Ihre Suche

Suche zurücksetzen

In authors or contributors

"Kirsch, Peter"

Thema

Photic Stimulation

Ergebnisse 3 Einträge

Abstracts

Tabbert, K., Stark, R., Kirsch, P., & Vaitl, D. (2005). Hemodynamic responses of the amygdala, the orbitofrontal cortex and the visual cortex during a fear conditioning paradigm. International Journal of Psychophysiology : Official Journal of the International Organization of Psychophysiology, 57(1), 15–23. https://doi.org/10.1016/j.ijpsycho.2005.01.007

Functional magnetic resonance imaging (fMRI) studies consistently demonstrate an enhanced activation of the visual cortex in reaction to emotionally salient visual stimuli. This increase of activation is probably modulated by top-down processes, that are initiated in emotion processing structures, specifically the amygdala and the orbitofrontal cortex. In the present fMRI study, a differential fear conditioning paradigm was applied to investigate this assumed modulation. Hemodynamic responses towards a neutral visual stimulus (CS+) predicting an electrical stimulation (UCS) were compared with responses towards a neutral and unpaired stimulus (CS-). Thereby, particularly the time courses of neural responses were considered. Skin conductance measures were concurrently recorded. Our results show that the differentiation between CS+ and CS- within the amygdala and the extended visual cortex was accomplished during a late acquisition phase. In the orbitofrontal cortex the differentiation occurred at an earlier stage and was then sustained throughout acquisition. It is suggested that these altering activation patterns are reflecting different phases of learning, integrating the analyzed regions to varying degrees. Additionally, the results indicate that statistical analyses comprising a temporal variation of hemodynamic responses are more likely to detect amygdala activation.
Stark, R., Schienle, A., Walter, B., Kirsch, P., Sammer, G., Ott, U., Blecker, C., & Vaitl, D. (2003). Hemodynamic responses to fear and disgust-inducing pictures: an fMRI study. International Journal of Psychophysiology : Official Journal of the International Organization of Psychophysiology, 50(3), 225–234. https://doi.org/10.1016/s0167-8760(03)00169-7

The majority of neuroimaging studies on affective processing have indicated that there are specific brain structures, which are selectively responsive to fear and disgust. Whereas the amygdala is assumed to be fear-related, the insular cortex is most likely involved in disgust processing. Since these findings are mainly a result of studies focusing exclusively either on fear, or on disgust, but rarely on both emotions together, the present experiment explored the neural effects of viewing disgusting and fear-inducing pictures in contrast to neutral pictures. This was done by means of functional magnetic resonance imaging (fMRI) with 19 subjects (nine males, ten females), who also gave affective ratings for the presented pictures. The fear and the disgust pictures were able to induce the target emotions and they received comparable valence and arousal ratings. The processing of both aversive picture types was associated with an increased brain activation in the occipital-temporal lobe, in the prefrontal cortex, and in the thalamus. The amygdala was significantly activated by disgusting, but not by fear-inducing, pictures. Thus, our data are in contrast with the idea of highly emotion-specific brain structures and rather suggest the existence of a common affective circuit.
Stark, R., Wolf, O. T., Tabbert, K., Kagerer, S., Zimmermann, M., Kirsch, P., Schienle, A., & Vaitl, D. (2006). Influence of the stress hormone cortisol on fear conditioning in humans: evidence for sex differences in the response of the prefrontal cortex. NeuroImage, 32(3), 1290–1298. https://doi.org/10.1016/j.neuroimage.2006.05.046

The stress hormone cortisol is known to influence declarative memory and associative learning. In animals, stress has often been reported to have opposing effects on memory and learning in males and females. In humans, the effects of cortisol have mainly been studied at the behavioral level. The aim of the present experiment was to characterize the effects of a single cortisol dose (30 mg) on the hemodynamic correlates of fear conditioning. In a double-blind group comparison study subjects (17 females and 17 males) received 30 mg cortisol or placebo orally before participating in a discriminative fear conditioning paradigm. Results revealed that cortisol impaired electrodermal signs of learning (the first interval response) in males, while no conditioned SCRs emerged for the females independent of treatment. fMRI results showed that cortisol reduced activity for the CS+ > CS- comparison in the anterior cingulate, the lateral orbitofrontal cortex and the medial prefrontal cortex in males. Opposite findings (increase in these regions under cortisol) were detected in females. In addition, cortisol reduced the habituation in the CS+ > CS- contrast in the dorsolateral prefrontal cortex independent of sex. Finally, cortisol also modified the response to the electric shock (the UCS) by enhancing the activity of the anterior as well as the posterior cingulate. In sum, these findings demonstrate that in humans cortisol mostly influences prefrontal brain activation during fear conditioning and that these effects appear to be modulated by sex.

Custom feed

Last update from database: 04.06.25, 15:35 (UTC)

Ihre Suche

Ergebnisse 3 Einträge

Erkunden

Team

Eintragsart

Sprache

Thema