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  • Merz, C. J., Tabbert, K., Schweckendiek, J., Klucken, T., Vaitl, D., Stark, R., & Wolf, O. T. (2010). Investigating the impact of sex and cortisol on implicit fear conditioning with fMRI. Psychoneuroendocrinology, 35(1), 33–46. https://doi.org/10.1016/j.psyneuen.2009.07.009

    Fear conditioning is influenced by stress but opposing effects in males and females have often been reported. In a previous human functional magnetic resonance imaging (fMRI) study, we observed acute effects of the stress hormone cortisol on prefrontal structures. Men showed evidence for impaired fear conditioning after cortisol treatment, while the opposite pattern was found for women. In the current experiment, we tested whether similar sex-dependent effects would occur on the neural level if contingency awareness was prevented experimentally to investigate implicit learning processes. A differential fear conditioning experiment with transcutaneous electrical stimulation as unconditioned stimulus and geometric figures as conditioned stimuli (CS) was conducted. One figure was always paired (CS+), whereas the other (CS-) was never paired with the UCS. Thirty-nine (19 female) subjects participated in this fMRI study, receiving either placebo or 30 mg cortisol (hydrocortisone) before conditioning. Dependent variables were skin conductance responses (SCRs) and neural activity (BOLD signal). In line with prior findings in unaware participants, no differential learning could be observed for the SCRs. However, a sex x cortisol interaction was detected with a reduced mean response to the CS after cortisol treatment in men, while the opposite pattern was observed in women (enhanced mean SCR under cortisol). In the contrast CS+ minus CS-, neural activity showed a sex x cortisol interaction in the insula and further trends in the hippocampus and the thalamus. In these regions, cortisol reduced the CS+/CS- differentiation in men but enhanced it in women. In contrast to these sex specific effects, differential amygdala activation was found in the placebo group but not in the cortisol group, irrespective of sex. Further, differential neural activity in the amygdala and thalamus were positively correlated with the SCRs in the placebo group only. The present study in contingency unaware participants illustrates that cortisol has in some brain regions sex specific effects on neural correlates of emotional learning. These effects might translate into a different vulnerability of the two sexes for anxiety disorders.

  • Hamm, A. O., & Vaitl, D. (1996). Affective learning: awareness and aversion. Psychophysiology, 33(6), 698–710. https://doi.org/10.1111/j.1469-8986.1996.tb02366.x

    In two studies, we investigated the influence of aversive and nonaversive reinforcers on startle reactivity, visceral responses, and self-report during Pavlovian conditioning. Furthermore, we assessed how awareness of the stimulus contingencies affect conditioned discrimination in the different response systems. Conditioned potentiation of the startle response was only observed in the context of aversive learning. Moreover, blink potentiation occurred without awareness of the relationship between the conditioned and unconditioned stimulus. In contrast, skin conductance conditioning was independent of the aversiveness of the reinforcer and was only obtained for those individuals who could correctly verbalize the stimulus contingency in a postconditioning recognition test. Cardiac responses varied with the task demands of the situation and covaried with individual response stereotypes.

  • Vaitl, D. (1996). Interoception. Biological Psychology, 42(1–2), 1–27. https://doi.org/10.1016/0301-0511(95)05144-9

    During the last two decades, research on interoception has experienced a surprising renaissance. New experimental approaches and methods have revealed much about the processing of afferent signals from the inner organs of the body, and have allowed more accurate descriptions of these processes, as well as a more accurate determination of their functional significance in the experience and behavior of humans. Besides neuromuscular, respiratory, and gastrointestinal interoceptive processes, the cardiovascular afferent influences are now known to be very important. Invariably, the central questions concern sensitivity to signals from the body, factors which may influence judgement of perception, and the degree to which conventional hypotheses regarding the interoceptive capabilities of humans may require revision. Findings from general psychological and clinical studies have shown that humans may attain remarkable levels of interoceptive performance. On the other hand, they also show how deep the chasm is between visceral processes and perception, and between that which is perceived and the reports thereof. Only interdisciplinary approaches to these complex processes promise success.

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