Cognitive-motor interference during goal-directed upper-limb movements

Reaching the cognitive-motor interface: effects of cognitive load on arm choice and motor performance after stroke

A vexing characteristic of motor disability after stroke is that many individuals fail to use their affected arm effectively despite having the capacity to do so, a phenomenon termed arm nonuse. Based on the hypothesis that nonuse is influenced by the competing cognitive demands of many daily activities, we examined the effects of cognitive load on arm choice and motor performance in individuals with stroke using a novel virtual reality paradigm that mimics the demands of real-life visual search, object selection, and reaching to targets. Twenty individuals with single left or right hemispheric chronic stroke (11 left cerebrovascular accident; 9 right cerebrovascular accident) and 10 age-matched neurotypical participants completed the Virtual Reality Arm Choice task, in which they reached for target objects in an array under varied cognitive demand. To manipulate cognitive demand, we varied the semantic similarity of objects in the reaching space and the presence or absence of a secondary task. The results showed reduced use of the paretic arm under increased demand. Under cognitive load, participants with stroke also showed slower reach initiation, slower movements, increased reach curvature, and increased performance differences between the paretic and non-paretic arms. The arm choice of neurotypical individuals was also modulated under cognitive load. These data indicate that cognitive factors influence arm choice and motor performance in naturalistic reaching tasks in individuals with chronic stroke. Performance decrements under cognitive load may in turn influence reduced paretic arm use during daily activities.

Increased dual-task interference during upper limb movements in stroke exceeding that found in aging - a systematic review and meta-analysis

Objective

To determine whether dual-task interference during upper limb tasks is increased in patients after stroke compared to healthy older subjects and to compare magnitude of stroke-induced change in interference to that explained by aging.

Methods

We conducted a systematic literature search in MEDLINE, CINAHL, Google Scholar and PEDro databases up to October 2023 for studies on upper limb dual-tasks in stroke and elderly healthy subjects. Eleven upper limb dual-task studies in stroke patients and 11 studies in healthy older subjects were identified and systematically reviewed. A meta-analysis was performed on seven stroke studies and on five studies in healthy older subjects that included control groups.

Results

Most stroke studies investigated proximal arm movements with kinematic measures, but few studies evaluated manual dexterity. In contrast, studies in healthy older subjects used more distal (finger tapping) tasks. The meta-analysis showed that stroke patients had on average a 19% (CI 95% = 1.0-37.3) increase in dual-task interference compared to age-matched healthy controls (Z = 2.06, p = 0.04). Older healthy subjects showed greater dual-task interference compared to younger subjects (19% greater, CI 95% = 6.5-31.2, Z = 2.98, p = 0.003).

Conclusion

Meta-analysis revealed an increase in dual-task interference during upper limb movements in stroke patients, exceeding age-related changes, supporting the presence of subclinical impairments in divided attention post-stroke that may impede motor recovery.

Does the introduction of a cobot change the productivity and posture of the operators in a collaborative task?

Musculoskeletal disorders (MSDs) are the main occupational diseases and are pathologies of multifactorial origin, with posture being one of them. This creates new human-robot collaboration situations that can modify operator behaviors and performance in their task. These changes raise questions about human-robot team performance and operator health. This study aims to understand the consequences of introducing a cobot on work performance, operator posture, and the quality of interactions. It also aims to evaluate the impact of two levels of difficulty in a dual task on these measures. For this purpose, thirty-four participants performed an assembly task in collaboration with a co-worker, either a human or a cobot with two articulated arms. In addition to this motor task, the participants had to perform an auditory task with two levels of difficulty (dual task). They were equipped with seventeen motion capture sensors. The collaborative work was filmed with a camera, and the actions of the participants and co-worker were coded based on the dichotomy of idle and activity. Interactions were coded based on time out, cooperation, and collaboration. The results showed that performance (number of products manufactured) was lower when the participant collaborated with a cobot rather than a human, with also less collaboration and activity time. However, RULA scores were lower-indicating a reduced risk of musculoskeletal disorders-during collaboration with a cobot compared to a human. Despite a decrease in production and a loss of fluidity, likely due to the characteristics of the cobot, working in collaboration with a cobot makes the task safer in terms of the risk of musculoskeletal disorders.

The reliability of simultaneous versus individual data collection during stuttering assessment

BACKGROUND

Speech-language pathologists often multitask in order to be efficient with their commonly large caseloads. In stuttering assessment, multitasking often involves collecting multiple measures simultaneously.

