EEG Source Reconstruction in Male Nonsmokers after Nicotine Administration during the Resting State

Abstract

Modern psychopharmacological research in humans focuses on how specific psychoactive molecules modulate oscillatory brain activity. We present state-of-the-art EEG methods applied in a resting-state drug study. Thirty healthy male nonsmokers were randomly allocated either to a nicotine group (14 subjects, 7 mg transdermal nicotine) or a placebo group (16 subjects). EEG activity was recorded in eyes-open (EO) and eyes-closed (EC) conditions before and after drug administration. A source reconstruction (minimum norm algorithm) analysis was conducted within a frequency range of 8.5-18.4 Hz subdivided into three different frequency bands. During EO, nicotine reduced the power of oscillatory activity in the 12.5- to 18.4-Hz frequency band in the left middle frontal gyrus. In contrast, in the EC condition, nicotine reduced the power in the 8.5- to 10.4-Hz frequency band in the superior frontal gyri and in the 10.5- to 12.4-Hz and 12.5- to 18.4-Hz frequency bands in the supplementary motor areas. In summary, nicotine reduced the power of the 12.5- to 18.4-Hz band in the left middle frontal gyrus during EO, and it reduced power from 8.5 to 18.4 Hz in a brain area spanning from the superior frontal gyri to the supplementary motor areas during EC. In conclusion, the results suggest that nicotine counteracts the phenomenon of anteriorization of α activity, hence potentially increasing the level of vigilance.

Encephalography Connectivity on Sources in Male Nonsmokers after Nicotine Administration during the Resting State

“…Therefore, our nicotine-induced increase of VL phase-amplitude CFC during EC could indicate that nicotine actually altered the neural signatures of vigilance. Corroborating the validity of our VL phase-amplitude CFC results, the effect of nicotine was found occipito-parietally despite the fact that nicotine-induced changes in the power spectrum were found frontally [20]. Furthermore, we conducted a Kullback-Leibler divergence analysis (not published) and found comparable results with our VL analysis.…”

“…Instead, during EO the brain activity is possibly already in a state of high vigilance. As a last point, note that the 5 general limitations mentioned in Ranzi et al [20] apply also to the present analyses (e.g. lack of blood sample, using standardized frequency ranges, etc.…”

“…We have previously shown in the same dataset as used here that nicotine increased the neural signatures of vigilance during EC activity [20]. The analysis presented here offers a new complementary perspective of the way the molecule modifies oscillatory brain activity.…”

“…As previously reported [20], a 2-way ANOVA was performed with the between-subject factor drug (either placebo or nicotine) and the within-subject factor time (PRE and POST), both for cardiovascular measures and mood ratings. We found a significant interaction between the 2 factors regarding systolic blood pressure (F 1, 28 = 4.33, p < 0.047), which meant a stronger decrease of systolic blood pressure under placebo as compared to nicotine.…”