How Does NARC Use EEG/ERP to Study Drug Addiction and Related Conditions?
NARC examined the effect of monetary reward salience on ERP components and behavior using a response inhibition paradigm in 16 healthy participants. The ERPs were recorded from 64 channels while subjects performed a warned reaction time Go/No-Go task; monetary reward (high, low, none) varied across blocks of trials. This study showed sensitivity of the P3 (but not CNV) to this sustained and graded monetary reward in young healthy adults (Goldstein et al., 2006). Validating our fMRI results (Goldstein et al., 2007), ERP results suggested a compromised P3 sensitivity to the same monetary reward in age-matched cocaine addicted individuals (Goldstein et al., 2008). More recently, with the same task, we have shown that this deficit in reward sensitivity is associated with recency of cocaine use, such that cocaine addicted individuals with less frequent recent cocaine use (i.e., more protracted withdrawal) show decreased P3 sensitivity as compared to those with more frequent recent cocaine use, whose P3 sensitivity did not differ from that of healthy controls (Parvaz et al., 2012).
In this project NARC looked at emotion processing in drug addiction by examining the late positive potential (LPP) component of ERP recorded while subjects passively viewed pleasant, unpleasant, neutral, and cocaine-related pictures. This project was carried out in collaboration with Greg Hajcak, PhD. Results showed that cocaine pictures initially elicited increased electrocortical measures of motivated attention (i.e., LPP amplitude) in ways similar to the affectively pleasant and unpleasant pictures, an effect that was no longer discernible during the late LPP window for current users. This group also exhibited deficient processing of the other emotional stimuli. Results supported a relatively early attention bias to cocaine stimuli in cocaine addicted individuals, further suggesting that recent cocaine use is characterized by deficient processing of emotional stimuli (Dunning et al., 2011).
In another related project, also in collaboration with Greg Hajcak, PhD, we explored if the explicit instruction to regulate emotion can result in emotion regulation and if it can be quantified using EEG and ERP biomarkers. Our results showed that anterior alpha ERO was sensitive to the activation of top-down prefrontal regulatory mechanisms involved in emotion regulation and the centro-parietal LPP amplitude was sensitive to the bottom-up processes of emotional valuation (Parvaz et al., 2012). These results show that ERP and ERO markers can be used to study emotion regulation in cocaine addicted individuals.
In this project, subjects are asked to make decisions on a forced-choice gambling task. Our goal here is to use ERP/EEG to assess reward prediction errors in psychopathologies of self-control.
Multimodal ERP Studies
We also used ERPs in conjunction with structural MRI to establish associations between the high temporal resolution functional biomarker of reward sensitivity (P3 amplitude) and the structural integrity of underlying brain structures. In this project, we showed that reward modulated P3 amplitude was positively correlated with gray-matter volume of orbitofrontal, dorso- and ventrolateral prefrontal cortex in healthy control subjects. In contrast, cocaine addicted individuals showed reduced structural integrity of these prefrontal brain regions, reduced P3 responses to reward, and they also failed to show the association between reward modulated P3 amplitude and gray-matter volumes of these brain regions (Parvaz, Konova et al., 2012).
EEG-Based Brain Computer Interface (BCI)
The main goal of this project is to develop and evaluate a BCI-based investigative and assessment tool that directly utilizes measurements of neural processing in real-time to decrease craving in drug addiction and anger in individuals with intermittent explosive disorder. Over the past few years, a number of BCI and neurofeedback techniques have been developed to translate deliberate neural responses into machine control; however, application to psychopathologies of decreased self-control is yet to be explored. This project is carried out in collaboration with Dennis McFarland, PhD.
Icahn School of Medicine at Mount Sinai
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