Roman Ferstl

Reduced olfactory performance in patients with major depression

The aim of the present study is to investigate olfactory sensitivity and odor evaluations in a homogeneous sample of unipolar depressive patients using pure olfactory odors. Twenty-four in-patients with major depressive disorder (MDD) were investigated during their acute depressive phase. Eighteen of them participated a second time after successful treatment. A group of healthy subjects, matched by age, sex, and smoking behavior, served as a control. Olfactory sensitivity, as measured by threshold tests, was strongly reduced in patients with severe depression. Additional correlative analyses revealed that the lowered sensitivity could partly be predicted by high depression scores. After successful medical treatment, these sensitivity differences were reduced and did not reach the significance level. The subjective odor evaluations (valence and intensity ratings) were not markedly changed in general. The results reveal that olfactory performance in MDD patients is reduced at an early perceptional level of stimulus processing. It is discussed whether this effect can be attributed to the close functional connection between the main olfactory bulb and the amygdala.

Induction of Empathy by the Smell of Anxiety

The communication of stress/anxiety between conspecifics through chemosensory signals has been documented in many vertebrates and invertebrates. Here, we investigate how chemosensory anxiety signals conveyed by the sweat of humans (N = 49) awaiting an academic examination are processed by the human brain, as compared to chemosensory control signals obtained from the same sweat donors in a sport condition. The chemosensory stimuli were pooled according to the donation condition and administered to 28 participants (14 males) synchronously to breathing via an olfactometer. The stimuli were perceived with a low intensity and accordingly only about half of the odor presentations were detected by the participants. The fMRI results (event-related design) show that chemosensory anxiety signals activate brain areas involved in the processing of social emotional stimuli (fusiform gyrus), and in the regulation of empathic feelings (insula, precuneus, cingulate cortex). In addition, neuronal activity within attentional (thalamus, dorsomedial prefrontal cortex) and emotional (cerebellum, vermis) control systems were observed. The chemosensory perception of human anxiety seems to automatically recruit empathy-related resources. Even though the participants could not attentively differentiate the chemosensory stimuli, emotional contagion seems to be effectively mediated by the olfactory system.

Olfactory information processing during the course of the menstrual cycle

In the present study we examined whether olfactory information processing depends on the phase of the menstrual cycle. Five female subjects were investigated during three phases (follicular, ovulatory, luteal) of their menstrual cycle. In each session chemosensory (olfactory) event-related potentials (CSERP) were recorded and olfactory thresholds and the hedonic tone of the test stimulus (citral) were determined. Threshold values were correlated with the salivary cortisol level. The results show that olfactory perception changes during the menstrual cycle. After the first stimulus presentations in a recording session, odors were perceived as more complex or novel during the ovulatory period (enhanced amplitude of P3-1). With continued stimulation, odor processing became faster (reduced latency of NI, P2 and P3-2) around ovulation and slower during the follicular phase. Moreover, odors were described more differentially during the ovulatory period. Olfactory sensitivity was correlated positively with the peripheral cortisol level.

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.

Sleep in children enhances preferentially emotional declarative but not procedural memories.

Although the consolidation of several memory systems is enhanced by sleep in adults, recent studies suggest that sleep supports declarative memory but not procedural memory in children. In the current study, the influence of sleep on emotional declarative memory (recognition task) and procedural memory (mirror tracing task) in 20 healthy children (10-13 years of age) was examined. After sleep, children showed an improvement in declarative memory. Separate analysis with respect to the emotional stimulus content revealed that sleep enhances the recognition of emotional stimuli (p>.001) rather than neutral stimuli (p=.084). In the procedural task, however, no sleep-enhanced memory improvement was observed. The results indicate that sleep in children, comparable to adults, enhances predominantly emotional declarative memory; however, in contrast to adults, it has no effect on the consolidation of procedural memory.

Startle response potentiation to chemosensory anxiety signals in socially anxious individuals.

The present study aimed to investigate whether withdrawal related behavior is activated in the context of chemosensory anxiety signals. Moreover, it was examined whether chemosensory perception of social stress is modulated by the degree of social anxiety. Axillary sweat was collected from students, awaiting an oral examination at the university (anxiety condition) and from the same students in a sport control condition. The chemosensory stimuli were presented to 32 participants (16 socially anxious) via an olfactometer during inhalation (duration=3 s). 102 dB white noise bursts served as startle probes. During a single session only male or female axillary sweat was presented, therefore, all participants were tested in two separate sessions. Even though the chemosensory stimuli were perceived at the perceptual threshold level, participants could identify (forced choice) the emotion of the donors in the anxiety condition. In the context of chemosensory anxiety signals the acoustic startle reflex was significantly augmented as compared to startle responses obtained in the context of sport sweat (p=0.002). This effect was more pronounced in socially anxious than in non-anxious participants. It is concluded that human motor systems automatically adapt to chemosensory stress signals. This adaptation is neither dependent on the gender of the odor donor nor on the gender of the perceiver, but is intensified in socially anxious participants.

