Neural correlates of cigarette health warning avoidance among smokers

Abstract

Background: Eye-tracking technology has indicated that daily smokers actively avoid pictorial cigarette package health warnings. Avoidance may be due to a pre-cognitive perceptual bias or a higher order cognitive bias, such as reduced emotional processing. Using electroencephalography (EEG), this study aimed to identify the temporal point at which smokers' responses to health warnings begin to differ.

Method: Non-smokers (n=20) and daily smokers (n=20) viewed pictorial cigarette package health warnings and neutral control stimuli. These elicited Event Related Potentials reflecting early perceptual processing (visual P1), pre-attentive change detection (visual Mismatch Negativity), selective attentional orientation (P3) and a measure of emotional processing, the Late Positive Potential (LPP).

Results: There was no evidence for a difference in P1 responses between smokers and non-smokers. There was no difference in vMMN and P3 amplitude but some evidence for a delay in vMMN latency amongst smokers. There was strong evidence for delayed and reduced LPP to health warning stimuli amongst smokers compared to non-smokers.

Conclusion: We find no evidence for an early perceptual bias in smokers' visual perception of health warnings but strong evidence that smokers are less sensitive to the emotional content of cigarette health warnings. Future health warning development should focus on increasing the emotional salience of pictorial health warning content amongst smokers.

Keywords: Health warnings; LPP; Smoking; Tobacco; vMMN.

Fig. 1

Example of the three stimulus types in the oddball paradigm.

Fig. 2

(a) Grand average waveforms for non-smokers and daily smokers for the oddball paradigm. Responses to health warnings when presented as standards, deviants and targets measured at the occipital region of interest (average of electrodes O1, Oz, O2). (b) Grand average waveforms for non-smokers and daily smokers for the oddball paradigm. Responses to health warnings and control stimuli, measured at the parietal region of interest (average of electrodes P3, Pz, P4). (c) P1 peak amplitudes and latencies in response to standard and deviant stimuli, error bars indicate the standard error of the mean. (d) Region of Interest (ROI) electrode groupings for P1, vMMN, P3 and LPP analysis.

Fig. 3

a) vMMN difference waveforms (i.e., responses to health warnings as deviants subtracted from responses to health warnings as standards) measured at the occipital region of interest (average of electrodes O1, Oz, O2), illustrating the vMMN response for non-smokers and daily smokers, shaded areas indicate the standard error of the mean. (b) P3 difference waveforms (i.e., responses to health warnings as targets subtracted from responses to health warnings as standards) measured at the parietal region of interest (average of electrodes P3, Pz, P4) illustrating the P3 response for non-smokers and daily smokers, shaded areas indicate the standard error of the mean. (c) vMMN and P3 peak amplitudes for UK and Non-UK health warnings, error bars indicate the standard error of the mean. (d) vMMN and P3 peak latencies for UK and Non-UK health warnings, error bars indicate the standard error of the mean.

Fig. 4

(a) Difference waveforms (i.e., responses to health warnings subtracted from responses to control stimuli) illustrating the LPP for non-smokers and daily smokers. Shaded areas indicated the standard error of the mean. Coloured horizontal bars indicate the epochs of significant difference (p< 0.05) between responses to health warning and control stimuli for each group. (b) Early and late LPP mean amplitudes for non-smokers and daily smokers for UK and non-UK health warnings. Error bars indicate the standard error of the mean.