Sensory Cortical Processing and the Biological Basis of Personality Ulrich Hegerl, Jtirgen Gallinat, and Dieter Mrowinski Action-oriented personality traits such as sensation seeking, extraversion, and impulsivity have been related to a pronounced amplitude increase of auditor)' evoked scalp potentials with increasing stimulus intensity. Dipole source analysis represents a crucial methodological progress in this context, because overlapping subcomponents of the scalp potentials can be separated and can be related to their generating cortical structures. In a stud)' on 40 health), subjects, it was found that sensation seeking is clearly related to the auditor)' evoked response pattern (N1/P2-component, stimulus intensities: 60, 70, 80, 90, 100 dB SPL) of the superior temporal plane including primary auditor)' cortex, but not to that of secondary auditor)' areas in the lateral temporal cortex. These results support the concept that the serotonergic brain system, which is supposed to modulate sensory processing in primary auditory cortices, is an important factor underlying individual differences in sensation seeking. Key Words: Auditory evoked potentials, auditory cortex, dipole, sensation seeking, personal- ity, serotonin Introduction Knowledge on the neurobiological basis of personality traits is of importance for the understanding of personality disorders or psychopathological states. High sensation seeking or extraversion has been interpreted as the autore- gulative behavioral response to a low tonic activity of an unspecific activating system. According to this concept, sensation seekers and extraverts are creating for themselves a stimulating environment, which elevates their activation level to a more optimal range (Zuckerman 1979, 1990; Eysenck 1967); however, this activation system has not been specified. Besides the reticular formation in the brain- stem, different monoaminergic systems have been dis- From the Department of Psychiatry, Laboratory of Clinical Psychophysiology (UH, JG), and ENT Clinic (DM) Freie Universit~it Berlin, Berlin, Germany. Address reprint requests to PD Dr. meal. Ulrich Hegerl, Psychiatrische Klinik der Ludwig-Maximilians-Universit~itMtinchen, Nupbaumstr. 7. D-80336 Miinchen. Received December 9, 1993; revised May 5, 1994. © 1995 Society of Biological Psychiatry cussed in this context as possible unspecific activating sys- tems (Zuckerman 1990). Relationships have been reported between personality and the stimulus intensity dependence of cortical sensory processing. Sensory processing was studied with scalp recordings of the electric brain potentials evoked by short sensory stimuli. Within the augmenting/reducing concept developed by Buchsbaum and Silverman (1968), it was found that subjects showing large increases of these sensory evoked potentials as a function of increases in stimulus intensity (augmenting) also have higher scores on sensation seeking (for review see Carrillo-de-la-Pena 1992, Zucker- man 1990) and on conceptually related personality traits such as extraversion and impulsivity (Barratt et al 1987; Friedman and Meares 1979; Soskis and Shagass 1974) than subjects with small increases or even amplitude decreases (reducing). Most consistent are the results concerning sen- sation seeking, which is characterized by the need for var- ied, novel, complex, and intensive sensations and experi- 0fX)6 3223/95/$09.5(l SSDI 0006-3223(94)00177-5