[ad_1]
In schizophrenics, the hippocampus, the area of the brain responsible for memory and emotions, atrophies drastically when the first symptoms appear. This usually happens in adolescence, according to a Geneva study.
Schizophrenia affects an average of 0.5% of the general population. It may be linked to a failure of chromosome 22, called deletion syndrome 22q11, said Monday the University of Geneva (UNIGE) in a statement.
But only 30% of people affected by this syndrome end up developing psychotic symptoms peculiar to schizophrenia, such as auditory hallucinations, memory and perception disorders, or difficulties in social interactions, marked by a strong paranoia.
"It is now known that schizophrenia is linked to the hippocampus, a complex area of the brain that carries out a lot of processes simultaneously, dealing with memory, imagination and emotions," says Stephan Eliez, professor at Department of Psychiatry of UNIGE, quoted in the press release.
Recent studies have shown that people with deletion syndrome have a smaller than average hippocampus. "That's why we studied in detail the development of this structure, to understand why some people affected by the deletion syndrome eventually develop psychotic symptoms, while others do not," continues the researcher.
An 18-year study
For 18 years, the Geneva team has followed 275 patients aged 6 to 35 years: 135 people "control", ie without genetic problems, and 140 people with the deletion syndrome, 53 of whom had moderate to severe psychotic symptoms.
"Every three years, we give them an MRI to observe the development of their brain, which allowed us to create a statistical model that measures and compares the development of the hippocampus in the two groups of patients", explains Valentina Mancini, researcher at UNIGE.
Result: although smaller from the beginning, the hippocampus of the group affected by the deletion syndrome follows a growth curve identical to that of the control group. "This allows us to hypothesize that the smaller size of the hippocampus originates in utero, during its development in the womb," the researcher continues.
The Geneva team also observed in detail the sub-parts of the hippocampus and discovered that one of them, called CA3, was not affected by this decrease in size. "This sub-part plays a crucial role in the work of memorization and seems stronger than the other sub-parts", notes Stephan Eliez.
Everything is played in adolescence
The researchers then compared the developmental curves of the hippocampus in people with deletion syndrome but no psychotic symptom, with those who developed psychotic symptoms.
"Our results are clear: around the age of 17-18, people with schizophrenic symptoms undergo a drastic atrophy of the size of their hippocampus, and more particularly of the CA3 zone, which nevertheless managed to develop normally. , unlike the other sub-parts, "wonders Valentina Mancini.
Researchers do not yet have an explanation for this drastic fall in the development of this capital structure of the brain. But their badumptions turn to environmental factors, such as stress or neuronal inflammation.
"The hippocampus of people with the deletion syndrome is smaller, it must compensate for its size by hyperactivity. In case of a big stress stroke, especially during the critical period of adolescence, this hyperactivity causes a significant increase in glutamate that "poisons" the hippocampus and causes its atrophy, "says Valentine Mancini.
Act before the critical period
The psychotic symptoms result from this hypercompensation which ends up destroying the hippocampus, according to this work published in the review Molecular Psychiatry.
This study suggests that the small size of the hippocampus in patients with 22q11 deletion syndrome is defined in the mother's womb probably due to poor vascularity.
As the critical age for schizophrenia is in adolescence, the Genevan team is now working on the possibility of preventing the atrophy of the hippocampus, in order to preserve its functions.
(Much / nxp / ats)
[ad_2]
Source link
