Electroceuticals "Introduction to Non-Invasive Brain Stimulation as a therapeutic Tool"

Electrical Tools for Treatment of Diseases (The future) 

Non-invasive brain stimulation (NIBS) include techniques like Transcranial Direct current stimulation (TDCS) and Transcranial Magnetic stimulation (TMS).  TMS techniques relate with change in the electrical activity of the neurons at the axonal level not at the cell bodies which has higher threshold.

TMS utilize the power of magnetic field which is generated by a coil. This magnetic field penetrate the scalp and cerebrospinal fluid and activate the intended area on which it is fixed. Thus, activate the neurons. The same effect of Faraday,s law of induction of current from a magnetic field (the concept of Higher secondary Schooling ) .  At the other side TDCS cause the activation of neurons by a small amount of current applied through the sponges connected to the specific area of the brain (i.e Dorsolateral Prefrontal Cortex in Depression).

Both techniques have been extensively studied in depression and has approval form therapeutic use in Depression. Methods and protocols needed to be refined for further therapeutic use in the neuropsychiatric disorders like schizophrenia, Autism and related moods disorders.

NIBS Available Techniques

TMS

TMS is one of the techniques as mentioned above induces current and cause cortical excitability through magnetic field.  In rTMS instead of single pulses, repetitive pulses are used, hence the name Repetitive Transcranial magnetic stimulation (r TMS).

As a convention the low frequency (LF) 1 Hz or less cause decrease in cortical excitability and High frequency (HF) 5Hz and above increase the cortical excitability. But it is just a simplistic view as some studies have shown decrease in the cortical excitability with 5HZ and above.

Various protocols are followed for rTMS, may include continues Transcranial brain stimulation (c TBS) decrease cortical excitability while intermittent TBS (i TBS) increase cortical excitability. Quadripulse stimulation (QPS) and thetaburst stimulation are also protocols applied in in the r TMS. Quadripulse (4 pulses) with short interstimulus interval (e.g 5ms) increase Motor Evoked Potential (MEPS) showing higher cortical excitability and vice versa for 50ms.

Transcranial Electrical Stimulation

Electrical Stimulation include techniques like transcranial direct current stimulation (t DCS), transcranial alternative current stimulation (t ACS) and transcranial random noise stimulation (t RNS).

Transcranial direct current stimulation uses a current of 0.5-2 mA to stimulate the brain and cause neuronal polarization. T DCS may be anodal or cathodal. Anodal stimulation causes cortical stimulation and cathodal stimulation cause suppression in the cortical activity.

NIBS Mechanism

The mechanism of NIBS is thought to be Long Term Potentiation and Long-Term depression (LTP/LDP) like effect. In which are considered to the mechanism involved in potentiating the synaptic interactions between neurons and the various brain circuits while weakening others (LTD).   In addition, other mechanism which can is considered to be responsible include Post tetanic Potentiation (which is a short term increase in the neurotransmitters release after a brief short term high frequency actional potentials).

Pharmacological manipulations have show the effect LTP/LDP like effect where the application of some antagonist of glutamate receptors like dextromethorphan and memantine prevented the TMS after-effects.  Like TMS TDCS is also considered to be generating LTP/LDP life effect.

Current NIBS Therapeutic Application

NIBS therapeutic applications have been tried for various diseases ranging from moods disorders like MDD, Anxiety disorder, OCD and other disorder including schizophrenia, drug addiction, eating disorder/food craving and tinnitus etc.

It has been show that the application bring definite efficacy in condition like in Pain (HF r TMS of M1 contralateral to the pain side) and Depression (HF  r TMS of Left DLPFC).  Condition with probable efficacy include Low Frequency (LF) r TMS of the right DLPFC for depression and HF r TMS of DLPFC for negative symptoms of Schizophrenia.

There is possible efficacy in conditions like tinnitus and auditory hallucinations, PD, LF r TMS for epilepsy (remember LF r TMS decrease cortical excitability), hemispatial neglect, PTSD and CRPS etc