Ten thousand steps and more. Having an imaginary companion to the point of sharing a chocolate bar to give him a piece, seeing a double of yourself, “a transformer in the clouds, a guy coming out of a cave”as described by Thomas Vennin, contributor to Mountains Magazinein the book The Hallucinated. A journey into altitude delirium (Paulsen, 2020). Many mountaineers, solo sailors and long-distance runners tell of hallucinations they have had while practicing their sport.
Renaud Jardri, professor of child and adolescent psychiatry in Lille, prefers to talk about“hallucinatory experience”. “It is something that we perceive in the absence of stimulation of the sense organs, that is to say things that we see when there is nothing, that we hears when there is no sound »explains the child psychiatrist, who opened a consultation dedicated to hallucinatory experiences in children and adolescents.
“While hallucinations can happen to everyone, they occur in different contexts, from neurological or psychiatric illnesses, to the consumption of toxic substances, but also in cases of physical and physiological stress”, he specifies. In athletes, this happens when the body is pushed to the extreme. For example, not sleeping for twenty-four or forty-eight hours during an ultra-trail race (over a distance of at least 80 kilometers), being in conditions of dehydration. Isolation can also encourage its emergence.
A warning flasher
At altitude, the phenomenon is relatively clear. “It causes a lack of oxygen [hypoxie] which induces hyperventilation. As a result, the CO rate2 in the blood decreases, which causes the cerebral blood vessels to contract”, explains Jean-Paul Richalet, professor of physiology at Sorbonne-Paris-Nord University. This less vascularization of certain areas of the brain can lead, he continues, “diverse and varied neurological symptoms, including hallucinations, which are not necessarily the most serious”. The hippocampus, located in the temporal lobe of the brain, involved in cognition, memory, learning and spatial location, and the temporoparietal junction, which is involved in particular in the self-non-self distinction, certainly play a role in the emergence of hallucinations. “These regions are also very sensitive to lack of oxygen, and can be involved in near-death experiencesexplains Renaud Jardri. They are also present during hallucinations occurring in people diagnosed with schizophrenia, or who have consumed LSD. »
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