Different descending pathways mediate early and late portions of lower limb responses to transcranial magnetic stimulation.

Although recent studies in nonhuman primates have provided evidence that transcranial magnetic stimulation (TMS) activates cells within the reticular formation, it remains unclear whether descending brain stem projections contribute to the generation of TMS-induced motor evoked potentials (MEPs) in skeletal muscles. We compared MEPs in muscles with extensive direct corticomotoneuronal input (first dorsal interosseous) versus a prominent role in postural control (gastrocnemius) to determine whether the amplitudes of early and late MEPs were differentially modulated by cortical suppression. Suprathreshold TMS was applied with and without a preceding suprathreshold TMS pulse at two interstimulus intervals (50 and 80 ms).

Parent's Cardiorespiratory Fitness, Body Mass, and Chronic Disease Status Is Associated with Metabolic Syndrome in Young Adults: A Preliminary Study.

We sought to determine if there was an intergenerational association between parental weight, cardiorespiratory fitness (CRF), and disease status, with the prevalence of metabolic syndrome (MetSyn) in their young adult offspring. Young adults ( = 270, 21 ± 1 years, 53.3% female) were assessed for MetSyn and self-reported parent's CRF, body mass status, and disease status.

EMG breakthrough during cortical silent period in congenital hemiparesis: a descriptive case series.

Background: The cortical silent period is a transient suppression of electromyographic activity after a transcranial magnetic stimulation pulse, attributed to spinal and supraspinal inhibitory mechanisms. Electromyographic breakthrough activity has been observed in healthy adults as a result of a spinal reflex response within the cortical silent period.

Objectives: The objective of this case series is to report the ipsilesional and contralesional cortical silent period and the electromyographic breakthrough activity of 7 children with congenital hemiparesis.

The use of transcranial magnetic stimulation to evaluate cortical excitability of lower limb musculature: Challenges and opportunities.

Neuroplasticity is a fundamental yet relatively unexplored process that can impact rehabilitation of lower extremity (LE) movements. Transcranial magnetic stimulation (TMS) has gained widespread application as a non-invasive brain stimulation technique for evaluating neuroplasticity of the corticospinal pathway. However, a majority of TMS studies have been performed on hand muscles, with a paucity of TMS investigations focused on LE muscles.

Revisiting interhemispheric imbalance in chronic stroke: A tDCS study.

Objective: Chronic stroke patients with moderate-severe motor impairment may have an increased reliance on contralesional vs ipsilesional motor areas to control the paretic arm. We hypothesised that increasing contralesional excitability with anodal transcranial direct current stimulation (a-tDCS) would benefit motor performance in patients with moderate-severe impairment.

Methods: Ten patients with motor impairment at the chronic stage after stroke received a-tDCS, cathodal (c-tDCS) and sham with the target electrode over contralesional motor cortex (M1).

Prevalence of metabolic syndrome and metabolic syndrome components in young adults: A pooled analysis.

Metabolic syndrome (MetSyn) represents a clustering of different metabolic abnormalities. MetSyn prevalence is present in approximately 25% of all adults with increased prevalence in advanced ages. The presence of one component of MetSyn increases the risk of developing MetSyn later in life and likely represents a high lifetime burden of cardiovascular disease risk.

Propriospinal cutaneous-induced EMG suppression is unaltered by anodal tDCS of healthy motor cortex.

Objective: Cervical propriospinal premotoneurons (PN) relay descending motor commands and integrate peripheral afferent feedback. Effects of anodal transcranial direct current stimulation (a-tDCS) on propriospinal excitability in the upper limbs are unknown.

Methods: Healthy right-handed adults received a-tDCS or sham tDCS over primary motor cortex (M1) at 1mA (Experiment 1, n=18) or 2mA current intensity (Experiment 2, n=15).

Effects of non-target leg activation, TMS coil orientation, and limb dominance on lower limb motor cortex excitability.

Transcranial magnetic stimulation (TMS) is used to examine corticospinal tract integrity after stroke, however, generating motor-evoked potentials (MEPs) in the lower limb (LL) can be difficult. Previous studies have used activation of the target leg to facilitate MEPs in the LL but this may not be possible after stroke due to hemiplegia. The dominance of the target limb may also be important, however the neurophysiological effects of LL dominance are not known.

