A new study by the University of Pisa, published in Science Advances, shows that even the adult brain retains a dormant yet reactivable potential for plasticity. The key lies in the pulvinar, a small deep-brain structure capable of ‘switching back on’ the ability of the visual cortex to change and learn. This discovery opens up significant possibilities for visual and cognitive rehabilitation. Understanding and modulating the role of the pulvinar could lead to new therapeutic approaches that can reactivate the brain plasticity and measure the brain’s “plastic potential”, which is a valuable indicator of the effectiveness of therapies.
Led by a team of researchers at the University of Pisa in collaboration with Maastricht University, IRCCS Fondazione Stella Maris and Fondazione Imago7, the study reveals that the pulvinar regulates cortical plasticity, particularly in the visual system. For a long time, it was thought that cortical plasticity was limited to the developmental stage, when even a minor visual impairment could result in altered brain maturation that is difficult to reverse in adulthood. However, the new findings show that the adult visual cortex retains a capacity for change, ready to be reactivated when the appropriate stimulus is provided.
To demonstrate this, the researchers asked a group of adult participants to undergo ultra-high-field (7 Tesla) functional magnetic resonance imaging, which can provide images of brain connectivity with high spatial and temporal resolution. Connectivity was measured twice: before and after the participants wore a patch over one eye in a procedure known as ‘short-term monocular deprivation’. The results show that a deprivation period of just two hours alters not only ocular dominance, but also communication among areas of the visual brain. Surprisingly, this change is not limited to the cortex, but mainly affects the pulvinar, which reduces its influence on the cerebral cortex following deprivation.
“The function of the pulvinar is still poorly understood, yet it exerts an inhibitory influence on the adult cortex. We observed that this influence decreases after deprivation, which is enough to open the door to plasticity. Thus, the brain does not rely on fixed connections, but can modify them to balance the need for stability with the drive for change. Our data suggest that the pulvinar decides when to remain stable and when to adapt to unexpected circumstances,” explains Miriam Acquafredda, the study’s first author.
“This work changes our perspective on not only brain plasticity, but also the functional organisation of the adult brain,” adds Maria Concetta Morrone, a professor at the University of Pisa and a member of the Accademia dei Lincei. “We tend to attribute all higher functions, such as thought, perception, and consciousness, to the cerebral cortex, relegating deep structures to instinct and emotion. These results overturn that view, showing that deep structures such as the pulvinar can orchestrate cortical function.”
Paola Binda, a professor at the University of Pisa, concludes: “The study we have just published fits into our main research line, in which we explore the idea that the brain is a ‘predictive machine’ that works to anticipate what is about to happen in order to respond promptly. When predictions clash with anomalous reality, the prediction-generating mechanism must update itself. We believe it is precisely this signal that triggers plasticity.
