Alpha oscillations in response to affective and cigarette-related stimuli in smokers

Abstract

Introduction: The presence of cigarette-related cues has been associated with smoking relapse. These cues are believed to activate brain mechanisms underlying emotion, attention, and memory. Electroencephalography (EEG) alpha desynchronization (i.e., reduction in alpha power) has been suggested to index the engagement of these mechanisms. Analyzing EEG alpha desynchronization in response to affective and smoking cues might improve our understanding of how smokers process these cues, and the potential impact of this processing on relapse.

Methods: Before the start of a medication-assisted cessation attempt, we recorded EEG from 179 smokers during the presentation of neutral, pleasant, unpleasant, and cigarette-related pictures. Wavelet analysis was used to extract EEG alpha oscillations (8-12 Hz) in response to these pictures. Alpha oscillations were analyzed as a function of picture valence and arousal dimensions.

Results: Emotional and cigarette-related stimuli induced a higher level of alpha desynchronization (i.e., less power in the alpha frequency band) than neutral stimuli. In addition, the level of alpha desynchronization induced by cigarette-related stimuli was similar to that induced by highly arousing stimuli (i.e., erotica and mutilations).

Conclusions: These results suggest that, for smokers, cigarette-related cues are motivationally significant stimuli that may engage emotional, attentional, and memory-related neural mechanisms at a level comparable to that seen in response to highly arousing stimuli. This finding suggests that activation of emotional, attentional, and memory-related brain mechanisms may be an important contributor to cue-induced smoking relapse.

Figure 1.

Picture-induced alpha ERD in the parieto-occipital area. Alpha ERD is defined as a decrease in alpha power in response to a stimulus and is quantified using a dB scale. Hence, larger decreases in alpha power are indicative of greater levels of alpha ERD. The box indicates the time window used to compute the alpha ERD for each category that was used in the statistical analyses. The head inset indicates the electrodes in the parieto-occipital area that were used to compute the alpha ERD. The vertical dashed line at 0ms indicates the onset of the picture stimulus.

Figure 2.

Emotional and cigarette-related stimuli induced greater alpha ERD than neutral stimuli. Values plotted depict the mean changes in alpha power between a prestimulus baseline and a window lasting 400–800ms after stimulus onset, where larger decreases in alpha power are indicative of greater levels of alpha ERD. Error bars are the standard errors of means. *Indicates a significant difference from neutral pictures (p < .001 after adjusting for multiple comparisons).

Figure 3.

Significant correlation between alpha ERD magnitude and the normative arousal levels of the stimulus subcategories. Mean normative arousal levels for each stimulus category are plotted on the x-axis. Mean changes in alpha power from a prestimulus baseline and a window lasting 400–800ms after stimulus onset are plotted on the y-axis, where larger decreases in alpha power are indicative of greater levels of alpha ERD. The diagonal line indicates the least-squares regression line from a model using the normative arousal ratings to predict the picture-induced changes in alpha power. Circles indicate groupings of Stimulus subcategories into overall categories of low, medium, and high arousal. Picture subcategories are indicated by the following abbreviations: NEUo = neutral objects; NEUp = neutral people; PLEo = pleasant objects; SAD = sad scenes; ROM = romantic scenes; UNPo = unpleasant objects; ERO = erotica; MUT = mutilations.

Figure 4.

Cigarette-related stimuli induced comparable alpha ERD to highly arousing emotional stimuli. Mean changes in alpha power from a prestimulus baseline and a window lasting 400–800ms after stimulus onset are plotted as a function of stimulus category, where Low, Medium, and High refer to pictures categorized on the basis of normative arousal ratings and Cigarette indicates cigarette-related pictures. Larger decreases in alpha power are indicative of greater levels of alpha ERD. Cigarette-related stimuli induced greater alpha ERD than low- and medium-arousing stimuli, but a similar level of alpha ERD to highly arousing stimuli. *Indicates a significant difference from cigarette-related stimuli (p < .001, adjusted for multiple comparisons).