Temporal profile of fronto-striatal-limbic activity during implicit decisions in drug dependence

Abstract

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 © 2014 Elsevier Ireland Ltd. All rights reserved.Corresponding author: Jody Tanabe, Department of Radiology, Mail Stop C278, 12700 E 19 th Avenue, Aurora, CO 80045, Office: 303-724-3768, Fax: 303-724-3795, jody.tanabe@ucdenver.edu. Contributors Yamamoto: design, analysis, data interpretation, manuscript; Reynolds: design, analysis, data interpretation, manuscript; Krmpotich: design, analysis, data interpretation, manuscript; Banich: data interpretation, manuscript; Thompson: data interpretation, manuscript; Tanabe: design, analysis, data interpretation, manuscript. All authors contributed to and have approved the final manuscript. Conflict of InterestThe authors report no conflicts of interest.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 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. NIH Public Access