ABSTRACT
An approach bias for alcohol stimuli (i.e. faster approach than avoidance reactions) might facilitate relapses in alcohol dependence. Neurobiological models suggest hypersensitivity in the reward system [inter alia nucleus accumbens and orbitofrontal cortex (OFC)] to cause pathologically enhanced approach impulses towards alcohol stimuli. At the same time, in alcohol dependence, these structures are only insufficiently controlled by a hypoactive dorsolateral prefrontal cortex (DLPFC). The present study investigated the cortical aspects of this model with functional near-infrared spectroscopy in 21 alcohol-dependent in-patients and 21 healthy controls (HC; comparable in age, gender and education) during performance of the Approach-Avoidance Task (AAT) for the first time. Complementing previous findings, in reaction times (RTs), patients showed stronger approach preferences for alcohol than non-alcohol stimuli. For non-alcohol stimuli, patients even displayed avoidance preferences. The reversed pattern was found in HC. Group differences in activity of the OFC were identical to those in RTs, revealing patients to assign higher subjective value to approaching alcohol stimuli. In both groups, regulatory activity in the right DLPFC was stronger during avoiding than approaching alcohol pictures. Probable awareness of the behavioural hypotheses due to explicit task instructions and patients' deficient prefrontal function might account for this equally aligned pattern. Results are discussed with regard to recent findings revealing a reduced behavioural approach bias and risk for relapse by applying a retraining version of the AAT. Functional measurements might serve as a method for monitoring the corresponding neurobiological changes and-possibly-predicting the success of such a training.
Subject(s)
Alcoholism/psychology , Patient Preference/psychology , Prefrontal Cortex/physiology , Adult , Alcoholism/physiopathology , Analysis of Variance , Avoidance Learning/physiology , Case-Control Studies , Female , Functional Neuroimaging , Hemoglobins/analysis , Humans , Male , Photic Stimulation , Psychological Tests , Psychomotor Performance/physiology , Spectroscopy, Near-InfraredABSTRACT
INTRODUCTION: The present pilot study investigated cortical processes during automatic and regulated approach-avoidance reactions for the first time. METHODS 1: In 15 healthy volunteers, prefrontal activity was measured with functional near-infrared spectroscopy (fNIRS) during performance of a joystick version of the Approach-Avoidance Task (AAT). In experiment 1, participants approached (pulled towards their body) and avoided (pushed away from their body) positive and negative pictures. RESULTS 1: Incompatible, regulated reactions (avoid positive, approach negative) compared to compatible, automatic reactions (approach positive, avoid negative) caused stronger activation in terms of a decrease of deoxygenated haemoglobin (HHb) in right dorsolateral prefrontal cortex (DLPFC) (i.e., in one of the main instances for behavioural control in humans). METHODS 2: In the context of pathologically enhanced approach tendencies in addiction disorders and of planned future studies, we presented alcohol and non-alcohol pictures in experiment 2. RESULTS 2: Here, left anterior lateral orbitofrontal cortex as part of the general reward system processing secondary rewards showed stronger activation in terms of increased oxygenated haemoglobin (O(2)Hb) during approaching compared to avoiding alcohol pictures. This difference was positively correlated with participants' expectation about beneficial effects of alcohol in terms of emotional regulation. DISCUSSION: Despite some limitations due to the pilot character of the study, our results suggest that further combinations of the AAT and functional imaging methods will reveal detailed insight into neuronal mechanisms constituting approach-avoidance as basic behavioural principles and into specifically altered sub-processes in alcohol dependence.
