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.

The finding could help clarify the consequences of damage to the small brain, since not only motoric impairment will appear, but also social cognition can be altered.

Smarter Than We Think

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.

[caption id=“attachment_101433” align=“aligncenter” width=“700”] Functional MRI results of the weight discrimination task.

(A) Voxels significantly activated by either the Sleeve (only kinematic information available) or the NoSleeve (both kinematic and shape information) condition (global null conjunction in SPM at PFWE < 0.05, t = 2.8, min 10 voxels). In blue the clusters identified by Van Overwalle et al. (2014), as responding to action perception.

(B) Voxels activated by both (conjunction-conjunction in SPM) the NoSleeve and Sleeve conditions (PFWE < 0.05; t = 4.5, min 10 voxels).

(C) Same as in A but within the clusters of activation found in Experiments 1–3 (Exp1 > 0 OR Exp2 > 0 OR Exp3 > 0). Results are shown at PFWE < 0.05, t = 2.8, min 10 voxel.

(D) Same as in C but within the clusters of activation found in Experiments 1–3 (PFWE < 0.05; t = 3.9, min 10 voxels). All activations are shown on the flat map of the cerebellum offered by the SUIT toolbox.

Credit: Abdel R Abdelgabar, et al CC-BY[/caption]

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.

Bicycle Chain

In collaboration with the Erasmus MC, the researchers further investigated the perceptual abilities of the cerebellum. For this, they recruited patients that suffer from spinocerebellar ataxia 6 (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.

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.

[1] Abdel R Abdelgabar, Judith Suttrup, Robin Broersen, Ritu Bhandari, Samuel Picard, Christian Keysers, Chris I De Zeeuw, Valeria Gazzola, Action perception recruits the cerebellum and is impaired in patients with spinocerebellar ataxia, Brain, , awz337, https://doi.org/10.1093/brain/awz337

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