Suchismita Ray

Heart rate variability response to alcohol, placebo, and emotional picture cue challenges: effects of 0.1-Hz stimulation.

Heart rate variability (HRV) supports emotion regulation and is reduced by alcohol. Based on the resonance properties of the cardiovascular system, a new 0.1-Hz methodology was developed to present emotional stimuli and assess HRV reaction in participants (N=36) randomly assigned to an alcohol, placebo, or control condition. Blocked picture cues (negative, positive, neutral) were presented at a rate of 5 s on, 5 s off (i.e., 0.1-Hz frequency). SDNN, pNN50, and HF HRV were reduced by alcohol, compared to the placebo and control. The 0.1-Hz HRV index was diminished by alcohol and placebo, suggesting that autonomic regulation can be affected by cognitive expectancy. The 0.1-Hz HRV index and pNN50 detected changes in arousal during emotional compared to neutral cues, and the 0.1-Hz HRV index was most sensitive to negative valence. The 0.1-Hz HRV methodology may be useful for studying the intersection of cognition, emotion, and autonomic regulation.

Acute alcohol effects on repetition priming and word recognition memory with equivalent memory cues.

Acute alcohol intoxication effects on memory were examined using a recollection-based word recognition memory task and a repetition priming task of memory for the same information without explicit reference to the study context. Memory cues were equivalent across tasks; encoding was manipulated by varying the frequency of occurrence (FOC) of words in the study lists. Twenty-two female and male social drinkers (age 21-24 years) completed equivalent versions of the memory tasks in two counterbalanced sessions (alcohol challenge, no-alcohol). Alcohol and the FOC manipulation affected recollection-based memory processing, but not repetition priming. Results supported alcohols dissociative effects on memory systems.

Alcohol's Dissociation of Implicit and Explicit Memory Processes: Implications of a Parallel Distributed Processing Model of Semantic Priming

Alcohols dissociation of implicit (unintentional) and explicit (intentional) memory processes in social drinkers was examined. It was hypothesized that an alcohol challenge would lower the percentage of words recalled and result in more retroactive interference in explicit recall tasks but would not lengthen reaction time in an implicit semantic priming task involving highly semantically similar words. Men and women completed all memory tasks in each of 2 counterbalanced sessions (alcohol challenge vs. no-alcohol) separated by 1 week. Alcohol significantly degraded processing in both explicit memory tasks, yet implicit semantic priming remained intact. A parallel distributed processing model that simulates semantic memory is presented. When this system is strongly activated, it does not appear to be altered during moderate alcohol intoxication.

Gender differences in acute alcohol effects on self-regulation of arousal in response to emotional and alcohol-related picture cues.

Basic mechanisms through which men and women self-regulate arousal have received little attention in human experimental addiction research, although stress-response-dampening and craving theories suggest an important role of emotional arousal in motivating alcohol use. This study examined gender differences in the effects of acute alcohol intoxication on psychophysiological and self-reported arousal in response to emotionally negative, positive, and neutral, and alcohol-related, picture cues. Thirty-six social drinkers (16 women) were randomly assigned to an alcohol, placebo, or control beverage group and exposed to picture cues every 10 s (0.1 Hz presentation frequency). Psychophysiological arousal was assessed via a 0.1-Hz heart rate variability (HRV) index. A statistically significant beverage group-by-gender interaction effect on psychophysiological, but not self-reported, arousal was found. The 0.1-Hz HRV responses to picture cues were suppressed by alcohol only in men. This gender-specific suppression pattern did not differ significantly across picture cue types. There were no significant gender differences in the placebo or control group. Greater dampening of arousal by alcohol intoxication in men, compared with women, may contribute to mens greater tendency to use alcohol to cope with stress.

fMRI BOLD response in high-risk college students (Part 1): during exposure to alcohol, marijuana, polydrug and emotional picture cues.

