Spatial attention deficits in patients with acquired or developmental cerebellar abnormality

Recent imaging and clinical studies have challenged the concept that the fu nctional role of the cerebellum is exclusively in the motor domain. We pres ent evidence of slowed covert orienting of visuospatial attention in patien ts with developmental cerebellar abnormality (patients with autism, a disor der in which at least 90% of all postmortem cases reported to date have Pur kinje neuron loss), and in patients with cerebellar damage acquired from tu mor or stroke. In spatial cuing tasks, normal control subjects across a wid e age range were able to orient attention within 100 msec of an attention-d irecting cue. Patients with cerebellar damage showed little evidence of hav ing oriented attention after 100 msec but did show the effects of attention orienting after 800-1200 msec. These effects were demonstrated in a task i n which results were independent of the motor response. In this task, small er cerebellar vermal lobules VI-VII (from magnetic resonance imaging) were associated with greater attention-orienting deficits. Although eye movements may also be disrupted in patients with cerebellar da mage, abnormal gaze shifting cannot explain the timing and nature of the at tention-orienting deficits reported here. These data may be consistent with evidence from animal models that suggest damage to the cerebellum disrupts both the spatial encoding of a location for an attentional shift and the s ubsequent gaze shift. These data are also consistent with a model of cerebe llar function in which the cerebellum supports a broad spectrum of brain sy stems involved in both nonmotor and motor function.