By studying the brains of primates, a team has discovered the brain mechanisms activated when something is checked. A result that opens up new avenues for treating OCD.
Check that the lights are off about ten times before leaving the house. Then then go up the stairs one last time to make sure the door is properly closed. These situations where we compulsively overcheck things sometimes plague our lives. But what circuits mobilize our brain to repeat these verifications? The question has challenged researchers.
While studies strongly suspected the involvement of the frontal cortex, the precise regions involved have so far remained unknown. Until recently. In the review Nature Communications, a French team from Inserm (1) reveals to have unmasked the conductor of this cerebral mechanism. This is the cingulate cortex.
411 neurons activate
The work of these researchers from Lyon was carried out on macaques equipped with electrodes recording the activity of their frontal cortex. “More precisely, we recorded the activity of 411 neurons in two regions of the frontal cortex, known for their involvement in decision-making: the middle cingulate cortex and the lateral prefrontal cortex”, indicates Emmanuel Procyk, co-author of the ‘study, in an Inserm press release.
And to study these neurons when the monkeys decide to check something, the team has developed a novel protocol that scientists have called: “work or check”. On each try, this test gave the monkeys two options: either work on a visual memorization task, or check a gauge that shows how long it takes before you can collect a reward (fruit juice). Correctly chaining the steps of the main task raised the bar.
Everything happens in 500 milliseconds
The researchers then discovered that when macaques check the level of the gauge, it activates neurons in the middle cingulate cortex first, and only then those in the lateral prefrontal cortex (500 milliseconds later). Using state-of-the-art statistical tools capable of analyzing in detail the information contained in neuronal discharges, the team even managed to correctly predict the imminence of an audit. This up to a second before the monkeys perform the movement to check the level of the gauge.
Finally, the study reveals that these neural pathways for verification are different from those involved in other types of decisions, such as when macaques decide to press a button to answer a question on the visual memory test.
Better care for OCD
And this discovery is not without consequences for treating mental disorders. A disruption of this cerebral mechanics could indeed explain the repeated checks of patients with obsessive-compulsive disorders (OCD). Inserm points out that certain studies have already demonstrated an alteration of the cingulate cortex in these patients.
“In some countries, such as the United States, doctors are already trying to treat OCD by destroying parts of the cingulate cortex of patients with electrodes,” recalls the Institute. However, “this electrocoagulation technique would only be effective in 30 to 40% of patients resistant to other available treatments,” he continues. He specifies that a lack of precision concerning the targeted areas of the cingulate cortex could explain the lack of effectiveness of the approach.
“For our part, we have just launched a new project with a double objective: to identify precisely the areas of the cingulate cortex involved in OCD in humans, on twenty volunteers, and to assess the impact of an alteration of the cortex. corresponding cingulate in macaques ”, announces Emmanuel Procyk.
The results are expected for 2017-2018. And if this lead is confirmed, it could pave the way for the development of specific treatments capable of regulating the activity of the cingulate cortex to better treat OCD: “drugs, electrostimulation, more precise electrocoagulation…? “, All these leads are on the table, concludes the researcher. To be continued … But not fifteen times a day!
(1) Inserm Unit 1028 / Claude Bernard Lyon 1 University, Strain Cell and Brain Institute, Bron
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