based exercise for the treatment of cognition in PD with and without cognitive impairment.

End-state comfort in two object manipulation tasks: Investigating how the movement context influences planning in children, young adults, and older adults.

The movement context (pantomime, pantomime with image/object as guide, and actual use) has been shown to influence end-state comfort-the propensity to prioritize a comfortable final hand position over an initially comfortable one-across the lifespan. The present study aimed to assess how the movement context (pantomime, using a dowel as the tool, and actual use) influences end-state comfort when acting with objects (glass/hammer) that differ in use-dependent experience. Children (ages 6-11, n = 70), young adults (n = 21), and older adults (n = 21) picked up an overturned glass to pour water and a hammer to hit a nail, where the handle faced away from the participant. End-state comfort was assessed in each movement context. Findings provide support for an increase in end-state comfort with age, adult-like patterns at age 10, and no difference between older adults and 8- to 9-year-old children. In addition, this work revealed that perception of "graspability" led to an increase in end-state comfort in the hammering task; therefore, suggesting our ability to act with objects and tools in the environment is influenced by use-dependent experience and object perception. Results add to our understanding of changes in motor planning abilities with age, and factors underlying these changes.

How the mode of action affects evidence of planning and movement kinematics in aging: End-state comfort in older adults.

Motor deficits are commonly observed with age; however, it has been argued that older adults are more adept when acting in natural tasks and do not differ from young adults in these contexts. This study assessed end-state comfort and movement kinematics in a familiar task to examine this further. Left- and right-handed older adults picked up a glass (upright or overturned) as if to pour water in four modes of action (pantomime, pantomime with image/cup as a guide, actual grasping). With increasing age, a longer deceleration phase (in pantomime without a stimulus) and less end-state comfort (in pantomime without a stimulus and image as a guide) was displayed as the amount of contextual information available to guide movement decreased. Changes in movement strategies likely reflect an increased reliance on feedback control and demonstration of a more cautious movement. A secondary aim of this study was to assess hand preference and performance, considering conflicting reports of manual asymmetries with age. Performance differences in the Grooved Pegboard place task indicate left handers may display a shift towards right handedness in some, but not all cases. Summarizing, this study supports age-related differences in planning and control processes in a familiar task, and changes in manual asymmetries with age in left handers.

Progression of limb apraxia in corticobasal syndrome: neuropychological and functional neuroimaging report of a case series.

The current study described the progression of limb apraxia in seven corticobasal syndrome patients through a comprehensive battery, including both gesture production tasks and conceptual tool/action knowledge tasks. The examination of the behavioral and neuroimaging (SPECT) data revealed two patient subgroups. One group consisted of patients with preserved conceptual tool/action knowledge, relatively mild gesture production and neuropsychological deficits with few significantly hypoperfused regions of interest. The other group consisted of those whose conceptual tool/action knowledge and general cognition eventually deteriorated and who were quite severely affected in their gesture production performance. These patients were characterized by bilateral hypoperfusion in parietal regions and in one case bilateral anterior cingulate regions.

Examining the construct validity of the Cognitive Competency Test for occupational therapy practice.

BACKGROUND: Enhancing occupational therapy practice requires critical examination of assessment tools and the conclusions being drawn from their use. When working with cognitively impaired older individuals, judgments about occupational competence are often informed by an assessment of cognitive competence. PURPOSE: The Cognitive Competency Test (CCT) is a frequently used measure in Canada to inform predictions of occupational competence. However, there is an absence of published evidence that addresses its validity. METHODS: To appraise validity of the CCT, a retrospective chart review (n = 107) of CCT reports for inpatient and outpatient clients with cognitive impairment was conducted. Data were subjected to exploratory factor analyses to examine the factor structure, and the measure was compared with commonly used clinical variables reflecting cognitive and occupational competence. FINDINGS: Results suggest that the CCT measures a unitary construct and provide some support for its predictive capacity. IMPLICATIONS: CCT scores can add incremental validity to cognitive screens, such as the Mini Mental State Exam, when evaluating occupational competence.

Components of cognitive competence predictive of occupational competence in persons with dementia: a Delphi study.