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

. 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.

Can motor imagery and hypnotic susceptibility explain Conversion Disorder with motor symptoms?

Marked distortions in sense of agency can be induced by hypnosis in susceptible individuals, including alterations in subjective awareness of movement initiation and control. These distortions, with associated disability, are similar to those experienced with Conversion Disorder (CD), an observation that has led to the hypothesis that hypnosis and CD share causal mechanisms. The purpose of this review is to explore the relationships among motor imagery (MI), hypnotic susceptibility, and CD, then to propose how MI ability may contribute to hypnotic responding and CD.

Are ipsilateral motor evoked potentials subject to intracortical inhibition?

Paired-pulse transcranial magnetic stimulation (TMS) can be used to examine intracortical inhibition in primary motor cortex (M1), termed short-interval intracortical inhibition (SICI). To our knowledge, SICI has only been demonstrated in contralateral motor evoked potentials (MEPs). Ipsilateral MEPs (iMEPs) are assumed to reflect excitability of an uncrossed oligosynaptic pathway, and can sometimes be evoked in proximal upper-limb muscles using high-intensity TMS.

Neurophysiological and behavioural effects of dual-hemisphere transcranial direct current stimulation on the proximal upper limb.

Dual-hemisphere transcranial direct current stimulation over the primary motor cortex (M1-M1 tDCS) is assumed to modulate neural excitability in a polarity-dependent manner and improve motor performance of the hand. In the proximal upper limb, the neurophysiological and behavioural after-effects of M1-M1 tDCS are not well known. This study investigated the after-effects of M1-M1 tDCS on contralateral, ipsilateral and transcallosal excitability to the proximal upper limb muscle biceps brachii (BB).

Delayed grip relaxation and altered modulation of intracortical inhibition with aging.

Grip relaxation is a voluntary action that requires an increase in short-interval intracortical inhibition (SICI) in healthy young adults, rather than a simple termination of excitatory drive. The way aging affects this voluntary inhibitory action and timing of grip relaxation is currently unknown. The objective of this study was to examine aging-related delays in grip relaxation and SICI modulation for the flexor digitorum superficialis muscle during grip relaxation.

'I-wave' Recruitment Determines Response to tDCS in the Upper Limb, but Only So Far.

Background: Anodal transcranial direct current stimulation (a-tDCS) can facilitate primary motor cortex (M1), but the modulation of motor evoked potentials (MEPs) by a-tDCS varies between participants, and may depend on the balance between early versus late I-wave recruitment, as assessed by the difference in MEP latency between latero-medial and anterior-posterior cortical currents induced by transcranial magnetic stimulation (TMS).

Objective: To date, the dependence of tDCS after-effects on I-wave recruitment has only been investigated in intrinsic hand muscles. In order to better understand the effects of tDCS across the upper limb, the present study examined I-wave recruitment and MEP modulation by a-tDCS or dual-hemisphere tDCS in muscles of the forearm (Extensor Carpi Radialis; ECR) and proximal upper limb (Biceps Brachii; BB).

Stance limb ground reaction forces in high functioning stroke and healthy subjects during gait initiation.

Background: Following stroke, little is known about ground reaction forces during gait initiation.

Objective: To compare stroke patients' with healthy subjects' anterior, medial, and lateral ground reaction forces generated during gait initiation.

Methods: Patients with left paresis, right paresis, and age-similar healthy subjects were recruited.

The effect of intensive nutrition interventions on weight gain after kidney transplantation: protocol of a randomised controlled trial.

Background: Weight gain and obesity are common after kidney transplantation, particularly during the first year. Obesity is a risk factor for the development of new-onset diabetes after transplantation, and is associated with reduced graft survival. There is a lack of evidence for effective interventions to prevent weight gain after kidney transplantation.

Corticomotor excitability of arm muscles modulates according to static position and orientation of the upper limb.

Objective: We investigated how multi-joint changes in static upper limb posture impact the corticomotor excitability of the posterior deltoid (PD) and biceps brachii (BIC), and evaluated whether postural variations in excitability related directly to changes in target muscle length.

