The final sample (n = 18) was 61.1% female (n = 11). Reported racial/ethnic group membership was 77.8% Caucasian (n = 14), 16.7% African-American (n = 3), and 5.6% Asian-American (n = 1). Mean age was 28.6 years (SD = 7.5). The sample reported smoking a mean of 17.8 cigarettes/day (SD = 2.8) for 11.6 years (SD = 6.7). Mean FTND score was 4.4 (SD = 1.4) suggesting the sample was moderately nicotine dependent. At screening, mean expired breath CO concentration was 26.9 (SD = 13.4) whereas mean salivary cotinine was 225.7 ng/ml (SD = 160.6).
Expired breath CO concentrations indicated compliance with study requirements. In the satiated condition, mean CO level (ppm) was 24.6 (SD = 10.7) whereas in the 24-hr abstinent condition mean CO was 2.4 (SD = 1.4). Mean CO 24 hrs after the abstinent fMRI session was 1.9 (SD = 2.3).
The results of salivary nicotine analyses were consistent with CO results and also indicative of compliance. In the satiated and abstinent conditions, mean salivary nicotine (ng/ml) was 443.5 (SD = 351.5) and 20.7 (SD = 21.8), respectively. Mean salivary nicotine 24 hrs after the abstinent fMRI session was 22.0 (SD = 23.8), again indicating compliance with the instruction to maintain abstinence for 24 hrs following the abstinent condition scanning session.
Twenty-four hour abstinence from smoking resulted in significant withdrawal symptoms (see ). Compared to the satiated condition, abstinence significantly increased prescan craving, negative affect, hunger, somatic symptoms and habit withdrawal, but significantly decreased arousal.
Figure 2 Pre-scan measures of withdrawal symptoms as reported on the Shiffman-Jarvik Withdrawal Questionnaire (SJWQ). Compared to the satiated condition, abstinence increased pre-scan craving [F(1,17) = 102.67, p < .001], negative affect [F(1,17) = 11.65, (more ...)
Craving scores measured during the cue-viewing task were not available for one participant due to technical problems. Across conditions, craving for cigarettes was greater following blocks of smoking cues as compared to control cues [F(1,16) = 6.95, p = .018]. Moreover, across cue types, abstinence increased ratings of craving during the cue viewing task [F(1,16) = 5.42, p = .033]. The Cue × Condition interaction was not significant.
Across satiated and abstinent conditions, smoking cues elicited greater activation than control cues in right paracentral lobule (BA 5), right cuneus (BA 19), bilateral hypothalamus, left middle occipital gyrus (BA 19), right superior and medial frontal gyri (BA 6) and left insula (see Table S1 and Figure S1). Control cues did not elicit greater activation than smoking cues in any brain regions.
The effect of smoking cues (compared to control cues) on brain activation was evaluated separately for each smoking condition (see and ). Following 24-hr abstinence, greater activation was found in response to smoking cues compared to control cues in parietal regions including right superior parietal lobule and bilateral precuneus (BA 7); bilateral posterior cingulate (BA 31); striatum including bilateral putamen and internal capsule; left superior frontal gyrus (BA 8/9); left occipital cortex (BA 19); right dorsal thalamus; bilateral cerebellum; and central cortical regions including right pre/postcentral gyrus and bilateral paracentral lobule (BA 4). In contrast, no smoking cue > control cue activations were observed in the satiated condition.
Brain areas of significant activation for smoking cues > control cues as measured by BOLD-fMRI in abstinent and satiated conditions
Figure 3 BOLD response to smoking cues versus control cues was greater following 24-hr abstinence in right paracentral lobule (PcL; BA 4), right posterior cingulate gyrus (PCG; BA 31), bilateral precuneus (Precun; BA 7), left superior frontal gyrus (SFG; BA 8), (more ...)
When activation was contrasted between the two conditions, 24-hr abstinence resulted in greater activation than satiety (see and ) in left superior frontal gyrus (BA 6), right superior parietal lobule (BA 7), right posterior cingulate gyrus (BA 31), bilateral occipital cortex (BAs 19 and 30), a region on the boundary between right pre- and post-central gyrus (BA 1/2/3/4), and right caudate/internal capsule. There were no regions in which smoking cue activation was greater in the satiated condition compared to the abstinent condition.
Brain areas of significant activation for smoking cues > control cues as measured by BOLD-fMRI when comparing abstinent versus satiated condition
fMRI/Self-Report Craving Correlations
Correlations between pre-scan craving (as measured by the SJWQ) and smoking cue activation (smoking cue > control cue) were examined separately for each smoking condition. In the abstinent condition, significant positive correlations between craving and smoking cue activation were observed in right frontal regions (BA 6/32/10) including a relatively large cluster in the superior frontal gyrus (BA 6). Significant correlations were also observed in right occipital cortex (BA 18/19), right inferior parietal cortex (BA 40), left postcentral gyrus (BA 1/2/3), and cerebellum (see and ). Negative correlations were not observed. Neither positive nor negative correlations between pre-scan craving and smoking cue activation were observed in the satiated condition.
Brain areas for smoking cues > control cues as measured by BOLD-fMRI that are significantly correlated with measures of pre-scan craving
Figure 4 A significant positive correlation between pre-scan craving and smoking cue > control cue activation was observed in right superior frontal gyrus (SFG; BA 6) during the abstinent condition (R2=0.59), but not in the satiated condition (R2=0.08). (more ...)
Correlations between cue-provoked craving (craving following smoking cue blocks – control cue blocks) and smoking cue activation were similarly examined but no significant correlations, positive or negative, were observed in either abstinent or satiated conditions.