Interhemispheric inhibition between dorsal premotor and primary motor cortices is released during preparation of unimanual but not bimanual movements.

Previous research applying transcranial magnetic stimulation during unimanual reaction time tasks indicates a transient change in the inhibitory influence of the dorsal premotor cortex over the contralateral primary motor cortex shortly after the presentation of an imperative stimulus. The degree of interhemispheric inhibition from the dorsal premotor cortex to the contralateral primary motor cortex shifts depending on whether the targeted effector representation in the primary motor cortex is selected for movement. Further, the timing of changes in inhibition covaries with the selection demands of the reaction time task. Less is known about modulation of dorsal premotor to primary motor cortex interhemispheric inhibition during the preparation of bimanual movements. In this study, we used a dual coil transcranial magnetic stimulation to measure dorsal premotor to primary motor cortex interhemispheric inhibition between both hemispheres during unimanual and bimanual simple reaction time trials. Interhemispheric inhibition was measured early and late in the 'pre-movement period' (defined as the period immediately after the onset of the imperative stimulus and before the beginning of voluntary muscle activity). We discovered that interhemispheric inhibition was more facilitatory early in the pre-movement period compared with late in the pre-movement period during unimanual reaction time trials. In contrast, interhemispheric inhibition was unchanged throughout the pre-movement period during symmetrical bimanual reaction time trials. These results suggest that there is greater interaction between the dorsal premotor cortex and contralateral primary motor cortex during the preparation of unimanual actions compared to bimanual actions.

Examining Sex Differences in Relationships Between Subjective and Objective Measures of Upper Extremity Motor Impairment in a Sample of Stroke Survivors.

BACKGROUND AND PURPOSE: Rehabilitation professionals use subjective and objective outcome measures to assess stroke-related impact and impairment. Understanding if subjective and objective findings correlate among stroke survivors, especially if these associations differ between females and males, can inform care decisions. METHODS: A retrospective cross-sectional design was used, with data selected from subacute to chronic stroke survivors on age, time since stroke, the hand domain from the Stroke Impact Scale version 3.0 (SIS-H), and the Fugl-Meyer Upper Extremity (FMUE) Assessment. Group differences were assessed for all outcomes based on sex and time poststroke. Separate correlations for females and males were performed between the subjective (SIS-H) and objective measures (FMUE) of upper limb function and impairment. RESULTS: Data from 148 participants (44 females) were included in this study. SIS-H was significantly correlated with FMUE in both females and males ( P s ≤ 0.001). No significant differences were found between the groups' mean SIS-H or FMUE scores based on sex or time poststroke. DISCUSSION AND CONCLUSIONS: Subjective and objective measures of physical functioning were correlated in both females and males. Although we found no sex differences in our primary outcomes, the sample size of females was disproportionately lower than the males. This is consistent with an ongoing problem in the stroke recovery research field, where females are often underrepresented and understudied, and where females who experience higher levels of impairment are less likely to participate in research.

White Matter Integrity and Chronic Poststroke Upper Limb Function: An ENIGMA Stroke Recovery Analysis.

BACKGROUND: Integrity of the corticospinal tract (CST) is an important biomarker for upper limb motor function following stroke. However, when structurally compromised, other tracts may become relevant for compensation or recovery of function. METHODS: We used the ENIGMA Stroke Recovery data set, a multicenter, retrospective, and cross-sectional collection of patients with upper limb impairment during the chronic phase of stroke to test the relevance of tracts in individuals with less and more severe (laterality index of CST fractional anisotropy ≥0.25) CST damage in an observational study design. White matter integrity was quantified using fractional anisotropy for the CST, the superior longitudinal fascicle, and the callosal fibers interconnecting the primary motor cortices between hemispheres. Optic radiations served as a control tract as they have no a priori relevance for the motor system. Pearson correlation was used for testing correlation with upper limb motor function (Fugl-Meyer upper extremity). RESULTS: From 1235 available data sets, 166 were selected (by imaging, Fugl-Meyer upper extremity, covariates, stroke location, and stage) for analyses. Only individuals with severe CST damage showed a positive association of fractional anisotropy in both callosal fibers interconnecting the primary motor cortices (r[21]=0.49; P=0.025) and superior longitudinal fascicle (r[21]=0.51; P=0.018) with Fugl-Meyer upper extremity. CONCLUSIONS: Our data support the notion that individuals with more severe damage of the CST depend on residual pathways for achieving better upper limb outcome than those with less affected CST.