BACKGROUND: Within the area of dementia care, occupational therapists are asked to predict occupational competence in everyday living and often do so by assessing cognitive competence. Considering the cognitive changes that occur with dementia over time, the construct of cognitive competence is a key consideration. Still, a gap exists in the literature examining the relationship between cognitive competence and occupational competence. PURPOSE: This study developed a consensus among participating Canadian occupational therapists regarding the components of cognitive competence they considered essential to predict occupational competence in people with dementia. METHOD: A three-round Delphi study was completed with English- and French-speaking occupational therapists (n = 127; 116; 125) experienced in dementia care. FINDINGS: Ten cognitive components were identified as essential to predict occupational competence in individuals with dementia. IMPLICATIONS: The 10 identified components provide direction for assessment practices and education in dementia care and for development of measurement tools.

An update on the Conceptual-Production Systems model of apraxia: evidence from stroke.

Limb apraxia is a neurological disorder characterized by an inability to pantomime and/or imitate gestures. It is more commonly observed after left hemisphere damage (LHD), but has also been reported after right hemisphere damage (RHD). The Conceptual-Production Systems model (Roy, 1996) suggests that three systems are involved in the control of purposeful movements: the conceptual, the production and the sensory/perceptual system. Depending on which system is damaged different patterns of apraxia are expressed. To determine the apraxia pattern, pantomime, delayed, and concurrent imitation tasks need to be administered, as well as conceptual tasks assessing one's knowledge of actions. Based on the model, eight patterns of apraxia should emerge. The purpose of this study is to determine whether these patterns are in fact observed in stroke patients and examine their frequency. If the performance of most stroke patients falls into one of the patterns, then we would have strong support for the conceptual-production model. Stroke (34 LHD and 39 RHD) patients and 27 age- and education-matched healthy controls participated in the study. Participants were assessed in four task modalities: pantomime, delayed imitation, concurrent imitation and conceptual knowledge (two tasks were used: tool naming by action and action identification). Patients were categorized as impaired on a task if they scored 2 SD below the mean performance of the controls for gesture production tasks, or below a cut-off score on the conceptual tasks. They were then classified into patterns depending on their performance on the four task modalities. Most patients (86%) fell into one of seven patterns originally predicted from the Conceptual-Production Systems model. The two most common patterns were deficits in pantomime and imitation with preserved gesture recognition and conduction apraxia (selective deficit in imitation). Four new patterns emerged, but mostly single cases of these were found. Overall, the study provides strong support for the Conceptual-Production Systems model.

The Slip Induction Task: creating a window into cognitive control failures.

Regardless of age, education, or social status, we all experience moments where we ask ourselves, "what was I thinking?!?" Typically, we experience errors of this sort, or slips of action, during routine tasks that require a whole sequence of movements. However, most action slip research has focused on creating response conflict within single movements. The Slip Induction Task (SIT) is a step toward creating response conflict within truer to life action routines. As such, the SIT attempts to induce action slips in a well-learned movement routine through the occasional presentation of unexpected cues. We find that the SIT is able to reliably induce action slips, especially when the unexpected cue necessitates a movement to an unexpected target location. Furthermore, when participants are able to avoid an action slip, these changes in movement routine are accompanied by a cost in speed.

Associations and dissociations of transitive and intransitive gestures in left and right hemisphere stroke patients.

The study investigated performance on pantomime and imitation of transitive and intransitive gestures in 80 stroke patients, 42 with left (LHD) and 38 with right (RHD) hemisphere damage. Patients were also categorized in two groups based on the time that has elapsed between their stroke and the apraxia assessment: acute-subacute (n=42) and chronic (n=38). In addition, patterns of performance in apraxia were examined. We expected that acute-subacute patients would be more impaired than chronic patients and that LHD patients would be more impaired than RHD patients, relative to controls. The hemisphere prediction was confirmed, replicating previous findings. The frequency of apraxia was also higher in all LHD time post-stroke groups. The most common impairment after LHD was impairment in both pantomime and imitation in both transitive and intransitive gestures. Selective deficits in imitation were more frequent after RHD for transitive gestures but for intransitive gestures they were more frequent after LHD. Patients were more impaired on imitation than pantomime, relative to controls. In addition, after looking at both gesture types concurrently, we have described cases of patients who suffered deficits in pantomime of intransitive gestures with preserved performance on transitive gestures. Such cases show that the right hemisphere may be in some cases critical for the successful pantomime of intransitive gestures and the neural networks subserving them may be distinct. Chronic patients were also less impaired than acute-subacute patients, even though the difference did not reach significance. A longitudinal study is needed to examine the recovery patterns in both LHD and RHD patients.

