Addiction Related Alteration In Resting-State Brain Functional Connectivity And The Function Of Reward System

Resting-state functional connectivity with fMRI is an approach thought to provide a measure of the“resting”brain’s functional organization and be relatively readily applicable in clinical settings, but rarely applied in the field of addiction. It is widely accepted that addictive drug use is related to abnormal functional organization in the user’s brain. In the present study, with functional magnetic resonance imaging (fMRI) data acquired during resting state from chronic heroin users and non-addicted controls, we investigated the addiction related alteration in resting-state functional connectivity. Compared with controls, chronic heroin users showed increased functional connectivity between nucleus accumbens and ventral/rostral anterior cingulate cortex (ACC), between nucleus accumbens and orbital frontal cortex (OFC), between amygdala and OFC; and reduced functional connectivity between prefrontal cortex and OFC, between prefrontal cortex and ACC. Default-mode network (DMN) involves a set of brain regions, such as cingulate cortex, hippocampus, parital lobe, exhibiting robust low frequency oscillations coherent during resting-state. As these regions are impaired in drug addiction, we compared the functional connectivity of DMN between heroin users and controls. Compared with controls, heroin users showed stronger contributions from right hippocampus but weaker contributions from right dorsal anterior cingulate cortex and left caudate to functional connectivity of the DMN. These observations of altered resting-state functional connectivity suggested abnormal functional organization in the addicted brain and may provide additional evidence supporting the theory of addiction that emphasizes enhanced salience value of a drug and its related cues but weakened cognitive control in the addictive state.For the similarities, such as the failure to resist one’s impulses to engage in a particular event despite serious consequences, between Excessive Computer Game Playing (ECGP) and drug addiction, speculations about the neurobiological mechanism of ECGP tend to focus on the dysfunction in the brain circuits implicated in drug addiction. In the present study, with fMRI, the neural correlates of reward processing of Excessive Computer Game Players and chronic heroin users (HU) were respectively investigated. (1) ECGPers showed enhanced activation in reward system toward computer games, which were in comparable patterns as HUs (toward heroin related cues rather than computer games). (2) In contrast to controls, HUs showed weakened neural response on biological reward related cues, while these was no difference between ECGPers and controls, who, but, exhibited different patterns in within group tests. These results suggest compromised sensitivity toward biological rewards in HUs and ECGPers, while the decrease is milder in ECGPers. (3) In the monetary incentive delay task, while HUs exhibited blunted sensitivity to the increase of incentive values of reward-indicating cues, it is not the case in ECGPers, who, in an opposite pattern, showed enhanced sensitivity to this increase. These findings suggest altered neural reward processing both in ECGPers and drug addicts and its similarities and differences between these two states.