Scientists have established a link between cortisol and the limitation of neuroplasticity of the brain

Scientists at Harvard Medical School have discovered a mechanism that controls the completion of critical periods of brain development: the stress hormone cortisol triggers a genetic program in astrocyte cells that gradually limits neural plasticity. This was reported on May 31 in the journal Medical Xpress.

Critical periods are time windows at an early age when the brain is particularly susceptible to external influences, and the experience gained during this time forms neural connections that last a lifetime. As we grow older, this increased plasticity fades away, but the mechanism that triggers this process has remained largely unknown.

In experiments on mice, the Harvard team found that when exposed to light, the adrenal glands release corticosterone, an analog of human cortisol, into the blood. The hormone selectively binds to receptors in astrocyte cells of the visual cortex, triggering an activation program of more than a hundred genes. This contributes to the maturation of the extracellular matrix around neurons, including structures called perineuronal networks. It is their consolidation that limits the formation of new synapses and "closes" the critical period.

In mice raised in the dark, the described pathway was not activated and the critical period did not end. When the glucocorticoid receptors were removed from adult animals, the critical periods that had ended earlier reopened. An analysis of existing data on human brain cells has confirmed that a similar mechanism works in humans — it appears in infancy and reaches its peak in adolescence.

According to the senior author of the study, Professor Michael Greenberg, this pathway is systemic in nature: cortisol is a blood hormone, which means it can activate the same processes in other parts of the brain, including areas responsible for learning and memory.

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