” Charles Dickens heard the voices of his characters and wrote the dialogues of his novels as if they were under dictation ‘,” points out Helen Lowenbrook, CNRS director of research at the Laboratory of Psychology and Neurocognition (LPNC) in Grenoble. Was he totally insane? Certainly not. Hyperaura is the ability of some people to imagine visual or sound scenes so intensely that simulated sensations can sometimes appear real. ‘, explains the neuroscientist. When hyper-aura is accompanied by a loss of feeling of being the author of the imagined scene, we are in the presence of hallucinations. People who report seeing a vision or hearing a sound attribute it to an external source. In our Western cultures, hallucinations are often associated with mental illness, most notably schizophrenia. But the neural mechanisms at the origin of such symptoms are beginning to be better understood and show that they are not necessarily a reflection of psychosis.

Hyper-aura: characteristic symptoms in a cultural context

Moreover, the presence of hallucinations in people without psychiatric disorders has been confirmed by a A study conducted on different cultures around the world It was published in the journal PNAS in February 2021. According to this work, two main factors could explain the presence of symptoms in so-called healthy people. The first factor relates to the proximity of a culture or religion in areas of the world where the idea of ​​the soul “permeable to the superworld” is most accessible. This is the case, for example, in Buddhist or shamanistic beliefs, found, for example, in Asia. This is called “porosity”.

The second factor relates to what scholars call “assimilation,” i.e. the individual’s personal ability to enter into introspection and focus in a sensitive way on his or her “inner world,” whether or not he is subservient. “Porous” culture or religion. If they are not dependent on each other, absorption and porosity can combine, leading to more hallucinatory symptoms.

According to Helen Lowenbrook, The ability to hear supernatural sounds is not widely accepted scientifically in Western cultures ’, where the boundaries between mind and environment are often impenetrable. It is the heightened sensitivity or empathy of some individuals that sharpens their awareness of the feelings or feelings of others allowing, in certain cases, to create the sensation of hearing the voices of spirits or supernatural beings. This college, the shamans say, that they spotted in the French writer Corinne Sombrun, known for her accounts of her travels with the shamans since the beginning of the 2000s, who learned to enter into a state of trance as she wished during her stay in Central Asia, especially in Mongolia. If his ability to “communicate with spirits” is still far from being proven, then neuroimaging data on his brain activity during periods of coma, on the other hand, made it possible to shed light on a very specific state of his nervous activity. , similar to that of people suffering from hallucinations. Depicting audio or visual scenes attributed to external sources, for example the appearance or hearing of the dead, deities, etc. So it will have a nervous origin, and it can be explained by the internal mechanisms of a person.

False predictive control

” Our studies in patients with schizophrenia with disturbed auditory hallucinations indicate that the voices perceived are subjective voices by the patients, but the latter does not have the impression of being author, Helen Lowenbrook explains. By comparing the activity of patients’ lip muscles in the hallucinating phase and in the resting phase, and then repeating the experiment on so-called “healthy” participants, the researcher’s team found that subtle traces of the activity appeared on the lips when the words were played. On the one hand it is perceived externally by participants in hyper-fantasy, and on the other hand it is consciously imagined by healthy participants. This seems to corroborate the hypothesis that self-formed sentences are not perceived as such by people prone to auditory hallucinations, which was probably the case of Joan of Arc, attributing voices calling for rebellion against the English language to the Two Saints and the Archangel.

© Lucille Rabin

These auditory hallucinations may be the result of a failure of the self-monitoring mechanism that allows prediction, control, and possibly correction of motor commands the brain sends to the muscles before a task is performed. ” Before holding a hot object for example, we will automatically adjust our gesture thanks to the prediction of the sensation of the object on our skin. Helen Lowenbrook explains. When the actual sensation corresponds to the expected one, we know that we are the authors of the running gesture. Then the active sensation is automatically relieved, explaining why tickling the breath is difficult. Another hypothesis appears to have been confirmed by neuroimaging experiments showing activity in the auditory cortex in subjects with auditory hallucinations, while in control participants, the activity of this same area is impaired during voluntary mental production of words. ” Theoretically, when a sentence is spoken in one’s head, the activity of the auditory cortex is reduced, and the perceived “voice” of the sound is lower, since the self-generated sentence does not need to be heard or processed. Produced by the brain. By reducing the intensity of self-generated sounds, we thus enhance the detection of sounds produced by others: we can hear others speak while we are immersed in our verbal thoughts. However, in the hallucinatory stage, the brain images do not show a decrease in the activity of the auditory areas, which explains the perception of the real sound, and not the attenuation. says the researcher.

© Helen Lowenbrook

Activation of the auditory cortex during the production of internal speech.

© Helen Lowenbrook

Activation of the auditory cortex during silent reading (with imagined intonation).

It is the boundary that remains unclear between fantasy and hallucinations

If many studies seem to support neuroscientists’ hypotheses, many gray areas remain around the phenomenon, which affects 4 to 10% of the general population. Helen Lowenbrook reassuring: “If sometimes voices are menacing, negative and intrusive, others on the contrary are positive and well-experienced. Zidane had himself witnessed a voice in 2005 urging him to wear his cleats, while Martin Luther King Jr. had rebelled against segregation. The racist after hearing an “inner voice”.

As long as the symptoms are not too intrusive, there is no need to panic, as you are at risk of falling into a mental illness. ” Many famous people have had auditory hallucinations. Helen Lowenbrook concludes. ” This is especially the case with Dali, Joan of Arc, Charles Dickens, etc. All of them had a great imagination. They were as if they were being guided by external signs. But we must realize that between fantasy and hallucinations, the boundary is sometimes very blurred. »