scholarly journals Arm choice post-stroke is habitual rather than optimal in right-, but not in left-paretic individuals

2020 ◽  
Author(s):  
Sujin Kim ◽  
Cheol Han ◽  
Bokkyu Kim ◽  
Carolee Winstein ◽  
Nicolas Schweighofer
Keyword(s):  
Motor Performance ◽  
Addition Reaction ◽  
Reaction Times ◽  
Chronic Stroke ◽  
Time Constraint ◽  
Fast Time ◽  
Constraint Condition ◽  
Pointing Movements ◽  
Fast Condition ◽  
Habitual Pattern

In non-disabled individuals, arm choice in pointing movements depends on expected biomechanical effort, expected success, and a handedness bias. Following a stroke, is arm choice re-optimized to account for the decreased motor performance, or does it follow a pre-injury habitual pattern? Because premorbidly right-handed individuals with left hemiparesis generally use their affected arm less than those with right hemiparesis, we hypothesized that arm choice follows a more habitual pattern in right- than in left-hemiparetic individuals. Participants with mild to moderate chronic stroke who were right-handed before stroke performed pointing movements in both free- and forced-choice blocks, both under a no-time constraint condition and under a fast-time constraint condition designed to promote habitual choice. Mixed-effects models of arm choice revealed that expected effort and side of stroke predicted choices overall. However, expected success predicted choice in left-, but not of right-hemiparetic individuals. Furthermore, while left-hemiparetic individuals tended to avoid unsuccessful movements in the fast condition by selecting their non-paretic arm, right-hemiparetic individuals persevered in choosing their more affected arm. In addition, reaction times decreased in left-hemiparetic individuals between the no-time and the fast condition but showed no changes in right-hemiparetic individuals. Finally, arm choice in the no-time condition correlated with a clinical measure of spontaneous arm use for right-, but not for left-hemiparetic individuals. Our results thus show that, in premorbidly right-handed individuals with mild to moderate chronic stroke, arm choice is habitual in right-hemiparetic individuals, but shows a greater degree of optimality by taking account expected success in left-hemiparetic individuals.

Effort, success, and side of lesion determine arm choice in chronic stroke survivors with mild-to-moderate impairment

2021 ◽  
Author(s):  
Sujin Kim ◽  
Cheol E Han ◽  
Bokkyu Kim ◽  
Carolee J. Winstein ◽  
Nicolas Schweighofer
Keyword(s):  
Regression Models ◽  
Reaction Times ◽  
Chronic Stroke ◽  
Time Constraint ◽  
Reaching Movements ◽  
Fast Time ◽  
Constraint Condition ◽  
Logistic Regression Models ◽  
Medium Time ◽  
Habitual Pattern

In neurotypical individuals, arm choice in reaching movements depends on expected biomechanical effort, expected success, and a handedness bias. Following a stroke, does arm choice change to account for the decreased motor performance, or does it follow a pre-injury habitual preference pattern? Participants with mild to moderate chronic stroke who were right-handed before stroke performed reaching movements in both spontaneous and forced-choice blocks, under no-time, medium-time, and fast-time constraint conditions designed to modulate reaching success. Mixed-effects logistic regression models of arm choice revealed that expected effort predicted choices. However, expected success only strongly predicted choice in left-hemiparetic individuals. In addition, reaction times decreased in left-hemiparetic individuals between the no-time and the fast-time constraint conditions but showed no changes in right-hemiparetic individuals. Finally, arm choice in the no-time constraint condition correlated with a clinical measure of spontaneous arm use for right-, but not for left-hemiparetic individuals. Our results are consistent with the view that right hemiparetic individuals show a habitual pattern of arm choice for reaching movements relatively independent of failures. In contrast, left hemiparetic individuals appear to choose their paretic left arm more optimally: that is, if a movement with the paretic arm is predicted to be not successful in the upcoming movement, the non-paretic right arm is chosen instead.

scholarly journals Manipulating Single-Trial Motor Performance in Chronic Stroke Patients by Closed-Loop Brain State Interaction

