Looking for traces of phylogenetic fears: Differences in EEG slow oscillations and complexity between spider- and flight phobic subjects1

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. Furthermore 1 This study was funded by Spanish Ministry of Science and Technology (Grants SEJ2005-00899/ PSIC and SEJ2006-14301/PSIC). 2 Correspondence: Departament de Psicologia. Universitat de les Illes Balears. Edifici Guillem Cifre de Colonya. Carretera de Valldemossa km. 7.5, 07122 Palma de Mallorca (España). E-mail: [email protected]