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

Abstract

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 2018retrospectively registered, https:// clinicaltrials.gov/ct2/show/NCT03492229.

Is High-Intensity Interval Training Suitable to Promote Neuroplasticity and Cognitive Functions after Stroke?

“…Additionally, a single bout of HIIT combined with motor practice could increase skill retention, suggesting a potential impact of HIIT to accelerate motor learning in individuals with stroke [141]. Moreover, priming HIIT through transcranial direct current stimulation enriched with a paretic ankle skill acquisition task could reduce poststroke cortical excitability asymmetry, known to be associated with less functional impairments [142][143][144][145][146], which is not observed when HIIT is performed alone [141] (Table 3). Both HIIT ➚ FNDC5 and Cyt C in the contralesional cortex ➚ indicate an increase; ➘ indicate a decrease; BDNF: brain-derived neurotrophic factor; proBDNF: precursor brain-derived neurotrophic factor; mBDNF: mature brain-derived neurotrophic factor; VEGF: vascular endothelial growth factor; IGF-1: insulin-like growth factor 1; NKCC1: Na + -K + -2Cl − cotransporter; KCC2: K + -Cl − cotransporter; HRR: heart rate reserve; HI: high-intensity; LI; low-intensity; HIIT: high-intensity interval training; MICT: moderate-intensity ➚ Serum BDNF after HIIT ➚ Dendritic growth with patient serum after HIIT ➚ indicate an increase; ⟺ indicate a maintenance; BDNF: brain-derived neurotrophic factor; VEGF: vascular endothelial growth factor; IGF-1: insulin-like growth factor 1; HRR: heart rate reserve; HI: high-intensity; LI; low-intensity; HIIT: high-intensity interval training; MICT: moderate-intensity.…”

“…Additionally, a single bout of HIIT combined with motor practice could increase skill retention, suggesting a potential impact of HIIT to accelerate motor learning in individuals with stroke [ 141 ]. Moreover, priming HIIT through transcranial direct current stimulation enriched with a paretic ankle skill acquisition task could reduce poststroke cortical excitability asymmetry, known to be associated with less functional impairments [ 142 , 143 , 144 , 145 146 ], which is not observed when HIIT is performed alone [ 141 ] ( Table 3 ).…”

Individualized Responses to Ipsilesional High-Frequency and Contralesional Low-Frequency rTMS in Chronic Stroke: A Pilot Study to Support the Individualization of Neuromodulation for Rehabilitation

“…Participants in some tDCS trials are being classified as up-or down-regulators depending on their response to anodal tDCS. This classification has been shown to explain some of the changes seen in tDCS and stroke rehabilitation studies (Madhavan et al, 2020).…”

Changes in Walking Speed After High-Intensity Treadmill Training Are Independent of Changes in Spatiotemporal Symmetry After Stroke

“…After 4 weeks of HISTT both comfortable and maximal walking speeds increased and remained elevated 3 months later ( 17 ). We expected to also detect improvements in spatiotemporal symmetry that were related to these improvements in walking speed because some studies have shown simultaneous improvements in speed and symmetry (although direct relations were not tested) in response to a variety of moderate-intensity walking training interventions ( 29 – 35 ).…”

“…The training protocol has been described in detail previously ( 17 , 26 ). Briefly, participants were assigned to one of four parallel groups receiving 15 min of transcranial direct current stimulation (tDCS; stimulation-based priming), ankle motor tracking (AMT; movement-based priming), tDCS and AMT, or rest immediately prior to HISTT described below.…”