2021 ◽  
Vol 29 ◽  
pp. 1806-1816
Author(s):  
Andreas Meinel ◽  
Jan Sosulski ◽  
Stephan Schraivogel ◽  
Janine Reis ◽  
Michael Tangermann
Keyword(s):  
Motor Performance ◽  
Closed Loop ◽  
Chronic Stroke ◽  
State Interaction ◽  
Brain State ◽  
Single Trial ◽  
Stroke Patients

Reaction Time and Psychophysiological Activity

1982 ◽  
Vol 54 (2) ◽  
pp. 379-390 ◽  
Author(s):  
Eugene A. Sersen ◽  
Johs. Clausen ◽  
Arnold Lidsky
Keyword(s):  
Skin Conductance ◽  
Motor Performance ◽  
Reaction Times ◽  
Heart Period ◽  
High Arousal ◽  
Activation Theory ◽  
Before And After ◽  
Complex Relationships ◽  
Relationship Of ◽  
The Relationship

Disjunctive reaction times (RT) involving two interstimulus intervals were obtained from 10 subjects during 4 sessions while recording heart period, skin conductance, and EEG. Multiple regression analysis indicated complex relationships between RT and skin conductance and heart period which varied with session level. The relationship of RT and skin conductance was predominantly linear but positive when level of skin conductance was low and negative when high. Heart period showed a predominantly curvilinear trend which also varied with level during the session. Fastest RTs tended to occur with long heart periods in short heart period sessions and vice versa. Fast RTs were also accompanied by relatively low EEG power before and after stimulation and by higher EEG frequency after the stimulus. The pattern of findings did not fully accord with the expectations of activation theory, and the proportion of RT variance accounted for was small. It is suggested that activation may vary to maintain a constant level of motor performance Faster RT may occur under relaxed conditions and high arousal, and concentrated attentiveness may be an attempt to compensate for boredom or distraction.

scholarly journals Proline Derived Ligands for the Titanium-Catalyzed Enantioselective Synthesis of Propargyl Alcohols in Presence of Diethylzinc

2019 ◽  
Author(s):  
Prianka Chohan ◽  
Giovanni Barrera ◽  
Kimberly Valdivia ◽  
Parminder Kaur
Keyword(s):  
Addition Reaction ◽  
Reaction Times ◽  
Catalyst System ◽  
Enantioselective Synthesis ◽  
Mild Conditions ◽  
Nucleophilic Addition Reaction ◽  
Proline Derivatives ◽  
Heterocyclic Aldehydes ◽  
Reaction Profile ◽  
Propargyl Alcohols

<div>A novel titanium/proline-derived catalyst system is reported for the enantioselective synthesis of propargyl alcohols. The reaction proceeded smoothly under mild conditions with efficient reaction times. A series of proline and proline-based ligands including Lproline, L-prolinol, trans-hydroxy-L-prolinol, and substituted trans hydroxy-L-proline derivatives were used to have a better stereocontrol on the reaction. Initially, lithium acetylide was employed to carry out the nucleophilic addition reaction, however poor reaction profile was achieved with poor enantioselectivities. When diethylzinc was used instead, high product yields (>85%) and moderate to high enantioselectivities were achieved (68-82%). Three different alkynes, aromatic as well as aliphatic, phenylacetylene, n-hexyne and 3,3-diethoxy-prop-1-yne were used to carry out the reaction with a series of different aromatic and heterocyclic aldehydes. Better reaction profiles were achieved with aromatic alkynes than with aliphatic ones.</div>

scholarly journals Offline effects of transcranial direct current stimulation on reaction times of lower extremity movements in people after stroke: a pilot cross-over study

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Milou J. M. Coppens ◽  
Wouter H. A. Staring ◽  
Jorik Nonnekes ◽  
Alexander C. H. Geurts ◽  
Vivian Weerdesteyn
Keyword(s):  
Motor Cortex ◽  
Lower Extremity ◽  
Motor Function ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Reaction Times ◽  
Chronic Stroke ◽  
Ankle Dorsiflexion ◽  
Gait Initiation ◽  
Direct Current Stimulation

