Non-invasive Brain Stimulation Technology Research Articles

Multiple sessions of transcranial direct current stimulation to the intact hemisphere improves visual function after unilateral ablation of visual cortex

Damage to cerebral systems is frequently followed by the emergence of compensatory mechanisms, which serve to reduce the effects of brain damage and allow recovery of function. Intrinsic recovery, however, is rarely complete. Non-invasive brain stimulation technologies have the potential to actively shape neural circuits and enhance recovery from brain damage. In this study, a stable deficit for detecting and orienting to visual stimuli presented in the contralesional visual hemifield was generated by producing unilateral brain damage of the right posterior parietal and contiguous visual cortical areas. A long regimen of inhibitory non-invasive transcranial direct-current stimulation (cathodal tDCS, 2mA, 20min) was applied to the contralateral (intact) posterior parietal cortex over 14weeks (total of 70 sessions, one per day, 5days per week) and behavioral outcomes were periodically assessed. In three out of four stimulated cats, lasting recovery of visuospatial function was observed. Recovery started after 2-3weeks of stimulation, and recovered targets were located first in the periphery, and moved to more central visual field locations with the accrual of stimulation sessions. Recovery for moving tasks followed a biphasic pattern before reaching plateau levels. Recovery did not occur for more difficult visual tasks. These findings highlight the ability of multiple sessions of transcranial direct-current stimulation to produce recovery of visuospatial function after unilateral brain damage.

OP 8. Modulating tactile perception and learning processes by tCS in animal models: Hyperinteraction viability experiments (HIVE)

The mission of the European HIVE (Hyperinteraction viability experiments) project is to develop new stimulation paradigms and to create a new generation of non-invasive brain stimulation technologies. The transcranial current stimulation (tCS) is a non-invasive brain stimulation technique that has been successfully applied in both basic and clinical researches. Whereas transcranial direct-current stimulation (tDCS) is capable of inducing changes in neuronal membrane potentials in a polarity-dependent way, transcranial alternating-current stimulation (tACS) has been proposed to interact with ongoing cortical oscillations enhancing or diminishing specific frequencies of cortical neural activities. Nevertheless, little is known about tCS effects on cortical circuits and its implications in sensory perception processes. The aim of the HIVE project is to investigate the biophysics of non-invasive brain stimulation at the theoretical, computational and experimental level – both in humans and animals. Specifically, the objective of this study was to investigate tDCS effects on the plastic properties of the somatosensory cortex, to provide a new animal model to study the effects of tCS in learning, and to test for the viability of hyperinteraction experiments, implying the direct generation of perceptions and, hence, transmission of information, by transcranial stimulation of the cerebral cortex. Rabbits were prepared for the chronic recording of local field potentials (LFP) in the somatosensory cortex (SS) in response to whisker and/or ventroposterior medial (VPM) thalamic nucleus stimulations in the presence of tDCS and tACS. A second group of animals was prepared for classical eyeblink conditioning and simultaneous tCS. tDCS and tACS applied over the SS modulated cerebral cortical processes subsequent to the localized stimulation of the whisker pad or of the corresponding area of the VPM nucleus. Longer stimulation periods indicate that post-stimulation effects were only observed in the SS after cathodal tDCS. Consistently with this polarity-specific effects, the acquisition of a classical eyeblink conditioning was potentiated or depressed by the application of anodal or cathodal tDCS respectively, when stimulation of whisker pad was used as a conditioned stimulus (CS). In addition, we noticed that tACS (100 ms, 30 Hz) can successfully substitute for whisker CS during an associative learning task. tACS-CS induced conditioned responses similar to those observed when a direct stimulation of the whisker pad was carried out. We also studied the putative mechanisms underlying immediate and after-effect of tDCS observed in the SS. Pairs of pulses applied to the thalamic VPM nucleus suggested that tDCS modifies thalamocortical synapses at presynaptic sites. In addition, blocking activation of adenosine A1 receptors prevented the long-term depression evoked in the SS following cathodal tDCS. Results reported here confirm earlier studies in humans regarding the effects of tDCS and tACS on the cerebral cortex, highlighting the potential of this technique for modulating associative learning. In addition, it is shown the participation of adenosine A1 receptors in tDCS actions on cortical circuits. We also show that peripheral whisker stimulation can be substituted by tACS as CS when the proper stimulation frequencies are applied. Supported by grants BFU2011-29089, P07-CVI-02487 to J.M.D.-G., and BFU2011-29286, P07-CVI-02686 to A.G., from Spain. In addition, this work was funded by the EU FP7 FET-Open HIVE (222079) Project.

OC-092 Contralesional application of the novel brain stimulation intervention transcranial direct current stimulation (TDCS) restores brain and swallowing function in the human pharyngeal motor cortex

IntroductionRecovery of swallowing function in unilateral dysphagic stroke patients is associated with increased pharyngeal motor cortex excitability of the unlesioned hemisphere. “Virtual-lesioning” the human pharyngeal motor cortex transiently disrupts swallowing...

Development and evaluation of a portable sham transcranial magnetic stimulation system

Transcranial magnetic stimulation (TMS) is a relatively noninvasive brain stimulation technology that can focally stimulate the human cortex. One significant limitation of much of the TMS research to date concerns the nature of the placebo or sham conditions used. When TMS pulses are delivered repetitively (especially prefrontal TMS), it is often experienced as painful. Most sham TMS techniques produce identical sounds to active TMS, but they do not cause much, if any, scalp or facial sensation or discomfort. This is a serious problem when investigators are attempting to evaluate the effects of TMS by using traditional sham techniques because of unintended systematic differences between real and sham TMS groups (ie, confounds). As long as traditional approaches to sham TMS are used, the validity of the inferences regarding the efficacy of TMS will be limited. Although some other sophisticated systems have been developed to address these concerns, they tend to be expensive and lack portability. Portability will likely become more and more important as TMS applications expand into different clinical areas (eg, TMS in the postanesthesia care unit after surgery). This study describes a portable electrical TMS sham system (eSham system) modeled after the James Long System that was designed to produce similar scalp sensations as real TMS. Preliminary results are presented on 9 healthy adults who received both real and eSham 10 Hz repetitive TMS (rTMS) (at 80%, 100%, and 120% of resting motor threshold) over the prefrontal cortex and rated the sensation quality (pain, tingling, sharpness, piercing, electric, tugging, pinching), tolerability, and location. Real TMS and eSham TMS were rated similarly across all seven sensory dimensions examined. Real and eSham TMS were also rated similarly with respect to tolerability and perceived location of the TMS-induced sensations. The eSham system may be a simple, affordable, and portable approach to providing convincing sham TMS for future clinical trials. This study provides preliminary evidence supporting the use of the eSham system. Future larger-scale studies are warranted.