Responsiveness and trajectory of changes in the rating of everyday arm-use in the community and home (REACH) scale over the first-year post-stroke.

OBJECTIVE: To examine the trajectory of the Rating of Everyday Arm-use in the Community and Home (REACH) scores over the first-year post-stroke, determine if REACH scores are modified by baseline impairment level and explore the responsiveness of the REACH scale through hypothesis testing. DESIGN: Consecutive sample longitudinal study. SETTING: Participants were recruited from an acute stroke unit and followed up at three, six, and 12 months post-stroke. PARTICIPANTS: Seventy-three participants with upper limb weakness (Shoulder Abduction and Finger Extension score ≤ 8). MAIN MEASURES: The REACH scale is a six-level self-report classification scale that captures how the affected upper limb is being used in one's own environment. The Fugl-Meyer Upper Limb Assessment (FMA-UL), Stroke Upper Limb Capacity Scale (SULCS), accelerometer-based activity count ratio and Global Rating of Change Scale (GRCS) were used to capture upper limb impairment, capacity, and use. RESULTS: The following proportions of participants improved at least one REACH level: 64% from baseline to three months, 37% from three to six months and 13% from six to 12 months post-stroke. The trajectory of REACH scores over time was associated with baseline impairment. Change in REACH had a moderate correlation to change in SULCS and the GRCS but not FMA-UL or the activity count ratio. CONCLUSIONS: Results of hypothesis testing provide preliminary evidence of the responsiveness of the REACH scale. On average, individuals with severe impairment continued to show improvement in use over the first year, while those with mild/moderate impairment plateaued and a small proportion decreased in the early chronic phase.

Premotor and Posterior Parietal Cortex Activity is Increased for Slow, as well as Fast Walking Poststroke: An fNIRS Study.

Methods: Twenty individuals in the chronic stage of stroke walked: (1) at their normal pace, (2) slower than normal, and (3) as fast as possible. Functional near-infrared spectroscopy was used to assess bilateral prefrontal, premotor, sensorimotor, and posterior parietal cortices during walking. Results: No significant differences in laterality were observed between walking speeds. The ipsilesional prefrontal cortex was overall more active than the contralesional prefrontal cortex. Premotor and posterior parietal cortex activity were larger during slow and fast walking compared to normal-paced walking with no differences between slow and fast walking. Greater increases in brain activation in the ipsilesional prefrontal cortex during fast compared to normal-paced walking related to greater gait speed modulation. Conclusions: Brain activation is not linearly related to gait speed. Ipsilesional prefrontal cortex, bilateral premotor, and bilateral posterior parietal cortices are important areas for gait speed modulation and could be an area of interest for neurostimulation.

The ENIGMA Stroke Recovery Working Group: Big data neuroimaging to study brain-behavior relationships after stroke.

The goal of the Enhancing Neuroimaging Genetics through Meta-Analysis (ENIGMA) Stroke Recovery working group is to understand brain and behavior relationships using well-powered meta- and mega-analytic approaches. ENIGMA Stroke Recovery has data from over 2,100 stroke patients collected across 39 research studies and 10 countries around the world, comprising the largest multisite retrospective stroke data collaboration to date. This article outlines the efforts taken by the ENIGMA Stroke Recovery working group to develop neuroinformatics protocols and methods to manage multisite stroke brain magnetic resonance imaging, behavioral and demographics data. Specifically, the processes for scalable data intake and preprocessing, multisite data harmonization, and large-scale stroke lesion analysis are described, and challenges unique to this type of big data collaboration in stroke research are discussed. Finally, future directions and limitations, as well as recommendations for improved data harmonization through prospective data collection and data management, are provided.

Discriminative Utility of Transcranial Magnetic Stimulation-Derived Markers of Cortical Excitability for Transient Ischemic Attack.