AIMS

The present study sought to determine reliability when collecting multiple measures simultaneously versus individually.

METHODS & PROCEDURES

Over two time periods, 50 graduate students viewed videos of four persons who stutter (PWS) and counted the number of stuttered syllables and total number of syllables uttered, and rated speech naturalness. Students were randomly assigned to one of two groups: the simultaneous group, in which all measures were gathered during one viewing; and the individual group, in which one measure was gathered per viewing. Relative and absolute intra- and inter-rater reliability values were calculated for each measure.

OUTCOMES & RESULTS

The following results were notable: better intra-rater relative reliability for the number of stuttered syllables for the individual group (intraclass correlation coefficient (ICC) = 0.839) compared with the simultaneous group (ICC = 0.350), smaller intra-rater standard error of measurement (SEM) (i.e., better absolute reliability) for the number of stuttered syllables for the individual group (7.40) versus the simultaneous group (15.67), and better inter-rater absolute reliability for the total number of syllables for the individual group (88.29) compared with the simultaneous group (125.05). Absolute reliability was unacceptable for all measures across both groups.

CONCLUSIONS & IMPLICATIONS

These findings show that judges are likely to be more reliable when identifying stuttered syllables in isolation than when simultaneously collecting them with total syllables spoken and naturalness data. Results are discussed in terms of narrowing the reliability gap between data collection methods for stuttered syllables, improving overall reliability of stuttering measurements, and a procedural change when implementing widely used stuttering assessment protocols.

WHAT THIS PAPER ADDS

What is already known on the subject The reliability of stuttering judgments has been found to be unacceptable across a number of studies, including those examining the reliability of the most popular stuttering assessment tool, the Stuttering Severity Instrument (4th edition). The SSI-4, and other assessment applications, involve collecting multiple measures simultaneously. It has been suggested, but not examined, that collecting measures simultaneously, which occurs in the most popular stuttering assessment protocols, may result in substantially inferior reliability when compared to collecting measures individually. What this paper adds to existing knowledge The present study has multiple novel findings. First, relative and absolute intra-rater reliability were substantially better when stuttered syllables data were collected individually compared to when the same data were collected simultaneously with total number of syllables and speech naturalness data. Second, inter-rater absolute reliability for total number of syllables was also substantially better when collected individually. Third, intra-rater and inter-rater reliability were similar when speech naturalness ratings were given individually compared to when they were given while simultaneously counting stuttered and fluent syllables. What are the potential or actual clinical implications of this work? Clinicians can be more reliable when identifying stuttered syllables individually compared to when they judge stuttering along with other clinical measures of stuttering. In addition, when clinicians and researchers use current popular protocols for assessing stuttering that recommend simultaneous data collection, including the SSI-4, they should instead consider collecting stuttering event counts individually. This procedural change will lead to more reliable data and stronger clinical decision making.

Assessing upper extremity-cognitive dual-task ability in neurological populations: A systematic review

BACKGROUND

Dual-task involves performing cognitive and motor tasks together, which requires executive functions that may be impaired in individuals with neurological conditions. Therefore, it is important to accurately assess executive functions to plan a therapeutic intervention.

OBJECTIVE

To characterize the use of upper extremity-cognitive dual-task assessment and to describe variables correlated with dual-task ability.

METHODS

An electronic search of databases (MEDLINE, EMBASE, CINAHL, and PsycINFO) was carried out using a combination of the following terms: upper-extremity, dual/concurrent task, and cognitive/motor tasks. Two reviewers independently completed data extraction and assessed study quality.

RESULTS

1,946 studies were identified; 25 studies met the inclusion criteria. The purpose of using an upper extremity-cognitive dual-task assessment varied between studies as well as the upper extremity motor tasks used: pegboard (N = 14), arm curl (N = 9), finger-tapping (N = 3), and reaching (N = 1) tests. Dual-task ability was reported as the motor-cognitive interference (N = 15) and as motor cost (N = 12). Dual-task ability was correlated to cognition, brain activity, and daily function, and was significantly different between healthy and neurological individuals.

CONCLUSION

Upper extremity cognitive dual-task paradigm is gaining popularity in clinical research, but lacks standardized tools, testing procedures, and calculations. A structured assessment procedure is needed for clinical use and future research.

