Somatosensory and transcranial direct current stimulation effects on manual dexterity and motor cortex function: A metaplasticity studyNon-invasive neuromodulation may provide treatment strategies for neurological deficits affecting movement, such as stroke. For example, weak electrical stimulation applied to the hand by wearing a “mesh glove” (MGS) can transiently increase primary motor cortex (M1) excitability. Conversely, transcranial direct current stimulation with the cathode over M1 (c-tDCS) can decrease corticomotor excitability. Objective/Hypothesis: We applied M1 c-tDCS as a priming adjuvant to MGS and hypothesised metaplastic effects would be apparent in improved motor performance and modulation of M1 inhibitory and facilitatory circuits.
Direction of TDCS current flow in human sensorimotor cortex influences behavioural learningRecent studies have shown that neurophysiological outcomes of transcranial direct current stimulation (TDCS) are influenced by current flow in brain regions between the electrodes, and in particular the orientation of current flow relative to the cortical surface.
Involvement of different neuronal components in the induction of cortical plasticity with associative stimulationPaired associative stimulation (PAS), with stimulus interval of 21.5 or 25 ms, using transcranial magnetic stimulation in the posterior-anterior (PA) current direction, produces a long-term-potentiation-like effect. Stimulation with PA directed current generates both early and late indirect (I)-waves while that in anterior-posterior (AP) current predominantly elicits late I-waves. Short interval intracortical inhibition (SICI) inhibits late I-waves but not early I-waves.
Short-interval intracortical inhibition: Comparison between conventional and threshold-tracking techniquesShort-interval intracortical inhibition (SICI) is conventionally measured as the relative amplitude reduction of motor evoked potentials (MEPs) by subthreshold conditioning stimuli. In threshold-tracking SICI (T-SICI), stimulus intensity is instead adjusted repeatedly to maintain a constant MEP and inhibition is measured as the relative threshold increase. T-SICI is emerging as a useful diagnostic test, but its relationship to conventional amplitude SICI (A-SICI) is unclear.
Long-lasting effects of transcranial static magnetic field stimulation on motor cortex excitabilityTranscranial static magnetic field stimulation (tSMS) was recently added to the family of inhibitory non-invasive brain stimulation techniques. However, the application of tSMS for 10–20 min over the motor cortex (M1) induces only short-lasting effects that revert within few minutes.
Modulation of motor cortex excitability predicts antidepressant response to prefrontal cortex repetitive transcranial magnetic stimulationRepetitive transcranial magnetic stimulation (rTMS) targeting the left dorsolateral prefrontal cortex (DLPFC) is a treatment option for patients with medication-resistant major depressive disorder (MDD). However, antidepressant response is variable and there are currently no response predictors with sufficient accuracy for clinical use.
No modulatory effects by transcranial static magnetic field stimulation of human motor and somatosensory cortexRecently, it was reported that the application of a static magnetic field by placing a strong permanent magnet over the scalp for 10 min led to an inhibition of motor cortex excitability for at least 6 min after removing the magnet. When placing the magnet over the somatosensory cortex, a similar inhibitory after effect could be observed as well.
Modulation of the Direction and Magnitude of Hebbian Plasticity in Human Motor Cortex by Stimulus Intensity and Concurrent InhibitionOne of the most fascinating and important properties of the mammalian brain is its remarkable capacity for plasticity. Synaptic plasticity is considered to be the primary neuronal substrate for learning and memory . As predicted in Hebb's postulate of associative plasticity in 1949 , synapses are strengthened if presynaptic activity precedes and contributes to postsynaptic firing, referred to as long term potentiation (LTP) , and weakened if the order is reversed, termed long term depression (LTD) .
A Comparison of Primed Low-frequency Repetitive Transcranial Magnetic Stimulation Treatments in Chronic StrokePreceding low-frequency repetitive transcranial magnetic stimulation (rTMS) with a bout of high-frequency rTMS called priming potentiates the after-effects of the former in healthy adults. The utility of primed rTMS in stroke remains under-explored despite its theoretical benefits in enhancing cortical excitability and motor function.
Reversal of Practice-related Effects on Corticospinal Excitability has no Immediate Effect on Behavioral OutcomeMotor training usually increases the excitability of corticospinal outputs to the trained muscles. However, it is uncertain to what extent the change in excitability is a critical component of behavioral learning or whether it is a non-specific side effect.
Characterizing the Mechanisms of Central and Peripheral Forms of Neurostimulation in Chronic Dysphagic Stroke PatientsSwallowing problems following stroke may result in increased risk of aspiration pneumonia, malnutrition, and dehydration.