title: Striatopallidal regulation of affect in bipolar disorder.
abstract: BACKGROUND
  Evidence from the neuroimaging literature suggests that the basal ganglia plays an important role in the regulation of affect. This conclusion stems almost exclusively from group comparisons and it remains unclear whether previous findings can be confirmed from a longitudinal study of mood change. The aim of this study was to increase our understanding of the functional role of the basal ganglia and thalamus in relation to change in affect in patients with bipolar disorder.
  
  
  METHODS
  Ten bipolar disorder subjects participated in a functional MRI study. We used a simple motor reaction time task to probe subcortical regions bilaterally. Subjects were scanned twice, once when their self-reported mood ratings indicated hypomania or euthymia and then again when they were in depressed states.
  
  
  RESULTS
  Subjects in their euthymic or hypomanic states exhibited increased caudate activity bilaterally and the globus pallidus of the left hemisphere. Longitudinal analyses revealed a significant association between an increase in severity of depression and a decrease in activity in the external segment of the right globus pallidus.
  
  
  CONCLUSIONS
  Our findings suggest that the globus pallidus is less responsive during a simple motor task in the depressed compared to the normal or euthymic states in patients with bipolar disorder. These results are consistent with current physiologic models of basal ganglia circuitry in which an increase in caudate activity results in an increase in inhibitory GABAergic outflow to the external globus pallidus and subsequent decrease in thalamocortical excitation and may underlie the clinical manifestations of depression in bipolar disorder.
  
  
  CONCLUSIONS
  The findings of this study need to be interpreted with caution as correlation coefficients may be overestimated in this small study sample.
authors.affiliation: Department of Psychiatry, University of California at San Diego, USA. mcaligiuri@ucsd.edu
authors.forename: Michael P
authors.initials: MP
authors.lastname: Caligiuri
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Brown
authors.forename: M J
authors.initials: MJ
authors.lastname: Meloy
authors.forename: Sonja
authors.initials: S
authors.lastname: Eberson
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Niculescu
authors.forename: James B
authors.initials: JB
authors.lastname: Lohr
mesh_terms: D000328:Adult; D000339:Affect / Q000502:physiology*; D000368:Aged; D001479:Basal Ganglia / Q000503:physiopathology; D001714:Bipolar Disorder / Q000503:physiopathology* / Q000628:therapy*; D003342:Corpus Striatum / Q000503:physiopathology*; D003863:Depression / Q000503:physiopathology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D005917:Globus Pallidus / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D013788:Thalamus / Q000503:physiopathology