Abstract Background Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has shown promise for rehabilitation after stroke. Ipsilesional anodal tDCS (a-tDCS) over the motor cortex increases corticospinal excitability, while contralesional cathodal tDCS (c-tDCS) restores interhemispheric balance, both resulting in offline improved reaction times of delayed voluntary upper-extremity movements. We aimed to investigate whether tDCS would also have a beneficial effect on delayed leg motor responses after stroke. In addition, we identified whether variability in tDCS effects was associated with the level of leg motor function. Methods In a cross-over design, 13 people with chronic stroke completed three 15-min sessions of anodal, cathodal and sham stimulation over the primary motor cortex on separate days in an order balanced across participants. Directly after stimulation, participants performed a comprehensive set of lower-extremity tasks involving the paretic tibialis anterior (TA): voluntary ankle-dorsiflexion, gait initiation, and backward balance perturbation. For all tasks, TA onset latencies were determined. In addition, leg motor function was determined by the Fugl-Meyer Assessment – leg score (FMA-L). Repeated measures ANOVA was used to reveal tDCS effects on reaction times. Pearson correlation coefficients were used to establish the relation between tDCS effects and leg motor function. Results For all tasks, TA reaction times did not differ across tDCS sessions. For gait initiation and backward balance perturbation, differences between sham and active stimulation (a-tDCS or c-tDCS) did not correlate with leg motor function. Yet, for ankle dorsiflexion, individual reaction time differences between c-tDCS and sham were strongly associated with FMA-L, with more severely impaired patients exhibiting slower paretic reaction times following c-tDCS. Conclusion We found no evidence for offline tDCS-induced benefits. Interestingly, we found that c-tDCS may have unfavorable effects on voluntary control of the paretic leg in severely impaired patients with chronic stroke. This finding points at potential vicarious control from the unaffected hemisphere to the paretic leg. The absence of tDCS-induced effects on gait and balance, two functionally relevant tasks, shows that such motor behavior is inadequately stimulated by currently used tDCS applications. Trial registration The study is registered in the Netherlands Trial Register (NL5684; April 13th, 2016).

Time

2017 ◽  
Author(s):  
Clement Guitton
Keyword(s):  
National Security ◽  
Reaction Times ◽  
Technical Aspect ◽  
Cyber Attacks ◽  
Time Constraint ◽  
Fast Reaction ◽  
Common Assumption ◽  
Security Incident ◽  
The Public ◽  
The Common

How important is the time constraint for attribution? How has the time constraint evolved? And what constitutes an appropriate time for attributing cyber attacks? Timing plays a significant role in attribution. The common assumption is that attribution is time-consuming, and warrants efforts to try to reduce the time it takes to identify instigators of cyber attacks. In the context of a national security incident, the rationale continues, this is problematic because fast reaction times are needed to ensure that any response will still be consistent with the fast-changing geopolitical context. Yet, counter-intuitively, focusing on time reduction can be misleading. In the national security context, timing matters, but not in terms of the measurable passage of time as much as in terms of external conjectures that influence the decision to attribute an act. Whether for a violent act of sabotage where the public expects a government reaction or for a less visible act of espionage, the time may not always be such that it is politically appropriate to attribute an attack. In this context, talking about reducing the time for attribution does not make much sense: such a proposal foregoes all the political elements that inform attribution, and over-emphasizes the technical aspect of attribution over the context in which an attack takes place.

scholarly journals Use of the Challenge Point Framework to Guide Motor Learning of Stepping Reactions for Improved Balance Control in People With Stroke: A Case Series

2014 ◽  
Vol 94 (4) ◽  
pp. 562-570 ◽  
Author(s):  
Courtney L. Pollock ◽  
Lara A. Boyd ◽  
Michael A. Hunt ◽  
S. Jayne Garland
Keyword(s):  
Motor Learning ◽  
Balance Control ◽  
Case Series ◽  
Reaction Times ◽  
Chronic Stroke ◽  
Community Level ◽  
Level Walking ◽  
Learning Principles ◽  
Walking Balance ◽  
Low Amplitude

