Older and younger adults differ in time course of skill acquisition but not in overall improvement in a bimanual visuomotor tracking task.

Manual motor performance declines with age, but the extent to which age influences the acquisition of new skills remains a topic of debate. Here, we examined whether older healthy adults show less training-dependent performance improvements during a single session of a bimanual pinch task than younger adults. We also explored whether physical and cognitive factors, such as grip strength or motor-cognitive ability, are associated with performance improvements.

Dynamic involvement of premotor and supplementary motor areas in bimanual pinch force control.

Many activities of daily living require quick shifts between symmetric and asymmetric bimanual actions. Bimanual motor control has been mostly studied during continuous repetitive tasks, while little research has been carried out in experimental settings requiring dynamic changes in motor output generated by both hands. Here, we performed functional magnetic resonance imaging (MRI) while healthy volunteers performed a visually guided, bimanual pinch force task.

Patient-tailored transcranial direct current stimulation to improve stroke rehabilitation: study protocol of a randomized sham-controlled trial.

Background: Many patients do not fully regain motor function after ischemic stroke. Transcranial direct current stimulation (TDCS) targeting the motor cortex may improve motor outcome as an add-on intervention to physical rehabilitation. However, beneficial effects on motor function vary largely among patients within and across TDCS trials.

Multipulse transcranial magnetic stimulation of human motor cortex produces short-latency corticomotor facilitation via two distinct mechanisms.

Single-pulse transcranial magnetic stimulation (TMS) of the precentral hand representation (M1) can elicit indirect waves in the corticospinal tract at a periodicity of ∼660 Hz, called I-waves. These descending volleys are produced by transsynaptic excitation of fast-conducting corticospinal axons in M1. Paired-pulse TMS can induce short-interval intracortical facilitation (SICF) of motor evoked potentials (MEPs) at interpulse intervals that match I-wave periodicity.

Transcranial magnetic stimulation of the brain: What is stimulated? - A consensus and critical position paper.

Transcranial (electro)magnetic stimulation (TMS) is currently the method of choice to non-invasively induce neural activity in the human brain. A single transcranial stimulus induces a time-varying electric field in the brain that may evoke action potentials in cortical neurons. The spatial relationship between the locally induced electric field and the stimulated neurons determines axonal depolarization.

Short periods of bipolar anodal TDCS induce no instantaneous dose-dependent increase in cerebral blood flow in the targeted human motor cortex.

Anodal transcranial direct current stimulation (aTDCS) of primary motor hand area (M1-HAND) can enhance corticomotor excitability, but it is still unknown which current intensity produces the strongest effect on intrinsic neural firing rates and synaptic activity. Magnetic resonance imaging (MRI) combined with pseudo-continuous Arterial Spin Labeling (pcASL MRI) can map regional cortical blood flow (rCBF). The measured rCBF signal is sensitive to regional changes in neuronal activity due to neurovascular coupling.

Corticomuscular coherence is reduced in relation to dorsiflexion fatigability to the same extent in adults with cerebral palsy as in neurologically intact adults.

Purpose: Fatigue is frequent in adults with cerebral palsy (CP) and it is unclear whether this is due to altered corticospinal drive. We aimed to compare changes in corticospinal drive following sustained muscle contractions in adults with CP and neurologically intact (NI) adults.

Methods: Fourteen adults with CP [age 37.

Cortical signatures of precision grip force control in children, adolescents, and adults.

Human dexterous motor control improves from childhood to adulthood, but little is known about the changes in cortico-cortical communication that support such ontogenetic refinement of motor skills. To investigate age-related differences in connectivity between cortical regions involved in dexterous control, we analyzed electroencephalographic data from 88 individuals (range 8-30 years) performing a visually guided precision grip task using dynamic causal modelling and parametric empirical Bayes. Our results demonstrate that bidirectional coupling in a canonical 'grasping network' is associated with precision grip performance across age groups.

Does pericentral mu-rhythm "power" corticomotor excitability? - A matter of EEG perspective.

Background: Electroencephalography (EEG) and single-pulse transcranial magnetic stimulation (spTMS) of the primary motor hand area (M1-HAND) have been combined to explore whether the instantaneous expression of pericentral mu-rhythm drives fluctuations in corticomotor excitability, but this line of research has yielded diverging results.

