Purpose: To determine whole-brain cerebral metabolic rate of oxygen (CMRO 2 ), an improved imaging approach, based on radial encoding, termed radial OxFlow (rOxFlow), was developed to simultaneously quantify draining vein venous oxygen saturation (SvO 2 ) and total cerebral blood flow (tCBF). Methods: To evaluate the efficiency and precision of the rOxFlow sequence, 10 subjects were studied during a paradigm of repeated breath-holds with both rOxFlow and Cartesian OxFlow (cOxFlow) sequences. CMRO 2 was calculated at baseline from OxFlow-measured data assuming an arterial O 2 saturation of 97%, and the SvO 2 and tCBF breath-hold responses were quantified. Results: Average neurometabolic-vascular parameters across the 10 subjects for cOxFlow and rOxFlow were, respectively: SvO 2 (%) baseline: 64.6 6 8.0 versus 64.2 6 6.6; SvO 2 peak: 70.5 6 8.5 versus 72.6 6 5.4; tCBF (mL/min/100 g) baseline: 39.2 6 3.8 versus 40.6 6 8.0; tCBF peak: 53.2 6 5.1 versus 56.1 6 11.7; CMRO 2 (mmol O 2 /min/100 g) baseline: 111.5 6 26.8 versus 120.1 6 19.6. The above measures were not significantly different between sequences (P > 0.05). Conclusion: There was good agreement between the two methods in terms of the physiological responses measured. Comparing the two, rOxFlow provided higher temporal resolution and greater flexibility for reconstruction while maintaining high SNR.

Background Inherited differences in the rate of metabolism of nicotine, the addictive chemical in tobacco, affect smoking behavior and quitting success. The nicotine metabolite ratio (NMR, 3′-hydroxycotinine/cotinine) is a reliable measure of nicotine clearance, and a well validated predictive biomarker of response to pharmacotherapy. To clarify the mechanisms underlying these associations, we investigated the neural responses to smoking cues in normal and slow nicotine metabolizers. Methods Sixty-nine treatment-seeking smokers (30 slow, 39 normal metabolizers) completed a visual cue reactivity task during functional magnetic resonance imaging on two separate occasions: once during smoking satiety and once following 24 hours of smoking abstinence. Results In whole brain analysis, normal (compared to slow) metabolizers exhibited heightened abstinence-induced neural responses to smoking cues in the left caudate, left inferior frontal gyrus, and left frontal pole. These effects were even more pronounced when extreme groups of slow and normal metabolizers were examined. Greater activation in the left caudate and left frontal pole was associated with abstinence-induced subjective cravings to smoke. Conclusion Inherited differences in rate of nicotine elimination may drive neural responses to smoking cues during early abstinence, providing a plausible mechanism to explain differences in smoking behaviors and response to cessation treatment. Normal metabolizers may benefit from adjunctive behavioral smoking cessation treatments, such as cue exposure therapy.

Psychosocial stress is considered to be an important mechanism underlying smoking behavior and relapse. Thus, understanding the effects of acute nicotine withdrawal on responses to stress is important to intervene to prevent stress-induced relapse. The current study investigated the neural correlates of psychosocial stress during acute nicotine withdrawal in chronic smokers. Thirty nine treatment-seeking smokers were randomized to one of two conditions (abstinent 24 hours (n=21) or smoking as usual (n=18)). They were then exposed to the Montreal Imaging Stress Task (MIST), a psychosocial stress task consisting of difficult mental arithmetic problems while receiving negative performance feedback while undergoing functional magnetic resonance imaging (fMRI). Subjective measures of stress increased following the MIST, compared to baseline. Whole brain between-group analysis identified significant activation clusters in four regions for the stress induction minus control contrast: inferior frontal gyrus (IFG), anterior/para cingulate cortex (ACC), precuneus, and supramarginal gyrus (SMG). In all regions, the deprived group showed significantly greater activation compared to the non-deprived group. No significant correlations were found between subjective stress and BOLD signal activation (ps>0.07). This study provides new evidence that brain regions previously shown to be predictive of relapse, such as the precuneus and IFG, display heightened neural responses to stress during nicotine deprivation. These data identify the brain regions that may be associated with withdrawal-related stress responses. Increased stress-related activation during nicotine withdrawal may identify those most vulnerable to relapse and represent a target for novel pharmacological intervention.

