Institute of Behavioural Sciences, Semmelweis University Budapest, Hungary
Department of Psychology, Károli Gáspár University, Budapest, Hungary

Previously we have reported correlations between sleep-related corticothalamic resonance and general fluid intelligence. This could be explained by morphological brain features corresponding with different IQ measures. However, there is indirect evidence for the relationship between cerebral cortical volume and the personality trait known as self-directedness (SD). SD is a personality trait reflecting the ability to define, set and pursue meaningful goals. Based on the previous reasoning we hypothesized that subjects with equal level of IQ, but different level of SD would differ in sleep-related corticothalamic resonance. Seventeen subjects with IQ above 135, with either low- or high SD were assessed by polysomnography and quantitative EEG on two consecutive nights. FFT based amplitude spectra of the slow oscillation (0.5-1.25 Hz), as well as slow- and fast sleep spindle density were determined for each derivation. Compared to the low SD group high SD subjects were characterized by higher relative amplitude spectra of the slow oscillation in derivation Fp l and also by a higher fast sleep spindle density over the left hemisphere (F7, T3, T5, P3). This results support the view that beside the individual differences in the cognitive domain some core personality dimensions are also reflected in corticothalamic resonance during sleep.