Thinking about the cerebellum.

Prompted by functional imaging studies, there have been a number of recent suggestions that the cerebellum may be involved in functions other than motor control. Lesions or abnormalities of the cerebellum have been claimed to be associated with cognitive deficits and autism; and the cerebellum is said to control shifting attention and be active both during the performance of cognitive tasks and in short-term memory. Many of these reports are summarized in Schmahmann and Sherman (1998). The paper by Susan Ravizza and colleagues in this issue of Brain reports the results of a series of studies comparing the performance of cerebellar patients with that of normal control subjects on short-term memory tasks. It is difficult to evaluate suggestions about affective or cognitive functions for several reasons. Lesions of the cerebellum may not occur in isolation. Traumatic, vascular, developmental anomalies and tumours typically cause damage to brain structures outside of the cerebellum and treatments associated with cerebellar resection, such as chemotherapy and radiation, may themselves produce cognitive deficits (Drepper et al ., 1999; Konczak et al ., 2005). Additionally, there is a one-way valve in the literature whereby negative results are harder to publish than positive results; failures to replicate published findings pose a challenge to the acceptance of claims for a role for the cerebellum in cognition or mental illness. Suggestions for a cognitive role of the cerebellar hemispheres are not new. Although nineteenth century neurologists recognized that lesions of the midline cerebellum produce deficits in eye movements and equilibrium, they found that cerebellar hemispheres often seemed to be unrelated to those functions. Thus, Gowers (1888) suggested that there might be some validity to the idea of a cognitive function for the cerebellum, whilst Andre-Thomas (1912) disagreed. Participation in short-term memory has been suggested to be one non-motor …