Ilona Croy

Friedrich Schiller University Jena | FSU · Department of Psychology

Olfactory and emotional higher processing pathways share common anatomical substrates. Hence, depression is often accompanied by alterations in olfactory function. These alterations are negative in nature and may involve decreased activation in olfactory eloquent structures or decreased volume in the olfactory bulb (OB). We suggest that olfaction a...

Background: Unmyelinated low-threshold mechanoreceptors-the so-called C-tactile (CT) afferents-play a crucial role in the perception and conduction of caressing and pleasant touch sensations and significantly contribute to the concept of erotic touch perception. Aim: To investigate the relations between sexual desire and sexual performance and t...

Introduction: Touch is important for individuals' subjective well-being, is typically rewarding, and is one of few sensory stimuli which are experienced as pleasant for a rather long time. This study tracked brain activation during slow stroking stimulation of the arm that was applied continuously for 40min - a much longer time than what previous...

Introduction: Touch has been found to entail positive effects in the person receiving it, whereas effects on the person giving touch have previously been unexplored. We investigated whether stroking the partner also is a pleasant experience for the person performing it, and whether it has similar effects on well-being and autonomic nervous functio...

The major histocompatibility complex (MHC, called HLA in humans) is an important genetic component of the immune system. Fish, birds and mammals prefer mates with different genetic MHC code compared to their own, which they determine using olfactory cues. This preference increases the chances of high MHC variety in the offspring, leading to enhance...

Burnout refers to characteristic stress symptoms resulting from chronic overload at the workplace. However, increased stress and strain are observed already in adolescents in the context of school. Previous work shows that school burnout is associated with female gender, immigration background, higher academic achievement, and increasing grade leve...

Stress is a wide-spread phenomenon and associated with various detrimental health effects. A significant resource for stress buffering is social support. How social support is perceived, however, depends on a multitude of individual and interindividual factors. This study aimed to explore the stress-reducing properties of relationship-inherent vari...

Interpersonal touch is an essential part of human social life, impacting emotional and physical well-being. Variations in touch behavior and perception can be assessed by the Touch Experiences and Attitudes Questionnaire (TEAQ). Although comprehensive, the TEAQ appears lengthy with 57 items, limiting its usability for large surveys. Therefore, we d...

Cracking the non‐verbal “code” of human emotions has been a chief interest of generations of scientists. Yet, despite much effort, a dictionary that clearly maps non‐verbal behaviours onto meaning remains elusive. We suggest this is due to an over‐reliance on language‐related concepts and an under‐appreciation of the evolutionary context in which a...

Humans are highly social, typically without this ability requiring noticeable efforts. Yet, such social fluency poses challenges both for the human brain to compute and for scientists to study. Over the last few decades, neuroscientific research in human sociality has witnessed a shift in focus from single-brain analysis to complex dynamics occurri...

Stress-related disorders are common in modern societies. What adds to the burden is empathic stress, arising when observing another’s stress elicits a stress response in the observer. In romantic couples, we investigated the association between empathic stress and adult attachment – a deep emotional bond in relationships – to understand facets of r...

The smell of the own baby is a salient cue for human kin recognition and bonding. We hypothesized that infant body odors function like other cues of the Kindchenschema by recruiting neural circuits of pleasure and reward. In two functional magnetic resonance imaging (fMRI) studies, we presented infantile and postpubertal body odors to nulliparae an...

Irregular menstrual cycles, affecting approximately 30% of women in their reproductive years, are often overlooked in research, limiting our insights into the broader spectrum of hormonal interactions. Understanding the relationship between endogenous hormone fluctuations and brain function across the menstrual cycle, particularly beyond regular me...

There appears to be no attempt to categorize the specific classes of behavior that the tactile system underpins. Awareness of how an organism uses touch in their environment informs understanding of its versatility in non-verbal communication and tactile perception. This review categorizes the behavioral functions underpinned by the tactile sense,...

This book provides a cutting-edge overview of emotion science from an evolutionary perspective. Part 1 outlines different ways of approaching the study of emotion; Part 2 covers specific emotions from an evolutionary perspective; Part 3 discusses the role of emotions in a variety of life domains; and Part 4 explores the relationship between emotion...

Previous studies have found a negative relationship between creativity and conservatism. However, as these studies were mostly conducted on samples of homogeneous nationality, the generalizability of the effect across different cultures is unknown. We addressed this gap by conducting a study in 28 countries. Based on the notion that attitudes can b...

