What is neurostimulation?

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Neurostimulation

Neurostimulation refers to a group of techniques used by neuroscientists to change brain activity, either by using electromagnetic pulses or a weak electrical current applied to the scalp. The idea is that voices might be due to over-activity in some areas (or networks of areas) in the brain, and that decreasing this over-activity might reduce the frequency of voices.

Neurostimulation is not the same as electro-shock therapyquestion icon. The types of neurostimulation that have been tested as a therapy for distressing voices are called ‘noninvasive’, because they are applied through the scalp, and do not require anything like surgery for the stimulation to reach the brain. They are not unpleasant to receive and involve very minimal side-effects (mild headaches that quickly go away, and perhaps some facial twitching during application).

The goal of neurostimulation for distressing voices is ultimately to reduce how often voices occur, and therefore how distressed the person is.

Different types of neurostimulation

There are two main types of noninvasive neurostimulation: transcranial magnetic stimulation (TMS)question icon and transcranial direct current stimulation (tDCMS)question icon.

TMS uses quickly changing magnetic fields to create an electrical current in a very small area of the brain. It involves a ‘coil’ being held against the scalp for the duration of stimulation and feels a bit like someone is gently tapping on the scalp while it is applied.

tDCS is different to TMS in that it involves two small electrodes being placed on the scalp during stimulation, with a very weak electrical current (about 1 milliamp) being run between these electrodes. People often describe the feeling as being ‘itchy’ or sometimes ‘prickly’ underneath the electrodes.

Previous trials have aimed stimulation at a region of the brain called the temporoparietal junctionquestion icon, in the left hemisphere. To reach this area, stimulation is applied just above and behind the ear. We know this brain area is strongly connected to lots of other brain areas that play important roles in language, and neuroimaging studies have shown that these areas tend to be active while people report hearing voices.

Is it available?

Neurostimulation as a therapy is not currently available in the UK outside clinical trials and is not currently licensed for the treatment of psychosis outside specific scientific studies. As we have seen, it is not clear quite how effective neurostimulation really is for reducing the frequency of voices, and much more work needs to be done to test this.

What does the research say?

Find out more

Read

Peter Moseley (2012). Is TMS a good treatment option for those seek help with voice hearing? Hearing the Voice project blog.

Peter Moseley (2016). Transcranial direct current stimulation – over-hyped or under-studied? Hearing the Voice project blog.

Peter Moseley et al (2016). Non-invasive brain stimulation and auditory verbal hallucinations: new techniques and future directions. Frontiers in Neuroscience.

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What does the research say?

The evidence for whether neurostimulation can actually reduce the frequency of voices is mixed. A study by Ralph Hoffman and colleagues in US in 2013 tested TMS with 83 voice-hearing participants (all with a diagnosis of schizophrenia), and reported that, compared to participants who didn’t receive the stimulation, participants reported their voices happening less often following the treatment. However, not all studies have found TMS to be effective. An analysis of 25 different studies, conducted by Christina Slotema, suggests that there may be a small benefit of TMS for voices.

There is less evidence about whether tDCS might be able to reduce the frequency of voices. The first study using this technique with voice-hearing participants was conducted by Jerome Brunelin and colleagues in France in 2012. They tested this technique with 30 voice-hearing participants and found a large reduction in the frequency of voices following treatment. However, other studies have not found tDCS to be effective, and an analysis of 5 studies by Fuyin Yang and colleagues in 2019 indicated no real reduction in voices following tDCS treatment.

One possibility is that neurostimulation techniques might work for some people but not others. One study by Sanne Koops and colleagues suggested that neurostimulation might work best for younger female participants – but we need much more evidence to know whether this is really the case.