Habit Learning Impaired in Tourette Syndrome

Children and adults afflicted with the tic-causing disease known as
Tourette syndrome have a harder time with tasks requiring habit
learning, report investigators publishing in this month's Archives
of General Psychiatry.

The finding could lead to an animal model of the disease that
researchers could use to study the areas of the brain affected by TS
and to come up with new medications aimed at treating its symptoms.

The study was carried out among 56 children and adults with TS and
67 healthy children and adults who served as the study controls. All
were given a standard test designed to measure people's ability to
learning through habit. Participants also took tests to see how well
they learned through declarative memory functioning, which includes
memorization of facts, words and experiences.

Results show people with TS had a significantly harder time learning
with the habit test than the healthy controls, and learning ability
decreased with the severity of TS symptoms. Conversely, TS
participants scored about the same as healthy controls on tests that
measure the ability to learn via declarative memory functioning.

The researchers believe further study of habit learning in animal
models of TS offers "the exciting promise not only of improving our
knowledge of the neurobiological origins of TS but also of
developing novel therapeutics through bona fide translational
research programs and methods that are not available to human
clinical studies alone."

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SOURCE:(Ivanhoe Newswire)Reported December 9, 2004
http://www.ivanhoe.com/channels/p_channelstory.cfm?storyid=10122
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2nd Source Content

Habit Learning in Tourette Syndrome
A Translational Neuroscience Approach to a Developmental
Psychopathology

Rachel Marsh, PhD; Gerianne M. Alexander, PhD; Mark G. Packard, PhD;
Hongtu Zhu, PhD; Jeffrey C. Wingard, MPhil; Georgette Quackenbush,
BA; Bradley S. Peterson, MD


Arch Gen Psychiatry. 2004;61:1259-1268.

Background The etiology of Tourette syndrome (TS) involves
disturbances in the structure and function of the basal ganglia. The
basal ganglia mediate habit learning.

Objective To study habit learning in persons with TS.

Design Patients with TS were compared with normal controls in
performance on a probabilistic classification, or habit-learning
task (weather prediction).

Setting University research institute.

Participants 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.

Results 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.

Conclusions 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 condition.


Author Affiliations: Division of Child and Adolescent Psychiatry in
the Department of Psychiatry, New York State Psychiatric Institute
and College of Physicians and Surgeons, Columbia University, New
York (Drs Marsh, Zhu, and Peterson and Ms Quackenbush); Department
of Psychology, Texas A&M University, College Station (Drs Alexander
and Packard); and Department of Psychology, Yale University, New
Haven, Conn (Mr Wingard).



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SOURCE: Archives of General Psychiatry, 2004;61:1259-1268
http://archpsyc.ama-assn.org/cgi/content/short/61/12/1259
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