Showing papers by "Simon Zhornitsky published in 2019"

Reward sensitivity and electrodermal responses to actions and outcomes in a go/no-go task

Abstract: Skin conductance response (SCR) is used in psychophysiological research to measure the reactions of the autonomic nervous system to reward and punishment. While there is consistent evidence that SCR increases to both aversive and appetitive stimuli, it remains unclear whether SCR simply represents a general index of arousal to motivationally significant outcomes or may also differentiate action or inhibition of action that lead to such outcomes. Furthermore, individual differences in trait sensitivity to reward and punishment can influence physiological arousal during approach and avoidance behaviors. Yet, their inter-relationships have not been examined. To address these gaps, we employed a reward go/no-go task with ⅔ go and ⅓ no-go trials and an individually titrated go response window. Correct go and no-go responses were rewarded while incorrect responses were penalized. We examined whether SCR varied with outcome (win vs. loss), action (go vs. no-go), and individual differences in reward sensitivity (SR) and sex. The results showed greater SCRs to loss vs. win, to go vs. no-go success, and to go success in positive correlation with SR. Further, SCR mediated the relationship between SR and go success rate. In sex differences, men exhibited greater SCR which was more predictive of go success rate relative to women. In contrast, SCR was more predictive of no-go success rate in women. Thus, SCR varies according to behavioral contingency, outcome, sex, and reward sensitivity. These findings add to the literature by characterizing the individual and behavioral factors that may influence physiological arousal in response to salient events.

Hypothalamic Responses to Cocaine and Food Cues in Individuals with Cocaine Dependence.

Abstract: BACKGROUND Individuals with cocaine addiction are characterized by under-responsiveness to natural reinforcers. As part of the dopaminergic pathways, the hypothalamus supports motivated behaviors. Rodent studies suggested inter-related roles of the hypothalamus in regulating drug and food intake. However, few studies have investigated hypothalamic responses to drugs and food or related cues in humans. METHODS We examined regional responses in 20 cocaine-dependent and 24 healthy control participants exposed to cocaine/food (cocaine dependent) and food (healthy control) vs neutral cues during functional magnetic resonance imaging. We examined the relationship between imaging findings and clinical variables and performed mediation analyses to examine the inter-relationships between cue-related activations, tonic cocaine craving, and recent cocaine use. RESULTS At a corrected threshold, cocaine-dependent participants demonstrated higher activation to cocaine than to food cues in the hypothalamus, inferior parietal cortex, and visual cortex. Cocaine-dependent participants as compared with healthy control participants also demonstrated higher hypothalamic activation to food cues. Further, the extent of these cue-induced hypothalamic activations was correlated with tonic craving, as assessed by the Cocaine Craving Questionnaire, and days of cocaine use in the prior month. In mediation analyses, hypothalamic activation to cocaine and food cues both completely mediated the relationship between the Cocaine Craving Questionnaire score and days of cocaine use in the past month. CONCLUSIONS The results were consistent with the proposition that the mechanisms of feeding and drug addiction are inter-linked in the hypothalamus and altered in cocaine addiction. The findings provide new evidence in support of hypothalamic dysfunction in cocaine addiction.

Posterior Cingulate Cortical Response to Active Avoidance Mediates the Relationship between Punishment Sensitivity and Problem Drinking.