Dual-Tasking in Daily Activities Among Adults With and Without Stroke

IMPORTANCE

In laboratory settings, dual-tasking is a performance strategy affected by dominance and stroke. However, the volitional use of dual-tasking has not been examined during naturalistic performance of activities of daily living (ADLs).

OBJECTIVE

To examine dual-tasking in the context of ADLs and identify whether dominance and stroke influence its use.

DESIGN

Cross-sectional, observational.

SETTING

Academic medical center.

PARTICIPANTS

Forty-three participants with chronic stroke and upper extremity (UE) motor impairment and 19 control participants without stroke.

OUTCOMES AND MEASURES

We identified dual-tasking as the performance of dual-object primitives (DOPs), a functional strategy to manage two objects simultaneously. We videotaped participants performing feeding and toothbrushing tasks and identified the initiation and frequency of DOPs. We assessed whether these outcomes were influenced by UE dominance or paresis and whether among participants with stroke these outcomes were influenced by motor impairment (using the Fugl-Meyer Assessment) or cognitive impairment (using the Montreal Cognitive Assessment).

RESULTS

DOP initiation was reduced on the nondominant side of control UEs and in the paretic UE of participants with stroke. After DOPs were initiated, however, their frequency was not significantly related to dominance or paresis. Among participants with stroke, DOP initiation but not DOP frequency was influenced by motor impairment, and neither were influenced by cognitive impairment.

CONCLUSIONS AND RELEVANCE

The initiation of dual-tasking is curtailed in the nondominant and paretic UEs, extending previous laboratory-based findings to a more naturalistic setting. These results may reflect a demand on neural resources that is exceeded when these limbs are used. What This Article Adds: DOPs, a functional strategy to simultaneously engage two objects during ADLs, could serve as a behavioral marker of dual-tasking in real-world activities, supporting their investigation more broadly. Practicing DOPs in rehabilitation could also train the integration of dual-tasking strategies in activity execution.

Tremor, finger and hand dexterity and force steadiness, do not change after mental fatigue in healthy humans

The effects of mental fatigue have been studied in relation to specific percentages of maximal aerobic or anaerobic efforts, maximal voluntary contractions or the performance of sport specific skills. However, its effects on tremor, dexterity and force steadiness have been only marginally explored. The present work aimed at filling this gap. In twenty-nine young individuals, measurement of postural, kinetic and isometric tremor, pinch force steadiness and finger and hand dexterity were performed before and after either 100 min of mental fatigue or control tasks. During the interventions blood pressure, oxygen saturation and heart rate and perceived effort in continuing the task were recorded every 10 minutes. Tremor was analysed in both time (standard deviation) and frequency domain (position, amplitude and area of the dominant peak) of the acceleration signal. Finger dexterity was assessed by Purdue pegboard test and hand dexterity in terms of contact time in a buzz wire exercise. Force steadiness was quantified as coefficient of variation of the force signal. Postural, kinetic and isometric tremors, force steadiness and dexterity were not affected. Higher oxygen saturation values and higher variability of heart rate and blood pressure were found in the intervention group during the mental fatigue protocol (p < .001). The results provide no evidence that mental fatigue affects the neuromuscular parameters that influence postural, kinetic or isometric tremor, force steadiness and dexterity when measured in single-task conditions. Increased variability in heart rate may suggest that the volunteers in the intervention group altered their alert/stress state. Therefore, it is possible that the alterations that are commonly observed during mental fatigue, and that could have affected tremor, steadiness and dexterity only last for the duration of the cognitive task and are not detectable anymore soon after the mental task is terminated.

Dual task effect on upper and lower extremity skills in different stages of Parkinson's disease

BACKGROUND AND PURPOSE

Loss of automaticity and deteriorated executive function give rise to dual task deficits in Parkinson's disease (PD). This study aimed to compare single task and dual task upper and lower extremity skills in people with PD (PwPD) at different stages of PD and to examine the dual task effect (DTE) on upper and lower extremity skills in PwPD at different stages of PD. The second aim was to investigate the relationship between the DTE and the quality of life in PwPD.

METHODS

30 patients divided into 2 groups as mild PD group and moderate PD group according to the Modified Hoehn & Yahr Scale. 15 age matched healthy adults were recruited as the control group. The Unified Parkinson's Disease Rating Scale (UPDRS), the Purdue Pegboard Test (PPT), the Timed Up and Go Test (TUG), the 10 Meter Walk Test (10MWT), and the Parkinson's Disease Questionnaire (PDQ-8) were used for assessments.

