The Multifunctional Small Brain

Imagine seeing an old person picking up a box and a young person picking up a comparable box. By merely looking at both movements, you can already tell the difference in, for example, strength, flexibility, and confidence of the two people. The brain region responsible for such higher perceptual abilities was thought to be the cerebral cortex, the outer layer of the brain. However, a study done by the Netherlands Institute for Neuroscience shows the cortex gets help from another region, namely, the cerebellum or small brain, an area involved in movement. This discovery can help understand the consequences of damage to the small brain, since not only motoric impairment will appear, but also social cognition can be altered. The study was published today in the prominent scientific journal Brain.

The small brains, also known as the cerebellum, is located at the backside of the brain and is mainly involved in fine tuning and co-ordination of movements. For a long time, it was assumed that the small brains 'only' helps smooth out bodily movements. "Our study provides the evidence that this belief is wrong - the cerebellum is smarter than we think" says Dr. Valeria Gazzola, group leader at the Netherlands Institute for Neuroscience (NIN) and associate professor at the University of Amsterdam.

Using neuroimaging the researchers of the NIN identified what parts of the brain are activated when people watch the actions of others. This resulted in the known cortical regions. Surprisingly, results also systematically showed activity in the cerebellum. "This area was supposed to be only involved in controlling the participants' own actions", says Ritu Bhandari, a Postdoctoral researcher at the NIN.

Malfunctioning small brains

In collaboration with the Erasmus MC, the researchers further investigated the perceptual abilities of the cerebellum. For this, they recruited patients that suffer from SCA6, a disease that affects the small brains. The patients had to watch a video of a hand lifting a black box, and they had to judge how heavy the box might have been. They found that the patients were not so good at doing this. "They found it hard to transform small differences in how the hand moves into a perception of effort and weight," Abdel Abdelgabar, a PhD student at the NIN, remarked.

A bicycle chain

These findings clearly show the importance of functioning small brains in social cognition. However, this doesn't mean that the area alone perceives other people. "If you remove the chain of your bicycle, it will no longer move forward. But that doesn't mean it was the chain alone that drove the bike" explains Valeria Gazzola. "What it does show, is that the cerebellum is a critical part of a cognitive system - a part we had neglected for too long. And we must realize, that problems with the cerebellum will most likely impair aspects of social cognition and that this requires support and patience," she concludes.

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