Improvement In Motor Learning Research Articles

Effects of Enriched Environment on Motor Learning Improvement in 6-Hydroxydopamine-Induced Parkinson��s Rats

Parkinson’s disease is a neurodegenerative disease that leads to impairments of motor control and learning. Enriched environment (EE) is noted to slow the disease progress and improve motor and memory functions in the Alzheimer’s rat model, which is also a neurodegenerative disease. The purpose of present study was to investigate the effects of EE on motor skilled learning in the Parkinson’s rat model. Male Sprague-Dawley rats were randomly assigned to the following groups: control group, standard environment (SE) group and EE group. Rats received unilateral intracranial administration of 6-hydroxydopamine (6-OHDA) or vehicle. Rats received four-week EE housing (4 rats/cage, EE group) or standard housing (1 rat/cage, control and SE groups) after intracranial administration. Motor learning, motor performance, and expressions of tyrosine hydroxylase cell in the affected substantia nigra were measured after the four-week intervention. Motor learning and skill motor performance of rats were significantly impaired in SE group when compared with the control. EE intervention could decrease such impairments, especially on the rapid phase of learning. The numbers of dopamine neuron in the affected substantia nigra were significantly decreased in SE group, but such reduction was partly prevented by EE intervention. These results indicated that four-week EE prevented dopaminergic neuron death and improved the motor learning ability and skill motor performance in 6-OHDA-indused Parkinson’s rat.

Effects of transcranial direct current stimulation on motor learning in healthy individuals: a systematic review

Introduction Transcranial direct current stimulation (tDCS) has been used to modify cortical excitability and promote motor learning. Objective To systematically review published data to investigate the effects of transcranial direct current stimulation on motor learning in healthy individuals. Methods Randomized or quasi-randomized studies that evaluated the tDCS effects on motor learning were included and the risk of bias was examined by Cochrane Collaboration’s tool. The following electronic databases were used: PubMed, Scopus, Web of Science, LILACS, CINAHL with no language restriction. Results It was found 160 studies; after reading the title and abstract, 17 of those were selected, but just 4 were included. All studies involved healthy, right-handed adults. All studies assessed motor learning by the Jebsen Taylor Test or by the Serial Finger Tapping Task (SFTT). Almost all studies were randomized and all were blinding for participants. Some studies presented differences at SFTT protocol. Conclusion The result is insufficient to draw conclusions if tDCS influences the motor learning. Furthermore, there was significant heterogeneity of the stimulation parameters used. Further researches are needed to investigate the parameters that are more important for motor learning improvement and measure whether the effects are long-lasting or limited in time.

Analysis of Taurine as Modulator of Neurotransmitter in Caenorhabditis elegans.

Taurine exists in large quantities in the skeletal and heart muscles, where it plays a substantial role in detoxification, membrane stability, and osmoregulation. In central nerve cells, taurine is believed to function as an inhibitory modulator and a protectant. In mice, extended taurine treatment modulates the γ-aminobutyric acid-producing (GABAergic) system during neonatal development. A sizable improvement in motor learning after training is apparent when adult mice are treated with taurine. Taurine has a significant affinity for several receptors including those for glycine, acetylcholine, and adrenalin or noradrenalin, supporting its prospective role in stress, mood, and behavior. Taurine is structurally similar to GABA, an efficient neurotransmitter in Caenorhabditis elegans. GABA acts primarily at neuromuscular synapses in nematodes, while vertebrates utilize GABA within synapses along the central nervous system. Some researchers, however, suspect that taurine’s positive effects on mental performance and learning may result from caffeine, which is usually used as a supplement in taurine-based foods or drugs. The purpose of the present study was to investigate taurine as a potential enhancer from a learning perspective in C. elegans. Throughout the present study, taurine positively affected associative learning in C. elegans, although caffeine may exert a synergistic effect to strengthen its stimulant properties. Additional research may be necessary to determine the optimal use of taurine in terms of scale and applicability. In conclusion, taurine can be used singularly as an enhancer for learning, associative or locomotive, and its effect can be enlarged in the presence of caffeine.

Beta-frequency EEG activity increased during transcranial direct current stimulation.

