2023-09-13 05:54:15
Abuse, loss of a parent, extreme forms of adversity resulting from poverty or racism… Children confronted with painful experiences very early on often retain a form of fragility: research shows in particular that these ordeals make them more vulnerable to depression and anxiety disorders in adulthood. But what is the nature of this fragility which remains permanently inscribed in the brain? Catherine Jensen Peña’s team at Princeton University has just identified it, in the form of groups of neurons that become hyperreactive to new difficult events.
In this study, young mice were subjected to chronic stress for a week – they were separated from their mother for several hours a day and grew up in an impoverished environment – before being bullied again as adults, confronted daily with harassment from another aggressive rodent. The researchers then showed that certain groups of neurons which had been activated during the first stress suffered in childhood, located in two areas called “ventromedial prefrontal cortex” and “nucleus accumbens”, lit up again with a particular intensity during this last painful experience. Rodents with painful childhoods also began to avoid their peers, a behavior typical of depression.
To confirm that it is indeed these groups of hyperreactive neurons which cause psychological fragility, the researchers inhibited them using biochemical manipulations. The rodents then better withstood the ordeals inflicted on them as adults. The techniques used are not applicable to human patients – they involve genetic modifications – but these results prove that it is possible to repair brain dysfunctions triggered by early stress, even years later. It remains to be found how to do this in humans: the avenues envisaged include, for example, the use of electrodes implanted in the brain or the development of new drugs capable of modulating the activity of the identified neuronal networks.
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