RESULTS

Single task and dual task scores of all assessments of all groups were significantly different. The DTE on PPT was greater in mild and moderate PD groups than control group and significantly lower in mild PD group than moderate PD group. However, DTE on the TUG and 10MWT was not different in mild PD group than control group and DTE significantly lower in both groups than moderate PD group. Significant correlations between the DTE on PPT, TUG and 10MWT and the PDQ-8 in PwPD were observed.

CONCLUSION

Dual task has a worsening effect on upper and lower extremity skills in PwPD. This effect can be observed earlier in upper extremity skills than lower extremity skills. Also, the DTE and the QoL in PwPD are related.

The effect of increased cognitive processing on reactive balance control following perturbations to the upper limb

Reactive balance control following hand perturbations is important for everyday living as humans constantly encounter perturbations to the upper limb while performing functional tasks while standing. When multiple tasks are performed simultaneously, cognitive processing is increased, and performance on at least one of the tasks is often disrupted, owing to attentional resources being divided. The purpose here was to assess the effects of increased cognitive processing on whole-body balance responses to perturbations of the hand during continuous voluntary reaching. Sixteen participants (8 females; 22.9 ± 4.5 years) stood and grasped the handle of a KINARM - a robotic-controlled manipulandum paired with an augmented visual display. Participants completed 10 total trials of 100 mediolateral arm movements at a consistent speed of one reach per second, and an auditory n-back task (cognitive task). Twenty anteroposterior hand perturbations were interspersed randomly throughout the reaching trials. The arm movements with random arm perturbations were either performed simultaneously with the cognitive task (combined task) or in isolation (arm perturbation task). Peak centre of pressure (COP) displacement and velocity, time to COP displacement onset and peak, as well as hand displacement and velocity following the hand perturbation were evaluated. N-back response times were 8% slower and 11% less accurate for the combined than the cognitive task. Peak COP displacement following posterior perturbations increased by 8% during the combined compared to the arm perturbation task alone, with no other differences detected. Hand peak displacement decreased by 5% during the combined compared to the arm perturbation task. The main findings indicate that with increased cognitive processing, attentional resources were allocated from the cognitive task towards upper limb movements, while attentional resources for balance seemed unaltered.

Differences in Dual Task Performance After Robotic Upper Extremity Rehabilitation in Hemiplegic Stroke Patients

Background: Cognitive–motor interference is a phenomenon in which the concomitant performance of cognitive and motor tasks results in poorer performance than the isolated performance of these tasks. We aimed to evaluate changes in dual-task performance after robotic upper extremity rehabilitation in patients with stroke-induced hemiplegia.

Methods: This prospective study included patients with left upper limb weakness secondary to middle cerebral artery stroke who visited a rehabilitation hospital. Participants performed a total of 640 robot-assisted planar reaching movements during a therapist-supervised robotic intervention that was conducted five times a week for 4 weeks. Cognitive and motor performance was separately evaluated in single- and dual-task conditions. The digit span test and Controlled Oral Word Association Test (COWAT) were used to assess cognitive performance, whereas motor performance was evaluated through kinematic assessment of the motor task.

Results: In single-task conditions, motor performance showed significant improvement after robotic rehabilitation, as did the scores of the COWAT subdomains of animal naming (p < 0.001), supermarket item naming (p < 0.06), and phonemes (p < 0.05). In dual-task conditions, all motor task performance variables except mean velocity showed improvement after robotic rehabilitation. The type of cognitive task did not affect the dual-task effect, and there were no significant differences in the dual-task effects of motor, cognitive, or the sum of motor and cognitive performance after robotic rehabilitation.

Conclusion: Post-stroke robotic rehabilitation has different effects on motor and cognitive function, with more consistent effects on motor function than on cognitive function. Although motor and cognitive performance improved after robotic rehabilitation, there were no changes in the corresponding dual-task effects.

