Non-paretic leg movements can facilitate cortical drive to the paretic leg in individuals post stroke with severe motor impairment: Implications for motor priming.

Cross-education, a phenomenon where unilateral strength (or skill) training enhances strength (or skill) in the contralateral untrained limb, has been well studied in able-bodied individuals. Cross-education effect accompanies bilateral changes of corticomotor activity in the motor cortex (M1). Recent reports demonstrated greater cross-education effect in stroke survivors compared to healthy individuals, however, corticomotor responses to cross-education in stroke remains unclear. This study aimed to determine the effects of non-paretic leg movements on corticomotor excitability (CME) and reaction time of the paretic leg in severely impaired stroke survivors. Seventeen post stroke individuals with severe leg motor impairment (Fugl-Meyer lower extremity score less than 21 and absence of motor evoked potential in the paretic leg) performed three 20-min motor trainings using their non-paretic ankle: skill (targeted dynamic movements), strength (isometric resistance) and sham (sub-threshold electrical nerve stimulation). During training, verbal instructions were given to the participants to limit their movement to the non-paretic leg and this was confirmed with visual observation of the paretic leg. Transcranial magnetic stimulation measured CME of the contralateral pathways from the non-lesioned M1 to the non-paretic tibialis anterior (TA) muscle, ipsilateral pathways to the paretic TA and transcallosal inhibition (TCI) from the non-lesioned to lesioned M1. Paretic ankle reaction time was measured using a reaction time paradigm. All outcomes were measured before, immediately post, 30-min post and 60-min post priming. CME of the non-paretic TA increased after skill (.08 ± .10 mV) and strength (.06 ± .05 mV) training (p < .01). Ipsilateral CME of the paretic TA (.02 ± .01 mV) and TCI (.01 ± .01 s, ipsilateral silent period; more inhibition to the lesioned M1) increased after skill (p < .05) but not strength training. Reaction time of the paretic ankle improved after skill and strength training (-.11 ± .2 and -.13 ± .20 s, respectively; p < .05) and was sustained at 60 min. No changes were observed during the sham condition. Our findings may inform future studies for using non-paretic leg movements as a priming modality, especially for those who are contraindicated to other priming paradigms (e.g., brain stimulation) or unable to perform paretic leg movements. Conclusion: Non-paretic leg movements can be used as a priming modality, especially for those who are contraindicated to other priming paradigms (e.g., brain stimulation) or unable to perform paretic leg movements.

Understanding corticomotor mechanisms for activation of non-target muscles during unilateral isometric contractions of leg muscles after stroke.

PURPOSE: Muscle activation often occurs in muscles ipsilateral to a voluntarily activated muscle and to a greater extent after stroke. In this study, we measured muscle activation in non-target, ipsilateral leg muscles and used transcranial magnetic stimulation (TMS) to provide insight into whether corticomotor pathways contribute to involuntary activation. MATERIALS AND METHODS: Individuals with stroke performed unilateral isometric ankle dorsiflexion, ankle plantarflexion, knee extension, and knee flexion. To quantify involuntary muscle activation in non-target muscles, muscle activation was measured during contractions from the ipsilateral tibialis anterior (TA), medial gastrocnemius (MG), rectus femoris (RF), and biceps femoris (BF) and normalized to resting muscle activity. To provide insight into mechanisms of involuntary non-target muscle activation, TMS was applied to the contralateral hemisphere, and motor evoked potentials (MEPs) were recorded. RESULTS: We found significant muscle activation in nearly every non-target muscle during isometric unilateral contractions. MEPs were frequently observed in non-target muscles, but greater non-target MEP amplitude was not associated with greater non-target muscle activation. CONCLUSIONS: Our results suggest that non-target muscle activation occurs frequently in individuals with chronic stroke. The lack of association between non-target TMS responses and non-target muscle activation suggests that non-target muscle activation may have a subcortical or spinal origin. Non-target muscle activation has important clinical implications because it may impair torque production, out-of-synergy movement, and muscle activation timing.

