[REVIEW] TRANSCRANIAL DIRECT CURRENT STIMULATION (tDCS) AND TRANSCRANIAL CURRENT ALTERNATING STIMULATION (tACS) REVIEW – Full Text PDF

Abstract

This literature review is aimed to explore the main technical characteristics of both transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS) using the latest research on both healthy and impaired subjects. These techniques have no official standards developed yet. Our intent is to underline the main properties and problems linked with the application of those techniques which show diverse, and sometimes even opposite, results depending mainly on electrode positioning and underlying brain activity.
1 INTRODUCTION
Among different impairments that can affect standard brain functions, we choose to focus primarily on stroke, because it is one of the most prevalent and severe disability worldwide [1]. It is known that after a cerebrovascular accident, reorganization of neural tissues takes place [18]. If the ischemic event occurs on the motor area and it is severe enough to block the spontaneous neural reorganization, it could lead to paresis or even paralysis of one or more body parts [24].
In order to ameliorate stroke rehabilitation, different approaches have been carried out. Over the last decade, within the field of functional rehabilitation, transcranial current stimulation (tCS) has garnered considerable attention. It is assumed to improve, above other, motor functions in both healthy and stroke individuals [25], [4], [23].
There are three different types of tCS: transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS) and random noise stimulation (tRNS). All of them are non-invasive and involve low intensity current induction into the brain. Some studies have investi
gated the physiological basis of tDCS and tACS in order to get the picture of standard pattern that can be used for future research [36], [32].
This paper is oriented towards a broad audience who wants to understand the basic mechanisms of tDCS and tACS techniques. The main parameters of each type of stimulation and the implications related to its application on healthy subjects, stroke patients and individuals with unusual brain oscillations are discussed.

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[ARTICLE] Spaced Noninvasive Brain Stimulation

Abstract

Neuroplasticity is critical for learning, memory, and recovery of lost function following neurological damage. Noninvasive brain stimulation (NIBS) techniques can induce neuroplastic changes in the human cortex that are behaviorally relevant, raising the exciting possibility that these techniques might be therapeutically beneficial for neurorehabilitation following brain injury. However, the short duration and instability of induced effects currently limits their usefulness.

To date, trials investigating the therapeutic value of neuroplasticity-inducing NIBS have used either single or multiple treatment sessions, typically repeated once-daily for 1 to 2 weeks.

Although multiple stimulation sessions are presumed to have cumulative effects on neuroplasticity induction, there is little direct scientific evidence to support this “once-daily” approach. In animal models, the repeated application of stimulation protocols spaced using relatively short intervals (typically of the order of minutes) induces long-lasting and stable changes in synaptic efficacy. Likewise, learning through spaced repetition facilitates the establishment of long-term memory. In both cases, the spacing interval is critical in determining the outcome.

Emerging evidence in healthy human populations suggests that the within-session spacing of NIBS protocols may be an effective approach for significantly prolonging the duration of induced neuroplastic changes. Similar to findings in the animal and learning literature, the interval at which spaced NIBS is applied seems to be a critical factor influencing the neuroplastic response.

In this Point of View article, we propose that to truly exploit the therapeutic opportunities provided by NIBS, future clinical trials should consider the optimal spacing interval for repeated applications.

Source: Spaced Noninvasive Brain Stimulation

[ARTICLE] Spaced Noninvasive Brain Stimulation

Abstract

Neuroplasticity is critical for learning, memory, and recovery of lost function following neurological damage. Noninvasive brain stimulation (NIBS) techniques can induce neuroplastic changes in the human cortex that are behaviorally relevant, raising the exciting possibility that these techniques might be therapeutically beneficial for neurorehabilitation following brain injury. However, the short duration and instability of induced effects currently limits their usefulness.

To date, trials investigating the therapeutic value of neuroplasticity-inducing NIBS have used either single or multiple treatment sessions, typically repeated once-daily for 1 to 2 weeks. Although multiple stimulation sessions are presumed to have cumulative effects on neuroplasticity induction, there is little direct scientific evidence to support this “once-daily” approach. In animal models, the repeated application of stimulation protocols spaced using relatively short intervals (typically of the order of minutes) induces long-lasting and stable changes in synaptic efficacy. Likewise, learning through spaced repetition facilitates the establishment of long-term memory. In both cases, the spacing interval is critical in determining the outcome.

Emerging evidence in healthy human populations suggests that the within-session spacing of NIBS protocols may be an effective approach for significantly prolonging the duration of induced neuroplastic changes. Similar to findings in the animal and learning literature, the interval at which spaced NIBS is applied seems to be a critical factor influencing the neuroplastic response. In this Point of View article, we propose that to truly exploit the therapeutic opportunities provided by NIBS, future clinical trials should consider the optimal spacing interval for repeated applications.

via Spaced Noninvasive Brain Stimulation.