Neural mechanisms underlying visual attention to health warnings on branded and plain cigarette packs

Abstract

Aims: To (1) test if activation in brain regions related to reward (nucleus accumbens) and emotion (amygdala) differ when branded and plain packs of cigarettes are viewed, (2) test whether these activation patterns differ by smoking status and (3) examine whether activation patterns differ as a function of visual attention to health warning labels on cigarette packs.

Design: Cross-sectional observational study combining functional magnetic resonance imaging (fMRI) with eye-tracking. Non-smokers, weekly smokers and daily smokers performed a memory task on branded and plain cigarette packs with pictorial health warnings presented in an event-related design.

Setting: Clinical Research and Imaging Centre, University of Bristol, UK.

Participants: Non-smokers, weekly smokers and daily smokers (n = 72) were tested. After exclusions, data from 19 non-smokers, 19 weekly smokers and 20 daily smokers were analysed.

Measurements: Brain activity was assessed in whole brain analyses and in pre-specified masked analyses in the amygdala and nucleus accumbens. On-line eye-tracking during scanning recorded visual attention to health warnings.

Findings: There was no evidence for a main effect of pack type or smoking status in either the nucleus accumbens or amygdala, and this was unchanged when taking account of visual attention to health warnings. However, there was evidence for an interaction, such that we observed increased activation in the right amygdala when viewing branded as compared with plain packs among weekly smokers (P = 0.003). When taking into account visual attention to health warnings, we observed higher levels of activation in the visual cortex in response to plain packaging compared with branded packaging of cigarettes (P = 0.020).

Conclusions: Based on functional magnetic resonance imaging and eye-tracking data, health warnings appear to be more salient on 'plain' cigarette packs than branded packs.

Keywords: Attention; eye-tracking; fMRI; health warnings; plain packaging; policy; smoking; standardised packaging; tobacco; tobacco control.

Figure 1

Examples of branded and plain stimuli. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 2

Blood oxygen level‐dependent (BOLD) activation for the confirmatory analysis examining the effect of the task (i.e. branded and plain packs versus control stimuli). Coordinates represent Z coordinates in Montreal Neurological Institute‐152 (MNI‐152) coordinate space. The colour bar represents significance levels with the intensity representing the P‐values

Figure 3

Mean number of fixations on branding and health warnings on branded and plain packs among non‐smokers, weekly smokers and daily smokers. Error bars represent adjusted 95% confidence intervals

Figure 4

(a) Blood oxygen level‐dependent (BOLD) activation in the right amygdala for the comparison plain > branded controlling for fixations to health warnings (i.e. eye‐tracking weighted analysis) among weekly smokers and (b) weekly smokers compared with daily smokers. Coordinates represent coordinates in Montreal Neurological Institute‐152 (MNI‐152) coordinate space. The red region shows the extent of the 30% threshold applied to the probabilistic right amygdala mask and the blue region is the activated cluster. (c) Relative BOLD signal change in the activated region of the right amygdala for the equally weighted analysis for the comparison branded > plain for weekly smokers. (d) Relative BOLD signal change in the activated region of the right amygdala for the equally weighted analysis for the comparison weekly smokers > daily smokers. Error bars represent the standard error of the mean

Figure 5

(a) Blood oxygen level‐dependent (BOLD) activation for the equally weighted analysis for the comparison branded > plain. Differences between conditions were assessed using permutation testing, and the levels of evidence presented using family‐wise error (FWE)‐corrected P‐values. Coordinates represent Z coordinates in Montreal Neurological Institute‐152 (MNI‐152) coordinate space. The colour bar represents significance levels with the intensity representing the P‐values. (b) Group average BOLD percentage signal difference extracted for plain and branded packaging types from the activated cluster (see Fig. 5a) for non‐smokers, weekly smokers and daily smokers. Error bars represent the standard error of the mean

Figure 6

(a) Difference in relationship between blood oxygen level‐dependent (BOLD) and visual attention depending on packaging type. The image represents the comparison plain > branded for the eye‐tracking weighted analysis. The intensity levels (and colour bar) represent inference levels determined with permutation testing (see Fig. 5 legend for details). Coordinates represent Z coordinates in Montreal Neurological Institute‐152 (MNI‐152) coordinate space. (b) Group average beta weights (i.e. for the individual eye‐tracking weighted contrasts for plain and branded packaging) from the activated cluster (see Fig. 6a) for non‐smokers, weekly smokers and daily smokers. Error bars represent the standard error of the mean