Changes in ventromedial prefrontal cortex functional connectivity are correlated with increased risk-taking after total sleep deprivation

There is evidence indicating that people are more likely to take risks when they are sleep-deprived than during resting wakefulness (RW). The ventromedial prefrontal cortex (vmPFC) could have a crucial psychophysiological role in this phenomenon. However, the intrinsic patterns of functional organization of the human vmPFC and their relationship with risk-taking during sleep deprivation (SD) are unclear. This study investigated the relationship between functional connectivity in the vmPFC and cerebral cortex and the risk-taking tendency after SD. The study participants were 21 healthy college students who underwent functional magnetic resonance imaging twice in the resting state, once during RW and once after 36 h of SD. The vmPFC was analyzed bilaterally for functional connectivity between the regions of interest. Correlation analysis was performed to evaluate changes in functional connectivity between the vmPFC and the cerebral cortex and risk-taking before and after SD. A single night of SD produced a definite deficit in functional connectivity between the vmPFC and thalamus bilaterally and an increase in functional connectivity between the vmPFC and dorsolateral prefrontal cortex (dlPFC) and the parietal lobe. We also found that the likelihood of risk-taking was positively correlated with increased functional connectivity between the vmPFC and dlPFC and negatively correlated with decreased functional connectivity between the vmPFC and thalamus bilaterally. These results demonstrate that lack of sleep substantially impairs functional connectivity between the vmPFC and the cerebral cortex, which in turn predicts the risk-taking behavior found after SD.

Transcranial Direct Current Stimulation Applied to the Dorsolateral and Ventromedial Prefrontal Cortices in Smokers Modifies Cognitive Circuits Implicated in the Nicotine Withdrawal Syndrome

BACKGROUND

The nicotine withdrawal syndrome remains a major impediment to smoking cessation. Cognitive and affective disturbances are associated with altered connectivity within and between the executive control network, default mode network (DMN), and salience network. We hypothesized that functional activity in cognitive control networks, and downstream amygdala circuits, would be modified by application of transcranial direct current stimulation (tDCS) to the left (L) dorsolateral prefrontal cortex (dlPFC, executive control network) and right (R) ventromedial prefrontal cortex (vmPFC, DMN).

METHODS

A total of 15 smokers (7 women) and 28 matched nonsmokers (14 women) participated in a randomized, sham-controlled, double-blind, exploratory crossover study of 3 tDCS conditions: anodal-(L)dlPFC/cathodal-(R)vmPFC, reversed polarity, and sham. Cognitive tasks probed withdrawal-related constructs (error monitoring, working memory, amygdalar reactivity), while simultaneous functional magnetic resonance imaging measured brain activity. We assessed tDCS impact on trait (nonsmokers vs. sated smokers) and state (sated vs. abstinent) smoking aspects.

RESULTS

Single-session, anodal-(L)dlPFC/cathodal-(R)vmPFC tDCS enhanced deactivation of DMN nodes during the working memory task and strengthened anterior cingulate cortex activity during the error-monitoring task. Smokers were more responsive to tDCS-induced DMN deactivation when sated (vs. withdrawn) and displayed greater cingulate activity during error monitoring than nonsmokers. Nicotine withdrawal reduced task engagement and attention and reduced suppression of DMN nodes.

CONCLUSIONS

Cognitive circuit dysregulation associated with nicotine withdrawal may be modifiable by anodal tDCS applied to L-dlPFC and cathodal tDCS applied to R-vmPFC. tDCS may have stronger effects as a complement to existing therapies, such as nicotine replacement, owing to possible enhanced plasticity in the sated state.