Background and PurposeStepping reactions are important for walking balance and community-level mobility. Stepping reactions of people with stroke are characterized by slow reaction times, poor coordination of motor responses, and low amplitude of movements, which may contribute to their decreased ability to recover their balance when challenged. An important aspect of rehabilitation of mobility after stroke is optimizing the motor learning associated with retraining effective stepping reactions. The Challenge Point Framework (CPF) is a model that can be used to promote motor learning through manipulation of conditions of practice to modify task difficulty, that is, the interaction of the skill of the learner and the difficulty of the task to be learned. This case series illustrates how the retraining of multidirectional stepping reactions may be informed by the CPF to improve balance function in people with stroke.Case DescriptionFour people (53–68 years of age) with chronic stroke (&gt;1 year) and mild to moderate motor recovery received 4 weeks of multidirectional stepping reaction retraining. Important tenets of motor learning were optimized for each person during retraining in accordance with the CPF.OutcomesParticipants demonstrated improved community-level walking balance, as determined with the Community Balance and Mobility Scale. These improvements were evident 1 year later. Aspects of balance-related self-efficacy and movement kinematics also showed improvements during the course of the intervention.DiscussionThe application of CPF motor learning principles in the retraining of stepping reactions to improve community-level walking balance in people with chronic stroke appears to be promising. The CPF provides a plausible theoretical framework for the progression of functional task training in neurorehabilitation.

scholarly journals Effects of Temporary Functional Deafferentation in Chronic Stroke Patients: Who Profits More?

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Elisabeth Sens ◽  
Marcel Franz ◽  
Christoph Preul ◽  
Winfried Meissner ◽  
Otto W. Witte ◽  
...  
Keyword(s):  
Motor Performance ◽  
Regression Models ◽  
Chronic Stroke ◽  
Sensory Deficit ◽  
Lesion Site ◽  
Stroke Patients ◽  
Orientation Task ◽  
Multiple Regression Models ◽  
Outcome Differences ◽  
Cortical Involvement

Temporary functional deafferentation (TFD) by an anesthetic cream on the stroke-affected forearm was shown to improve sensorimotor abilities of stroke patients. The present study investigated different predictors for sensorimotor improvements during TFD and indicated outcome differences between patients grouped in subcortical lesions only and lesions with any cortical involvement. Thirty-four chronic stroke patients were temporarily deafferented on the more affected forearm by an anesthetic cream. Somatosensory performance was assessed using von Frey Hair and grating orientation task; motor performance was assessed by a shape-sorter-drum task. Seven potential predictors were entered into three linear multiple regression models. Furthermore, effects of TFD on outcome variables for the two groups (cortical versus subcortical lesion) were compared. Sex and sensory deficit were significant predictors for changes in motor function while age accounted for changes in grating orienting task. Males, patients with a stronger sensory deficit, and older patients profited more. None of the potential predictors made significant contributions to changes in threshold for touch. Furthermore, there were no differences in sensorimotor improvement between lesion site groups. The effects of TFD together with the low predictability of the investigated parameters suggest that characteristics of patients alone are not suitable to exclude some patients from TFD.

scholarly journals Recovery of Motor Performance following Startle

1970 ◽  
Vol 30 (1) ◽  
pp. 279-292 ◽  
Author(s):  
Richard I. Thackray ◽  
R. Mark Touchstone
Keyword(s):  
Heart Rate ◽  
Motor Performance ◽  
Random Noise ◽  
Tracking Error ◽  
Reaction Times ◽  
Subjective Response ◽  
Recovery Curves ◽  
Tracking Tasks ◽  
Rate Acceleration ◽  
Rate Of Recovery

The present study was designed to provide information concerning the extent to which startle disrupts motor performance, the rate of recovery, and characteristics of Ss who differ in susceptibility to startle. 30 Ss were trained on both reaction time and tracking tasks. Continuous recordings were taken of heart rate and skin conductance. During a subsequent period of continuous tracking, “startle” stimuli (115 db random noise) were unexpectedly presented. Results showed the recovery of tracking performance following startle to be quite rapid; performance returned to pre-stimulus levels within 15 sec. following stimulation. Contrary to several previous studies, reaction times to the startle stimuli decreased relative to nonstartle reaction times. Ss with the greatest increase in tracking error following startle were least proficient prior to startle. There was also an indication that these Ss reacted more strongly to startle, in terms of both their subjective response and heart-rate acceleration, than those Ss whose tracking was least impaired by startle. An apparent covariation between recovery curves for heart rate and tracking error was found following startle.

Sign in / Sign up

Export Citation Format

Share Document