Xiaoliu Zhang,
Chao Suo,
Amir Dezfouli,
Ben J.Harrison,
Leah Braganza,
Ben Fulcher,
Lenardo Fontenelle,
Carsten Murawski,
Murat YuceliDiscussion on NeurostarsImpulsivity and compulsivity are behavioural traits that underlie many aspects of decision-making and form the characteristic symptoms of Obsessive Compulsive Disorder (OCD) and Gambling Disorder (GD). The neural underpinnings of aspects of reward and avoidance learning under the expression of these traits and symptoms are only partially understood.
The present study combined behavioural modelling and neuroimaging technique to examine brain activity associated with critical phases of reward and loss processing in OCD and GD.
Forty-two healthy controls (HC), forty OCD and twenty-three GD participants were recruited in our study to complete a two-session reinforcement learning (RL) task featuring a “probability switch (PS)” with imaging scanning. Finally, 39 HC (20F/19M, 34 yrs ±9.47), 28 OCD (14F/14M, 32.11 yrs ±9.53) and 16 GD (4F/12M, 35.53yrs ±12.20) were included with both behavioural and imaging data available. The functional imaging was conducted by using 3.0-T SIEMENS MAGNETOM Skyra syngo MR D13C at Monash Biomedical Imaging. Each volume compromised 34 coronal slices of 3 mm thickness with 2000 ms TR and 30 ms TE. A total of 479 volumes were acquired for each participant in each session in an interleaved-ascending manner.
The standard Q-learning model was fitted to the observed behavioural data and the Bayesian model was used for the parameter estimation. Imaging analysis was conducted using SPM12 (Welcome Department of Imaging Neuroscience, London, United Kingdom) in the Matlab (R2015b) environment. The pre-processing commenced with the slice timing, realignment, normalization to MNI space according to T1-weighted image and smoothing with a 8 mm Gaussian kernel.
The frontostriatal brain circuit including the _putamen and_ _medial orbitofrontal (_ _mOFC_ _)_ were significantly more active in response to receiving reward and avoiding punishment compared to receiving an aversive outcome and missing reward at _p < 0.001_ with FWE correction at cluster level; While the _right insula_ showed greater activation in response to missing rewards and receiving punishment. Compared to healthy participants, GD patients showed significantly lower activation in the _left superior frontal_ and _posterior cingulum_ at _p < 0.001_ for the gain omission.
The reward prediction error (PE) signal was found positively correlated with the activation at several clusters expanding across cortical and subcortical region including _the striatum, cingulate, bilateral insula, thalamus and superior frontal_ at _p < 0.001_ with FWE correction at cluster level. The GD patients showed a trend of decreased reward PE response in the _right precentral_ extending to _left posterior cingulate_ compared to controls at _p < 0.05_ with FWE correction. The aversive PE signal was negatively correlated with brain activity in regions including _bilateral thalamus, hippocampus, insula and striatum_ at _p < 0.001_ with FWE correction. Compared with the control group, GD group showed an increased aversive PE activation in the cluster encompassing _right thalamus_ and _right hippocampus_ , and also the _right middle frontal_ extending to the _right anterior cingulum_ at _P < 0.005_ with FWE correction.
Through the reversal learning task, the study provided a further support of the dissociable brain circuits for distinct phases of reward and avoidance learning. Also, the OCD and GD is characterised by aberrant patterns of reward and avoidance processing.
