Biomedical subjects

Bernfried Sojka

Publications and source records attributed to Bernfried Sojka.

4 recordsLinked to original sources

PubMed2006

Central odor processing in subjects experiencing helplessness.

The aim of the present study was to investigate whether central nervous odor processing is affected by the temporary experience of helplessness. To induce helplessness, an unsolvable social discrimination test in combination with false feedback was used. The EEG was recorded from 60 scalp locations, while two standard odors were presented via a constant-flow olfactometer. Helplessness attenuated olfactory stimulus processing at an early perceptual stage: the P2 and P3-1 amplitudes were reduced in response to both odors. Furthermore, the early potentials (N1, P2 and P3-1) of the chemosensory event-related potential (CSERP) appeared with longer latencies when subjects received negative feedback. The state effects of helplessness resemble the deviations in the CSERP found in depressed patients, suggesting a general mood effect.

Adolescent↗

PubMed2006

The human brain is a detector of chemosensorily transmitted HLA-class I-similarity in same- and opposite-sex relations.

Studies on subjective body odour ratings suggest that humans exhibit preferences for human leucocyte antigen (HLA)-dissimilar persons. However, with regard to the extreme polymorphism of the HLA gene loci, the behavioural impact of the proposed HLA-related attracting signals seems to be minimal. Furthermore, the role of HLA-related chemosignals in same- and opposite-sex relations in humans has not been specified so far. Here, we investigate subjective preferences and brain evoked responses to body odours in males and females as a function of HLA similarity between odour donor and smeller. We show that pre-attentive processing of body odours of HLA-similar donors is faster and that late evaluative processing of these chemosignals activates more neuronal resources than the processing of body odours of HLA-dissimilar donors. In same-sex smelling conditions, HLA-associated brain responses show a different local distribution in male (frontal) and female subjects (parietal). The electrophysiological results are supported by significant correlations between the odour ratings and the amplitudes of the brain potentials. We conclude that odours of HLA-similar persons function as important social warning signals in inter- and intrasexual human relations. Such HLA-related chemosignals may contribute to female and male mate choice as well as to male competitive behaviour.

Adult↗

PubMed2005

Chemosensory anxiety signals augment the startle reflex in humans.

The aim of the present study was to investigate whether chemosensory anxiety signals can activate behavioral withdrawal systems in humans. Twelve male university students donated their axillary sweat in two situations: right before an oral academic examination (anxiety condition) and during ergometric training (exercise condition). Subjective ratings revealed that the odor donors experienced significantly more anxiety and less pleasure during the anxiety condition than during the exercise condition. Seven subjects (three females) participated in the psychophysiological experiment. The chemosensory stimuli from pooled sweat samples of the donors, and from unused cotton pads (pad condition) were presented via a constant-flow olfactometer. Acoustic startle probes (100 dB (A)) were delivered during and between the presentations of the chemosensory stimuli. Only three subjects were able to discriminate the chemosensory stimuli of the human sweat samples from room air. However, the startle reflex amplitude (EMG of the eyeblink response) recorded in the context of chemosensory anxiety signals was increased, as compared to the amplitude recorded in the context of chemosensory stimuli from either exercise (p = 0.018) or cotton pad (p = 0.012). It is concluded that chemosensory anxiety signals may pre-attentively prime defensive behavior.

Acoustic Stimulation↗

PubMed2003

Convergent and divergent effects of odors and emotions in depression.

The aim of the present study was to investigate the similarities and differences in the olfactory and visual processing of emotional stimuli in healthy subjects and in patients with major depressive disorder (MDD). Twenty-five inpatients were investigated after admission to the psychiatric clinic. Fifteen of them participated a second time, shortly before their discharge from the hospital. A group of healthy subjects, matched according to age and sex, served as a control. Chemsosensory event-related potentials (CSERPs) were recorded using the constant flow method. In addition, event-related potentials (ERPs), in response to colors and emotional slides, were obtained to control modality and emotion-specific effects. The subjects' task was to discriminate the colors (red/yellow) and odors (phenyl-ethylalcohol = rose/ isobutyraldehyde = rotten butter) according to their quality and to judge the valence of the emotional slides (IAPS slides). The EEG was recorded from 32 scalp locations. At the beginning of the therapy, visual stimulus processing was attenuated in depressive subjects at a relatively late processing level (reduced amplitudes of the P3 and pSW in response to colors and emotional slides), whereas olfactory stimulus processing had already been affected at an early level (reduced amplitudes of the P2 and P3-1 peaks in MDD patients). However, after successful medical treatment, ERPs did not differentiate between depressive patients and healthy controls. We discuss whether functional deviations within the primary olfactory cortex are responsible for the lower olfactory sensitivity, as well as for the altered emotional stimulus processing in MDD patients.

Adult↗