Abstract

Rationale Substances of misuse (such as nicotine) are associated with increases in activation within the mesocorticolimbic
brain system, a system thought to mediate the rewarding effects of drugs of abuse. Pharmacological treatments have been designed to reduce cigarette cravings during temporary abstinence. Exercise has been found to be an effective tool for controlling cigarette cravings.
Objective The objective of this study is to assess the effect of exercise on regional brain activation in response to smoking related images during temporary nicotine abstinence.
Method In a randomized crossover design, regular smokers (n=10) undertook an exercise (10 min moderate-intensity
stationary cycling) and control (passive seating for same duration) session, following 15 h of nicotine abstinence.
Following treatments, participants entered a functional Magnetic Resonance Imaging (fMRI) scanner. Subjects viewed
a random series of smoking and neutral images for 3 s, with an average inter-stimulus-interval (ISI) of 10 s. Self-reported
cravings were assessed at baseline, mid-, and post-treatments.
Results A significant interaction effect (time by group) was found, with self-reported cravings lower during and
following exercise. During control scanning, significant activation was recorded in areas associated with reward
(caudate nucleus), motivation (orbitofrontal cortex) and visuo-spatial attention (parietal lobe, parahippocampal, and
fusiform gyrus). Post-exercise scanning showed hypoactivation in these areas with a concomitant shift of
activation towards areas identified in the ‘brain default mode’ (Broadmanns Area 10).
Conclusion The study confirms previous evidence that a single session of exercise can reduce cigarette cravings, and
for the first time provides evidence of a shift in regional activation in response to smoking cues.