Parenting in place: Young children's living arrangement and migrants' sleep health in South Africa.

Migration research tends to treat childrearing as a secondary role for migrants. By prioritising the economic objectives of migration, most models present migrants as either delaying childbearing or, if they have young children, not living with them. However, migration has become increasingly feminised, the types of mobility more varied, while the returns to migration remain uncertain at best. At the same time, norms around childrearing are shifting, and the capacity of kin to take care of children may be weakening. In such contexts, migrants may not want to or be able to be separated from their children. Confronting such difficult decisions and their consequences may be reflected in poor sleep health for the migrant parent. We draw on data from the Migration and Health Follow-Up Study (MHFUS) in South Africa to examine the following questions: (i) To what extent is children's coresidence associated with sleep health for migrant parents? (ii) Do effects vary by sex of migrant? and (iii) Do effects vary by location of migrant? Results from propensity score matching confirm that migrants who coreside with all their young children are more likely to experience healthy sleep compared to those who have nonresident or no young children. However, stratified analysis shows that these effects are only significant for women and those not living in Gauteng province. The value of these findings is underscored by the need for research on the well-being of migrant parents who are negotiating multiple agendas in economically precarious and physically insecure destinations.

Motor overflow in the lower limb after stroke: Insights into mechanisms.

Motor overflow (involuntary muscle activation) is common after stroke, particularly in the non-paretic upper limb. Two potential cortical mechanisms are as follows: (1) The contralesional hemisphere controls both limbs, and (2) inhibition from the ipsilesional to the contralesional hemisphere is diminished. Few studies have differentiated between these hypotheses or investigated motor overflow in the lower limb after stroke. To investigate these potential mechanisms, individuals with chronic stroke performed unilateral isometric and dynamic dorsiflexion. Motor overflow was quantified in the contralateral, resting (non-target) ankle. Transcranial magnetic stimulation (TMS) was applied, and responses were measured in both legs. Relations between motor overflow, excitability of ipsilateral motor pathways, and interhemispheric inhibition were assessed. Non-target muscle activity (motor overflow) was greater during isometric and dynamic conditions than rest in both legs (p ≤ 0.001) and was higher in the non-paretic than the paretic leg (p = 0.03). Some participants (25%) had motor overflow >4SD above the group mean in the non-paretic leg. Greater motor overflow in the non-paretic leg was associated with lesser inhibition from the ipsilesional to the contralesional hemisphere (p = 0.04). In both legs, non-target TMS responses were greater during the isometric and dynamic than the rest condition (p ≤ 0.01) but not when normalized to background muscle activity. Overall, motor overflow occurred in both legs after stroke, suggesting a common bilateral mechanism. Our correlational results suggest that alterations in interhemispheric inhibition may contribute to motor overflow. Furthermore, the lack of differences in non-target motor evoked potentials MEPs between rest, isometric, and dynamic conditions suggests that subcortical and/or spinal pathways may contribute to motor overflow.

Ipsilateral motor pathways to the lower limb after stroke: Insights and opportunities.

Stroke-related damage to the crossed lateral corticospinal tract causes motor deficits in the contralateral (paretic) limb. To restore functional movement in the paretic limb, the nervous system may increase its reliance on ipsilaterally descending motor pathways, including the uncrossed lateral corticospinal tract, the reticulospinal tract, the rubrospinal tract, and the vestibulospinal tract. Our knowledge about the role of these pathways for upper limb motor recovery is incomplete, and even less is known about the role of these pathways for lower limb motor recovery. Understanding the role of ipsilateral motor pathways to paretic lower limb movement and recovery after stroke may help improve our rehabilitative efforts and provide alternate solutions to address stroke-related impairments. These advances are important because walking and mobility impairments are major contributors to long-term disability after stroke, and improving walking is a high priority for individuals with stroke. This perspective highlights evidence regarding the contributions of ipsilateral motor pathways from the contralesional hemisphere and spinal interneuronal pathways for paretic lower limb movement and recovery. This perspective also identifies opportunities for future research to expand our knowledge about ipsilateral motor pathways and provides insights into how this information may be used to guide rehabilitation.

