The Relationship Between Craving And Response Inhibition In In Smokers–a Functional MRI Study

Exposure to smoking-related cues can trigger relapse in smokers attempting to maintain abstinence.This study systematically investigated effects and its underlying neural and cognitive mechanism of short-term abstinence on cue induced craving in smokers.Besides,we tried to explore the response inhibitory ability in smokers with stop signal anticipation task.We also further investigated the effects and underlying neural mechanism of smoking related cue on response inhibition in smokers after 10-hour smoking abstinence.In study one,we aimed to investigate how the smoking related cue effects smokers' craving level after 10 hour smoking abstinence using functional magnetic resonance imaging(fMRI).Twenty-seven eligible college smokers were paid to undergo fMRI scanning following at least 10 hour abstinence twice in 2-3 weeks.Abstinence was verified through piCO+ Smokerlyzer every time upon their arrival.During scanning they were asked to watch and respond to a series of photographic smoking or neutral cues.The results indicated that smoking related cues could significantly improve smokers' craving level compared to neutral cues.In the whole brain analysis,greater activation was found in response to smoking related cues compared to neutral cues in bilateral anterior cingulate cortex,left inferior frontal gyrus,bilateral insula,bilateral orbital frontal cortex,bilateral putamen and occipital lobe in smokers following 10-hour smoking abstinence.The further regions of interest analysis showed that,positive correlations between brain activation and post-scanning craving level were observed in right anterior cingulate cortex(r = 0.593,p = 0.002),right insula(r = 0.432,p = 0.031),and bilateral orbital frontal cortex(r = 0.533,p = 0.006;r = 0.585,p = 0.002),which indicated that these regions above maybe serve as the neural basis of craving.In study two,we aimed to investigate the difference of response inhibition ability between smoking students and normal contrast college students.Twenty-four smokers and twenty-nine normal college students were recruited to complete a stop signal anticipation task,a modified version of stop signal task which can separate proactive inhibition from passive inhibition.All smokers was asked to abstain from smoking for at least 10 hours.The results revealed that the categorization RT(Go RT)was modulated by stop signal probability(F(3,153)= 207.1,p = 0.000).Mixed-model analysis of variance was used with indices of proactive inhibition as within-subjects factors;groups as between-subjects factor;and reaction time as dependent measure,results showed a marginally significant main effect of group(F(1,51)= 0.295,p = 0.59),indicating the possibility of higher proactive adjustment in smokers than normal college students.Independentsample T-test showed a marginally significantly shorter stop signal response time in smokers than normal college students(t(30.9)= 1.924,p = 0.064),which means smokers has a trend of better passive response inhibition ability;Pearson correlation analysis showed no significant effect between response inhibition and trait impulsiveness in smokers(r =-0.05,p = 0.815;Motor impulsiveness: r =-0.26,p = 0.228).In study three,we aimed to further evaluate how the smoking related cue effects smokers' response inhibitory ability following at least 10-hour smoking abstinence using functional magnetic resonance imaging(f MRI).Twenty-two eligible college smokers were paid to undergo fMRI scanning following at least 10 hour abstinence twice in 2-3 weeks.Abstinence was verified through piCO+ Smokerlyzer every time upon their arrival.During scanning they were asked to complete a stop signal anticipation task following watching a series of smoking or neutral cues.The results revealed that no significant differences were observed on proactive adjustment and passive response inhibition in smokers between smoking cue and neutral cue condition.However,brain imaging results showed that 1)For proactive adjustment,greater activations were observed in smoking cue condition on “Yellow-Green_go” in right superior frontal gyrus,right posterior cingulate cortex,right supplementary motor area,right precentral gyrus,right postcentral gyrus,right precuneus cortex,and superior parietal lobule;The further regions of interest analysis showed that,positive correlations between brain activation and “YellowGreen_go” RT were observed in right superior frontal gyrus cortex(r = 0.549,p = 0.01)and right supplementary motor area(r = 0.604,p = 0.004),which indicated that these regions may exert key roles in the process of proactive response inhibition.2)For passive response inhibition,we observed that left precentral gyrus and left postcentral gyrus showed greater activation was on “Red_stop vs Green_go” in smoking cue condition than neutral cue condition.Taken these results together,we concluded that 1)Following at least 10 hour smoking abstinence,smoking related cues could further increase smokers' craving level,which was positively correlate with activation in right insula,right anterior cingulate cortex,and bilateral orbital frontal cortex,results indicated that these regions maybe serve as the neural basis of craving.2)Smokers did not differ from normal college students on proactive adjustment and passive response inhibition in behavioral performance,which was not associated with trait impulsiveness.3)Smokers' proactive adjustment and passive response inhibition were not modulated by smoking cues in behavioral performance,however,smoking cues could potentiates fMRI-BOLD activation in the regions involved with response inhibition,attention,sensory motor and somatic sensation in smokers,these finding may reflect a compensatory mechanism in brain regions,that is,smokers need to transfer more cognitive resource to complete response inhibition task under exposure of smoking related cues.