Transcranial direct current stimulation (tDCS) is a technique for noninvasively stimulating specific cortical regions of the brain with small (<2 mA) and constant direct current on the scalp. tDCS has been widely applied, not only for medical treatment, but also for cognitive and somatosensory function enhancement, motor learning improvement, and social behavioral change. However, the mechanism that underlies the effect of tDCS is unclear. In this study, we performed simultaneous electroencephalogram (EEG) monitoring during tDCS to understand the dynamic electrophysiological changes throughout the stimulation. A total of 10 healthy individuals participated in this experiment. We recorded EEGs with direct current stimulation, as well as during a 5-min resting state before and after the stimulation. All participants kept their eyes closed during the experiment. Anode and cathode patches of tDCS were placed on the left and the right dorsolateral prefrontal cortex, respectively. In addition, an EEG electrode was placed on the medial prefrontal cortex. The beta-frequency power increased promptly after starting the stimulation. The significant beta-power increase was maintained during the stimulation. Other frequency bands did not show any significant changes. The results indicate that tDCS of the left dorsolateral prefrontal cortex changed the brain to a ready state for efficient cognitive functioning by increasing the beta-frequency power. This is the first attempt to simultaneously stimulate the cortex and record the EEG and then systematically analyze the prestimulation, during-stimulation, and poststimulation EEG data.

Functional connectivity in the resting-state motor networks influences the kinematic processes during motor sequence learning.

Neuroimaging studies support the involvement of the cerebello-cortical and striato-cortical motor loops in motor sequence learning. Here, we investigated whether the gain of motor sequence learning could depend on a-priori resting-state functional connectivity (rsFC) between motor areas and structures belonging to these circuits. Fourteen healthy subjects underwent a resting-state functional magnetic resonance imaging session. Afterward, they were asked to reproduce a verbally-learned sequence of finger opposition movements as fast and as accurately as possible. All subjects increased their movement rate with practice, by reducing the touch duration and/or intertapping interval. The rsFC analysis showed that, at rest, the left and right primary motor cortex (M1) and left and right supplementary motor area (SMA) were mainly connected with other motor areas. The covariate analysis taking into account the different kinematic parameters indicated that the subjects achieving greater movement rate increase were those showing stronger rsFC of the left M1 and SMA with the right lobule VIII of the cerebellum. Notably, the subjects with greater intertapping interval reduction showed stronger rsFC of the left M1 and SMA with the association nuclei of the thalamus. Conversely, the regression analysis with the right M1 and SMA seeds showed only a few significant clusters for the different covariates not located in the cerebellum and thalamus. No common clusters were found between the right M1 and SMA. All of these findings indicated important functional connections at rest of those neural circuits responsible for motor learning improvement, involving the motor areas related to the hemisphere directly controlling the finger movements, the thalamus and cerebellum.

Impact of 5-Hz rTMS over the primary sensory cortex is related to white matter volume in individuals with chronic stroke.

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique that may facilitate mechanisms of motor learning. In a recent single-blind, pseudo-randomized study, we showed that 5-Hz rTMS over ipsilesional primary somatosensory cortex followed by practice of a skilled motor task enhanced motor learning compared with sham rTMS + practice in individuals with chronic stroke. However, the beneficial effect of stimulation was inconsistent. The current study examined how differences in sensorimotor cortex morphology might predict rTMS-related improvements in motor learning in these individuals. High-resolution T1-weighted magnetic resonance images were acquired and processed in FreeSurfer using a newly developed automated, whole brain parcellation technique. Gray matter and white matter volumes of the ipsilesional primary somatosensory and motor cortices were extracted. A significant positive association was observed between the volume of white matter in the primary somatosensory cortex and motor learning-related change, exclusively in the group that received active 5-Hz rTMS. A regression model with age, gray matter and white matter volumes as predictors was significant for predicting motor learning-related change in individuals who received active TMS. White matter volume predicted the greatest amount of variance (47.6%). The same model was non-significant when volumes of the primary motor cortex were considered. We conclude that white matter volume in the cortex underlying the TMS coil may be a novel predictor for behavioral response to 5-Hz rTMS over the ipsilesional primary somatosensory followed by motor practice.

Simultaneous high-definition transcranial direct current stimulation of the motor cortex and motor imagery.