Motor evoked potential latency and duration from tibialis anterior in individuals with chronic stroke.

Ipsilateral motor pathways from the contralesional hemisphere to the paretic limbs may be upregulated to compensate for impaired function after stroke. Onset latency and duration of motor evoked potentials (MEPs) evoked by transcranial magnetic stimulation (TMS) provide insight into compensatory pathways but have been understudied in the lower limb. This study assessed MEP onset latency and duration in the lower limb after stroke, and compared ipsilateral and contralateral MEPs in the paretic and non-paretic limb. We hypothesized that: (1) onset latency would be longer for ipsilateral than contralateral MEPs and longer for the paretic than the non-paretic limb, and (2) duration would be shorter for ipsilateral than contralateral MEPs and longer for the paretic than the non-paretic limb. Data were collected as a part of a pre-test of a randomized controlled trial. TMS was applied to the ipsilateral and contralateral hemisphere of the paretic and non-paretic limb. MEP onset latency and duration were calculated from the tibialis anterior. Thirty-five participants with chronic stroke were included in the final analysis. Onset latency was longer in the paretic than the non-paretic limb (~ 6.0 ms) and longer after ipsilateral than contralateral stimulation (~ 1.8 ms). Duration was longer in the paretic than the non-paretic limb (~ 9.2 ms) and longer after contralateral than ipsilateral stimulation (~ 5.2 ms). Ipsilateral MEPs may be elicited through ipsilateral pathways with fewer fibers with a higher activation threshold and/or greater spinal branching. MEPs from the paretic limb may reflect slower central motor conduction, peripheral changes, or changes in motor pathway.

Game-based movement facilitates acute priming effect in stroke.

OBJECTIVE: Cortical priming is an emerging strategy to enhance motor recovery after stroke, however, limited information exists on the neuromodulatory effects of lower limb movement-based priming to facilitate corticomotor excitability after stroke. In this study, we investigated the feasibility and effectiveness of game-based ankle movement priming using the DIG-I-PRIME™ on corticomotor excitability and motor performance in chronic stroke survivors. METHODS: Nineteen stroke survivors participated in a 20-min session of game-based priming. A period of rest served as a control for the priming condition. Transcranial magnetic stimulation (TMS) was used to measure corticomotor excitability of the paretic and non-paretic tibialis anterior (TA) muscle representations. Motor performance was quantified by assessing the accuracy to track a sinusoidal target wave with paretic dorsiflexion and plantarflexion. RESULTS: Ipsilesional corticomotor excitability increased by 25% after game-based movement priming (p = 0.02) while changes were not observed after the control condition. No change in motor performance was noted. CONCLUSION: Game-based ankle movement priming demonstrated a significant acute priming effect on the ipsilesional lower limb M1. These data provide preliminary evidence for the potential benefits of game-based priming to promote functional recovery after stroke.

Cortical priming strategies for gait training after stroke: a controlled, stratified trial.

