Resting-State Connectivity in Former, Current, and Never Smokers.

INTRODUCTION: Understanding the neural mechanisms that support successful smoking cessation is vital to the development of novel treatments for nicotine dependence. METHOD: To this end, we compared resting-state functional connectivity across three smoking groups: current, never, and former smokers. We used an independent component analysis (ICA) that allowed us to compare differences in intrinsic, large-scale networks across our groups. Using this technique, we were able to compare group differences across resting-state networks without the requirement of identifying coordinate-based regions of interest. RESULTS: Overall, the ICA resulted in networks that were largely consistent with previous reports, including bilateral executive control networks, salience, and a default mode network. Group comparisons among the three groups revealed differences in three networks including sensorimotor, dorsal attention, and default mode networks, with differences localized to pre/postcentral gyrus, lateral occipital cortex, and superior parietal lobe. In all regions showing a difference, current smokers showed increased network amplitude compared to former and never smokers. CONCLUSION: Although some theoretical models of recovery have suggested an important role of frontal cortex and cognitive control, the current results seem to suggest that reductions in posterior regions including superior parietal lobe and somatosensory cortex may play a key role in maintaining long-term abstinence from cigarettes. IMPLICATIONS: The submitted research is a novel contribution to the study of successful nicotine abstinence, in part, because it includes individuals who have successfully overcome nicotine dependence. The use of ICA allowed for examination of large-scale resting-state networks throughout the brain without the need for specifying numerous regions of interest. This research supports the view that overcoming nicotine dependence may depend on reducing spontaneous activity in posterior regions of the brain rather than solely enhancing frontal control.

Neural correlates of response inhibition in current and former smokers.

Loss of behavioral control is a hallmark of addiction. Individual differences in basic cognitive processes such as response inhibition may be important for interrupting automatic behaviors associated with smoking and supporting prolonged abstinence. To examine how response inhibition and error monitoring processes differ as a function of smoking status, current smokers, former smokers and never smokers (N=126) completed a simple Go/No-Go task while undergoing functional magnetic resonance imaging. All groups performed similarly on the task and similarly engaged the inferior frontal gyrus and dorsal anterior cingulate cortex, regions traditionally associated with response inhibition and error monitoring, respectively. During response inhibition (i.e., Correct Rejects>Hits contrast), overall group differences emerged in the recruitment of the cerebellum, while individual group differences in error monitoring (False Alarms>Hits contrast) were seen for regions of the parietal lobe and thalamus (current smokers>former smokers), as well as regions of the bilateral cerebellum, parahippocampal gyrus and superior parietal lobe (i.e., ever smokers>never smokers). We discuss how our results replicate two previous large-sample studies that used the same Go/No-Go task and review these data in terms of network models of inhibitory and error monitoring abnormalities in addiction.

Voluntary modulation of anterior cingulate response to negative feedback.

Anterior cingulate and medial frontal cortex (dACC/mFC) response to negative feedback represents the actions of a generalized error-monitoring system critical for the management of goal-directed behavior. Magnitude of dACC/mFC response to negative feedback correlates with levels of post-feedback behavioral change, and with proficiency of operant learning processes. With this in mind, it follows that an ability to alter dACC/mFC response to negative feedback may lead to representative changes in operant learning proficiency. To this end, the present study investigated the extent to which healthy individuals would show modulation of their dACC/mFC response when instructed to try to either maximize or minimize their neural response to the presentation of contingent negative feedback. Participants performed multiple runs of a standard time-estimation task, during which they received feedback regarding their ability to accurately estimate a one-second duration. On Watch runs, participants were simply instructed to try to estimate as closely as possible the one second duration. On Increase and Decrease runs, participants performed the same task, but were instructed to "try to increase [decrease] their brain's response every time they received negative feedback". Results indicated that participants showed changes in dACC/mFC response under these differing instructional conditions: dACC/mFC activity following negative feedback was higher in the Increase condition, and dACC activity trended lower in the Decrease condition, compared to the Watch condition. Moreover, dACC activity correlated with post-feedback performance adjustments, and these adjustments were highest in the Increase condition. Potential implications for neuromodulation and facilitated learning are discussed.

The role of verbal short-term memory in task selection: how articulatory suppression influences task choice in voluntary task switching.

The roles of verbal short-term memory (vSTM) in task selection and task performance processes were examined when individuals were asked to voluntarily choose which of two tasks to perform on each trial randomly. Consistent with previous voluntary task-switching (VTS) research, we hypothesized that vSTM would support random task selection by maintaining a sequence of previously executed tasks that would be used by a representativeness heuristic. Furthermore, because using a representativeness heuristic requires sufficient time for updating and comparison processes, we expected that vSTM would have a greater effect on task selection when more time was available. Participants completed VTS under concurrent articulatory suppression and foot tapping at short and long response-to-stimulus intervals (RSIs). Task selection in VTS was more repetitive under suppression than under foot tapping, but this effect did not vary with RSI, suggesting that vSTM does not maintain the sequence of executed tasks to guide task selection. Instead, vSTM is critical for maintaining the intended task and ensuring that it is carried out. In contrast to the finding that a working memory load impairs task performance, we found no difference in reaction times and no switch costs between suppression and foot-tapping conditions, suggesting that vSTM is not critical for task performance.