The cerebellar language: is it a universal one?

Abstract

The cerebellar language: is it a universal one?

In the past few decades, researchers have shown more and more interest in the cognitive and affective role of the cerebellum. Before, the “little brain” was seen as a primitive structure, primarily involved in motor functions. However, due to anatomical, functional, and clinical studies, it has now been proven that the cerebellum is also involved in higher cognitive and emotional functions. Moreover, it has been shown that even in motor tasks such as writing, the cerebellum might also be involved in the non-motor coordination. Although it is difficult to establish the precise role of the cerebellum in writing, more and more studies discuss the possibility of a non-motor role. The right posterior cerebellum is consistently activated in functional MRI studies using writing tasks, even when contrasted with motor tasks (Planton, Jucla, Roux, & Démonet, 2013), and differences only disappear when the level of difficulty of the motor control task is similar to handwriting (e.g. writing of letters) (Beeson et al., 2003). Our functional MRI study in children, however, shows that the level of difficulty of the motor control task is not the most important factor. In children between the age of 9 and 12 the posterior cerebellar activation might be effectively eliminated by a simple thumb-tapping task. It was argued that the same level of planning is needed for the sequential thumb-tapping task as for writing in children who are still developing their finger and hand movement coordination. This implies that the (posterior) cerebellar activation is related to planning of skilled movements (praxis). The main theories about the cerebellar role in cognition consider the cerebellum as a computational device that coordinates and modulates the supratentorial processes on the basis of information conveyed through the cerebro-cerebellar pathways (Schmahmann, 1996, 1998). The unique neuro-anatomical structure of the cerebellum and its dense interconnectivity with most supratentorial areas allow the cerebellum to fulfill the role of “motherboard” of the brain. Although it is not yet entirely clear which information the cerebellum uses, it can be stated that it contributes in a unique way to the modulation and coordination of a variety of motor and non-motor processes (van Dun, Manto, & Mariën, 2016). This, however, also implies that rehabilitation of cerebellar-related symptoms might need a different approach than rehabilitation of similar symptoms caused by cerebral lesions (Schmahmann, 2010; van Dun, Overwalle, Manto, & Marien, 2018). It seems that an approach in which awareness is created, making the patient act as “an external cerebellum” (Ruffieux et al., 2017), might be the most effective in adult patients with cerebellar damage. This approach might also be effective in children with neurodevelopmental disorders and learning disabilities. However, since these developmental disorders are often characterized by an immature cerebellum, an intervention that trains the cerebellum with motor learning exercises also seems to affect cognitive abilities (Reynolds & Nicolson, 2007; Reynolds, Nicolson, & Hambly, 2003; Zhou et al., 2014).