BACKGROUND: Several guidelines currently recommend acute diffusion weighted imaging (DWI) for the detection of ischemia in transient ischemic attack (TIA). However, DWI hyperintensities resolve early and only 30%-50% with clinically defined TIA show acute DWI positivity. A recent meta-analysis reported an unexplained 7-fold variation in DWI positivity in TIA across studies, concluding that DWI does not provide a consistent basis for defining ischemia. Intracortical excitability, measured using transcranial magnetic stimulation (TMS), has previously been shown to be altered after TIA and associated with ABCD2 scores; however, whether altered cortical excitability is associated with clinical and DWI-based definitions of TIA remains unclear. METHODS: Individuals with TIA symptoms (N = 23; mean age = 61 ± 12) were prospectively recruited and underwent DWI and paired-pulse TMS. Multivariate linear regression was used to estimate associations between TMS-derived excitability thresholds, and clinical TIA diagnosis, and imaging-based evidence of cerebral ischemia (DWI positivity). Area under the curve (AUC) analyses was used to compare the discriminability of TMS-derived thresholds and clinical TIA diagnoses. RESULTS: Thresholds for intracortical inhibition in the TIA-unaffected hemisphere were significantly associated with the clinical diagnosis of TIA. No associations between TMS-derived thresholds and DWI positivity were observed. TMS thresholds showed low-moderate discriminability and values differed by age (65+) and sex. CONCLUSIONS: In this small sample, TMS-derived markers of intracortical excitability were associated with clinical TIA diagnoses but not DWI positivity. Our results provide preliminary evidence for the potential discriminative utility of TMS for the diagnosis of TIA and highlight the need for future work in larger cohorts.

Experiences of Children and Youth With Concussion: A Qualitative Study.

IMPORTANCE: Concussions are common among children and youth. To date, the pediatric concussion literature has focused on quantitative reports of the effects of concussion and return-to-activity guidelines. However, the subjective experiences of children and youth returning to occupations postconcussion have largely been ignored. An understanding of these experiences is critical to inform effective concussion management. OBJECTIVE: To investigate the experiences of children and youth returning to occupations after sustaining a concussion and the impacts on their future engagement in occupation. DESIGN: Qualitative interpretive description was used for data analysis and interpretation. SETTING: Community. PARTICIPANTS: Children and youth ages 11 to 18 yr from a cohort study were recruited to be interviewed about their experiences of engaging in occupations postconcussion. OUTCOMES AND MEASURES: Interviews were conducted 3 to 24 mo postconcussion, transcribed verbatim, and analyzed using interpretive description to identify themes. RESULTS: Eight children and youth (5 male, 3 female) were included. Analyses revealed three themes of the experiences of children and youth returning to occupations after concussion: diverse experiences of concussion, knowledge is key to concussion management, and concussions affect occupational engagement. CONCLUSIONS AND RELEVANCE: This study highlights the importance of considering a person's needs to enable effective concussion treatment plans. The results suggest the need for an occupation-based framework to guide interventions in pediatric concussion management. What This Article Adds: Our findings indicate that children and youth report variable recovery patterns, a lack of knowledge about concussion recovery, and a negative effect of concussion on occupational engagement.

Cortical N-acetylaspartate concentrations are impacted in chronic stroke but do not relate to motor impairment: A magnetic resonance spectroscopy study.

Magnetic resonance spectroscopy (MRS) measures cerebral metabolite concentrations, which can inform our understanding of the neurobiological processes associated with stroke recovery. Here, we investigated whether metabolite concentrations in primary motor and somatosensory cortices (sensorimotor cortex) are impacted by stroke and relate to upper-extremity motor impairment in 45 individuals with chronic stroke. Cerebral metabolite estimates were adjusted for cerebrospinal fluid and brain tissue composition in the MRS voxel. Upper-extremity motor impairment was indexed with the Fugl-Meyer (FM) scale. N-acetylaspartate (NAA) concentration was reduced bilaterally in stroke participants with right hemisphere lesions (n = 23), relative to right-handed healthy older adults (n = 15; p = .006). Within the entire stroke sample (n = 45) NAA and glutamate/glutamine (GLX) were lower in the ipsilesional sensorimotor cortex, relative to the contralesional cortex (NAA: p < .001; GLX: p = .003). Lower ipsilesional NAA was related to greater extent of corticospinal tract (CST) injury, quantified by a weighted CST lesion load (p = .006). Cortical NAA and GLX concentrations did not relate to the severity of chronic upper-extremity impairment (p > .05), including after a sensitivity analysis imputing missing metabolite data for individuals with large cortical lesions (n = 5). Our results suggest that NAA, a marker of neuronal integrity, is sensitive to stroke-related cortical damage and may provide mechanistic insights into cellular processes of cortical adaptation to stroke. However, cortical MRS metabolites may have limited clinical utility as prospective biomarkers of upper-extremity outcomes in chronic stroke.