Olfactory dysfunction in patients with narcolepsy with cataplexy is restored by intranasal Orexin A (Hypocretin-1)

Until recently, olfactory dysfunction was an unknown feature of narcolepsy. Orexin A, also called hypocretin-1, is abnormally decreased or undetectable in the cerebrospinal fluid of narcoleptic patients with cataplexies. As hypothalamic orexin-containing neurons project throughout the entire olfactory pathway, from the olfactory mucosa to the olfactory cortex, disturbed orexinergic transmission may crucially be involved in impaired olfactory performance of narcolepsy patients. In our study we analysed the olfactory performance (threshold, discrimination, identification and sum score of these measurements, the TDI score) of narcoleptic patients with cataplexies (n = 10) and of age-, gender-, BMI- and smoker/non-smoker-matched healthy controls (n = 10). We then in a double-blind, randomized, placebo-controlled cross-over design applied orexin A intranasally to seven of the patients and measured 2-phenyl-ethyl alcohol (PEA) single-staircase odour detection thresholds. Compared to the controls, patients showed significantly lower scores for olfactory threshold (patients: median 8.0, range 4.0-10.5; controls: median 9.4, range 7.5-13.3; P < 0.05), discrimination (patients: median 12.5, range 10-15; controls: median 15.0, range 12-16; P < 0.005), identification (patients: median 13.0, range 10-16; controls: median 14.0, range 13-16; P < 0.05) and TDI score (patients: median 33.4, range 30-36; controls: median 38.4, range 35-43; P < 0.0001). In all patients, the PEA olfactory threshold score increased after administration of orexin A (median 11.5, range 6.5-13.25) compared to placebo (median 7.75, range 6.25-11.25; P < 0.05). Our results support the hypothesis that mild olfactory dysfunction is an intrinsic symptom of narcolepsy with cataplexies. The observation that intranasal orexin A restores olfactory function is in favour of this hypothesis. Furthermore, our data support that the pathophysiological mechanism underlying olfactory dysfunction in narcolepsy is the lack of CNS orexin.

Olfactory cues associated with the major histocompatibility complex

Besides its immunological function of self/non‐self discrimination the major histocompatibility complex (MHC) has been recognized as a possible source of individual specific body odors. Dating back to speculations on the role of the extraordinary polymorphism of the MHC as background of an individual chemosensory identity and to early observations of MHC‐dependent mate choice in inbred strains of mice, systematic experimental studies revealed a first evidence for H‐2 related body odors in this species. Meanwhile a large number of animal studies with rodents and a series of field studies and experiments with humans have extended our knowledge of MHC‐related odor signals and substantiated the hypothesis of immunogenetic associated odortypes. These results suggest that the most prominent feature of the MHC, its extraordinary genetic diversity, seems in part to be selectively maintained by behavioral mechanisms which operate in contemporary natural populations. The high degree of heterozygosity found in natural populations of most species seems to be promoted by non‐disease‐based selection such as mating preferences and selective block of pregnancy.

Normative data and psychometric properties for qualitative and quantitative scoring criteria of the Five-point Test

The Five-point Test (Regard, Strauss, & Knapp, 1982) was introduced for the measurement of figural fluency as part of the examination of executive functions. Until now, no differentiated norms exist. We present normative data for adults aged 18–80 (n = 280) for the number of unique designs (productivity), the percent of perseverations (flexibility), the percent of rotated (strategic) designs, and the number of rule breakings. As age and education were correlated with test performance, norms were stratified by these two variables. Test–retest reliability and inter-rater reliability were calculated. Moreover, convergent and divergent validity as well as factorial validity were assessed through intercorrelations and correlations with other neuropsychological tests. All together, the Five-point Test proved to be reliable and valid.

Sensitivity to androstenone in female subjects is associated with an altered brain response to male body odor

Androstenone is a boar pheromone. and has also been found within different human body fluids. However, it is still unclear whether it carries pheromonal information in humans and whether it contributes significantly to the complex human body odor at all. Some humans fail to perceive the odor of androstenone, but most of these anosmics can achieve sensitivity by daily sniffing. The following study was designed to investigate whether sensitivity to androstenone influences the perception of body odors. Four females osmic to and four females anosmic to androstenone attended two EEG sessions. Anosmics were successfully sensitized to androstenone between sessions. CSERPs (chemosensory event-related potentials) were obtained while subjects perceived their own body odor and a male body odor within an olfactory oddball paradigm. The CSERPs showed a general decrease in amplitude from the first to the second session except for the sensitized anosmics in response to male body odor. The results indicate that the sensitivity to androstenone in females is associated with a stronger brain response to male body odor.