International Journal of Clinical and Health Psychology, 2009, 9, 37-49. Looking for traces of phylogenetic fears: Differences in EEG slow oscillations and complexity between spiderand flight phobic subjects. Xavier Bornas (Universitat de les Illes Balears, Spain), Andreas Mühlberger (University of Wurzburg, Germany), Jordi Llabrés (Universitat de les Illes Balears, Spain), Georg Wiedemann (University of Frankfurt, Germany), and Paul Pauli (University of Wurzburg, Germany)
Phylogenetic fears involve stimuli representing a real or potential threat to the species¿ evolutionary ancestors. We tested whether individuals with a phylogenetic fear (spider phobics, n = 17) differed in EEG general activity (delta band power) of the oldest brain system and in complexity from individuals with a non-phylogenetic fear (flight phobics, n = 15) during eyes open and eyes closed resting states. Delta band power was higher during the eyes-closed condition at central sites FZ, CZ and PZ as well as at frontal sites FP1, FP2, and F4. No differences existed in the upper bands theta, alpha, and beta. The EEG complexity was significantly lower among individuals with spider phobia. Differences were found under both eyes closed and eyes open conditions at FZ, F4, CZ, and C4. Lower complexity was also found at PZ and O2 during eyes open. In general, the results of this ex post facto study lend support to the hypothesized prevalence of slow oscillations in phylogenetic fears. Furthermorethese results show that the EEG output of spider phobic participants is less complex than the output from flight phobic participants. The prevalence of slow brain oscillations and the lowered EEG complexity could be interpreted as traces of phylogenetic fears.