Objectives: To re-assess the relationship between the mu-rhythm power expressed in left pericentral cortex and the amplitude of motor potentials (MEP) evoked with spTMS in left M1-HAND.

Methods: 15 non-preselected healthy young participants received spTMS to the motor hot spot of left M1-HAND.

Multimodal Assessment of Precentral Anodal TDCS: Individual Rise in Supplementary Motor Activity Scales With Increase in Corticospinal Excitability.

Background: Transcranial direct current stimulation (TDCS) targeting the primary motor hand area (M1-HAND) may induce lasting shifts in corticospinal excitability, but after-effects show substantial inter-individual variability. Functional magnetic resonance imaging (fMRI) can probe after-effects of TDCS on regional neural activity on a whole-brain level.

Objective: Using a double-blinded cross-over design, we investigated whether the individual change in corticospinal excitability after TDCS of M1-HAND is associated with changes in task-related regional activity in cortical motor areas.

Functional and Structural Plasticity Co-express in a Left Premotor Region During Early Bimanual Skill Learning.

: Motor skill learning already triggers the functional reorganization of regional brain activity after short periods of training. Recent studies suggest that microstructural change may emerge at similar timescales, but the spatiotemporal profiles of functional and structural plasticity have rarely been traced in parallel. Recently, we demonstrated that 5 days of endoscopic skill training induces changes in task-related brain activity in the ventral premotor cortex (PMv) and other areas of the frontoparietal grasping network.

Beneficial effects of cerebellar tDCS on motor learning are associated with altered putamen-cerebellar connectivity: A simultaneous tDCS-fMRI study.

Non-invasive transcranial stimulation of cerebellum and primary motor cortex (M1) has been shown to enhance motor learning. However, the mechanisms by which stimulation improves learning remain largely unknown. Here, we sought to shed light on the neural correlates of transcranial direct current stimulation (tDCS) during motor learning by simultaneously recording functional magnetic resonance imaging (fMRI).

Cerebellar - Premotor cortex interactions underlying visuomotor adaptation.

Visuomotor adaptation (VMA) is a form of motor learning essential for performing day to day routines. Theoretical models and empirical evidence suggest a specific cortico-striato-cerebellar loop that mediates early and late learning in VMA. Here, we investigated dynamic changes in neural activity and connectivity when learning a novel visuomotor rotation using fMRI.

Directed connectivity between primary and premotor areas underlying ankle force control in young and older adults.

The control of ankle muscle force is an integral component of walking and postural control. Aging impairs the ability to produce force steadily and accurately, which can compromise functional capacity and quality of life. Here, we hypothesized that reduced force control in older adults would be associated with altered cortico-cortical communication within a network comprising the primary motor area (M1), the premotor cortex (PMC), parietal, and prefrontal regions.

Probing Context-Dependent Modulations of Ipsilateral Premotor-Motor Connectivity in Relapsing-Remitting Multiple Sclerosis.

We employed dual-site TMS to test whether ipsilateral functional premotor-motor connectivity is altered in relapsing-remitting Multiple Sclerosis (RR-MS) and is related to central fatigue. Twelve patients with RR-MS and 12 healthy controls performed a visually cued Pinch-NoPinch task with their right hand. During the reaction time (RT) period of Pinch and No-Pinch trials, single-site TMS was applied to the left primary motor cortex (M1) or dual-site TMS was applied to the ipsilateral dorsal premotor cortex (PMd) and to M1.

Anterior and Posterior Left Inferior Frontal Gyrus Contribute to the Implementation of Grammatical Determiners During Language Production.

The left inferior frontal gyrus (IFG) is a key region for language comprehension and production. Previous studies point to a preferential involvement of left anterior IFG (aIFG) in lexical and semantic processes, while the posterior IFG (pIFG) has been implicated in supporting syntactic and phonological processes. Here we used focal neuronavigated transcranial magnetic stimulation (TMS) to probe the functional involvement of left IFG in lexical and grammatical processing at the sentence level.

