Dissociation between attentional set shifting and habit learning: a longitudinal case study.

We report a patient (ST) with predominant damage to the right neostriatum, caused by a rare cerebral angiitis. The testing procedure was focused on attentional set shifting (Wisconsin Card Sorting Test; WCST) and habit learning (probabilistic classification learning; PCL). ST showed impairments in the WCST, digit span backward, alphabet span, and PCL procedures, whereas he exhibited spared IQ, short-term verbal memory, object recognition, episodic and semantic memory. After 1 month of steroid therapy, there was a significant improvement in the WCST, digit span backward and alphabet span tests, whereas PCL remained severely impaired. The three control patients with damage to the parietal lobe displayed normal learning rates in PCL. These results suggest that separate frontostriatal mechanisms exist for attentional set shifting and habit learning.