Obstacle Avoidance and Dual-Tasking During Reaching While Standing in Patients With Mild Chronic Stroke

Background. Poststroke individuals use their paretic arms less often than expected in daily life situations, even when motor recovery is scored highly in clinical tests. Real-world environments are often unpredictable and require the ability to multitask and make decisions about rapid and accurate arm movement adjustments. Objective. To identify whether and to what extent cognitive-motor deficits in well-recovered individuals with stroke affect the ability to rapidly adapt reaching movements in changing cognitive and environmental conditions. Methods. Thirteen individuals with mild stroke and 11 healthy controls performed an obstacle avoidance task in a virtual environment while standing. Subjects reached for a virtual juice bottle with their hemiparetic arm as quickly as possible under single- and dual-task conditions. In the single-task condition, a sliding glass door partially obstructed the reaching path of the paretic arm. A successful trial was counted when the subject touched the bottle without the hand colliding with the door. In the dual-task condition, subjects repeated the same task while performing an auditory-verbal working memory task. Results. Individuals with stroke had significantly lower success rates than controls in avoiding the moving door in single-task (stroke: 51.8 ± 21.2%, control: 70.6 ± 12.7%; P = .018) and dual-task conditions (stroke: 40.0 ± 27.6%, control: 65.3 ± 20.0%; P = .015). Endpoint speed was lower in stroke subjects for successful trials in both conditions. Obstacle avoidance deficits were exacerbated by increased cognitive demands in both groups. Individuals reporting greater confidence using their hemiparetic arm had higher success rates. Conclusion. Clinically well-recovered individuals with stroke may have persistent deficits performing a complex reaching task.

Sensorimotor vs. Motor Upper Limb Therapy for Patients With Motor and Somatosensory Deficits: A Randomized Controlled Trial in the Early Rehabilitation Phase After Stroke

Background: Somatosensory function plays an important role in motor learning. More than half of the stroke patients have somatosensory impairments in the upper limb, which could hamper recovery. Question: Is sensorimotor upper limb (UL) therapy of more benefit for motor and somatosensory outcome than motor therapy? Design: Randomized assessor- blinded multicenter controlled trial with block randomization stratified for neglect, severity of motor impairment, and type of stroke. Participants: 40 first-ever stroke patients with UL sensorimotor impairments admitted to the rehabilitation center. Intervention: Both groups received 16 h of additional therapy over 4 weeks consisting of sensorimotor (N = 22) or motor (N = 18) UL therapy. Outcome measures: Action Research Arm test (ARAT) as primary outcome, and other motor and somatosensory measures were assessed at baseline, post-intervention and after 4 weeks follow-up. Results: No significant between-group differences were found for change scores in ARAT or any somatosensory measure between the three time points. For UL impairment (Fugl-Meyer assessment), a significant greater improvement was found for the motor group compared to the sensorimotor group from baseline to post-intervention [mean (SD) improvement 14.65 (2.19) vs. 5.99 (2.06); p = 0.01] and from baseline to follow-up [17.38 (2.37) vs. 6.75 (2.29); p = 0.003]. Conclusion: UL motor therapy may improve motor impairment more than UL sensorimotor therapy in patients with sensorimotor impairments in the early rehabilitation phase post stroke. For these patients, integrated sensorimotor therapy may not improve somatosensory function and may be less effective for motor recovery. Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT03236376.

The patients' perspective on the perceived difficulties of dual-tasking: development and validation of the Dual-task Impact on Daily-living Activities Questionnaire (DIDA-Q)

BACKGROUND

Everyday-life activities often require performing dual tasks (DT), with consequent possible occurrence of motor-cognitive or motor-motor interference. This could reduce quality of life, in particular in people with neurological diseases. However, there is lack of validated tools to assess the patients' perspective on DT difficulties in this population. Therefore, we developed the Dual-task Impact on Daily-living Activities-Questionnaire (DIDA-Q) and tested its psychometric properties in people with multiple sclerosis (PwMS).

METHODS

Items were generated based on existing scales, DT paradigms used in previous studies and the opinion of a multi-stakeholder group, including both experts and PwMS. Twenty DT constituted the preliminary version of the DIDA-Q which was administered to 230 PwMS. The psychometric properties of the scale were evaluated including internal consistency, validity and reliability.

RESULTS

Nineteen items survived after exploratory factor analysis, showing a three-factor solution which identifies the components mostly contributing to DT perceived difficulty (i.e., balance and mobility, cognition and upper-limb ability). The DIDA-Q appropriately fits the graded response model, with first evaluations supporting internal consistency (Cronbach's alpha=0.95), validity (70% of the hypotheses for convergent and discriminant constructs confirmed) and reliability (intraclass correlation coefficients=0.95) of this tool.

CONCLUSION

The DIDA-Q could be used in research and clinical settings to discriminate individuals with low vs. high cognitive-motor or motor-motor interference, and to develop and evaluate the efficacy of personalized DT rehabilitative treatments in PwMS.