Aberrant Cerebellar Resting-State Functional Connectivity Related to Reading Performance in Struggling Readers.

Reading is a critical neurodevelopmental skill for school-aged children, which requires a distributed network of brain regions including the cerebellum. However, we do not know how functional connectivity between the cerebellum and other brain regions contributes to reading. Here we used resting-state functional connectivity to understand the cerebellum's role in decoding, reading speed, and comprehension in a group of struggling readers (RD) and a group of adolescents and children with typical reading abilities (TD). We observed an increase in functional connectivity between the sensorimotor network and the left angular gyrus, left lateral occipital cortex, and right inferior frontal gyrus in the RD group relative to the TD group. Additionally, functional connectivity between the cerebellum network and the precentral gyrus was decreased and was related to reading fluency in the RD group. Seed-based analysis revealed increased functional connectivity between crus 1, lobule 6, and lobule 8 of the cerebellum and brain regions related to the default mode network and the motor system for the RD group. We also found associations between reading performance and the functional connectivity between lobule 8 of the cerebellum and the left angular gyrus for both groups, with stronger relationships in the TD group. Specifically, the RD group displayed a positive relationship between functional connectivity, whereas the TD group displayed the opposite relationship. These results suggest that the cerebellum is involved in multiple components of reading performance and that functional connectivity differences observed in the RD group may contribute to poor reading performance.

Evidence of altered interhemispheric communication after pediatric concussion.

OBJECTIVES: To investigate neurophysiological alterations within the typical symptomatic period after concussion (1-month) and throughout recovery (6-months) in adolescents; and (2) to examine relationships between neurophysiological and upper limb kinematic outcomes.METHODS: 18 adolescents with concussion were compared to 17 healthy controls. Transcranial magnetic stimulation (TMS) was used to assess neurophysiological differences between groups including: short- and long-interval intracortical inhibition, intracortical facilitation, short- and long-latency afferent inhibition, afferent facilitation, and transcallosal inhibition (TCI). Behavioral measures of upper limb kinematics were assessed with a robotic device.RESULTS: Mixed model analysis of neurophysiological data identified two key findings. First, participants with concussion demonstrated delayed onset of interhemispheric inhibition, as indexed by TCI, compared to healthy controls. Second, our exploratory analysis indicated that the magnitude of TCI onset delay in adolescents with concussion was related to upper limb kinematics.CONCLUSIONS: Our findings indicate that concussion in adolescence alters interhemispheric communication. We note relationships between neurophysiological and kinematic data, suggesting an affinity for individuals with less concussion-related physiological change to improve their motor behavior over time. These data serve as an important step in future development of assessments (neurobiological and clinical) and interventions for concussion.

Brain activity during real-time walking and with walking interventions after stroke: a systematic review.

Investigations of real-time brain activations during walking have become increasingly important to aid in recovery of walking after a stroke. Individual brain activation patterns can be a valuable biomarker of neuroplasticity during the rehabilitation process and can result in improved personalized medicine for rehabilitation. The purpose of this systematic review is to explore the brain activation characteristics during walking post-stroke by determining: (1) if different components of gait (i.e., initiation/acceleration, steady-state, complex) result in different brain activations, (2) whether brain activations differ from healthy individuals. Six databases were searched resulting in 22 studies. Initiation/acceleration showed bilateral activation in frontal areas; steady-state and complex walking showed broad activations with the majority exploring and finding increases in frontal regions and some studies also showing increases in parietal activation. Asymmetrical activations were often related to performance asymmetry and were more common in studies with slower gait speed. Hyperactivations and asymmetrical activations commonly decreased with walking interventions and as walking performance improved. Hyperactivations often persisted in individuals who had experienced severe strokes. Only a third of the studies included comparisons to a healthy group: individuals post-stroke employed greater brain activation compared to young adults, while comparisons to older adults were less clear and limited. Current literature suggests some indicators of walking recovery however future studies investigating more brain regions and comparisons with healthy age-matched adults are needed to further understand the effect of stroke on walking-related brain activation.

