Fronto-temporal function may distinguish bipolar disorder from schizophrenia.
OBJECTIVE
There is evidence for differential neural alterations within the prefrontal cortex (PFC) in bipolar disorder I (BDI) and schizophrenia that may translate into different cognitive deficits. Our objective was to compare the cognitive profile of stable BDI and schizophrenic patients using neuropsychological tasks which utilize frontal systems but differ in terms of the exact neural circuits and cognitive processes involved.


METHODS
We studied 43 patients with BDI, 54 with schizophrenia and 46 matched healthy participants. All participants completed (i) the Wisconsin Card Sorting Test (WCST) which is known to recruit the dorsal and ventral PFC, (ii) the verbal fluency task (VFT), which engages frontal-temporal regions, and (iii) the Stroop Colour Word Test (SWCT) which depends on the integrity of the cingulo-frontal network. A series of multivariate analyses examined differences between the cognitive profiles of BD and schizophrenic patients relative to that of healthy participants controlling for general intellectual ability and gender.


RESULTS
Bipolar disorder I patients showed minimal verbal fluency impairment while schizophrenic patients demonstrated marked deficits on this task relative to the control and BDI groups. The two patient groups had comparable performance on the WCST. In the SWCT, schizophrenic patients showed impairment in both congruent and incongruent conditions while BD patients had deficits only in the latter.


CONCLUSIONS
Absence of significant verbal fluency abnormalities and by inference dysfunction in the associated fronto-temporal circuitry may distinguish BDI from schizophrenia. Both disorders may show impairment in tasks involving cingulo-frontal networks with evidence of greater cingulate dysfunction in schizophrenia.
Frangou
S
S
Section of Neurobiology of Psychosis, Institute of Psychiatry, King's Coillege London, London, UK. s.frangou@iop.kcl.ac.uk
Dakhil
N
N
Landau
S
S
Kumari
V
V
D000328:Adult; D000367:Age Factors; D000553:Ambulatory Care / Q000706:statistics & numerical data; D001714:Bipolar Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology* / Q000523:psychology; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology*; D006179:Gyrus Cinguli / Q000503:physiopathology; D006801:Humans; D038801:International Classification of Diseases; D008131:London; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D012042:Registries; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D012564:Schizophrenic Language; D012737:Sex Factors; D013702:Temporal Lobe / Q000503:physiopathology*; D014705:Verbal Behavior / Q000502:physiology