Scientists have shown that psychotic symptoms experienced by people with schizophrenia could be caused by a faulty ‘switch’ within the brain.

In a study published in the journal Neuron, they have demonstrated that the severity of symptoms such as delusions and hallucinations is caused by a disconnection between two important regions in the brain — the insula and the lateral frontal cortex.

The breakthrough, say the academics, could form the basis for better, more targeted treatments for schizophrenia with fewer side effects.

The four-year study, led by Professor Peter Liddle and Dr Lena Palaniyappan in the University’s Division of Psychiatry and based in the Institute of Mental Health, centred on the insula region, a segregated ‘island’ buried deep within the brain, which is responsible for seamless switching between the inner and outer world.

Dr Palaniyappan, a Wellcome Trust Research Fellow, said: “In our daily life, we constantly switch between our inner, private world and the outer, objective world. This switching action is enabled by the connections between the insula and frontal cortex. This switch process appears to be disrupted in patients with schizophrenia. This could explain why internal thoughts sometime appear as external objective reality, experienced as voices or hallucinations.”

Several brain regions are engaged when we are lost in thought or, for example, remembering a past event. However, when interrupted by a loud noise or a person speaking we are able to switch to using our brain’s frontal cortex. With a disruption in the connections from the insula, such switching may not be possible.

The Nottingham scientists used functional MRI (fMRI) imaging to compare the brains of 35 healthy volunteers with those of 38 schizophrenic patients. The results showed that whereas the majority of healthy patients were able to make this switch between regions, the patients with schizophrenia were less likely to shift to using their frontal cortex.

The results suggest that detecting the lack of a positive influence from the insula to the frontal cortex using fMRI could help identify patients with schizophrenia.

Researchers in Nottingham are also looking at a technique called TMS – transcranial magnetic stimulation — which uses a powerful magnetic pulse to stimulate the brain regions that are malfunctioning.

Despite the fact that the insular region is buried so deeply within the brain that TMS would usually be ineffective, the results of the Nottingham study suggest that the loop between the insular and the frontal cortex could be exploited for TMS — if a pulse is delivered to the frontal lobe it could stimulate the insula and reset the ‘switch’.

Other future treatment options could include the use of a compassion-based meditation therapy called mindfulness, which may have the potential to ‘reset’ the switching function of the insula and can promote physical changes within the brain.