Exploring Non Invasive Brain Stimulation Techniques

Introduction

Wide exploration on the issue of non-Invasive brain stimulation (NIBS) has proved that it is a possible technical adjuvant of neurorehabilitative treatments that are customarily used (Liew et al, 2014). This process temporarily inhibits or excites activity in target brain regions; it employs magnetically or electrically- induced currents aiming to stimulate the brain via the scalp. This process is used in both basic science and neuroscience; there are two most commonly used techniques within this process: the transcranial magnetic stimulation and the transcranial direct current stimulation.

Types of Non- Invasive Brain Stimulation

Various clinical settings and research have shown and tested the effect NIBS has on human performance and neurorehabilitation (Dayan and Cohen, 2011; Ziemann, 2011). Particular attention has even been given over the recent years on the use of NIBS in the modulation of memory and learning processes (Tanaka, 2011). As earlier stated, there are two most common techniques derived from various empirical studies; the transcranial magnetic stimulation (TMS) and the transcranial direct current stimulation (tDCS). In regards to choosing the best technique for the process, there are always safeties considerations, for instance, potential side effects arise in the use of TMS. There are common side effects such as patient discomfort, transient pain and headaches, as well as rare induction of seizures (Rossi et al, 2009). On the other hand, tDCS is relatively easier to use and safer compared to TMS.

Effects of None- Invasive Brain Stimulation

Various studies have demonstrated that brain stimulation does not only cause changes to the targeted stimulated electrodes or coils, but also to various other regions of the brain (Ziemann, 2011). The process causes distant effects throughout regions of the brain in interconnected brain parts. Concerted actions of different brain regions are required in successful behaviors. The activities of these networks have been depicted in important information provided by neuroimaging studies (Liew et al, 2014). As a result, certain regions are considered to be highly synchronized in communication with one another.

Clinically, such connectivity can be analyzed as simple correlations between phase-locked coherence in neural oscillations and regions’ activations. More complex approaches can also be used to model them; such to include the a priori hypotheses. From this information, it can be concluded that in healthy individuals, functional connectivity patterns are predictive of motor recovery and motor behaviors, thereby providing the brain stimulation process a foundational basis; it seems valuable to modulate both local and interconnected network activity via the process.

In Censor et al’s study (2013), it was shown that the application of brain stimulation, particularly TMS over M1 modifies the connectivity between SMA, anterior cerebellum and M1, furthermore, it depicts a correlation between the modulation of such connectivity and the possible modification of a previously consolidated motor memory of healthy humans. In another study by Bestmann et al (2005), it was found that the application of TMS over other regions leads to modulation of functional activity. For instance, local BOLD signal is increased by the suprathreshold rTMS over the left dorsal premotor cortex and under the stimulating coil. In a nutshell, the positive stimulation of the ipsilesional M1 increses functional connectivity between the M1 and SMA, on the other hand, the inhibitory stimulation of the contralesional M1 increases ipsilesional connectivity, which in turn improves motor performance (Rehme et al, 2011). Substantial connectivity changes can also be witnessed in cases of stimulation of other regions other than the M1.

The effects of stimulation of the TMS can also be replicated in the tDCS. The effects of tDCS application of functional connectivity before, during and after application have been clinically reviewed with fMRI, arterial spin labeling (ASL), magnetoencephalography and EEG (Miniussi et al, 2012). According to Polania et al (2011), the application of tDCS over M1 causes cortical connectivity changes in measurements with EEG; the extent of these changes were felt more during measurement of connectivity during voluntary hand movements rather than during rest. From basic science study predictions, most of these studies show that substantial brain activity changes that result from the application of tDCS are augmented by its association with an active behavioral task performance (Fritsch et al, 2010).

Parasuraman and McKinley (2014) aimed to evaluate the impact of noninvasive brain stimulation in the acceleration and enhancement of learning and human performance on complex tasks; they particularly looked at tDCS. Noninvasive brain stimulation has proved to be a promising new method in the study of humans at work that result in modulations of the functioning of the human brain; neuroergonomic investigations have offered and provided empirical findings on the constraints and refinements of theories of human performance. An acceleration of learning and augmentation of brain plasticity has been described in the study (Parasuraman and McKinley, 2014). Ranging from rule- based learning to threat detection, the impact of tDCS in skill acquisition has been demonstrated.