Transcranial direct current stimulation (tDCS) has been used to affect the excitability of neurons within the cerebral cortex. Improvements in motor learning have been found in multiple studies when tDCS was applied to the motor cortex during or before task learning is performed. The application of tDCS to motor imagery, a cognitive task showing activation in similar areas to motor execution, has resulted in differing effects based on the amplitude and duration of stimulation. We utilize high definition tDCS, a more spatially localized version of tDCS, to investigate the effect of anodal stimulation on human motor imagery performance. In parallel, we model this stimulation using a finite element model to calculate stimulation area and electrical field amplitude within the brain in the motor cortex and non-stimulated frontal and parietal regions. Overall, we found a delayed increase in resting baseline power 30 minutes post stimulation in both the right and left sensorimotor cortices which resulted in an increase in event-related desynchronization.

Motor learning through virtual reality in cerebral palsy - a literature review

Cerebral palsy is a well-recognized neurodevelopmental condition beginning in early childhood and persisting throughout life. It is considered the most common non-progressive neurological disease of childhood. Subjects with cerebral palsy present complex motor skill disorders, the primary deficits being abnormal muscle tone that affects posture and movement, alterations of balance and of motor coordination, decrease in strength and loss of selective motor control, with secondary issues of contracture and bone deformity. This population may have difficulties in motor skill learning processes. Skill learning is learning as a result of repeated exposure and practice. Due to the increasing use of virtual reality in rehabilitation and the significance of motor development learning of subjects with cerebral palsy, we have recognized the need for studies in this area. The purpose of this study was to investigate the results of previous studies on motor learning using virtual reality with patients with cerebral palsy. Initially, 40 studies were found, but 30 articles were excluded, as they did not fulfil the inclusion criteria. The data extracted from the ten eligible studies is summarized. The studies showed benefits from the use of virtual reality in children with cerebral palsy in gross motor function and improvements in motor learning with skill transfer to real-life situations. Therefore, virtual reality seems to be a promising resource and a strategic option for care of these children. However, there are few studies about motor learning with virtual reality use. The long term benefits of virtual reality therapy are still unknown.

Mouse neurexin-1α deletion causes correlated electrophysiological and behavioral changes consistent with cognitive impairments

Deletions in the neurexin-1alpha gene were identified in large-scale unbiased screens for copy-number variations in patients with autism or schizophrenia. To explore the underlying biology, we studied the electrophysiological and behavioral phenotype of mice lacking neurexin-1alpha. Hippocampal slice physiology uncovered a defect in excitatory synaptic strength in neurexin-1alpha deficient mice, as revealed by a decrease in miniature excitatory postsynaptic current (EPSC) frequency and in the input-output relation of evoked postsynaptic potentials. This defect was specific for excitatory synaptic transmission, because no change in inhibitory synaptic transmission was observed in the hippocampus. Behavioral studies revealed that, compared with littermate control mice, neurexin-1alpha deficient mice displayed a decrease in prepulse inhibition, an increase in grooming behaviors, an impairment in nest-building activity, and an improvement in motor learning. However, neurexin-1alpha deficient mice did not exhibit any obvious changes in social behaviors or in spatial learning. Together, these data indicate that the neurexin-1alpha deficiency induces a discrete neural phenotype whose extent correlates, at least in part, with impairments observed in human patients.

Influence of 5 Hz repetitive transcranial magnetic stimulation on motor learning

The aim of our study was to assess a possible improvement in motor learning induced by 5Hz repetitive transcranial magnetic stimulation (rTMS) of human motor cortex. The same stimulation protocol previously enhanced perceptual learning as assessed by tactile discrimination performance when applied to the human primary somatosensory cortex. We applied 1250 pulses of 5Hz “real” rTMS at 90% of resting motor threshold to the motor hotspot of the abductor pollicis brevis (APB) muscle in 15 healthy subjects before 1h of motor training. Furthermore, 15 subjects received 5Hz “sham” rTMS and served as control group. The motor task consisted of a synchronized co-contraction of the right APB and deltoid muscle. The latency between the onsets of muscle contractions was measured during training and served as a parameter for motor learning. MEP amplitudes were assessed in a subgroup of 10 subjects before and after rTMS as a parameter of corticospinal excitability. We found a significant learning effect in both groups as indicated by a reduction of latencies between the onsets of muscle contractions in the course of the training. Corticospinal excitability increased after “real”, but not after “sham” rTMS. However, “real” rTMS did not significantly influence motor learning as compared to “sham” rTMS. We conclude that 5Hz rTMS of human primary motor cortex is not able to improve motor learning in healthy subjects, which might be due to the higher complexity of motor learning as compared to perceptual learning in the tactile domain.