Abstract: Many people drink to alleviate negative affect, reflecting an avoidance strategy which can lead to alcohol misuse. Individuals with heightened sensitivity to punishment (SP) are especially susceptible to problem drinking via this maladaptive coping mechanism. As imaging studies have largely focused on sensation-seeking traits and approach behavior, the neural substrates underlying behavioral avoidance as well as their relationship with punishment sensitivity and alcohol use remain unclear. Here, we examined in humans the cerebral correlates of response inhibition to avoid a penalty in relation to both problem drinking and SP, as evaluated by the Alcohol Use Disorders Identification Test and the Sensitivity to Punishment and Sensitivity to Reward Questionnaire, respectively. Seventy nondependent female and male drinkers performed a reward go/no-go task with approximately two-thirds go and one-third no-go trials. Correct go and no-go responses were rewarded, and incorrect responses were punished. The results showed that SP and Alcohol Use Disorders Identification Test scores were both positively correlated with brain activations during response inhibition, and these activations overlapped in the posterior cingulate cortex (PCC). Thus, the PCC may represent a shared neural substrate for avoidance, punishment sensitivity, and problem drinking. Mediation analyses further suggested that PCC response to avoidance completely and bidirectionally mediated the relationship between SP and hazardous alcohol use. These findings substantiated the role of the PCC in behavioral avoidance and its link to problem drinking in punishment-sensitive nondependent drinkers.SIGNIFICANCE STATEMENT Many people drink to alleviate negative affect, reflecting an avoidance strategy that can lead to alcohol misuse. Individuals with heightened punishment sensitivity (SP) trait are particularly vulnerable to this maladaptive coping mechanism. The current study examined the neural substrates underlying behavioral avoidance and their relationship with SP and problem drinking. Using a reward go/no-go task, we showed both SP and drinking severity were positively correlated with the posterior cingulate cortex (PCC) activation during action inhibition. Thus, the PCC may represent a shared neural substrate for avoidance behavior, punishment sensitivity, and problem drinking. Further, PCC response to avoidance mediated the relationship between SP and alcohol use. These findings substantiated the neural processes linking avoidance tendency to alcohol misuse in punishment-sensitive drinkers.

Cerebral responses to self-initiated action during social interactions.

Abstract: Social interaction involves self-initiated actions that engage subjective awareness of one's own volition. Individuals with social communication needs or social anxiety find it particularly difficult to initiate social interactions. However, extant studies have not specifically addressed how perceived exclusion may influence self-initiated actions during social interaction. As a first step to address this question, we scanned 24 healthy adults participating in a Cyberball game with two fictive players. By contrasting events of observing, receiving, and initiating ball toss during a scenario of fair game (FG) and of exclusion (EX), we examined the neural correlates of self-initiated action during social interactions. Behaviorally, participants were faster in catching but slower in tossing the ball in EX compared with FG, suggesting a burden during self-initiated actions during social exclusion. Tossing versus receiving (or observing) engaged higher activity during EX than FG in the precuneus and angular gyrus, regions that have been widely implicated in theory of mind processing and social emotions. Across subjects these cortical activities correlated positively with the difference between EX and FG in the percentage of trials where participants tossed the ball back to the same player (r = 0.69, p < 0.001). Together, the results suggested that, in healthy adults, social exclusion encumbered and engaged higher posterior cortical activations during self-initiated actions. The findings may facilitate future research of neural markers of social behavioral disorders.

Cultural differences in anterior cingulate cortical response to prediction error

Abstract: Previous studies have shown cultural differences in the behavioral and neural processes of perspective taking and social emotional processing. It is less clear whether culture influences cognitive functions that do not explicitly involve face perception, group membership or social interactions. Here, we addressed this issue by imaging 29 Asians and 168 European Americans while they performed a stop signal task (SST)—a behavioral paradigm widely used to study cognitive control. In the SST participants responded to a frequent go signal and interrupted their response to an infrequent stop signal. Imaging data were processed by published routines implemented in Statistical Parametric Mapping. Behaviorally Asians and European Americans did not differ in SST performance measures, including the go and stop success rates, go and stop signal reaction time, and the sequential effect, an index of performance monitoring and behavioral adjustment. In a Bayesian model of the SST performance, we identified regional responses to stimulus prediction error (expecting go while encountering stop signal or vice versa) and showed that the dorsal anterior cingulate cortex (dACC) responded to Bayesian prediction error, a surprise signal. Importantly, compared to European Americans, Asians showed higher dACC response to prediction error in a voxelwise analysis examined at a corrected threshold. This finding suggested that, although an increased response to surprise did not impact behavioral performance, Asians appeared to exhibit higher arousal to a salient signal than European Americans, a process likely mediated by midbrain catecholaminergic system. This finding supports racial cultural differences in cognitive and affective processes that go beyond the domains of social emotions, and adds to a growing literature of cultural neuroscience.