Resting State and Functional Connectivity: Previous studies have shown diverse effects of alcoholism on resting state MRI (rsMRI) connectivity. Long-term alcoholics who are currently in a period of sobriety showed decreased synchrony of limbic reward regions with respect to both the anterior cingulate cortex (ACC) and the nucleus accumbens (NAcc) seeds (Camchong et al., 2013). However, few have examined task-free rsMRI connectivity with a population of alcohol-dependent subjects. We sought to investigate rsMRI connectivity with alcohol-dependent subjects (n = 22) and healthy control subjects (n = 22). Five minutes of closed-eyes rsMRI images were collected. Preliminary results indicate that compared to alcoholics, healthy controls had an increased functional connectivity in the default mode network (DMN), especially around the seed area (left posterior cingulate). Similarly, healthy controls also demonstrated stronger connectivity in the left executive control network (lECN). The regions of connectivity were, however, more diffuse in alcoholics On the other hand, alcoholics showed stronger connectivity in the visual occipital network (VON). Although in general control subjects demonstrated stronger resting state connectivity in various networks, including the default mode network (DMN), alcoholics showed more diffused connectivity. This suggests that long-term alcohol use may result in recruiting more regions of the brain in order to compensate for localized adverse effects of alcohol (Zhu et al., manuscript in preparation). Conditioned Place Preference: Classical conditioning is widely used to study motivational properties of addictive drugs in animals, but has rarely been used in humans. We established a procedure suitable for studying the neurobiology and individual determinants of conditioned place preference in humans. In a collaborative work with the University of Chicago (Harriett de Wits Lab) healthy volunteers were randomly assigned to four groups that received methamphetamine or placebo in the presence of distinctive environmental cues under paired or unpaired conditions. During each session, subjects performed tasks known to activate the ventral striatum. Tasks were performed in the presence of a distinctive context, consisting of a screen background image of a beach or mountains, accompanied by corresponding sounds. Separate groups of subjects carried out the tasks under high ($35-50) or low ($5-20) reward conditions. Within each of the two reward conditions, one group (paired), received methamphetamine (20 mg, oral) or placebo consistently associated with one of the contexts, while the other (unpaired) received drug or placebo unrelated to context. A fifth group (paired) performed the tasks with contextual cues but in the absence of monetary incentives. Before and after conditioning, participants carried out a series of forced choice tasks for the contextual cues and change of preference over time was analyzed. All paired groups showed a significant increase in preference for the drug-associated context, with a linear trend for increase in preference across the levels of reward. Preference was unrelated to subjective drug effects and did not change in the unpaired group. These data support the translational utility of our conditioning procedure for studies of reward mechanisms in humans (Mayo, et al., 2013) Medication Studies: a) Naltrexone Our section has designed fMRI tasks and analyzed the imaging data of Effect of Naltrexone on Craving and Ethanol-Induced Brain Activity, by the CATE (Dr. George) section. Positively reinforcing properties of alcohol are in part mediated by activation of the ventral striatum (VS). Alcohol-induced release of endogenous opioids is thought to contribute to this response. Preclinical studies show that the opioid antagonist naltrexone (NTX) can block this cascade, but its ability to do so in treatment seeking alcoholics has not been examined. In order to address this question we randomized sixty-three treatment-seeking alcoholics to NTX (50 mg) or placebo (PLC) daily. On day 7, participants underwent an alcohol cue reactivity session, and craving was measured. On day 9, participants received a saline infusion followed by alcohol, and also viewed affective stimuli in an MR scanner. Irrespective of medication treatment condition, and in contrast to prior findings in social drinkers, alcohol infusion did not activate the VS in the alcohol dependent patients. Unexpectedly, and across all other conditions, VS activation was greater in NTX treated patients than in the PLC group. NTX treated patients also reported increased craving in response to alcohol cue exposure compared to PLC subjects (Spagnolo et al., submitted). b) PTSD: Our section has designed fMRI imaging tasks and analyzed the imaging data of The Effect of NK1R Antagonism on Alcohol Craving and PTSD Symptoms in Alcohol Dependent Patients with PTSD, by the CATE (Dr. George) Section. Post-traumatic stress disorder (PTSD) and alcoholism are frequently co-morbid. This study was designed to determine the neural effects of neurokinin 1 (NK1) antagonist aprepitant on alcohol-dependent subjects with PTSD. Fifty-three patients with PTSD and alcoholism were admitted for 4 weeks to this experimental medicine study. In this randomized and double-blind study subjects fMRI responses to stimuli with positive or negative emotional valence were analyzed. In this study we found treatment group robustly potentiated ventromedial prefrontal cortex (mPFC) responses to aversive visual stimuli. This region of brain is critical for extinction of fear memories and in alcohol craving and relapse risk, our finding suggests that NK1 antagonism, rather than acutely attenuating stress responses, might be a useful pharmacological treatment to enhance the effect of extinction-based cue-exposure therapies (Kwako, et al., submitted manuscript). c) Varenicline: Our section has designed fMRI imaging tasks and analyzed the imaging data of as study conducted by Section on Human Psychopharmacology (Dr. Ramchandani). In this double-blind randomized study, 36 male and female heavy drinkers, aged 21-58 years, were randomized to receive Varenicline (2 mg/day) or placebo for 3 weeks. Following 2 weeks of treatment, participants underwent an fMRI scan while performing a variation of the MID task designed to evaluate the incentive salience of alcohol cues. In this version, instead of monetary rewards, participants were presented with visual cues signaling alcohol (intravenous alcohol infusion), food (highly palatable snacks) or no rewards. Results indicated that participants in the placebo group (n=17) showed significantly higher BOLD activation in striatal regions during anticipation of working for alcohol reward (alcohol cue) than the Varenicline group (n=19). The placebo group showed robust striatal activation to alcohol cue that was attenuated in the Varenicline group. A direct contrast of treatment groups showed significantly lower activation in the caudate for Varenicline compared to placebo group. There were no significant differences in response to food cues between treatment groups. The placebo group also showed striatal activation in response to notification of alcohol reward (alcohol hits), and this response was also attenuated in the Varenicline group. A direct contrast of treatment groups showed significantly lower activation in Varenicline compared to placebo group. These results indicate significant activation of striatal regions to alcohol cues and notification of alcohol reward in the placebo but not in the Varenicline group. This suggests that Varenicline may exert its effects by modulating the neural substrates underlying motivation for and incentive salience of alcohol reward in heavy drinkers (Vatsalya, et al., manuscript in preparation).
Showing the most recent 10 out of 15 publications
