Neural biomarkers for assessing different types of imagery in pictorial health warning labels for cigarette packaging: a cross-sectional study

Abstract

Objective: Countries around the world have increasingly adopted pictorial health warning labels (HWLs) for tobacco packages to warn consumers about smoking-related risks. Research on how pictorial HWLs work has primarily analysed self-reported responses to HWLs; studies at the neural level comparing the brain's response to different types of HWLs may provide an important complement to prior studies, especially if self-reported responses are systematically biased. In this study we characterise the brain's response to three types of pictorial HWLs for which prior self-report studies indicated different levels of efficacy.

Methods: Current smokers rated pictorial HWLs and then observed the same HWLs during functional MRI (fMRI) scanning. Fifty 18-50-year-old current adult smokers who were free from neurological disorders were recruited from the general population and participated in the study. Demographics, smoking-related behaviours and self-reported ratings of pictorial HWL stimuli were obtained prior to scanning. Brain responses to HWLs were assessed using fMRI, focusing on a priori regions of interest.

Results: Pictorial HWL stimuli elicited activation in a broad network of brain areas associated with visual processing and emotion. Participants who rated the stimuli as more emotionally arousing also showed greater neural responses at these sites.

Conclusions: Self-reported ratings of pictorial HWLs are correlated with neural responses in brain areas associated with visual and emotional processing. Study results cross-validate self-reported ratings of pictorial HWLs and provide insights into how pictorial HWLs are processed.

Keywords: PUBLIC HEALTH.

Figure 1

Graphical representation of the construction of each functional run. All stimuli types (graphic, suffering and symbolic) were presented in block format. Each block consisted of the presentation of five pseudorandomly selected stimuli of the appropriate type presented for 2 s each, and separated by 1 s of fixation. Block order was pseudorandomized for each functional run.

Figure 2

Behavioral effectiveness ratings of health warning labels (HWLs). All participants rated all HWLs prior to functional MRI (fMRI) scanning by responding to the question: “How much does this warning make you feel afraid?” ***Significant p<0.001 (within subjects one-tailed t test); error bars represent SEM.

Figure 3

Main effects of health warning labels on BOLD signal (graphic, suffering, symbolic) on BOLD signal. All results are thresholded at p<0.05 and corrected for family-wise error. Results are overlaid on a standard inflated brain (cortex_20484.surf.gii) for illustration purposes.

Figure 4

(A) Results from ROI analyses. (B) Adaptation of BOLD signal in ROIs across four functional scanning runs. L_AMG, left amygdala (XYZ_mni=−26, −2, −17); R_AMG, right amygdala (XYZ_mni=23, 7, −17); L_INS, left insula (XYZ_mni=−30, 30, 4); R_INS, right insula (XYZ_mni=28, 32, −8); L_OCC, left occipital cortex(XYZ_mni=−26, −94, 4); OCC, occipital cortex(XYZ_mni=−26, −94, 4; XYZ_mni=24, −90, −6); *significant p<0.05 (within subjects one-tailed t test); **significant p <0.05, ***significant p<0.001 (within subjects one-tailed t test); error bars represent SEM. ROI, regions of interest.

Figure 5

Correlation between BOLD signal in the visual association cortex (BA 18) and participant self-reported ratings of different subtypes of HWL. The site of maximal correlation between the parameter estimates for the contrast (graphic-Rest) and self-reported ratings of graphic HWL stimuli was located at (XYZ_mni=−19, −92, 20). The site of maximal correlation between the parameter estimates for the contrast (suffering-Rest) and self-reported ratings of suffering HWL stimuli was located at (XYZ_mni=−20, −88, 12). The site of maximal correlation between parameter estimates for the contrast (symbolic-Rest) and self-reported ratings of symbolic HWL stimuli was located at (XYZ_mni=−14, −92, 12). HWL, health warning label; ROI, regions of interest.