D. Barloscio

Spinal Direct Current Stimulation Modulates Short Intracortical Inhibition

Transcutaneous spinal direct current stimulation (tsDCS) is a new and safe technique for modulating spinal cord excitability. We assessed changes in intracortical excitability following tsDCS by evaluating changes in cortical silent period (cSP), paired‐pulse short intracortical inhibition (SICI), and intracortical facilitation (ICF).

Impaired interhemispheric processing in early Huntington’s Disease: A transcranial magnetic stimulation study

Background and Rationale Changes in interhemispheric connectivity in Huntington’s Disease (HD) have been only recently investigated and little is known about their temporal relation with clinical features or grey matter atrophy: callosal disruption could contribute both to cognitive dysfunction and impairment of associative functions (Rosas et al. , 2010) and likely occurs many years before clinical onset, along a posterior-to-anterior direction (Phillips et al. , 2013). Here, we evaluated changes in ipsilateral Silent Period (iSP: onset latency, iSPOL, and duration, iSPD) and Transcallosal Conduction Time (TCT) in HD patients and correlated electrophysiological findings with mutational load and motor score.

Unilateral Application of Cathodal tDCS Reduces Transcallosal Inhibition and Improves Visual Acuity in Amblyopic Patients

Objective: Amblyopia is a neurodevelopmental disorder characterized by visual acuity and contrast sensitivity loss, refractory to pharmacological and optical treatments in adulthood. In animals, the corpus callosum (CC) contributes to suppression of visual responses of the amblyopic eye. To investigate the role of interhemispheric pathways in amblyopic patients, we studied the response of the visual cortex to transcranial Direct Current Stimulation (tDCS) applied over the primary visual area (V1) contralateral to the “lazy eye.” Methods: Visual acuity (logMAR) was assessed before (T0), immediately after (T1) and 60’ following the application of cathodal tDCS (2.0 mA, 20’) in 12 amblyopic patients. At each time point, Visual Evoked Potentials (VEPs) triggered by grating stimuli of different contrasts (K90%, K20%) were recorded in both hemispheres and compared to those obtained in healthy volunteers. Results: Cathodal tDCS improved visual acuity respect to baseline (p < 0.0001), whereas sham polarization had no significant effect. At T1, tDCS induced an inhibitory effect on VEPs amplitudes at all contrasts in the targeted side and a facilitation of responses in the hemisphere ipsilateral to the amblyopic eye; compared with controls, the facilitation persisted at T2 for high contrasts (K90%; Holm–Sidak post hoc method, p < 0.001), while the stimulated hemisphere recovered more quickly from inhibition (Holm–Sidak post hoc method, p < 0.001). Conclusions: tDCS is a promising treatment for amblyopia in adults. The rapid recovery of excitability and the concurrent transcallosal disinhibition following perturbation of cortical activity may support a critical role of interhemispheric balance in the pathophysiology of amblyopia.

5. Cerebellar direct current stimulation modulates pain perception and its neural correlates in humans

Here, we investigated whether level of cortical excitability changes with the distance from the last migraine attack could explain previous inconsistent results. Twenty-six patients with untreated migraine without aura (MO) underwent MEP study between attacks and were compared to a group of 24 healthy volunteers (HV). The TMS figure-of-eight coil was positioned over the left motor area. We first identified the resting motor threshold (RMT) and then amplitude of MEP was evaluated by delivering and averaging 10 single pulses of TMS using a stimulus intensity of 120% RMT at a rate of 0.1 Hz. Mean RMTs (54.2 in MO vs. 55.8 in HV) and MEP amplitudes (3057 microV in MO vs. 3675 microV in HV) were not significantly different between MO and HV. In MO, the RMT negatively correlated with days elapsed since the last migraine attack (r = 0.426, p = 0.03), i.e. RMT was minimal at a long time interval after an attack while it was greater and within the range of normative values approaching to an attack. The dynamic RMT variations found here resemble those we have previously reported for visual and somatosensory evoked potentials, and may represent timedependent plastic changes in brain excitability in relation with the migraine cycle.