The influence of an acute bout of moderate-intensity cycling exercise on sensorimotor integration.

Acute cycling exercise can modulate motor cortical circuitry in the non-exercised upper-limb. Within the primary motor cortex, measures of intracortical inhibition are reduced and intracortical facilitation is enhanced following acute exercise. Further, acute cycling exercise decreases interhemispheric inhibition between the motor cortices and lowers cerebellar-to-motor cortex inhibition. Yet, investigations into the effects of acute exercise on sensorimotor integration, referring to the transfer of incoming afferent information from the primary somatosensory cortex to motor cortex, are lacking. The current work addresses this gap in knowledge with two experimental sessions. In the first session, we tested the exercise-induced changes in somatosensory and motor excitability by assessing somatosensory (SEP) and motor evoked potentials (MEPs). In the second session, we explored the effects of acute cycling exercise on short- (SAI) and long-latency afferent inhibition (LAI), and afferent facilitation. In both experimental sessions, neurophysiological measures were obtained from the non-exercised upper-limb muscle, tested at two time points pre-exercise separated by a 25-min period of rest. Next, a 25-min bout of moderate-intensity lower-limb cycling was performed with measures assessed at two time points post-exercise. Acute lower-limb cycling increased LAI, without modulation of SAI or afferent facilitation. Further, there were no exercise-induced changes to SEP or MEP amplitudes. Together, these results suggest that acute exercise has unique effects on sensorimotor integration, which are not accompanied by concurrent changes in somatosensory or motor cortical excitability.

Neuroplasticity of Cortical Planning for Initiating Stepping Poststroke: A Case Series.

BACKGROUND AND PURPOSE: Therapeutic exercise improves balance and walking ability in individuals after stroke. The extent to which motor planning improves with therapeutic exercise is unknown. This case series examined how outpatient physical therapy affects motor planning and motor performance for stepping. CASE DESCRIPTION: Individuals poststroke performed self-initiated stepping before (baseline), after (postintervention), and 1 month after (retention) intervention. Amplitude and duration of the movement-related cortical potential (MRCP) was measured using an electroencephalograph from the Cz electrode. Electromyography (EMG) of biceps femoris (BF) was collected. Additionally, clinical measures of motor impairment and function were evaluated at all 3 time points by a blinded assessor. INTERVENTION: Two types of outpatient physical therapy were performed for 6 weeks: CONVENTIONAL (n = 3) and FAST (n = 4, Fast muscle Activation and Stepping Training). OUTCOMES: All 7 participants reduced MRCP duration, irrespective of the type of physical therapy. The MRCP amplitude and BF EMG onset changes were more variable. Clinical outcomes improved or were maintained for all participants. The extent of motor impairment was associated with MRCP amplitude. DISCUSSION: Changes in MRCP duration suggest that outpatient physical therapy may promote neuroplasticity of motor planning of stepping movements after stroke; however, a larger sample is needed to determine whether this finding is valid.This case series suggests motor planning for initiating stepping may improve after 6 weeks of outpatient physical therapy for persons with stroke.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A307).

Exercise increases caudate dopamine release and ventral striatal activation in Parkinson's disease.