Previous studies have found a negative relationship between creativity and conservatism. However, as these studies were mostly conducted on samples of homogeneous nationality, the generalizability of the effect across different cultures is unknown. We addressed this gap by conducting a study in 28 countries. Based on the notion that attitudes can b...

Childhood adversity, a prevalent experience, is related to a higher risk for externalizing and internalizing psychopathology. Alterations in the development of cognitive processes, for example in the attention-interference domain may link childhood adversity and psychopathology. Interfering stimuli can vary in their salience, i.e. ability to captur...

Body odors change during development, and this change influences the interpersonal communication between parents and their children. The molecular basis for this chemical communication has not been elucidated yet. Here, we show by combining instrumental and sensory analyses that the qualitative odorant composition of body odor samples is similar in...

The sense of smell is based on sensory detection of the molecule(s), which is then further perceptually interpreted. A possible measure of olfactory perception is an odor independent olfactory perceptual fingerprint (OPF) defined by Snitz et al. We aimed to investigate, whether OPF can distinguish patients with olfactory dysfunction due to COVID-19...

Gonadal hormone fluctuations in females have been associated with symptoms of mental health, yet the underlying brain mechanisms remain understudied. Recent advances in neuroscience have shifted the paradigm towards longitudinal tracking, enabling the detection of subtle changes overlooked in conventional cross-sectional analyses. This dense-sampli...

Background: Adequate adaptation of the autonomic nervous system (ANS) is crucial in potentially life-threatening situations. The defence cascade provides a descriptive model of progressing dominant physiological reactions in such situations, including cardiovascular parameters and body mobility. The empirical evidence for this model is scarce, and...

The COVID-19 pandemic has led to the introduction of unprecedented safety measures, one of them being physical distancing recommendations. Here, we assessed whether the pandemic has led to long-term effects on two important physical distancing aspects, namely interpersonal distance preferences and interpersonal touch behaviors. We analyzed nearly 1...

Previous research on the impact of odors on current emotional state has been mixed, with some studies finding odors can induce feelings of relaxation while others have not. The aim of Part 1 of the current study was to investigate whether a feeling of relaxation, measured by a self‐report positive and negative affect scale and heart rate (HR), coul...

Although chemical signaling is an essential mode of communication in most vertebrates, it has long been viewed as having negligible effects in humans. However, a growing body of evidence shows that the sense of smell affects human behavior in social contexts ranging from affiliation and parenting to disease avoidance and social threat. This article...

Background The menstrual cycle is a critical indicator of women's reproductive, physical, and mental health, influenced by neuromodulatory sex steroid hormones, including estrogens like 17β-estradiol, and estrone. Irregular menstrual cycles can lead to various health conditions. Understanding the relationship between endogenous hormone fluctuations...

Temporal neural synchrony disruption can be linked to a variety of symptoms of major depressive disorder (MDD), including mood rigidity and the inability to break the cycle of negative emotion or attention biases. This might imply that altered dynamic neural synchrony may play a role in the persistence and exacerbation of MDD symptoms. Our study ai...

Body odors serve as signals of kinship, with parents exhibiting a preference for the scent of their infants, and vice versa. The reciprocal perception of body odors can promote bonding through two mechanisms. Firstly, as an indirect pathway, through associative chemosensory learning, which leads to changes in proximity-seeking behaviors. Secondly,...

Perceptual experience is shaped by a complex interaction between our sensory systems in which each sense conveys information on specific properties of our surroundings. This multisensory processing of complementary information improves the accuracy of our perceptual judgments and leads to more precise and faster reactions. Sensory impairment or los...

Depression is associated with reduced olfactory function. This relationship is assumed to be based on either a reduced olfactory bulb volume or diminished functioning of higher cortical areas. As previous results are controversial, we aimed to re-evaluate central olfactory processing in depression. We recorded the BOLD signal of 21 patients with Ma...

Disgust serves to defend the body from the entry of toxins and disease. Central to this function is a strong relationship with the proximate senses of smell, taste, and touch. Theory suggests that distinct and reflexive facial movements should be evoked by gustatory and olfactory disgusts, serving to impede bodily entry. While this hypothesis has r...

As the sense of the body's internal state, interoception represents the afferent component of the brain-body feedback loop essential for linking internal sensation with body regulation, thereby minimizing erroneous feedback and maintaining homeostasis. The anticipation of potential future interoceptive states enables organisms to take regulatory ac...

Zusammenfassung Für viele Spezies ist der Geruchssinn das bedeutsamste Sinnessystem, um mit der Umwelt und Artgenossen zu interagieren. Demgegenüber wurde die Rolle der Wahrnehmung und Kommunikation chemosensorischer Informationen beim Menschen lange Zeit unterschätzt. Der menschliche Geruchssinn galt als weniger zuverlässig, sodass diesem im Vergl...