AIM This functional magnetic resonance imaging (fMRI) study examined reactivity to alcohol, polydrug, marijuana and emotional picture cues in students who were referred to a college alcohol and drug assistance program. METHODS The fMRI data of 10 participants (5 females; 5 males) were collected while they viewed standardized emotional and appetitive cues. RESULTS Positive and negative emotional cues produced greater activity than neutral cues in the expected brain areas. Compared with neutral cues, alcohol cues produced greater brain activation in the right insula, left anterior cingulate, left caudate and left prefrontal cortex (Z = 2.01, 1.86, 1.82, 1.81, respectively; P < 0.05). Drug cues produced significantly greater left prefrontal activity compared with neutral cues, with polydrug cues activating the right insula and marijuana cues activating left anterior cingulate. CONCLUSIONS Students at-risk for alcohol abuse showed neural reactivity to alcohol cues in four brain regions, which is consistent with their greater use of alcohol. Insula activation to appetitive cues may be an early marker of risk for progression to alcohol/drug abuse.

Modeling Causal Relationship Between Brain Regions Within the Drug-Cue Processing Network in Chronic Cocaine Smokers.

The cues associated with drugs of abuse have an essential role in perpetuating problematic use, yet effective connectivity or the causal interaction between brain regions mediating the processing of drug cues has not been defined. The aim of this fMRI study was to model the causal interaction between brain regions within the drug-cue processing network in chronic cocaine smokers and matched control participants during a cocaine-cue exposure task. Specifically, cocaine-smoking (15M; 5F) and healthy control (13M; 4F) participants viewed cocaine and neutral cues while in the scanner (a Siemens 3 T magnet). We examined whole brain activation, including activation related to drug-cue processing. Time series data extracted from ROIs determined through our General Linear Model (GLM) analysis and prior publications were used as input to IMaGES, a computationally powerful Bayesian search algorithm. During cocaine-cue exposure, cocaine users showed a particular feed-forward effective connectivity pattern between the ROIs of the drug-cue processing network (amygdalahippocampusdorsal striatuminsulamedial frontal cortex, dorsolateral prefrontal cortex, anterior cingulate cortex) that was not present when the controls viewed the cocaine cues. Cocaine craving ratings positively correlated with the strength of the causal influence of the insula on the dorsolateral prefrontal cortex in cocaine users. This study is the first demonstration of a causal interaction between ROIs within the drug-cue processing network in cocaine users. This study provides insight into the mechanism underlying continued substance use and has implications for monitoring treatment response.

Altered Functional Connectivity Strength in Abstinent Chronic Cocaine Smokers Compared to Healthy Controls

Past research involving cocaine and resting-state functional connectivity (RSFC) has shown altered functional connectivity within the frontal and between the frontal and other cortical and subcortical brain regions in chronic users of cocaine. However, there have been discrepancies in literature regarding the relationship between RSFC between brain regions and cocaine use behavior. This study explored the RSFC between brain regions in cocaine smokers abstinent from cocaine use for 72 h and healthy controls. Also, the relationship between RSFC between brain regions and various cocaine use measures (cocaine use duration; frequency, and money spent on cocaine/week) was examined. Twenty chronic cocaine users and 17 controls completed a resting-state scan and an anatomical MPRAGE scan. Group independent component analysis performed on functional magnetic resonance imaging data identified 13 ICs pertaining to distinct resting-state networks, and group-level differences were examined. To examine inter-network functional connectivity between brain regions, these 13 ICs were divided into 61 distinct regions of interest (ROIs). Correlations were calculated between 61 ROI time series. For the ROI pairs that significantly differed from controls in connectivity strength, correlations were computed between connectivity strength and cocaine use measures. Results showed an enhanced RSFC within the sensory motor cortex and the left frontal-parietal network in cocaine users than controls. An increased inter-network RSFC between frontal-temporal and frontal-parietal brain regions, and a decreased RSFC between parietal-parietal, occipital-limbic, occipital-occipital, and occipital-parietal brain regions was found in cocaine users. This study demonstrated that intra-network connectivity strength of sensory motor cortex was negatively correlated with years of cocaine use. Inter-network connectivity strength between occipital-limbic brain regions was positively correlated with years of cocaine use, while connectivity strength within occipital brain regions was negatively related to cocaine use frequency and money spent on cocaine per week in abstinent cocaine users.