Carotid pulse pressure and intima media thickness are independently associated with cerebral hemodynamic pulsatility in community-living older adults.

Vascular aging is associated with markers of cerebrovascular impairment. Whether discrete characteristics of arterial structure and function have independent and/or additive effects on cerebral hemodynamics, however, is not completely understood. We examined the association of cerebral hemodynamics with common carotid artery intima-media thickness (IMT) and pulse pressure (PP) in 61 older adults with prevalent cardiometabolic risk but no history of cerebrovascular disease. We calculated pulsatility index (PI) and hypercapnic reactivity of the middle cerebral artery, as well as global blood flow through the extracranial arteries. The dominant effects were related to hemodynamic pulsatility. In adults with metabolic syndrome, PI was related to IMT (r = 0.48, P = 0.003) after adjustment for age and sex. Without metabolic syndrome, PI was directly related to PP (r = 0.63, P = 0.003). Across the whole cohort, PP [ß (95%CI) = 0.42 (0.18, 0.67), P = 0.001] and IMT [0.42 (0.18, 0.67), P < 0.001] remained significant predictors of PI, after accounting for individual cardiometabolic risk factors. The independent and combined effects of IMT and PP were tested by binarizing PP and IMT at the sample median. Participants with both IMT and PP above their respective medians had elevated PI compared with those with both vascular markers below the median [median (interquartile range) = 1.06 (0.22) vs. 0.84 (0.14), P = 0.003)]. PI was not different from the low risk group if only one of IMT or PP were above the median. Although overall vascular burden was low, moderate associations with PI persisted, suggesting pulsatile characteristics represent one of the earliest markers linking vascular aging to changes in brain health.

A model-based approach to understanding apraxia in Corticobasal Syndrome.

Limb apraxia is a neurological disorder of higher cognitive function characterized by an inability to perform purposeful skilled movements and not attributable to an elementary sensorimotor dysfunction or comprehension difficulty. Corticobasal Syndrome (CBS) is an akinetic rigid syndrome with asymmetric onset and progression with at least one basal ganglia feature (rigidity, limb dystonia or myoclonus) and one cortical feature (limb apraxia, alien hand syndrome or cortical sensory loss). Even though limb apraxia is highly prevalent in CBS (70-80%), very few studies have examined the performance of CBS patients on praxis measures in detail. This review aims to (1) briefly summarize the clinical, neuroanatomical and pathological findings in CBS, (2) briefly outline what limb apraxia is and how it is assessed, (3) to comprehensively review the literature on limb apraxia in CBS to date and (4) to briefly summarize the literature on other forms of apraxia, such as limb-kinetic apraxia and buccofacial apraxia. Overall, the goal of the review is to bring a model-based perspective to the findings available in the literature to date on limb apraxia in CBS.

End-State Comfort Across the Lifespan: A Cross-Sectional Investigation of How Movement Context Influences Motor Planning in an Overturned Glass Task.

Young adults plan actions in advance to minimize the cost of movement. This is exemplified by the end-state comfort (ESC) effect. A pattern of improvement in ESC in children is linked to the development of cognitive control processes, and decline in older adults is attributed to cognitive decline. This study used a cross-sectional design to examine how movement context (pantomime, demonstration with image/glass as a guide, actual grasping) influences between-hand differences in ESC planning. Children (5- to 12-year-olds), young adults, and two groups of older adults (aged 60-70, and aged 71 and older) were assessed. Findings provide evidence for adult-like patterns of ESC in 8-year-olds. Results are attributed to improvements in proprioceptive acuity and proficiency in generating and implementing internal representations of action. For older adults early in the aging process, sensitivity to ESC did not differ from young adults. However, with increasing age, differences reflect challenges in motor planning with increases in cognitive demand, similar to previous work. Findings have implications for understanding lifespan motor behavior.

