Intact artificial grammar learning in patients with cerebellar degeneration and advanced Parkinson's disease

In an artificial grammar learning, task. subjects were asked to memorise short lists of letter strings formed according to complex rules for letter order. After an interval they Were unexpectedly asked to discriminate new grammatical strings from strings which used the same letters but violated the sequential constraints of the grammer. Artificial grammer learning can be mastered Successfully by amnesic patients and is considered to be an implicit learning task independent of declarative learning and memory mechanisms. In this Study, 10 patients with cerebellar degeneration (CD), 2 1 Parkinson's disease (PD) and 15 control subjects were tested on artificial grammer learning. Additionally PD patients with advanced disease were examined under adequate medication and dopaminergic withdrawal. All patient groups Showed intact artificial grammer learning. Neither cerebellar damage nor basal ganglia dysfunction nor dopaminergic medication impairs or affects artificial grammer learning. Although the patients showed significant executive dysfunction, implicit learning remains Intact. The The conclusion is that cerebellar and basal ganglia circuits play no essential part in this kind of implicit learning. The results suggest that artificial grammar learning is a cortically mediated function comparable to the mechanism of visual priming. (C) 2002 Elsevier Science Ltd. All rights reserved.