Eyeblink conditioning anomalies in bipolar disorder suggest cerebellar dysfunction


  • The authors of this paper do not have any commercial associations that might pose a conflict of interest in connection with this manuscript.

William P. Hetrick, PhD, Department of Psychological and Brain Sciences, Indiana University, 1101 E. Tenth Street, Bloomington, IN 47405, USA.
Fax: 812 856 4544; e-mail: whetrick@indiana.edu


Objectives:  Accumulating research implicates the cerebellum in non-motor psychological processes and psychiatric diseases, including bipolar disorder (BD). Despite recent evidence that cerebellar lesions have been documented to trigger bipolar-like symptoms, few studies have directly examined the functional integrity of the cerebellum in those afflicted with BD.

Methods:  Using a single-cue delay eyeblink conditioning procedure, the functional integrity of the cerebellum was examined in 28 individuals with BD (9 manic, 8 mixed, and 11 euthymic) and 28 age-matched healthy controls.

Results:  Analysis of the bipolar group as a whole indicated a conditioned response acquisition and timing deficit compared to controls. However, when the bipolar group was categorized according to mood state (mixed, manic, euthymic), individuals tested during mixed episodes were strikingly impaired, performing significantly worse than all other groups on both the acquisition and timing of conditioned responses.

Conclusions:  These findings extend prior research implicating cerebellar functional abnormalities in BD and suggest that cerebellar dysfunction may be associated with mood state and course of illness.