Temporal profile of fronto-striatal-limbic activity during implicit decisions in drug dependence.
BACKGROUND
Substance dependence is associated with impaired decision-making and altered fronto-striatal-limbic activity. Both greater and lesser brain activity have been reported in drug users compared to controls during decision-making. Inconsistent results might be explained by group differences in the temporal profile of the functional magnetic resonance imaging (fMRI) response. While most previous studies model a canonical hemodynamic response, a finite impulse response (FIR) model measures fMRI signal at discrete time points without assuming a temporal profile. We compared brain activity during decision-making and feedback in substance users and controls using two models: a canonical hemodynamic response function (HRF) and a FIR model.


METHODS
37 substance-dependent individuals (SDI) and 43 controls performed event-related decision-making during fMRI scanning. Brain activity was compared across group using canonical HRF and FIR models.


RESULTS
Compared to controls, SDI were impaired at decision-making. The canonical HRF model showed that SDI had significantly greater fronto-striatal-limbic activity during decisions and less activity during feedback than controls. The FIR model confirmed greater activity in SDI during decisions. However, lower activity in SDI during feedback corresponded to a lower post-stimulus undershoot of the hemodynamic response.


CONCLUSIONS
Greater activity in fronto-striatal-limbic pathways in SDI compared to controls is consistent with prior work, further supporting the hypothesis that abnormalities in these circuits underlie impaired decision-making. We demonstrate for the first time using FIR analysis that lower activity during feedback may simply reflect the tail end of the hemodynamic response to decision, the post-stimulus undershoot, rather than an actual difference in feedback response.
Department of Radiology, University of Colorado Denver, 12700 E. 19th Avenue, Mail Stop C278, Aurora, CO 80045, USA.
Dorothy J
DJ
Yamamoto
Department of Psychology, University of Denver, 2155 S. Race Street, Denver, CO 80208, USA.
Jeremy
J
Reynolds
Department of Radiology, University of Colorado Denver, 12700 E. 19th Avenue, Mail Stop C278, Aurora, CO 80045, USA.
Theodore
T
Krmpotich
Department of Psychiatry, University of Colorado Denver, 13001 E. 17th Place, Mail Stop F546, Aurora, CO 80045, USA; Institute of Cognitive Science, University of Colorado Boulder, D420 Muenziger Building, Campus Box 345, Boulder, CO 80309, USA.
Marie T
MT
Banich
Department of Psychiatry, University of Colorado Denver, 13001 E. 17th Place, Mail Stop F546, Aurora, CO 80045, USA.
Laetitia
L
Thompson
Department of Radiology, University of Colorado Denver, 12700 E. 19th Avenue, Mail Stop C278, Aurora, CO 80045, USA; Department of Psychiatry, University of Colorado Denver, 13001 E. 17th Place, Mail Stop F546, Aurora, CO 80045, USA. Electronic address: jody.tanabe@ucdenver.edu.
Jody
J
Tanabe
D000328:Adult; D001519:Behavior; D002560:Cerebrovascular Circulation / Q000502:physiology; D003657:Decision Making / Q000502:physiology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D005625:Frontal Lobe / Q000098:blood supply / Q000503:physiopathology*; D005715:Gambling / Q000523:psychology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007175:Impulsive Behavior / Q000523:psychology; D007297:Inpatients; D008032:Limbic System / Q000098:blood supply / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D017072:Neostriatum / Q000098:blood supply / Q000503:physiopathology*; D009415:Nerve Net / Q000503:physiopathology*; D012959:Socioeconomic Factors; D019966:Substance-Related Disorders / Q000503:physiopathology* / Q000523:psychology*; D016896:Treatment Outcome
Canonical hemodynamic response function; Decision-making; Finite impulse response (FIR); Fronto-striatal-limbic system; Iowa Gambling Task; Substance dependence