Since their initial discovery in cats, low-threshold C-fiber mechanoreceptors have become a central interest of scientists studying the affective aspects of touch. Their pursuit in humans, here termed C-tactile (CT) afferents, has led to the establishment of a research field referred to as "affective touch", which is differentiated from "discrimina...

Touch is the primary way people communicate intimacy in romantic relationships, and affectionate touch behaviors such as stroking, hugging and kissing are universally observed in partnerships all over the world. Here, we explored the association of love and affectionate touch behaviors in romantic partnerships in two studies comprising 7880 partici...

Objectives: As part of the quality assurance of inpatient treatment, the severity of the disease and the course of therapy must be mapped. However, there is a high degree of heterogeneity in the implementation of basic diagnostics in psychosomatic facilities.There is a lack of scientifically based standardisation in determining the quality of outco...

Recent cross-cultural and neuro-hormonal investigations have suggested that love is a near universal phenomenon that has a biological background. Therefore, the remaining important question is not whether love exists worldwide but which cultural, social, or environmental factors influence experiences and expressions of love. In the present study, w...

Introduction: Germany is one of the few countries with a medical specialty of psychosomatic medicine and psychotherapy and many treatment resources of this kind. Objective: This observational study describes the psychosomatic treatment programs as well as a large sample of day-hospital and inpatients in great detail using structured diagnostic i...

Introduction The human sense of smell has different functions which can be categorized as “food,” “social,” and “environment.” Different questionnaires about the importance of olfaction in adults are available, but little attention has been paid to children and adolescents. Therefore, we aimed to develop a questionnaire about children’s personal si...

Background: Neurophysiological models link dissociation (e.g. feeling detached during or after a traumatic event) to hypoarousal. It is currently assumed that the initial passive reaction to a threat may coincide with a blunted autonomic response, which constitutes the dissociative subtype of post-traumatic stress disorder (PTSD). Objective: Within...

Preterm infants are challenged to adapt to an extrauterine milieu, while their interoceptive system and autonomic regulation capacity is still immature. Caressing parental touch is known to foster parasympathetic regulation in infants by stimulating C-tactile (CT) afferents and in preterm infants, slow stroking stimulation also leads to a heart rat...

The theory of the behavioral immune system (BIS) describes a set of behaviors that protect the individual from infectious diseases and that are motivated by disgust and the perceived vulnerability to disease. As interpersonal touch is one of the most common situations of potential transmission of infectious diseases in our everyday life, it seems l...

There is an ongoing discussion on the relevance of brain reorganization following amputation for phantom limb pain. Recent attempts to provide explanations for seemingly controversial findings—specifically, maladaptive plasticity versus persistent functional representation as a complementary process—acknowledged that reorganization in the primary s...

Study question Do infertile couples differ from the average population in Human Leukocyte Antigen (HLA) similarity? Summary answer Infertile couples share a significantly higher number of genes than expected by chance in four out of six HLA loci. What is known already HLA genes encode the peptides for the formation of the innate immune system and...

This study examined how touch role and culture shape affective touch experiences. Germans (N = 130) and Chinese (N = 130) were surveyed once as toucher and once as touchee. For different touch actions, they (a) provided free-text descriptions of what prompts touch, (b) indicated with whom touch feels comfortable, and (c) highlighted areas of touch...

Objective: With the increasing presence of burnout symptoms in clinical and social everyday life, it is necessary to closely examine patients with symptoms of burnout and to classify their respective symptoms in the spectrum of mental disorders. Methods: The sample includes 83 patients who presented themselves in a burnout consultation of the un...

Introduction The Sniffin’ Sticks threshold test is widely used to assess olfactory threshold due to its high reliability and validity. Nevertheless, this test procedure is quite long with an average duration of 10 to 20 min. In study designs that require multiple olfactory threshold tests on short intervals, this could exhaust participants. To coun...

Traditionally, nonverbal behaviors have been understood as coded messages one person sends to another. Following this tradition, social touch has been pursued by asking what it communicates. We argue this question is misleading and ask instead how touch impacts on those giving and receiving it. Indeed, a growing literature investigating gentle phys...

Background: The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we ha...

Although previous research revealed sex differences in affective touch, the implicated processes and the manner in which men and women differ have been left uncertain. Here we addressed this issue in two studies examining sensory and social processes, respectively. Study 1 comprised a series of lab-based experiments in which a robot stroked 214 par...