BACKGROUND: Stroke survivors experience chronic gait impairments, so rehabilitation has focused on restoring ambulatory capacity. High-intensity speed-based treadmill training (HISTT) is one form of walking rehabilitation that can improve walking, but its effectiveness has not been thoroughly investigated. Additionally, cortical priming with transcranial direct current stimulation (tDCS) and movement may enhance HISTT-induced improvements in walking, but there have been no systematic investigations. The objective of this study was to determine if motor priming can augment the effects of HISTT on walking in chronic stroke survivors. METHODS: Eighty-one chronic stroke survivors participated in a controlled trial with stratification into four groups: 1) control-15 min of rest (n = 20), 2) tDCS-15 min of stimulation-based priming with transcranial direct current stimulation (n = 21), 3) ankle motor tracking (AMT)-15 min of movement-based priming with targeted movements of the ankle and sham tDCS (n = 20), and 4) tDCS+AMT-15 min of concurrent tDCS and AMT (n = 20). Participants performed 12 sessions of HISTT (40 min/day, 3 days/week, 4 weeks). Primary outcome measure was walking speed. Secondary outcome measures included corticomotor excitability (CME). Outcomes were measured at pre, post, and 3-month follow-up assessments. RESULTS: HISTT improved walking speed for all groups, which was partially maintained 3 months after training. No significant difference in walking speed was seen between groups. The tDCS+AMT group demonstrated greater changes in CME than other groups. Individuals who demonstrated up-regulation of CME after tDCS increased walking speed more than down-regulators. CONCLUSIONS: Our results support the effectiveness of HISTT to improve walking; however, motor priming did not lead to additional improvements. Upregulation of CME in the tDCS+AMT group supports a potential role for priming in enhancing neural plasticity. Greater changes in walking were seen in tDCS up-regulators, suggesting that responsiveness to tDCS might play an important role in determining the capacity to respond to priming and HISTT. TRIAL REGISTRATION: ClinicalTrials.gov , NCT03492229. Registered 10 April 2018 - retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03492229 .

Influence of neurovascular mechanisms on response to tDCS: an exploratory study.

The beneficial effects of transcranial direct current stimulation (tDCS) for stroke rehabilitation are limited by the variability in changes in corticomotor excitability (CME) after tDCS. Neuronal activity is closely related to cerebral blood flow; however, the cerebral hemodynamics of neuromodulation in relation to neural effects have been less explored. In this study, we examined the effects of tDCS on cerebral blood velocity (CBv) in chronic stroke survivors using transcranial Doppler (TCD) ultrasound in relation to changes in CME and described the neurovascular characteristics of tDCS responders. Middle cerebral artery (MCA) CBv, cerebrovascular resistance (CVRi) and other cerebral hemodynamics-related variables were continuously measured before and after 15 min of 1 mA anodal tDCS to the lesioned lower limb M1. tDCS did not modulate CBv in the whole group and upon TMS-based stratification of responders and non-responders. However, at baseline, responders demonstrated lower CME levels, lower CBv and higher CVRi as compared to non-responders. These results indicate a possible difference in baseline CME and CBv in tDCS responders that may influence their response to neuromodulation. Future trials with a large sample size and repeated baseline measurements may help validate these findings and establish a relationship between neuromodulation and neurovascular mechanisms in stroke.

Recumbent stepping aerobic exercise in amyotrophic lateral sclerosis: a pilot study.

OBJECTIVES: Aerobic exercise can promote neuroplastic responses in the healthy and injured brain. Although the role of exercise in amyotrophic lateral sclerosis (ALS) is debated, new evidence suggests that exercise may reduce disease progression. While common exercise modalities such as the treadmill and cycle ergometer have been explored in ALS, the safety and feasibility of a total body recumbent stepper have not been investigated. Additionally, the functional and neurophysiological effects of recumbent stepping in ALS are still unknown. Here, we investigated the safety and feasibility of a 4-week recumbent stepping program to slow disease progression in ALS and possibly facilitate neuroplasticity. METHOD: Nine individuals with ALS performed moderate intensity recumbent stepping for four weeks. Outcomes included participation satisfaction questionnaire, ALS Functional Rating Scale Revised (ALSFRS-R), clinical tests of walking and endurance, fatigue severity scale, Beck depression inventory, SF-12, and transcranial magnetic stimulation-induced motor evoked potentials (MEPs). All measurements were collected at baseline, post-intervention, and at the 1-month follow-up. RESULTS: Eight participants completed the study without any adverse events. The ALSFRS-R scores were similar at the end of the study and at follow-up. No significant differences were noted for any of the clinical outcomes. MEPs were present only in two participants and changes in corticomotor excitability after exercise were minimal. CONCLUSIONS: Results from this preliminary study support the safety and feasibility of 12 sessions of total body recumbent stepping in individuals with ALS.

WITHDRAWN: Immediate Adaptations to Poststroke Walking Performance Using a Wearable Robotic Exoskeleton.

