Biology subjects

Branscheidt, M.

Publications and source records attributed to Branscheidt, M..

5 recordsLinked to original sources

bioRxiv2025

Impaired Peri-infarct Long-Term Potentiation Suggests Alternative Mechanisms of Post-stroke Recovery in Rats

BackgroundEarly after stroke, a period of heightened plasticity in the peri-infarct cortex is thought to provide the physiological substrate for functional motor recovery through increased expression of long-term potentiation (LTP). Prior slice electrophysiology studies on the capacity for LTP after stroke reported conflicting results. Slice preparation could have influenced the results by disrupting neuromodulatory processes altered after stroke. Therefore, whether LTP can be induced in the peri-infarct cortex remains to be elucidated. We investigated LTP in the peri-infarct cortex of anesthetized rats using a novel in vivo method that preserves local and long-range circuit dynamics. MethodsLTP, synaptic transmission and short-term plasticity were assessed under urethane anaesthesia in 15 rats (11 with focal stroke to the primary motor cortex, and 4 sham operated controls). Rats were tested one or two weeks after stroke using a minimally perturbed in vivo LTP induction protocol validated in naive rats. Motor function was evaluated using the cylinder test at baseline and at one or two-weeks post stroke. ResultsLTP in the peri-infarct cortex was supressed in the stroke group compared to sham controls. In addition, synaptic transmission was reduced for higher stimulation intensities, and short-term plasticity shifted from facilitation to depression, indicating impaired synaptic function at one- and two-weeks post-stroke. Behaviorally, the lesioned rats exhibited motor deficits at one week but showed full recovery by two weeks post-stroke. ConclusionIn recovering animals, both LTP and synaptic transmission are profoundly impaired in the peri-infarct cortex. These findings suggest that mechanisms other than LTP-based plasticity underlie motor recovery during this stage.

neuroscience↗

bioRxiv2023

Reinforcement Learning Is Impaired in the Sub-acute Post-stroke Period

BackgroundNeurorehabilitation approaches are frequently predicated on motor learning principles. However, much is left to be understood of how different kinds of motor learning are affected by stroke causing hemiparesis. Here we asked if two kinds of motor learning often employed in rehabilitation, (1) reinforcement learning and (2) error-based adaptation, are altered at different times after stroke. MethodsIn a cross-sectional design, we compared learning in two groups of patients with stroke, matched for their baseline motor execution deficit on the paretic side. The early group was tested within 3 months following stroke (N = 35) and the late group was tested more than 6 months after stroke (N = 30). Two types of task were studied: one based on reinforcement learning and the other on error-based learning. ResultsWe found that reinforcement learning was impaired in the early but not the late group, whereas error-based learning was unaffected compared to controls. These findings could not be attributed to differences in baseline execution, cognitive impairment, gender, age, or lesion volume and location. ConclusionsThe presence of a specific impairment in reinforcement learning in the first 3 months after stroke has important implications for rehabilitation. It might be necessary to either increase the amount of reinforcement feedback given early or even delay onset of certain forms of rehabilitation training, e.g., like constraint-induced movement therapy, and instead emphasize others forms of motor learning in this early time period. A deeper understanding of stroke-related changes in motor learning capacity has the potential to facilitate the development of new, more precise treatment interventions.

neuroscience↗

bioRxiv2019

No evidence for motor recovery-related cortical reorganization after stroke using resting-state fMRI

Cortical reorganization has been suggested as mechanism for recovery after stroke. It has been proposed that a form of cortical reorganization (changes in functional connectivity between brain areas) can be assessed with resting-state fMRI. Here we report the largest longitudinal data-set in terms of overall sessions in 19 patients with subcortical stroke and 11 controls. Patients were imaged up to 5 times over one year. We found no evidence for post-stroke cortical reorganization despite substantial behavioral recovery. These results could be construed as questioning the value of resting-state imaging. Here we argue instead that they are consistent with other emerging reasons to challenge the idea of motor recovery-related cortical reorganization post-stroke when conceived as changes in connectivity between cortical areas.

neuroscience↗

bioRxiv2018

Fatigue induces long lasting detrimental changes in motor skill learning

Fatigue due to physical exertion is a ubiquitous phenomenon in everyday life and especially common in a range of neurological diseases. While the effect of fatigue on limiting skill execution are well known, its influence on learning new skills is unclear. This is of particular interest as it is common practice to train athletes, musicians or perform rehabilitation exercises up to and beyond a point of fatigue. In a series of experiments, we describe how fatigue impairs motor skill learning beyond its effects on task execution. The negative effects on learning are evidenced by impaired task acquisition on subsequent practice days even in the absence of fatigue. Further, we found that this effect is in part mediated centrally and can be alleviated by altering motor cortex function. Thus, the common practice of training while, or beyond, fatigue levels should be carefully reconsidered, since this affects overall long-term skill learning.

neuroscience↗

bioRxiv2017

Finger recruitment patterns during mirror movements suggest two systems for hand recovery after stroke

Accumulating behavioural and neurophysiological evidence suggests that upper-limb control relies on contributions from both cortical and subcortical motor circuits, with cortical inputs providing fine-finger function and subcortical inputs providing the ability for gross movements, respectively. During recovery of function after stroke, the relative contributions from these pathways may shift. Here we propose that mirror movements that appear after stroke provide a non-invasive assay through which relative contributions from cortical and subcortical pathways towards hand recovery can be studied. We hypothesized that mirror movements, like hand function, are generated by summed contributions from cortical and subcortical pathways, and suggest that subcortical contributions should be characterized by a broad recruitment of fingers, while cortical contributions primarily recruit the homologous finger in the passive hand. In a longitudinal stroke recovery study (Xu et al., 2016), we quantified mirror movements and paretic hand function in 53 stroke patients in the year following unilateral stroke. Mirror movements in the non-paretic hand were exaggerated early after damage (week 2), with paretic finger presses broadly recruiting multiple fingers in the non-paretic hand. On average, however, mirroring in homologous fingers was 1.76 times larger than in non-homologous fingers. Over the year, mirroring in the non-paretic hand progressively normalized with a time-course that mimicked that for the fine-finger deficits in the paretic hand. In comparison, during non-paretic finger presses, the homologous component of mirroring in the paretic hand was reduced early after stroke (week 2) but progressively normalized. Altogether, we conclude that the pattern of mirror movements across homologous and non-homologous fingers reflect the summed contributions of both cortical and subcortical systems, and we discuss the implications of our results towards hand recovery after stroke.

neuroscience↗