Methods: The amplitude of individual motor evoked potentials (MEPs) was evaluated in each of thirteen different static postures. Four functional postures were investigated that varied in shoulder and elbow angle, while the forearm was positioned in each of three orientations.

A dissociation between propriospinal facilitation and inhibition after bilateral transcranial direct current stimulation.

Propriospinal premotoneurons (PN) are essential for accurate control of the upper limb. They receive bilateral input from premotor (PM) and primary motor (M1) cortices. In humans, excitability of PNs can be estimated from motor-evoked potentials (MEPs) by pairing a descending volley using transcranial magnetic stimulation (TMS) to summate with an ascending volley from peripheral nerve stimulation at the C3-C4 level of the spinal cord.

Primary motor and premotor cortex in implicit sequence learning--evidence for competition between implicit and explicit human motor memory systems.

Implicit and explicit memory systems for motor skills compete with each other during and after motor practice. Primary motor cortex (M1) is known to be engaged during implicit motor learning, while dorsal premotor cortex (PMd) is critical for explicit learning. To elucidate the neural substrates underlying the interaction between implicit and explicit memory systems, adults underwent a randomized crossover experiment of anodal transcranial direct current stimulation (AtDCS) applied over M1, PMd or sham stimulation during implicit motor sequence (serial reaction time task, SRTT) practice.

Rewiring the brain: potential role of the premotor cortex in motor control, learning, and recovery of function following brain injury.

The brain is a plastic organ with a capability to reorganize in response to behavior and/or injury. Following injury to the motor cortex or emergent corticospinal pathways, recovery of function depends on the capacity of surviving anatomical resources to recover and repair in response to task-specific training. One such area implicated in poststroke reorganization to promote recovery of upper extremity recovery is the premotor cortex (PMC).

Descending control to the nonparetic limb degrades the cyclic activity of paretic leg muscles.

During anti-phased locomotor tasks such as cycling or walking, hemiparetic phasing of muscle activity is characterized by inappropriate early onset of activity for some paretic muscles and prolonged activity in others. Pedaling with the paretic limb alone reduces inappropriate prolonged activity, suggesting a combined influence of contralesional voluntary commands and movement-related sensory feedback. Five different non-target leg movement state conditions were performed by 15 subjects post-stroke and 15 nonimpaired controls while they pedaled with the target leg and EMG was recorded bilaterally.

Corticospinal tract integrity correlates with knee extensor weakness in chronic stroke survivors.

Objective: Muscle weakness develops rapidly after stroke, adversely affecting motor performance, and contributing to reduced functional ability. While the contributions of structural and functional alterations in skeletal muscle to post-stroke weakness have been well described, the relationship between motor pathway integrity, measured using both radiological and electrophysiological techniques, and post-stroke muscle weakness is not clear. This study sought to determine the role of corticospinal tract (CST) integrity on knee extensor weakness in chronic stroke survivors.

Cortical stimulation as an adjuvant to upper limb rehabilitation after stroke.

Recovery of upper limb function after stroke remains a clinical challenge in rehabilitation. New insights into the role of activity-dependent motor recovery have guided clinicians to develop novel task-oriented therapies that are effective in reducing functional limitations in hand use after stroke. A number of brain-stimulation techniques have been examined as therapeutic adjuvants applied to enhance functional outcomes.

Non-invasive brain stimulation enhances fine motor control of the hemiparetic ankle: implications for rehabilitation.

We set out to answer two questions with this study: 1. Can stroke patients improve voluntary control of their paretic ankle by practising a visuo-motor ankle-tracking task? 2. Are practice effects enhanced with non-invasive brain stimulation? A carefully selected sample of chronic stroke patients able to perform the experimental task attended three data collection sessions.

The effects of paired associative stimulation on knee extensor motor excitability of individuals post-stroke: a pilot study.

Objective: Paired associative stimulation (PAS) modulates bilateral distal lower limb motor pathways during walking. We assessed the effects of inhibitory PAS applied to the vastus medialis (VM) motor pathways of chronic stroke patients.

Methods: PAS consisted of 120 electrical stimuli applied to the femoral nerve paired with transcranial magnetic stimulation (TMS) of the lower limb primary motor cortex so that the estimated arrival of the afferent volley occurred 8 ms after delivery of the magnetic stimulus.