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LTD-like plasticity of the human primary motor cortex can be reversed by γ-tACS
Cortical oscillatory activities play a role in regulating several brain functions in humans. However, whether motor resonant oscillations (i.e. β and γ) modulate long-term depression (LTD)-like plasticity of the primary motor cortex (M1) is still unclear.Effects of cerebellar transcranial direct current stimulation on cerebellar-brain inhibition in humans: A systematic evaluation
Cerebellar transcranial direct current stimulation (ctDCS) is increasingly used to modulate cerebellar excitability and plasticity in healthy subjects and various patient populations. ctDCS parameters are poorly standardized, and its physiology remains little understood. Our aim was to compare the physiological effects of three different non-target electrode positions (buccinator muscle, supraorbital region, deltoid muscle).Interhemispheric cortico-cortical paired associative stimulation of the prefrontal cortex jointly modulates frontal asymmetry and emotional reactivity
As advances in neuroimaging further our understanding of the brain's functional connectivity, neuropsychology has moved away from a regional approach of attributing behavior to a specific region towards a network approach, attributing behavior to interconnected regions. A prime example of this is the suggested relevance of frontal asymmetry of the lateral prefrontal cortex (LPFC) in emotional processing. Yet, while neuroimaging defines relevant networks, it can only establish correlations and not causality.Involvement of different neuronal components in the induction of cortical plasticity with associative stimulation
Paired 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.Brain stimulation patterns emulating endogenous thalamocortical input to parvalbumin-expressing interneurons reduce nociception in mice
The bursting pattern of thalamocortical (TC) pathway dampens nociception. Whether brain stimulation mimicking endogenous patterns can engage similar sensory gating processes in the cortex and reduce nociceptive behaviors remains uninvestigated.Long-lasting effects of transcranial static magnetic field stimulation on motor cortex excitability
Transcranial 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.No modulatory effects by transcranial static magnetic field stimulation of human motor and somatosensory cortex
Recently, 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 Inhibition
One 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 [1]. As predicted in Hebb's postulate of associative plasticity in 1949 [2], synapses are strengthened if presynaptic activity precedes and contributes to postsynaptic firing, referred to as long term potentiation (LTP) [3], and weakened if the order is reversed, termed long term depression (LTD) [4].Effect of Repetitive Transcranial Magnetic Stimulation on Physical Function and Motor Signs in Parkinson's Disease: A Systematic Review and Meta-Analysis
The progressive loss of dopaminergic neurons in Parkinson's disease (PD) results in functional disruption within the cortico-basal ganglia–thalamo-cortical motor circuit [1,2]. In particular, there is an excessive inhibition of thalamocortical projection to various cortical targets, including the primary motor cortex (M1), supplementary motor cortex (SMA) and dorsolateral prefrontal cortex (DLPFC) [2–4]. Abnormal neural activities in these cortical areas were evident in neuroimaging studies that showed hypo-activations of SMA and DLPFC [5].Targeting of White Matter Tracts with Transcranial Magnetic Stimulation
TMS activations of white matter depend not only on the distance from the coil, but also on the orientation of the axons relative to the TMS-induced electric field, and especially on axonal bends that create strong local field gradient maxima. Therefore, tractography contains potentially useful information for TMS targeting.A numerically optimized active shield for improved transcranial magnetic stimulation targeting
Transcranial magnetic stimulation (TMS) devices suffer of poor targeting and penetration depth. A new approach to designing TMS coils is introduced in order to improve the focus of the stimulation region through the use of actively shielded probes. Iterative optimization techniques were used to design different active shielding coils for TMS probes. The new approach aims to increase the amount of energy deposited in a thin cylindrical region below the probe relative to the energy deposited elsewhere in the region (“sharpness”), whereas, simultaneously increase the induced electric field deep in the target region relative to the surface (“penetration”).Optically tracked neuronavigation increases the stability of hand-held focal coil positioning: Evidence from “transcranial” magnetic stimulation-induced electrical field measurements
The stability of hand-held coil positioning with neuronavigated versus conventional transcranial magnetic stimulation (TMS) is still underinvestigated. Eleven operators naïve for neuronavigation were asked to position and maintain a figure-of-eight-shaped coil over a dipole probe placed within of a polystyrene reproduction of the human head and scalp, in correspondence of the right primary motor cortex. Ten monophasic magnetic pulses were delivered at 46% maximal stimulator output (MSO) in two different experimental conditions: (1) assisted by an optically tracked neuronavigational system; and (2) without neuronavigation.