Learning involves two different systems; procedural memory systems and interplay of declaratives. Brain stimulation affects both these systems. Depending on the desired strategy, however, the parameters of stimulation may differ. As shown in other studies, the result may either be from excitation of a functionally relevant region of the brain, or the inhibition of certain targeted competing circuits or coils; either way the process is effective in acceleration of learning (Parasuraman and McKinley, 2014). These beneficial effects of brain stimulation have been shown to persist for at least 24 hours. According to Angius et al (2017), the effects of brain stimulation may extend even to the physical limits of performance in healthy individuals. In their study, they depicted the fact that bilateral extra cephalic transcranial direct current stimulation can improve performance in healthy individuals in terms of endurance.

Conclusion

From various reviews, it can be clear that brain stimulation can accelerate the acquisition of skills in different types of complex learning tasks (Parasuraman and McKinley, 2014). This review on empirical evidence has shown the types of brain stimulation methods, the processes involved and the effects on various functional activities. Noninvasive brain stimulating processes have been used severally in the modulation of cortical excitability. In stroke instances, plastic changes have been induced by differential modulation of cortical excitability in both targeted and unaffected areas of the brain. The neuroimaging and neurophysiological changes caused by the application of such processes have been widely reviewed (Sandrini and Cohen, 2013)

Introduction

In regards to clinical rehabilitation, brain stimulation has been generally shown in various empirical studies to enhance motor recovery and affect regional neural activity (Liew et al, 2014). Extensive practice is required in complex work- related tasks; even though there are many training techniques in place, neuroergonomic investigations on the modulation of human brain functional and neurorehabilitation have provided empirical findings that refine the theories and constrains of human performance; this includes noninvasive brain stimulation (Parasuraman and McKinley, 2014).

Objectives

The main aim of this study will be to investigate the current gaps in literature relating to the effectiveness of brain stimulation in human functioning or neurorehabilitation.

Study rationale

In light of brain stimulation as a training method, there are still a lot of significant issues that need to be answered in relation to the impact different brain stimulation methods have on human performance and/or neurorehabilitation. For instance, according to Parasuraman and McKinley (2014), optimal stimulation schedules to maximize the effects on training still have to be determined. Furthermore, various studies have highlighted limitations in regards to the availability of little evidence on the definite period in which new knowledge from stimulation is retained. The effects of noninvasive brain stimulation need to be carefully evaluated as the method is not a panacea; these effects may be extensive and wide (Brem et al, 2014).

Methodology

This novel investigation will adopt a systematic literature review which will critically analyze and evaluate evidence collected from various research on the effectiveness of brain stimulation on human performance and/ or neurorehabilitation. Through intensive review and analysis on existing research, the aims of the study will be achievable and easily met.

Study implications

The impact of identifying gaps in existing literature will provide a positive outcome in clinical practice. The existence of little research on various points of concerns only necessitates positive action to be taken towards the improvement of brain stimulation methods and the impacts created by these methods on different clinical areas. Through positive action, the potential costs of brain stimulation methods and the consequent benefits will be netter understood and its effects in association with other traditional training methods can also be looked at; in cases of human performance (Parasuraman and McKinley, 2014).

Conclusion

Although various literature have shown that brain stimulation, both tDCS and TMS, can cause various effects on brain functionality and can even be used in the acceleration of skill acquisition in different complex learning tasks (Parasuraman and McKinley, 2014), there are still various important issues that need to be thoroughly addressed in future research.

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References

Angius , L., Mauger, A., Hopker, A., Pascual- Leone, E., Santarnecchi, E., Marcora,S. (2017) Bilateral extra cephalic transcranial direct current stimulation improves endurance performance in healthy individuals. Brain Stimulation

Bestmann, S., Baudewig, J., Siebner, H., Rothwell, J., Frahm. (2005). BOLD MRI responses to repetitive TMS over human dorsal premotor cortex. Neuroimage, 28, pp. 22-29

Brem, A., Fired, P., Horvah, J., Robertson, E., Pascuale- Leone, A. (2014) Is neuroenhancement by noninvasive brain stimulation a net zero- sum proposition? NeuroImage, 85, pp. 1058-1068

Censor, N., Dayan, E., Cohen, L. (2013) Cortico- subcortical neuronal circuitry associated with reconsolidation of human procedural memories. Cortex

Dayan, E., Cohen, L. (2011) Neuroplasticity sub serving motor skill learning. Neuron, 72, pp. 443- 454

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Parasuraman, R and McKinley, A. (2014) Using Noninvasive Brain Stimulation to Accelerate Learning and Enhance Human Performance. Human Factors and Ergonomics Society

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