Authors: Alice Weatherston
The cerebellum, traditionally associated with motor control, is a brain region that you rarely hear much about; not being thought of as linked to any form of higher-level functioning such as thought processing or social interaction. However, in 1998 an influential paper by Jeremy Schmahmann  shed new light on the potential role of the cerebellum within the brain, highlighting its cognitive and emotional influences.
Since then, interest has grown in this little-know region of the brain, with a new consensus on the definition of the disorder produced this year  and an increasing number of research groups working in the area. While at the International Symposium on Pediatric Neuro-oncology (ISPNO; 12–15 June 2016, Liverpool, UK) I sat down with Jeremy Schmahmann himself, following the first ever dedicated session for cerebellar mutism syndrome (CMS) at the conference, to discuss some of his work into the functioning of the cerebellum and how this has and will influence clinical practice.
Can you introduce yourself and tell us a bit more about your interest in the cerebellum?
I am a neurologist and neuroanatomist, with a particular focus on behavioral neurology and disorders of the cerebellum, including the cerebellar ataxias and cerebellar cognition.
In the first year of my residency in the early 1980’s I had the idea that the cerebellum should have something to do with cognitive control. Cerebellum is such a large part of the brain and for 200 years it had been regarded as devoted solely to motor control. There had been suggestions that other motor regions, such as the basal ganglia, were involved in cognition, which led me to ask the question: “is the cerebellum involved in cognition?”
I initially approached the hypothesis from the perspective of neural circuits. With my mentor Deepak Pandya (Boston University, MA, USA), I studied anatomy in monkeys to define the circuits that link the cerebral cortex with the cerebellum, by way of the projections to the pontine nuclei. I demonstrated that there were strong and precisely arranged projections to the pons from association areas in the prefrontal cortex, posterior parietal cortex and temporal lobe regions involved in higher order functioning, all of which ‘talk’ to the cerebellum through the pons . This effectively means that there are anatomical pathways linking the cerebellum with cerebral areas important for cognition, as well as with motor control.
I then moved on to investigate the manifestations of cerebellar injury in patients. From interviewing and examining patients with disease confined to the cerebellum it became clear to me that there is a constellation of deficits that occur in people with cerebellar damage, a new syndrome that I termed the cerebellar cognitive affective syndrome (CCAS/Schmahmann syndrome). This has redefined the way we think about the cerebellum [1, 4, 5].
That is a very novel view of the cerebellum!
Yes, it turns out that only a small portion of the cerebellum is involved in motor control. Most of the human cerebellum is linked up with and involved in modulation of areas that have nothing to do with motor control. But that leaves many questions: “What is cerebellum doing?”, “What is its function in the nervous system?”, “If you damage it what happens?” We’re starting to learn some of the answers now.
The opinions expressed in this interview are those of the interviewee and do not necessarily reflect those of Neurology Central or Future Science Group.