Acute effects of aerobic exercise on cognitive function in individuals with Parkinson's disease.

Deficits in executive functions are highly prevalent in Parkinson's disease (PD). Although chronic physical exercise has been shown to improve executive functions in PD, evidence of acute exercise effects is limited. This study aimed to evaluate the effects of an acute bout of exercise on cognitive processes underlying executive functions in PD. Twenty individuals with PD were assessed in both a Control and an Exercise conditions. In each condition, individuals started performing a simple and a choice reaction time (RT) task. Subsequently, participants were asked to sit on a cycle ergometer (Control) or cycle (Exercise) for 20 min in counterbalanced order. Participants were asked to repeat both reaction time tasks after 15-min rest period in both conditions. While no differences were found in simple RT, participants showed faster choice RT post Exercise as well as Control conditions (p = .012). Participants had slower choice RT for target stimulus compared to non-target stimuli irrespective of time or experimental condition (p < .001). There was no change in accuracy following experimental conditions. Results suggest that individuals with PD may not respond behaviourally to a single bout of exercise. The lack of selective effects of exercise on cognition suggests that practice effects may have influenced previous research. Future studies should assess whether neurophysiological changes might occur after an acute bout of exercise in PD.

Object-Tool-Actor Interaction: Object Information Drives Intended Action.

Tool use is typically explored via actor-tool interactions. However, the target-object (that which is being acted on) may influence perceived action possibilities and thereby guide action. Three different tool-target-object pairings were tested (Experiment 1). The hammering action demonstrated the greatest sensitivity and therefore subsequently used to further investigate target-object pairings. The hammer was removed as an option and instructions were provided using pictorial (Experiment 2), written (Experiment 3), and both pictorial and written formats (Experiment 4). The designed tool is chosen when available (Experiment 1) and when removed as a choice (i.e., the hammer), participants perform the same action associated with the designed tool (i.e., hammering) regardless of instruction method (Experiments 2, 3, and 4).

Speech perception and motor control in children with Down syndrome.

Twelve children with and without Down syndrome (DS) performed eight subtests of an apraxia battery to determine under what conditions children with DS had difficulty performing representational and nonrepresentational gestures. Participants with DS also completed a dichotic listening test. Participants with DS performed just as well as control participants on all aspects of the apraxia battery except a subtest in which they were required to pantomime tool use from verbal instruction. This suggests that children with DS have difficulty generating an action from memory following verbal instruction. Given the sufficient context or visual demonstration, children with DS performed similar to the other participants. As well, there was a great deal of within-group variability for dichotic listening ear advantage. Participants with a greater left ear advantage on the dichotic listening test committed more errors on an imitation test that also included a verbal component than participants with a greater right ear advantage.

Neuropsychological profile of acute alcohol intoxication during ascending and descending blood alcohol concentrations.

Numerous studies have investigated the effects of alcohol on motor processes during rising and declining blood alcohol concentrations (BAC), however, relatively little research has examined the alcohol-induced impairment of cognitive performance on the two limbs of the BAC curve. This experiment administered a neuropsychological test battery to assess the degree to which rising and declining BACs during an acute dose of alcohol impair nine cognitive processes within an individual. In all, 20 healthy male social drinkers (university students) were assigned to one of two groups (n = 10) who received a beverage containing either 0.0 g/kg (placebo) or 0.65 g/kg alcohol and performed the test battery when BAC was increasing and was decreasing. Comparisons of alcohol and placebo groups revealed impairment (slower response and/or increased errors) in seven of the cognitive processes: long-term verbal memory; information processing; declarative memory; inhibitory control; short-term visual memory; long-term visual memory, and visual-spatial working memory. However, some processes were impaired only during rising BACs whereas the impairment of others during declining BACs was evident only by an increase in errors. These results show cognitive tasks performed by an individual are not similarly affected by rising and declining BACs, and call attention to the importance of assessing both speed and accuracy on both limbs of the BAC curve. The particular cognitive processes differentially affected by rising vs declining BACs raised the possibility that acute alcohol intoxication may impair one cerebral hemisphere to a greater degree than the other, and this could be explored by neuroimaging techniques.