No trace of phase: Corticomotor excitability is not tuned by phase of pericentral mu-rhythm.

Background: The motor potentials evoked by transcranial magnetic stimulation (TMS) over the motor hand area (M1-HAND) show substantial inter-trial variability. Pericentral mu-rhythm oscillations, might contribute to inter-trial variability. Recent studies targeting mu-activity based on real-time electroencephalography (EEG) reported an influence of mu-power and mu-phase on the amplitude of motor evoked potentials (MEPs) in a preselected group with strong pericentral mu-activity.

Can Transcranial Electrical Stimulation Localize Brain Function?

Transcranial electrical stimulation (TES) uses constant (TDCS) or alternating currents (TACS) to modulate brain activity. Most TES studies apply low-intensity currents through scalp electrodes (≤2 mA) using bipolar electrode arrangements, producing weak electrical fields in the brain (<1 V/m). Low-intensity TES has been employed in humans to induce changes in task performance during or after stimulation.

Getting to grips with endoscopy - Learning endoscopic surgical skills induces bi-hemispheric plasticity of the grasping network.

Endoscopic surgery requires skilled bimanual use of complex instruments that extend the peri-personal workspace. To delineate brain structures involved in learning such surgical skills, 48 medical students without surgical experience were randomly assigned to five training sessions on a virtual-reality endoscopy simulator or to a non-training group. Brain activity was probed with functional MRI while participants performed endoscopic tasks.

Centre-surround organization of fast sensorimotor integration in human motor hand area.

Using the short-latency afferent inhibition (SAI) paradigm, transcranial magnetic stimulation (TMS) of the primary motor hand area (M1) can probe how sensory input from limbs modulates corticomotor output in humans. Here we applied a novel TMS mapping approach to chart the spatial representation of SAI in human hand-knob. We hypothesized SAI is somatotopically expressed in M1 depending on both the site of peripheral electrical nerve stimulation and the cortical spot targeted by TMS within M1.

Modulation of fronto-parietal connections during the rubber hand illusion.

Accumulating evidence suggests that parieto-frontal connections play a role in adjusting body ownership during the Rubber Hand Illusion (RHI). Using a motor version of the rubber hand illusion paradigm, we applied single-site and dual-site transcranial magnetic stimulation (TMS) to investigate cortico-spinal and parietal-frontal connectivity during perceived rubber hand ownership. Healthy volunteers received a conditioning TMS pulse over left anterior intraparietal sulcus (aIPS) and a test TMS pulse over left primary motor cortex (M1).

Transcranial brain stimulation: closing the loop between brain and stimulation.

Purpose Of Review: To discuss recent strategies for boosting the efficacy of noninvasive transcranial brain stimulation to improve human brain function.

Recent Findings: Recent research exposed substantial intra- and inter-individual variability in response to plasticity-inducing transcranial brain stimulation. Trait-related and state-related determinants contribute to this variability, challenging the standard approach to apply stimulation in a rigid, one-size-fits-all fashion.

Combining non-invasive transcranial brain stimulation with neuroimaging and electrophysiology: Current approaches and future perspectives.

Non-invasive transcranial brain stimulation (NTBS) techniques such as transcranial magnetic stimulation (TMS) and transcranial current stimulation (TCS) are important tools in human systems and cognitive neuroscience because they are able to reveal the relevance of certain brain structures or neuronal activity patterns for a given brain function. It is nowadays feasible to combine NTBS, either consecutively or concurrently, with a variety of neuroimaging and electrophysiological techniques. Here we discuss what kind of information can be gained from combined approaches, which often are technically demanding.

Consensus Paper: Probing Homeostatic Plasticity of Human Cortex With Non-invasive Transcranial Brain Stimulation.

Homeostatic plasticity is thought to stabilize neural activity around a set point within a physiologically reasonable dynamic range. Over the last ten years, a wide range of non-invasive transcranial brain stimulation (NTBS) techniques have been used to probe homeostatic control of cortical plasticity in the intact human brain. Here, we review different NTBS approaches to study homeostatic plasticity on a systems level and relate the findings to both, physiological evidence from in vitro studies and to a theoretical framework of homeostatic function.