BACKGROUND: The objective of this study was to examine the effects of aerobic exercise on evoked dopamine release and activity of the ventral striatum using positron emission tomography and functional magnetic resonance imaging in Parkinson's disease (PD). METHODS: Thirty-five participants were randomly allocated to a 36-session aerobic exercise or control intervention. Each participant underwent an functional magnetic resonance imaging scan while playing a reward task before and after the intervention to determine the effect of exercise on the activity of the ventral striatum in anticipation of reward. A subset of participants (n = 25) completed [11 C] raclopride positron emission tomography scans to determine the effect of aerobic exercise on repetitive transcranial magnetic stimulation-evoked release of endogenous dopamine in the dorsal striatum. All participants completed motor (MDS-UPDRS part III, finger tapping, Timed-up-and-go) and nonmotor assessments (Starkstein Apathy Scale, Beck Depression Inventory, reaction time, Positive and Negative Affect Schedule, Trail Making Test [A and B], and Montreal Cognitive Assessment) before and after the interventions. RESULTS: The aerobic group exhibited increased activity in the ventral striatum during functional magnetic resonance imaging in anticipation of 75% probability of reward (P = 0.01). The aerobic group also demonstrated increased repetitive transcranial magnetic stimulation-evoked dopamine release in the caudate nucleus (P = 0.04) and increased baseline nondisplaceable binding potential in the posterior putamen of the less affected repetitive transcranial magnetic stimulation-stimulated hemisphere measured by position emission tomography (P = 0.03). CONCLUSIONS: Aerobic exercise alters the responsivity of the ventral striatum, likely related to changes to the mesolimbic dopaminergic pathway, and increases evoked dopamine release in the caudate nucleus. This suggests that the therapeutic benefits of exercise are in part related to corticostriatal plasticity and enhanced dopamine release. © 2019 International Parkinson and Movement Disorder Society.

The effects of acute exercise on visuomotor adaptation, learning, and inter-limb transfer.

Pairing an acute bout of lower-limb cycling exercise with skilled motor practice enhances acquisition and learning. However, it is not known whether an acute bout of exercise enhances a specific form of motor learning, namely motor adaptation, and if subsequent inter-limb transfer of this adaptation is enhanced. Seventeen young healthy participants performed a bout of cycling exercise and rest, on separate days, prior to right-arm reaching movements to visual targets under 45° rotated feedback of arm position (acquisition), followed by an immediate test of inter-limb transfer with the untrained left arm. After a 24-h delay, participants returned for a no-exercise retention test using the right and left arm with the same rotated visual feedback as acquisition. Results demonstrated that exercise enhanced right-arm adaptation during the acquisition and retention phases, and transiently enhanced aspects of inter-limb transfer, irrespective of usual levels of physical activity. Specifically, exercise enhanced movement accuracy, decreased reaction and movement time during acquisition, and increased accuracy during retention. Exercise shortened reaction time during the inter-limb transfer test immediately after right-arm acquisition but did not influence left-arm performance assessed at retention. These results indicate that an acute bout of exercise before practice enhances right-arm visuomotor adaptation (acquisition) and learning, and decreases reaction time during untrained left arm performance. The current results may have implications for the prescription of exercise protocols to enhance motor adaptation for healthy individuals and in clinical populations.

Decreased white matter fractional anisotropy is associated with poorer functional motor skills following spinal cord injury: a pilot study.

STUDY DESIGN: Prospective cross-sectional study OBJECTIVES: The objective of this study was to assess associations between white matter changes and functional motor markers including grip strength and prehension in the upper limb. SETTING: Single Center Imaging Study, in Vancouver Canada. METHODS: Diffusion tensor imaging produced FA (Fractional Anisotropy) maps of the brain for participants with SCI (n = 7) and controls (n = 6). These FA maps were analyzed using tract-based spatial statistics. Correlations between the FA values (of the genu of the corpus callosum, the left superior longitudinal fasciculus and the right anterior thalamic radiation) of the SCI group and functional outcomes (grip strength, Graded Redefined Assessment of Strength, Sensibility and Prehension (GRASSP)) were assessed. RESULTS: Significant differences (p < 0.05) were found between the FA values of the controls and the SCI group in two white matter clusters, with lower values in the SCI group. Strong correlations were found between the FA values of the identified clusters and the age of SCI participant, and the right GRASSP Quantitative Prehension and right total GRASSP score. CONCLUSIONS: This preliminary data suggests that decreased FA in the genu of the corpus callosum may be a biomarker for functional motor ability of the upper limb with higher FA indicating better ability. Further research needs to be done to determine if other white matter tracts are also associated with strength and use of the hand following SCI. SPONSORSHIP: The International Collaboration on Repair Discoveries (operating grant) and Canada Research Chair Program (for JJE) provided support for this research.

The Impact of Covert Lacunar Infarcts and White Matter Hyperintensities on Cognitive and Motor Outcomes After Stroke.