A single session of exercise as a modulator of short-term learning in healthy individuals.

BACKGROUND: A single session of aerobic exercise is linked to faster motor responses; however, the effect on rate of short-term learning is less clear. The objective was to evaluate the influence of a single bout of aerobic exercise on the rate of short-term acquisition of a shape-letter association task requiring a motor response. METHODS: 23 [11 females, age 20.8±2.7years] healthy young adults were evaluated using a randomly assigned crossover design which was counterbalanced for order before and after moderate (exercise) and light (control) intensity cycle ergometry. Participants performed 3 blocks, with each block consisting of one round of training and testing. During training, participants were tasked with learning 6 unique shape-letter associations. Subsequent testing required a key press response to a visually presented shape pattern. Response time and error rates were used to assess acquisition over the 3 blocks of testing. RESULTS: Mean response time was faster post-exercise relative to the other testing periods, and approached statistical significance compared to post-control (p<0.07). However, no significant difference in response time reduction (difference between test block 1 and test block 3) was identified between the four evaluations (pre and post the exercise and control conditions). Error rate reduction (test block 1 minus test block 3) revealed that individuals had the smallest change in error rate post-exercise (p<0.05). Follow-up analyses revealed fewer errors in test block 1 and test block 2 post-exercise which approached statistical significance (p=0.06) suggesting near-perfect error rates were obtained after only 2 testing blocks post-exercise compared to 3 blocks in the other testing periods. CONCLUSIONS: Support for augmentation of short-term learning was mixed as errors were reduced post-exercise while response time was not different between evaluations. Future work should include neurophysiological evaluation and a retention test to better elucidate the influence of aerobic exercise on rate of short-term learning.

Unilateral basal ganglia damage causes contralesional force control deficits: a case study.

When grasping to lift an object, the grip force is usually scaled to the mass of the object. However, it has been shown that lifting objects of different sizes but equal masses results in the generation of higher forces for larger compared to smaller objects. The objective of this study was to investigate whether a similar effect is present in an individual (RI) with a unilateral lesion to the basal ganglia (BG). It was hypothesized that if the BG have an influence on the use of visual information in updating of the internal model used to anticipate the forces required for grasping, damage to these structures should result in the inability of RI's contralesional hand to anticipate object mass based on size cues. To test this hypothesis three objects of equal mass but different sizes were grasped and lifted by RI and six control individuals. The forces that were generated during these lifts were quantified. The controls showed the expected increases in peak grip force as object size increased. RI showed no effect of object size for his contralesional hand, but did show force scaling with his ipsilesional hand. In conclusion, RI's BG damage affected the on-line control of grip forces and the inability to integrate visual and tactile information in the programming of finger forces.

Relative processing demands influence cerebral laterality for verbal-motor integration in persons with Down syndrome.

The study of cerebral specialization in the Down syndrome (DS) population has revealed an anomalous pattern of organization. In particular, dichotic-listening studies have suggested a left-ear/right hemisphere dominance for speech perception, whereas motor control research has revealed a left hemisphere dominance for executive-motor control. In the present investigation, we employed a recent adaptation of the dichotic listening procedure to examine interhemispheric integration during the performance of a lateralized verbal-motor task. Specifically, using the selective dichotic-listening procedure, participants were required to complete a rapid left or right hand pointing movement to one of two pictorial icons corresponding to the word presented to their precued ear. We observed that persons with DS (N = 17) and age-matched controls (N = 35) exhibited a right-ear advantage (REA) for our dichotic-aiming task. While these results appear to contradict previous dichotic listening studies, we propose that the manifestation of a lateral ear advantage in the DS population may have more to do with the response requirements of the task than with the characteristics or complexity of the stimulus material.