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So-called auditory imagination varies enormously from person to person and remains mysterious. We do not know how the brain regulates the internal experience of sound, but postdoc David Ricardo Quiroga-Martinez from the Department of Psychology at the University of Copenhagen intends to find out. 

With his new research group, he will investigate the phenomenon in both healthy individuals and patients with schizophrenia. The long-term goal is a treatment using magnetic brain stimulation for people plagued by, for example, hearing inner voices. 

The starting point is an earlier study in which David Ricardo Quiroga-Martinez discovered a link between a particular type of brain wave — alpha waves — and auditory imagination. Brain waves are electrical oscillations in the brain that reflect neuronal activity; alpha waves are associated with a wakeful but mentally relaxed state in which neurons are less active. 

"We found a connection suggesting that alpha waves act as a kind of gatekeeper for the imagination. When alpha wave activity is highly synchronised across the brain, auditory imagination is more subdued than when alpha wave synchrony is low," he explains. 

"If alpha waves do regulate auditory imagination, this may be a mechanism that is disturbed in people with auditory hallucinations," explains David Ricardo Quiroga-Martinez. 

In the study, he will develop a research platform. Using a electroencephalograph — a cap-like device fitted with electrodes — he will record alpha brain waves distributed across the entire brain in both healthy individuals and patients with schizophrenia. 

He will also measure the activity of individual neurons in patients already having their brain activity measured using implanted electrodes in preparation for epilepsy surgery. 

"This is a unique combination of methods that I have great expectations for, and that other researchers will also be able to use," he says. 

In both cases, participants first listen to a piece of music, and when the music stops, they are asked to imagine that it continues playing. 

David Ricardo Quiroga-Martinez will also investigate how often people perceive speech in noise, even when there is in reality only noise. 

A third technology is involved in the development of a treatment: transcranial magnetic stimulation (TMS), which is currently used, among other things, to treat depression. The patient sits in a chair and a large magnetic coil is positioned over the area of the brain to be treated. Brief magnetic pulses induce a weak electrical current that can influence the activity of neural circuits. 

The theory is that TMS can be used to generate more alpha wave activity and thereby reduce auditory hallucinations in patients who, for example, hear voices. 

In the long run, David Ricardo Quiroga-Martinez also hopes to combine his methods with computer modelling of what happens in the brain. But right now, he is looking forward to getting the project started. 

"I have long dreamed of setting up my own research group. And I look forward to working with the group and to recording brain signals together with the patients. It is always fascinating to observe the activity of the brain."