Touch plays an important role in the development of infants and children. In this review, we highlight the neural conditioning of affective touch and the related physiological responses, especially in the form of parasympathetic activation, pain suppression and stress relief. Based on recent studies, we show that the functionality of a population o...

Bridging the gap between the neurophysiology of C-tactile mediated touch and the psychology of how social touch makes us feel, we present a definition of affective touch as mediated through CT afferents. We clarify how gentle stroking activating the CT system communicates a signal for social exchange. We describe what is already known about the nat...

Generally, three functions are assigned to the sense of smell, namely warning of potential danger, social communication, and importance for eating and drinking. These functions are also reflected in some of the complaints of patients with smell disorders: occurrence of household accidents, inability to smell other people like family members, loss o...

Zusammenfassung Häusliche Gewalt ist laut Studien gesundheitsgefährdend. Ärzt*innen werden von Gewaltopfern als primäre Ansprechpersonen wahrgenommen. Zur Prävention weiterer Gewalt interessiert deren Wahrnehmung von sich selbst als Schlüsselstelle. 1346 bei der Sächsischen Landesärztekammer 2015 gemeldete (Zahn-)Ärzt*innen beantworteten einen Frag...

Zusammenfassung Fragestellung (Teil-)stationäre Psychotherapie ist in Deutschland gut implementiert. Um Wirksamkeitsfaktoren und Effekte besser zu verstehen, sind Effektivitätsstudien notwendig. Diese naturalistische Studie untersucht die Effektivität stationärer und teilstationärer Psychotherapie sowie patientenzentrierte und störungsbezogene Einf...

Public Significance Statement The current, cross-cultural study based on data from 9,198 participants across 41 countries suggests that the country-level early dynamics of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) spread variable was related to more frequent nonaffective touch behaviors between strangers and lower preferred inter...

Major depressive disorder (MDD) is associated with abnormal neural circuitry. It can be measured by assessing functional connectivity (FC) at resting-state functional MRI, that may help identifying neural markers of MDD and provide further efficient diagnosis and monitor treatment outcomes. The main aim of the present study is to investigate, in an...

People differ in their touch preferences and in the ways in which they touch others. People who are blind are particularly sensitive to tactile stimulation as a result of sensory compensation, and sense of touch can support their interpersonal communication. In the article presented here, we aimed to explore whether visual status predicts preferenc...

The study of affectionate touch centers on gentle stroking. Yet friendly physical contact entails other actions, such as embracing, holding, kissing, leaning, petting, squeezing, or tickling. Here, we probed whether these actions are redundant or can be meaningfully differentiated by asking participants (N = 161) to complete a few tasks for each ac...

A wide range of literature connects sex ratio and mating behaviours in non-human animals. However, research examining sex ratio and human mating is limited in scope. Prior work has examined the relationship between sex ratio and desire for short-term, uncommitted mating as well as outcomes such as marriage and divorce rates. Less empirical attentio...

A wide range of literature connects sex ratio and mating behaviours in non-human animals. However, research examining sex ratio and human mating is limited in scope. Prior work has examined the relationship between sex ratio and desire for short-term, uncommitted mating as well as outcomes such as marriage and divorce rates. Less empirical attentio...

Introduction: Slow brushing over the skin activates C-tactile nerve fibers that transmit pleasant tactile experiences in healthy subjects, leading to an inverted U-shaped velocity dependence of ratings: C-tactile optimal stroking stimulations are rated as more pleasant than slower or faster stimulations. Chronic pain diseases such as postherpetic...

Body odours and their importance for human chemical communication, e.g., in the mother–child relationship, are an increasing focus of recent research. Precise examination of sampling methods considering physiology and feasibility aspects in order to obtain robust and informative odour samples is therefore necessary. Studies comparing body odour sam...

Psychological treatments of posttraumatic stress disorder (PTSD) are associated with non-response rates of up to 50%. This fact highlights the need to identify characteristics of poorer treatment outcome. Among others, previous evidence focused on the role of dysfunctional cortisol secretion which has been related to the development, maintenance an...

Background So far findings on emotional face processing among depressed individuals reveal an inconsistent image, with only some studies supporting a mood-congruent bias in salience processing. Thereby, many results are based on the processing of sad emotions and mostly focused on resting-state connectivity analysis. The present study aimed to targ...

The existence of pheromones in humans is controversial, partly because of definitional difficulties and partly because of the question of possible chemical substances. The synthetic compound Methyl dihydrojasmonate (Hedione) is potent to bind to vomeronasal-type 1 receptors (VN1R1s) and activate limbic areas of the brain in a sex-specific manner. H...