Sleep-related improvements in motor learning following mental practice

A wide range of experimental studies have provided evidence that a night of sleep may enhance motor performance following physical practice (PP), but little is known, however, about its effect after motor imagery (MI). Using an explicitly learned pointing task paradigm, thirty participants were assigned to one of three groups that differed in the training method (PP, MI, and control groups). The physical performance was measured before training (pre-test), as well as before (post-test 1) and after a night of sleep (post-test 2). The time taken to complete the pointing tasks, the number of errors and the kinematic trajectories were the dependent variables. As expected, both the PP and the MI groups improved their performance during the post-test 1. The MI group was further found to enhance motor performance after sleep, hence suggesting that sleep-related effects are effective following mental practice. Such findings highlight the reliability of MI in learning process, which is thought consolidated when associated with sleep.

Effects of dietary restriction on motor learning and cerebellar noradrenergic dysfunction in aged F344 rats.

Fisher 344 rats were fed either ad libitum or with a diet containing a 40% reduction of calories beginning at 4 months of age. At 14 months and 22 months male rats were tested for their ability to learn a complex motor skill. At both ages the diet restricted rats reached criterion of performing 10 successful crosses in 10 min at an earlier time than ad libitum fed controls. At 22 months of age the diet restricted rats showed improved acquisition of running times for the task. Male rats at 14 and 22 months and female rats at 24 months were examined electrophysiologically for the ability of isoproterenol to augment the action of GABA in the cerebellum when both substances were applied iontophoretically from an extracellular multibarreled glass electrode. In all 3 age and sex groups there was an improvement in the beta-adrenergic receptor modulation of GABA responses in the dietary restricted vs. ad libitum rats. However, no difference was observed between dietary restricted and ad libitum rats when the number and affinity of cerebellar beta-adrenergic receptors was assessed with 125I-iodopindolol binding. Overall, there was a significant improvement in cerebellar noradrenergic function in the dietary restricted rats and this was accompanied by an improvement in motor learning.

Further Reduction in Hospital Infection of Wounds

<h3>Abstract</h3> Vagus nerve stimulation (VNS) is a neuromodulation therapy for a broad and rapidly expanding set of neurologic conditions. Classically used to treat epilepsy and depression, VNS has recently received FDA approval for stroke rehabilitation and is under preclinical and clinical investigation for other neurologic indications. Despite benefits across a diverse range of neurological disorders, the mechanism through which VNS influences central nervous system circuitry is not well described, limiting therapeutic optimization. A deeper understanding of the influence of VNS on neural circuits and activity is needed to maximize the use of VNS therapy across a broad range of neurologic conditions. To investigate how VNS can influence the neurons and circuits that underlie behavior, we paired VNS with upper limb movement in mice learning a skilled motor task. We leveraged genetic tools to perform optogenetic circuit dissection, as well as longitudinal <i>in vivo</i> imaging of calcium activity in cortical neurons to understand the effect of VNS on neural function. We found that VNS robustly enhanced motor learning when temporally paired with successful movement outcome, while randomly applied VNS impaired learning. This suggests that temporally-precise VNS may act through augmenting outcome cues, such as reinforcement signals. Within motor cortex, VNS paired with movement outcome selectively modulates the neural population that represents outcome, but not other movement-related neurons, across both acute and behaviorally-relevant timescales. Phasic cholinergic signaling from basal forebrain is required both for VNS-driven improvements in motor learning and the effects on neural activity in M1. These results indicate that VNS enhances motor learning through precisely-timed phasic cholinergic signaling to reinforce outcome, resulting in the recruitment of specific, behaviorally-relevant cortical circuits. A deeper understanding of the mechanisms of VNS on neurons, circuits and behavior provides new opportunities to optimize VNS to treat neurologic conditions.