Not just a motor (inter)face

Abstract

The cerebellum has been traditionally discussed in terms of its contribution to the initiation and control of movement. Nevertheless, its inspired name (‘little brain’) may reflect more than merely its looks. An important body of evidence is pointing to implications of the cerebellum in ‘higher’ brain functions (see 1 The Cerebellum: Connections, Computations and Cognition (Special Issue) (1998) Trends Cognit. Sci. Vol. 2, No. 9 Google Scholar for reviews). A number of imaging studies have reported activation of the structure associated with attentional, mnemonic, perceptual and other non-motoric processes, results that are supported by clinical studies of patients with developmental or acquired cerebellar damage. In a recent study, Townsend and colleagues compared the performance of such patients with that of control subjects on an attentional paradigm based on a spatial cueing task 2 Townsend J. et al. Spatial attention deficits in patients with acquired or developmental cerebellar abnormality. J. Neurosci. 1999; 19: 5632-5643 PubMed Google Scholar . The paradigm was designed to dissociate attentional and motoric components of the behaviour involved, as one of its conditions indexed attention by using measures of accuracy but not speed. The latter would be expected to be selectively impaired in the case of motor deficits. In this experiment, subjects were required to fixate a central point of a display and wait for the onset of a visual cue, either to the left or to the right of the fixation point. The cue was followed – after a variable delay – by the presentation of a target stimulus on the same side (‘valid priming’) or the opposite side (‘invalid priming’) of the display. The target was present only for a fraction of a second and subjects were subsequently asked to report its orientation by moving a joystick. They were instructed to do so ‘accurately’ rather than ‘quickly’. Patients with acquired damage to the cerebellum following tumours or stroke, and patients with autism (a condition that has been linked to decreased cerebellar volume) both showed significant deficits in the task. Typically, control subjects gained the highest benefit from valid, rather than invalid, cues, at very small delays between cue and target presentation. Patient groups however, were slower at using spatial information to orient attention, and so required much longer delays to benefit from the presence of the cue. The authors propose the integration of their results in a model that discusses the cerebellum as supporting a wide variety of cognitive functions by tracking information and preparing other brain systems for imminent events 3 Courchesne E. Allen G. Prediction and preparation, fundamental functions of the cerebellum. Learn. Mem. 1997; 4: 1-35 Crossref PubMed Scopus (202) Google Scholar .