In smokers, neural responses to smoking cues can be sensitive to acute abstinence, but the degree to which abstinence-related cue reactivity contributes to relapse is not fully understood. This study addressed this question in a sample of 75 smokers who were motivated to quit smoking. Participants underwent blood-oxygen-leveldependent (BOLD) functional magnetic resonance imaging (fMRI) during presentation of visual smoking cues and neutral stimuli on two occasions: once during smoking satiety and once following 24-hour abstinence (order counterbalanced). Following the imaging sessions, participants received brief smoking cessation counseling prior to a short-term (7-day) quit attempt. The primary smoking cessation outcome was biochemically confirmed 7-day relapse. The secondary smoking cessation outcome measure was total number of self-reported days of abstinence. During abstinence (vs satiety), smoking cue reactivity was significantly increased only in the anterior cingulate cortex (ACC); other regions showing a cue (vs neutral) response did not exhibit an abstinence effect in the stringent whole-brain analysis. Participants who showed greater smoking cue reactivity in the ACC during acute abstinence (compared with smoking satiety) were more likely to relapse (OR = 2.10 per standard deviation increase in percent signal change [abstinence minus smoking satiety], 95% CI: 1.05 to 4.20, P = 0.036). Greater abstinence-induced change in ACC activation also predicted fewer total days abstinent (β = −0.63, 95% CI = 0.43 to 0.66, P < 0.0001). This study provides the first evidence that changes in smoking cue reactivity in the ACC during acute abstinence predict smoking relapse, thereby improving our understanding of the neurobiology of smoking cessation. KEYWORDSBOLD fMRI, short-term relapse, smoking cue reactivity | INTRODUCTIONEach year, millions of smokers try to quit, but most smokers relapse within a few days. 1 One factor that may contribute to the risk of relapse is exposure to smoking-related cues. Frequent pairings between the visual, tactile, and olfactory sensations of smoking with the rewarding effects of nicotine result in a classical conditioning effect, such that even a picture of a cigarette can evoke strong cravings in chronic smokers. 2 Among smokers who are trying to quit, these cue-induced subjective cravings can promote relapse. 3,4 Clinical trial registry identifier: NCT02837510

Many healthy women with no history of cognitive dysfunction experience subjective executive difficulties during menopause. Preclinical literature suggests latent effects of early life adversity on serotonin function may play a role in this phenomenon. However, evidence in human participants regarding the mechanisms by which loss of estradiol contributes to this vulnerability is lacking. Here we examined the impact of tryptophan depletion (TD) and adverse childhood experiences (ACE) on brain activation during a working memory task in menopausal women. We hypothesized that an interactive effect between ACE and TD would be observed when women were hypogonadal, and that treatment with estradiol would attenuate this effect. Thirty-three women underwent functional imaging at four time points (123 total scans) in this double-blind, placebo controlled, cross-over study. The effects of TD, ACE, and TD × ACE were evaluated using a voxel-wise, mixed-effects, 2 × 2 ANOVA. In the absence of exogenous estradiol, a TD by ACE interaction was observed on BOLD signal in the right DLPFC such that TD increased activation in high ACE subjects but decreased activation in low ACE subjects. While a similar interaction was observed with placebo treatment, treatment with estradiol attenuated the effects of ACE and TD such that no between or within group differences were observed. Together, these results suggest that early life adversity may have a lasting impact on serotonergic circuits underlying executive function that are unmasked by loss of estradiol during menopause.