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Absence of a Transcranial Magnetic Stimulation-Induced Lower Limb Corticomotor Response Does Not Affect Walking Speed in Chronic Stroke Survivors.

Background and Purpose- Transcranial magnetic stimulation is used to measure the functional integrity of the corticomotor system via motor evoked potentials (MEPs) in stroke. The association between corticomotor mechanisms and walking recovery is still not completely understood. This study determined the association between transcranial magnetic stimulation-induced MEPs and walking outcomes and examined the contribution of the contralesional hemisphere to walking recovery. Methods- Contralateral and ipsilateral transcranial magnetic stimulation responses from the contralesional and ipsilesional hemispheres were collected from 61 chronic stroke survivors. Clinical assessments included gait speeds, 6-minute walk distance, Timed Up and Go test, Fugl Meyer lower extremity scale, and strength measurements. Results- Stroke participants were classified based on the presence (MEP+ [n=28]) or absence (MEP- [n=33]) of MEPs in the paretic tibialis anterior and rectus femoris muscles. A between-group analyses showed no significant differences for any gait variable. MEP+ group showed significantly higher Fugl Meyer lower extremity and ankle dorsiflexor strength. Ipsilateral conductivity was not significantly different between groups. Finally, in the MEP+ group, MEP parameters did not predict gait recovery. Conclusions- Our study investigated the association between walking outcomes and neurophysiological parameters of lower limb function in a large cohort of stroke survivors. We did not find an associations between transcranial magnetic stimulation-induced tibialis anterior and rectus femoris MEPs and walking speeds. Further work is required to develop more comprehensive models in stroke for predicting walking recovery.

Kin support and child health: Investigating two approaches in an African slum.

Extensive research from sub-Saharan Africa shows that mothers frequently rely on help from other family members to ensure their children's health and well-being. Yet, there is considerable debate about the relative importance of support from grandmothers versus fathers. Using an innovative survey instrument to interview 462 unmarried mothers in a slum area of Nairobi, Kenya, we provide insight into this debate by showing that a status versus transfers approach to measuring kin support asks subtly different questions and yields different results. A status approach reflects an evolutionary perspective that argues that maternal grandmothers have a greater incentive than non-residential fathers to provide material and practical support for young children. In contrast, a transfers approach is consistent with social support theories whereby the social capital provided by fathers may be more beneficial to children's health than that afforded by grandmothers. Demonstrating that different approaches to measuring kin support matter highlights the need for kin research that crosses disciplinary boundaries and encourages the development of more nuanced family policies designed to protect children's health in Africa.

Gendered Emotional Support and Women's Well-Being in a Low-Income Urban African Setting.

Emotional support is crucial to the well-being of low-income, single women and their children in most contexts. Support from women may be especially important for single mothers because of precarious ties to their children's fathers, the prevalence of extended matrifocal living arrangements, and gendered norms that place men as providers of financial rather than emotional support. However, in contexts marked by economic insecurity, spatial dispersion of families, and changing gender norms and kinship obligations, such an expectation may be problematic. Applying theories of emotional capital and family bargaining processes, we address three questions: 1) what is the gender composition of emotional support that single mothers receive? 2) how does gender composition change over time? and 3) does the gender composition of emotional support affect self-reported stress of single mothers? Drawing on data from a unique dataset on 462 low-income single mothers and their kin from Nairobi, Kenya, we uncover three key findings. One, whereas the bulk of strong emotional support comes from female kin, about 20% of respondents report having male dominant support networks. Two, nearly 30% of respondents report change in the composition of their emotional support over six months favoring men. Three, having a male dominant emotional support network is associated with lower stress. These results challenge what is commonly taken for granted about gender norms and kinship obligations in non-Western contexts.

Measuring extended families over time in informal settlements in Nairobi, Kenya: Retention and data consistency in a two-round survey.