BACKGROUND AND AIMS: In addition to overt stroke lesions, co-occurring covert lesions, including white matter hyperintensities (WMH) and covert lacunar infarcts (CLI), contribute to poststroke outcome. The purpose of this study was to examine the relationship between covert lesions, and motor and cognitive outcomes in individuals with chronic stroke. METHODS: Volumetric quantification of clinically overt strokes, covert lesions (periventricular and deep: pWMH, dWMH, pCLI, dCLI), ventricular and sulcal CSF (vCSF, sCSF), and normal appearing white (NAWM) and gray matter (NAGM) was performed using structural magnetic resonance imaging. We assessed motor impairment and function, and global cognition, memory, and other cognitive domains. When correlation analysis identified more than one MR parameter relating to stroke outcomes, we used regression modeling to identify which factor had the strongest impact. RESULTS: Neuropsychological and brain imaging data were collected from 30 participants at least 6 months following a clinically diagnosed stroke. Memory performance related to vCSF (r = -0.52, P = .004). The strongest predictor of nonmemory domains was pCLI (r2 = 0.28, P = .004). Motor impairment and function were most strongly predicted by the volume of stroke and NAWM (r2 = 0.36; P = .001), and dWMH (r2 = 0.39; P = .001) respectively. CONCLUSIONS: Covert lesion type and location have important consequences for post-stroke cognitive and motor outcome. Limiting the progression of covert lesions in aging populations may enhance the degree of recovery post-stroke.

Suppression of somatosensory stimuli during motor planning may explain levels of balance and mobility after stroke.

The ability to actively suppress, or gate, irrelevant sensory information is required for safe and efficient walking in sensory-rich environments. Both motor attention and motor planning alter somatosensory evoked potentials (SEPs) in healthy adults. This study's aim was to examine the effect of motor attention on processing of irrelevant somatosensory information during plantar flexion motor planning after stroke. Thirteen healthy older adults and 11 individuals with stroke participated. Irrelevant tibial nerve stimulation was delivered while SEPs were recorded over Cz, overlaying the leg portion of the sensorimotor cortex at the vertex of the head. Three conditions were tested in both legs: (1) Rest, (2) Attend To, and (3) Attend Away from the stimulated limb. In conditions 2 and 3, relevant vibration cued voluntary plantar flexion movements of the stimulated (Attend To) or non-stimulated (Attend Away) leg. SEP amplitudes were averaged during motor planning per condition. Individuals with stroke did not show attention-mediated gating of the N40 component associated with irrelevant somatosensory information during motor planning. It may be that dysfunction in pathways connecting to area 3b explains the lack of attention-mediated gating of the N40. Also, attention-mediated gating during motor planning explained significant and unique variance in a measure of community balance and mobility combined with response time. Thus, the ability to gate irrelevant somatosensory information appears important for stepping in both older adults and after stroke. Our data suggest that therapies that direct motor attention could positively impact walking after stroke.

Unilateral wrist extension training after stroke improves strength and neural plasticity in both arms.

Stroke induces bilateral neurological impairment and muscle weakness yielding neurologically more (MA; paretic) and less affected (LA; non-paretic) sides. "Cross-education" refers to training one side of the body to increase strength in the same muscles on the untrained side. Past work showed dorsiflexion training of the LA side produced bilateral strength increases after stroke. The current study explored the presence and extent of cross-education after arm strength training in chronic stroke. Twenty-four chronic stroke participants completed 5 weeks of maximal wrist extension training using their LA arm. Maximal voluntary contraction force, arm motor impairment and functional performance were measured before and after training. Both spinal cord plasticity (n = 12: reciprocal inhibition and cutaneous reflexes, University of Victoria) and cortical plasticity (n = 12: cortical silent period, short-interval intracortical inhibition, intracortical facilitation and transcallosal inhibition, University of British Columbia) were assessed. Five weeks after training, 20 participants completed a follow-up maximal wrist extension retention test. LA wrist extension force increased 42% and MA by 35%. Strength gains were maintained in the follow-up test. Clinically meaningful increases in Fugl-Meyer scores were noted in four participants. Muscle activation was correlated with cutaneous reflex amplitudes after training in the MA arm. LA cortical silent period and transcallosal inhibition from both hemispheres significantly decreased after training. This study shows that high-intensity training with the neurologically less affected "non-paretic" arm can improve strength bilaterally and alter both spinal and cortical plasticity. The extent to which this plasticity can be enhanced or functionally exploited remains to be examined.