Dissociable mechanisms for memory impairment in bipolar disorder and schizophrenia.
BACKGROUND
Although memory deficits are consistently reported in schizophrenia and bipolar disorder, the mechanisms underlying these impairments are poorly understood. Clarifying the nature and degree of overlap in memory deficits between the two illnesses could help to distinguish brain systems disrupted in these illnesses, and indicate cognitive remediation strategies to improve patient outcomes.


METHODS
We examined performance on a non-verbal memory task in clinically stable out-patients with bipolar disorder (n=40), schizophrenia (n=40), and healthy comparison subjects (n=40). This task includes conditions in which distinct mnemonic strategies -- namely, using context to organize familiar stimuli or using holistic representation of novel stimuli -- facilitate performance.


RESULTS
When compared to a reference condition, bipolar patients had deficits consistent with organizational dysfunction and poor detection of novel information. Although patients with schizophrenia performed worse than the other groups, they were only differentially impaired when organizational demands were significant. Task performance was not correlated with severity of clinical symptomatology.


CONCLUSIONS
This pattern of distinct memory impairments implies disturbances in partially overlapping neural systems in bipolar disorder and schizophrenia. Evidence of impairment in detection of novel stimuli that is unique to bipolar disorder suggests that, while the absolute level of cognitive dysfunction is less severe in bipolar disorder as compared to schizophrenia, subtle disruptions in memory are present. These findings can be used to plan targeted cognitive remediation programs by helping patients to capitalize on intact functions and to learn new strategies that they do not employ without training.
Glahn
David C
DC
Department of Psychiatry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA. glahn@uthscsa.edu
Barrett
Jennifer
J
Bearden
Carrie E
CE
Mintz
Jim
J
Green
Michael F
MF
Serap Monkul
E
E
Najt
Pablo
P
Soares
Jair C
JC
Velligan
Dawn I
DI
D000328:Adult; D001245:Association Learning; D001288:Attention; D001714:Bipolar Disorder / Q000175:diagnosis* / Q000523:psychology; D003463:Cues; D004193:Discrimination Learning; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis* / Q000523:psychology; D008570:Memory, Short-Term; D008875:Middle Aged; D010364:Pattern Recognition, Visual; D011214:Practice, Psychological; D011618:Psychotic Disorders / Q000175:diagnosis* / Q000523:psychology; D012016:Reference Values; D012153:Retention, Psychology; D012559:Schizophrenia / Q000175:diagnosis*; D012565:Schizophrenic Psychology