The etiology of Tourette syndrome (TS) involves disturbances in the
structure and function of the basal ganglia. The basal ganglia mediate habit
To study habit learning in persons with TS.
Patients with TS were compared with normal controls in performance on
a probabilistic classification, or habit-learning task (weather prediction).
University research institute.
One hundred twenty-three children and adults, 56 with a diagnosis of
TS and 67 healthy control subjects.
Main Outcome Measures
Habit learning was assessed by the extent of improvement in accuracy
of predictions and reaction times over trial blocks during performance of
the weather prediction task. Declarative learning was assessed by performance
on 3 tasks that required intact declarative memory functioning.
Children with TS were impaired at habit learning relative to normal
controls (P = .01). This finding was replicated
in the independent sample of adults with TS (P = .01).
The rate of learning correlated inversely with the severity of tic symptoms
across both samples (r = −0.34; P = .01). Thus, impaired learning accompanied
more severe symptoms. Measures of declarative memory functioning, in contrast,
were normal in the TS groups.
Striatal learning systems are uniquely dysfunctional in both children
and adults with TS. The correlation of habit learning with symptom severity
suggests that the number and severity of tics are a function of the degree
to which the system for habit learning is dysfunctional. Thus, both the deficits
in habit learning and the tic symptoms of TS are likely to be consequences
of the previously reported anatomical and functional disturbances of the striatum
in children and adults who have TS. The existence of a well-developed animal
model for this learning system, which permits study of the neural and molecular
bases of habit learning, has important implications for the neurobiological
study of TS and for the development of new or improved therapeutics for this