Can a schizophrenic hear his own voice?

Question to the brain

Prof. Dr. med. Dr. phil. David Linden, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University: We are only slowly beginning to understand the mechanics of this relevant problem. Researchers estimate that up to one percent of the population suffers from schizophrenia - and of these people up to 70 percent from acoustic hallucinations. There are patients who hear commanding or other voices for their entire life, others only in an acute phase.

Where these arise in the brain, we know from a few evident cases in which the hearing of voices was directly induced by electrical stimulation. The Canadian brain surgeon Wilder Penfield examined around a thousand patients with brain diseases preoperatively and mapped the function of the clinically relevant area. Through the electrical stimulation of the various areas, he was able to evoke imaginations of familiar voices and melodies in less than a hundred cases. One of the results was that hallucinations are detectable in the temporal lobe. To what extent Penfield's findings apply to schizophrenia patients is still unclear in individual cases.

Indeed, in these patients there is activity in the auditory cortex, which is part of the temporal lobe, even without the auditory stimulation being altered. Colleagues and I helped find this out with the help of functional magnetic resonance imaging (fMRI) in Frankfurt at the end of the 1990s. Although hearing voices is a common phenomenon, the number of suitable study participants is small. Nevertheless, the studies suggest that dysregulated activity, a form of spontaneous activity, can be measured. But where does this activity come from?

There are various theories on this: The fact that synapses in the child's brain recede in the course of adolescence lead to an imbalance in the nerve cells, which we call “pruning”. Whether this explains hallucinative phenomena cannot be directly proven, since the synapse structure is complex and can hardly be analyzed using non-invasive methods.

On the other hand, a kind of local derailment of activity, similar to an epileptic seizure, would be conceivable. This is countered by the fact that the dysregulation sometimes lasts for a long time and no epileptic seizure patterns can be detected.

It is also conceivable that our inner language could be a cause. The assumption: those who speak to themselves in their thoughts simulate internal speech and hearing processes. In healthy people, there could be a counter-regulation that prevents this language from being audible. If this process is disturbed, i.e. the suppression of the auditory cortex no longer works, the inner language could become audible, usually as a particularly vivid perception. Sooner or later the patient might no longer be able to distinguish the source of the voices.

However, this is difficult to prove at the neural level. The researchers are currently concentrating on the areas of language in their investigations: the Broca area, the higher auditory areas, the Wernicke area, the primary auditory cortex .

Incidentally, some researchers estimate that several percent of the population regularly hear voices without any direct disease value. Hallucinations can also be triggered by medication or drugs. Many children seem to have hallucination-like experiences that can last into adulthood.

Recorded by Martina Gauder