Subthalamic nucleus conditioning reduces premotor-motor interaction in Parkinson's disease.

Background: Deep brain stimulation of the subthalamic nucleus is effective to alleviate motor symptoms in advanced Parkinson's disease. Using a novel conditioning paradigm, it has been shown that deep brain stimulation pulses from electrodes in the subthalamic nucleus modulate corticospinal excitability as determined with transcranial magnetic stimulation applied to the motor cortex. The mechanism of action is unclear.

Impaired motor cortical facilitatory-inhibitory circuit interaction in Parkinson's disease.

Objective: Motor cortical (M1) inhibition and facilitation can be studied with short-interval intracortical inhibition (SICI) and short-interval intracortical facilitation (SICF). These circuits are altered in Parkinson's disease (PD). The sensorimotor measure short latency afferent inhibition (SAI) is possibly altered in PD.

Motor blocks during bilateral stepping in Parkinson's disease and effects of dopaminergic medication.

Introduction: Freezing of gait (FOG) is a complex symptom in Parkinson's disease (PD) that manifests during walking as limited forward progression despite the intention to walk. It is unclear if lower limb motor blocks (LLMB) that occur independently from FOG are related to overground FOG and the effects of dopaminergic medications.

Methods: Nineteen patients with PD were tested on two separate days in the dopaminergic medication "on" and "off" states.

Interhemispheric interactions between the right angular gyrus and the left motor cortex: a transcranial magnetic stimulation study.

The interconnection of the angular gyrus of right posterior parietal cortex (PPC) and the left motor cortex (LM1) is essential for goal-directed hand movements. Previous work with transcranial magnetic stimulation (TMS) showed that right PPC stimulation increases LM1 excitability, but right PPC followed by left PPC-LM1 stimulation (LPPC-LM1) inhibits LM1 corticospinal output compared with LPPC-LM1 alone. It is not clear if right PPC-mediated inhibition of LPPC-LM1 is due to inhibition of left PPC or to combined effects of right and left PPC stimulation on LM1 excitability.

A Distinct EEG Marker of Celiac Disease-Related Cortical Myoclonus.

Background: Celiac disease is associated with motor cortex hyperexcitability and neurological manifestations including cortical myoclonus. Electroencephalography abnormalities have been described, but no distinct pattern has been reported.

Methods: We describe the neurophysiological characteristics of 3 patients with celiac-associated cortical myoclonus using electroencephalography, magnetoencephalography, and transcranial magnetic stimulation.

Single-pulse subthalamic deep brain stimulation reduces premotor-motor facilitation in Parkinson's disease.

Introduction: Deep brain stimulation improves motor symptoms in Parkinson's disease and changes primary motor cortex excitability, but how subthalamic nucleus stimulation affects premotor-motor cortical connectivity remains unclear.

Methods: We investigated 10 Parkinson patients in whom single subthalamic nucleus stimulation was time-locked to transcranial magnetic dual-coil, paired-pulse stimulation of the dorsal premotor and primary motor cortex. Premotor-motor interaction with deep brain stimulation switched off was compared to 10 controls.

Somatosensory-motor cortex interactions measured using dual-site transcranial magnetic stimulation.

Background: Dual-site transcranial magnetic stimulation (ds-TMS) is a neurophysiological technique to measure functional connectivity between cortical areas.

Objective/hypothesis: To date, no study has used ds-TMS to investigate short intra-hemispheric interactions between the somatosensory areas and primary motor cortex (M1).

Methods: We examined somatosensory-M1 interactions in the left hemisphere in six experiments using ds-TMS.

Subclinical recurrent neck pain and its treatment impacts motor training-induced plasticity of the cerebellum and motor cortex.

The cerebellum processes pain inputs and is important for motor learning. Yet, how the cerebellum interacts with the motor cortex in individuals with recurrent pain is not clear. Functional connectivity between the cerebellum and motor cortex can be measured by a twin coil transcranial magnetic stimulation technique in which stimulation is applied to the cerebellum prior to stimulation over the motor cortex, which inhibits motor evoked potentials (MEPs) produced by motor cortex stimulation alone, called cerebellar inhibition (CBI).

Influence of inter-train interval on the plastic effects of rTMS.

Background: High frequency repetitive transcranial magnetic stimulation (rTMS) elicits plastic effects in excitatory and inhibitory circuits. Inter-train intervals (ITI) were initially incorporated into rTMS paradigms to avoid overheating and for safety considerations. Recent studies have shown that inclusion of ITI, as opposed to continuous stimulation, is essential for eliciting excitatory effects, but the optimal ITI remains unknown.

The effects of upper limb posture and a sub-maximal gripping task on corticospinal excitability to muscles of the forearm.

Variations in handgrip force influences shoulder muscle activity, and this effect is dependent upon upper limb position. Previous work suggests that neural coupling between proximal and distal muscles with changes in joint position is a possible mechanism but these studies tend to use artificially constrained postures that do not reflect activities of daily living. The purpose of this study was to examine the effects of upper limb posture on corticospinal excitability to the forearm muscles during workplace relevant arm positions.

Influence of Subclinical Neck Pain on the Ability to Perform a Mental Rotation Task: A 4-Week Longitudinal Study With a Healthy Control Group Comparison.

Objective: Mental rotation of objects and the frame of reference of those objects are critical for executing correct and skillful movements and are important for object recognition, spatial navigation, and movement planning. The purpose of this longitudinal study was to compare the mental rotation ability of those with subclinical neck pain (SCNP) to healthy controls at baseline and after 4 weeks.

Methods: Twenty-six volunteers (13 SCNP and 12 healthy controls) were recruited from a university student population.

A novel protocol to investigate motor training-induced plasticity and sensorimotor integration in the cerebellum and motor cortex.

Our group set out to develop a sensitive technique, capable of detecting output changes from the posterior fossa following a motor acquisition task. Transcranial magnetic stimulation (TMS) was applied over the right cerebellar cortex 5 ms in advance of test stimuli over the left cerebral motor cortex (M1), suppressing test motor-evoked potentials (MEPs) recorded in a distal hand muscle. Ten participants typed the letters Z, D, F, and P in randomized 8-letter sequences for ∼15 min, and 10 participants took part in the control condition.

Alterations in cortical and cerebellar motor processing in subclinical neck pain patients following spinal manipulation.

Objective: The purpose of this study was investigate whether there are alterations in cerebellar output in a subclinical neck pain (SCNP) group and whether spinal manipulation before motor sequence learning might restore the baseline functional relationship between the cerebellum and motor cortex.

Methods: Ten volunteers were tested with SCNP using transcranial magnetic stimulation before and after a combined intervention of spinal manipulation and motor sequence learning. In a separate experiment, we tested 10 healthy controls using the same measures before and after motor sequence learning.