Psychological Medicine



Original Article

Dissociable mechanisms for memory impairment in bipolar disorder and schizophrenia


DAVID C. GLAHN a1c1, JENNIFER BARRETT a1, CARRIE E. BEARDEN a2, JIM MINTZ a2a3, MICHAEL F. GREEN a2a3, E. SERAP MONKUL a4, PABLO NAJT a1a5, JAIR C. SOARES a1a5 and DAWN I. VELLIGAN a1
a1 Department of Psychiatry, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
a2 Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, CA, USA
a3 Veterans Administration of Greater Los Angeles Healthcare System, USA
a4 Department of Psychiatry, Dokuz Eylul University School of Medicine, Izmir, Turkey
a5 South Texas Veterans Health Care System, USA

Article author query
glahn dc   [PubMed][Google Scholar] 
barrett j   [PubMed][Google Scholar] 
bearden ce   [PubMed][Google Scholar] 
mintz j   [PubMed][Google Scholar] 
green mf   [PubMed][Google Scholar] 
serap monkul e   [PubMed][Google Scholar] 
najt p   [PubMed][Google Scholar] 
soares jc   [PubMed][Google Scholar] 
velligan di   [PubMed][Google Scholar] 

Abstract

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.

Method. 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.

Result. 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.

(Published Online May 31 2006)


Correspondence:
c1 Department of Psychiatry, The University of Texas Health Science Center at San Antonio, Mail Code 7792, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA. (Email: glahn@uthscsa.edu)


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