BACKGROUND: Researchers have increasingly turned to longitudinal data to understand how the family environment of children changes over time and how this change affects their well-being. While the value of such efforts is clear, the inherent challenges of collecting robust data over time may limit or bias our understanding of family complexity. OBJECTIVE: Drawing on data from an exploratory study on kinship structure and support for low income single mothers and their young children in Nairobi, Kenya, this paper aims to (1) assess the strengths and weaknesses of our approach in reflecting the complexities of kinship dynamics and (2) analyze how methodological issues such as selection and reporting inconsistency can influence our understanding of the role of kin in children's lives. METHODS: The analysis used data from two waves of the Kinship Support Tree (KST) project. The starting sample consisted of 462 single mothers with at least one child under the age of 7, with data collected on approximately 5,000 resident and nonresident kin. Descriptive statistics and conventional tests of significance were used to analyze selection factors and inconsistencies in reporting across waves. RESULTS: The study yielded a 91% retention rate after six months and the analysis provides some assurance that selectivity from attrition and reporting inconsistency are not entirely driven by shifts in support provision by kin. However, the selectivity of the sample underscores caution in generalizing the results. CONCLUSIONS: While the challenges of conducting follow-up surveys such as the KST are serious, these findings suggest that it is possible to collect consistent data on kinship structure and support from the perspective of children in a mobile population. Tracking kinship structure over time using the KST is not only feasible but more importantly is unlikely to lead to incomplete or biased understanding of kinship. CONTRIBUTION: After further testing with a wider range of women, we hope to disseminate our results for use in a wide range of contexts both in and out of Africa. We believe this data is vital to designing appropriate interventions to improve the well-being of children growing up in these communities.

Moving beyond the household: Innovations in data collection on kinship.

Across settings, it has been shown that the co-residential household is an insufficient measure of family structure and support. However, it continues to be the primary means of population data collection. To address this problem, we developed a new instrument, the Kinship Support Tree (KST), to collect kinship structure and support data on co-residential and non-residential kin and tested it on a sample of 462 single mothers and their children in a slum community in Nairobi, Kenya. This instrument is unique in four important ways: (1) it is not limited to the co-residential household; (2) it distinguishes potential from functional kin; (3) it incorporates multiple geospatial measures; and (4) it collects data on kin relationships specifically for children. In this paper, we describe the KST instrument, assess the data collected in comparison to data from household rosters, and consider the challenges and feasibility of administration of the KST.

Household structure vs. composition: Understanding gendered effects on educational progress in rural South Africa.

BACKGROUND: Demographers have long been interested in the relationship between living arrangements and gendered outcomes for children in sub-Saharan Africa. Most extant research conflates household structure with composition and has revealed little about the pathways that link these components to gendered outcomes. OBJECTIVES: First, we offer a conceptual approach that differentiates structure from composition with a focus on gendered processes that operate in the household; and second, we demonstrate the value of this approach through an analysis of educational progress for boys and girls in rural South Africa. METHODS: We use data from the 2002 round of the Agincourt Health and Demographic Surveillance System. Our analytical sample includes 22,997 children aged 6-18 who were neither parents themselves nor lived with a partner or partner's family. We employ ordinary least squares regression models to examine the effects of structure and composition on educational progress of girls and boys. RESULTS: The results suggest that non-nuclear structures are associated with similar negative effects for both boys and girls compared to children growing up in nuclear households. However, the presence of other kin in the absence of one or both parents results in gendered effects favouring boys. CONCLUSION: The absence of any gendered effects when using a household structure typology suggests that secular changes to attitudes about gender equity trump any specific gendered processes stemming from particular configurations. On the other hand, gendered effects that appear when one or both parents are absent show that traditional gender norms and/or resource constraints continue to favour boys. CONTRIBUTION: Despite the wealth of literature on household structure and children's educational outcomes in sub-Saharan Africa, the conceptual basis of these effects has not been well articulated. We have shown the value of unpacking household structure to better understand how gender norms and gendered resource allocations impact education.

