Neurostimulation: any intervention intended to alter nervous system function by using energy fields such as electricity, magnetism, or both.
- Electroconvulsive therapy (ECT)
- Vagus nerve stimulation (VNS)
- Repetitive transcranial magnetic stimulation (rTMS)
- Deep brain stimulation (DBS)
a recent surge of interest
- targeting specific brain regions or circuits – a level of focality
- increased use of medical technology
- superior tolerability for use alone or in combination with pharmacotherapy or psychotherapy
- potential to improve cognition or nonspecific symptoms
SECTION 1: Electrical Engineering and Neurophysiology
- tDCS (direct current stimulation): a constant, or “direct”, waveform
- CES (cranial electrial stimulation): proprietary waveforms that may fluctuate over time
- tACS (alternating current stimulation): sine waves
- tRNS (random noise stimulation) : broadband noise
- eTNS (external trigeminal nerve stimulation)
- tVNS (transcutaneous vagus nerve stimulation)
Ohm’s law (V = I x R)
Spatial Targeting: Electrode Montages
- Spatial targeting using computer simulations of the electrical field distribution, as a function of electrode number, size, and location, has been proposed (8) but lacks validation as an approach to guide clinical tCS.
given the distrib- uted and complex deficits in neuronal networks associated with psychiatric disorders, identifying the correct target area(s) for therapeutic stimulation in a specific disorder or symptom remains an important challenge for the field.
Neurophysiological Effects of tCS
Communication between individual neurons and neuronal networks is nonlinear and complex, with a large number of inputs influencing the activity of any individual neuron. Therefore, even a small change in the membrane voltage may impact neuronal firing.
SECTION 2: REVIEW OF PUBLISHED RANDOMIZED CONTROLLED TRIALS
Randomized Controlled Trials of tCS for Schizophrenia
- anode: left DLPFC
- cathode: temporoparietal junction, supraorbital area
- Brunelin et al (40) (N=30) conducted the first randomized controlled trial and observed that active tDCS reduced auditory hallucinations acutely (p,0.001) and over 3 months (p,0.001) and reduced negative symptoms (p=0.01).
- This was followed by a study by Smith et al. (45) (N=33) that found active stimulation improved cognition (p=0.008) but had no effect on positive or negative symptoms (all p.0.1),
- whereas Palm et al. (44) found that tDCS reduced negative symptoms (p=0.016) and Mondino et al. (43) found that tDCS reduced hallucinations (p,0.001).
- Several studies using tDCS (Fitzgerald et al. , N=24, and Frohlich et al. , N=26) and tVNS (Hasan et al. , (N=20) found no difference between active and sham stimulation.
- The currently available data do not support use of tCS for schizophrenia. The evidence base comprises a small number of randomized controlled trials with conflicting results.
- More work is clearly needed to develop tCS for treatment of patients with schizophrenia.
SECTION 3: POTENTIAL RISKS OF tCS
Risk of Adverse Cognitive Effects
Risk of Interference With Psychiatric Treatment
SUMMARY: EFFICACY AND SAFETY OF tCS IN PSYCHIATRIC DISORDERS