Assessment of Cognitive-Motor Performance Costs, Task Prioritization, and Adaptation to Dishwashing Under Increased Demand in Older Women With Arthritis

Background and Objectives

Hand arthritis can limit upper-limb instrumental activities of daily living (IADLs) and require the recruitment of additional cognitive and motor resources to support performance. We devised a dual-task protocol for dishwashing to examine cognitive-motor performance costs and prioritizations under increased demands, processes of adaptation, and individual differences in performance costs.

Research Design and Methods

Sixty women with hand arthritis (aged 60–91) completed a standardized dishwashing protocol. Motor demand was increased via the properties of the soap dispenser. Cognitive demand was increased using audial attention and response inhibition tasks. The protocol was completed twice per lab visit on 3 occasions. Response time and dishwashing time provided measures of cognitive and motor task performance. Prioritization was determined by comparing the magnitude of dual-task cost (DTC) across tasks. Adaptation to the dishwashing protocol and novel dispenser was assessed by change in DTC across lab visits. Individual differences in cognitive and physical ability were assessed with the trail making B test and gait speed.

Results

Estimates from linear mixed-effects models revealed that response time increased, whereas dishwashing time decreased, during the dual-task study stages. Cognitive-motor prioritization effects were most pronounced among women with lower cognitive and physical ability. Evidence of prioritization and individual differences in DTC diminished across lab visits.

Discussion and Implications

The pattern of results suggests that older women with arthritis prioritize the motor over cognitive components of dishwashing, a common IADL. Adaptation across lab visits resulted in improved performance, reduced evidence of prioritization, and attenuated differences in DTC across physical and cognitive abilities.

The effects of anxiety and dual-task on upper limb motor control of chronic stroke survivors

This study was designed to investigate the effects of anxiety and dual-task on reach and grasp motor control in chronic stroke survivors compared with age- and sex-matched healthy subjects (HC). Reach and grasp kinematic data of 68 participants (high-anxiety stroke (HA-stroke), n = 17; low-anxiety stroke (LA-stroke), n = 17; low-anxiety HC, n = 17; and high-anxiety HC, n = 17) were recorded under single- and dual-task conditions. Inefficient reach and grasp of stroke participants, especially HA-stroke were found compared with the control groups under single- and dual-task conditions as evidenced by longer movement time (MT), lower and earlier peak velocity (PV) as well as delayed and smaller hand opening. The effects of dual-task on reach and grasp kinematic measures were similar between HCs and stroke participants (i.e., increased MT, decreased PV that occurred earlier, and delayed and decreased hand opening), with greater effect in stroke groups than HCs, and in HA-stroke group than LA-stroke group. The results indicate that performing a well-learned upper limb movement with concurrent cognitive task leads to decreased efficiency of motor control in chronic stroke survivors compared with HCs. HA-stroke participants were more adversely affected by challenging dual-task conditions, underlying importance of assessing anxiety and designing effective interventions for it in chronic stroke survivors.

Cognitive-motor interference during goal-directed upper-limb movements

Research and clinical practice have focused on effects of a cognitive dual‐task on highly automated motor tasks such as walking or maintaining balance. Despite potential importance for daily life performance, there are only a few small studies on dual‐task effects on upper‐limb motor control. We therefore developed a protocol for assessing cognitive‐motor interference (CMI) during upper‐limb motor control and used it to evaluate dual‐task effects in 57 healthy individuals and two highly prevalent neurological disorders associated with deficits of cognitive and motor processing (57 patients with Parkinson's disease [PD], 57 stroke patients). Performance was evaluated in cognitive and motor domains under single‐ and dual‐task conditions. Patterns of CMI were explored to evaluate overall attentional capacity and attention allocation. As expected, patients with neurological deficits showed different patterns of CMI compared to healthy individuals, depending on diagnosis (PD or stroke) and severity of cognitive and/or motor symptoms. Healthy individuals experienced CMI especially under challenging conditions of the motor task. CMI was greater in PD patients, presumably due to insufficient attentional capacity in relation to increased cognitive involvement in motor control. Although no general increase of CMI was observed in stroke patients, correlation analyses suggested that especially patients with severe motor dysfunction experienced CMI. Clinical ratings of cognitive and motor function were weakly associated with CMI, suggesting that CMI reflects a different construct than these unidimensional clinical tests. It remains to be investigated whether CMI is an indicator of difficulties with day‐to‐day activities.