Effects of anodal tDCS of the lower limb M1 on ankle reaction time in young adults.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that modulates cortical excitability and influences motor behavior. There is limited information available regarding the effects of anodal tDCS on lower limb reaction time. In this study, we aimed to investigate the effects of anodal tDCS on lower limb simple reaction time (SRT) and choice reaction time (CRT). We probed this question further by examining the effects of anodal tDCS of the lower limb M1 on an upper limb RT task and a cognitive measure. Fourteen healthy young adults received anodal tDCS and sham tDCS to the lower limb M1 on two separate testing days in a counterbalanced order. After stimulation, we assessed the effects of tDCS on ankle dorsiflexion SRT and CRT, ankle plantarflexion SRT and CRT, wrist extension SRT and CRT and the symbol digit modality test (SDMT). Anodal tDCS significantly improved response times from baseline for ankle CRT but not for ankle SRT or wrist SRT or CRT. A significant decrement (i.e., longer response time) was noted for the sham tDCS conditions. There was a significant difference between anodal and sham conditions for all RT tasks, suggesting that anodal tDCS improved RT compared to sham. No change in SDMT scores was observed for both conditions. Anodal tDCS appeared to differentially modulate ankle SRT and CRT, suggesting an influence of anodal tDCS on complex motor processes and/or the supplementary motor area. Absence of effects on wrist CRT or SDMT suggests a spatial specificity of the influence of tDCS. Anodal tDCS also appears to potentially negate the effects of fatigue or task switching that was detrimental to RT in the sham condition.

Effects of a Single Session of High Intensity Interval Treadmill Training on Corticomotor Excitability following Stroke: Implications for Therapy.

Objective. High intensity interval treadmill training (HIITT) has been gaining popularity for gait rehabilitation after stroke. In this study, we examined the changes in excitability of the lower limb motor cortical representation (M1) in chronic stroke survivors following a single session of HIITT. We also determined whether exercise-induced changes in excitability could be modulated by transcranial direct current stimulation (tDCS) enhanced with a paretic ankle skill acquisition task. Methods. Eleven individuals with chronic stroke participated in two 40-minute treadmill-training sessions: HIITT alone and HITT preceded by anodal tDCS enhanced with a skill acquisition task (e-tDCS+HIITT). Transcranial magnetic stimulation (TMS) was used to assess corticomotor excitability of paretic and nonparetic tibialis anterior (TA) muscles. Results. HIIT alone reduced paretic TA M1 excitability in 7 of 11 participants by ≥ 10%. e-tDCS+HIITT increased paretic TA M1 excitability and decreased nonparetic TA M1 excitability. Conclusions. HIITT suppresses corticomotor excitability in some people with chronic stroke. When HIITT is preceded by tDCS in combination with a skill acquisition task, the asymmetry of between-hemisphere corticomotor excitability is reduced. Significance. This study provides preliminary data indicating that the cardiovascular benefits of HIITT may be achieved without suppressing motor excitability in some stroke survivors.

Motor priming in neurorehabilitation.

Priming is a type of implicit learning wherein a stimulus prompts a change in behavior. Priming has been long studied in the field of psychology. More recently, rehabilitation researchers have studied motor priming as a possible way to facilitate motor learning. For example, priming of the motor cortex is associated with changes in neuroplasticity that are associated with improvements in motor performance. Of the numerous motor priming paradigms under investigation, only a few are practical for the current clinical environment, and the optimal priming modalities for specific clinical presentations are not known. Accordingly, developing an understanding of the various types of motor priming paradigms and their underlying neural mechanisms is an important step for therapists in neurorehabilitation. Most importantly, an understanding of the methods and their underlying mechanisms is essential for optimizing rehabilitation outcomes. The future of neurorehabilitation is likely to include these priming methods, which are delivered prior to or in conjunction with primary neurorehabilitation therapies. In this Special Interest article, we discuss those priming paradigms that are supported by the greatest amount of evidence, including (i) stimulation-based priming, (ii) motor imagery and action observation, (iii) sensory priming, (iv) movement-based priming, and (v) pharmacological priming.Video Abstract available. (see Supplemental Digital Content 1, http://links.lww.com/JNPT/A86) for more insights from the authors.