The integration of object properties

Is a complex object learned as a whole from the onset of learning, or is property recall fragmented and only integrated with repeated experience? The authors studied the recall of 3-property visual objects and found that even when property recall was low, recall coherence was high. Properties not organized as visual objects did not show high recall coherence. In addition, the authors failed to find evidence that spatial location, spatial proximity, spatial distinctiveness, distinctive motion, or perceptual grouping induced by common motion affected the integration of properties. Unitariness, temporal contiguity, and intention, however, were factors that influenced memory coherence. The authors concluded that integration occurs when properties are encoded as the constituents of a cognitive structure.

Effective Connectivity within the Mesocorticolimbic System during Resting-State in Cocaine Users.

Objective: Although effective connectivity between brain regions has been examined in cocaine users during tasks, no effective connectivity study has been conducted on cocaine users during resting-state. In the present functional magnetic resonance imaging study, we examined effective connectivity in resting-brain, between the brain regions within the mesocorticolimbic dopamine system, implicated in reward and motivated behavior, while the chronic cocaine users and controls took part in a resting-state scan by using a spectral Dynamic causal modeling (spDCM) approach. Method: As part of a study testing cocaine cue reactivity in cocaine users (Ray et al., 2015b), 20 non-treatment seeking cocaine-smoking (abstinent for at least 3 days) and 17 control participants completed a resting state scan and an anatomical scan. A mean voxel-based time series data extracted from four key brain areas (ventral tegmental area, VTA; nucleus accumbens, NAc; hippocampus, medial frontal cortex) within the mesocorticolimbic dopamine system during resting-state from the cocaine and control participants were used as input to the spDCM program to generate spDCM analysis outputs. Results: Compared to the control group, the cocaine group had higher effective connectivity from the VTA to NAc, hippocampus and medial frontal cortex. In contrast, the control group showed a higher effective connectivity from the medial frontal cortex to VTA, from the NAc to medial frontal cortex, and on the hippocampus self-loop. Conclusions: The present study is the first to show that during resting-state in abstaining cocaine users compared to controls, the VTA initiates an enhanced effective connectivity to NAc, hippocampus and medial frontal cortex areas within the mesocorticolimbic dopamine system, the brain’s reward system. Future studies of effective connectivity analysis during resting-state may eventually be used to monitor treatment outcome.

fMRI BOLD Response of High-risk College Students (Part 2): During Memory Priming of Alcohol, Marijuana and Polydrug Picture Cues

AIMS This study examined brain activity using functional magnetic resonance imaging (fMRI) and reaction time (RT) during an implicit repetition priming memory task involving alcohol, polydrug, marijuana and emotional picture cues. METHODS Participants were 5 male and 5 female high-risk college students who had just participated in a cue exposure study (Ray et al., this issue). fMRI and RT data were collected while participants made decisions about previously seen and new picture cues. RESULTS Both behavioral RT and brain imaging data revealed strong memory priming for drug and alcohol cues. Neurologically, a repetition priming effect (suppression in neural activity for repeated cues) was observed in response to alcohol cues in the left prefrontal, bilateral occipital, and bilateral occipitotemporal regions, as well as right insula and right precuneus (Z ranged from 3.03 to 3.31 P < 0.05). Polydrug cues elicited priming in the occipital and temporal areas, and marijuana cues in the occipital area. CONCLUSIONS Prefrontal and insular cortex involvement both in reactivity to alcohol cues (Ray et al., this issue) and subsequent implicit memory processing of these cues, as found in this study, suggests their potential role in the maintenance of high-risk alcohol use behaviors.