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Thomas Hummel

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17 papers

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YNIMG Journal 2025 Journal Article

Differential neural correlates of oral capsaicin pleasantness in habitual and non-habitual spicy eaters

Luyi Zhou
Yihang Ma
Thomas Hummel
Pengfei Han

Repeated exposure to spicy flavor can shift individuals' preferences for capsaicin-containing stimuli, however, the neural mechanisms underlying the hedonic processing of oral capsaicin remain unclear. Here, we investigated how habitual spicy food consumption modulates brain responses involved in hedonic perceptions of oral capsaicin. Using functional magnetic resonance imaging, we compared brain activity between high-frequency (HF, N = 19) and low-frequency (LF, N = 17) spicy food consumers during oral administration of three concentrations of capsaicin (10, 30, 60 μM) and water as a control stimulus. Participants rated the pleasantness and intensity after each stimulus. Compared with the LF group, the HF group reported significantly higher pleasantness ratings across all capsaicin concentrations, an effect that was independent of perceived intensity. At the neural level, a significant group × concentration interaction was observed. For the high-concentration of capsaicin stimulation (60 μM), the HF group exhibited increased activation in the left postcentral gyrus and decreased activation in the right hippocampus relative to the LF group. In the LF group, pleasantness for the high concentration of capsaicin was positively correlated with activation in the right hippocampus. For the low-concentration of capsaicin (10 μM), the LF group showed weakened hippocampus-postcentral and hippocampus-caudate connectivity, but stronger insula-parahippocampal connectivity compared to the HF group. In addition, pleasantness ratings for low-concentration of capsaicin were positively correlated with hippocampus-postcentral connectivity in LF participants. Together, these findings suggest that the neural substrates subserving the hedonic processing of oral capsaicin vary as a function of habitual spicy food intake and stimulus concentration, reflecting experience-dependent plasticity within chemosensory and affective brain networks.

YNIMG Journal 2023 Journal Article

Reduced neural responses to pleasant odor stimuli after acute psychological stress is associated with cortisol reactivity

Yun Ai
Thomas Hummel
Haoyu Nie
Juan Yang
Pengfei Han

Acute stress alters olfactory perception. However, little is known about the neural processing of olfactory stimuli after acute stress exposure and the role of cortisol in such an effect. Here, we used an event-related olfactory fMRI paradigm to investigate brain responses to odors of different valence (unpleasant, pleasant, or neutral) in healthy young adults following an acute stress (Trier Social Stress Test, TSST) induction (N = 22) or a non-stressful resting condition (N = 22). We obtained the odor pleasantness, intensity, and familiarity ratings after the acute stress induction or resting condition. We also measured the participants' perceived stress and salivary cortisol at four time points during the procedure. We found a stress-related decrease in brain activation in response to the pleasant, but not to the neutral or unpleasant odor stimuli in the right piriform cortex extending to the right amygdala, the right orbitofrontal cortex, and the right insula. In addition, activation of clusters within the regions of interest were negatively associated with individual baseline-to-peak increase in salivary cortisol levels after stress. We also found increased functional connectivity between the right piriform cortex and the right insula after stress when the pleasant odor was presented. The strength of the connectivity was positively correlated with increased perceived stress levels immediately after stress exposure. These results provide novel evidence for the effects of acute stress in attenuating the neural processing of a pleasant olfactory stimulus. Together with previous findings, the effect of acute stress on human olfactory perception appears to depend on both the valence and the concentration (e.g., peri-threshold or suprathreshold levels) of odor stimuli.

YNICL Journal 2023 Journal Article

The potential for clinical application of automatic quantification of olfactory bulb volume in MRI scans using convolutional neural networks

Elbrich M. Postma
Julia M.H. Noothout
Wilbert M. Boek
Akshita Joshi
Theresa Herrmann
Thomas Hummel
Paul A.M. Smeets
Ivana Išgum

The olfactory bulbs (OBs) play a key role in olfactory processing; their volume is important for diagnosis, prognosis and treatment of patients with olfactory loss. Until now, measurements of OB volumes have been limited to quantification of manually segmented OBs, which is a cumbersome task and makes evaluation of OB volumes in large scale clinical studies infeasible. Hence, the aim of this study was to evaluate the potential of our previously developed automatic OB segmentation method for application in clinical practice and to relate the results to clinical outcome measures. To evaluate utilization potential of the automatic segmentation method, three data sets containing MR scans of patients with olfactory loss were included. Dataset 1 (N = 66) and 3 (N = 181) were collected at the Smell and Taste Center in Ede (NL) on a 3 T scanner; dataset 2 (N = 42) was collected at the Smell and Taste Clinic in Dresden (DE) on a 1. 5 T scanner. To define the reference standard, manual annotation of the OBs was performed in Dataset 1 and 2. OBs were segmented with a method that employs two consecutive convolutional neural networks (CNNs) that the first localize the OBs in an MRI scan and subsequently segment them. In Dataset 1 and 2, the method accurately segmented the OBs, resulting in a Dice coefficient above 0. 7 and average symmetrical surface distance below 0. 3 mm. Volumes determined from manual and automatic segmentations showed a strong correlation (Dataset 1: r = 0. 79, p < 0. 001; Dataset 2: r = 0. 72, p = 0. 004). In addition, the method was able to recognize the absence of an OB. In Dataset 3, OB volumes computed from automatic segmentations obtained with our method were related to clinical outcome measures, i. e. duration and etiology of olfactory loss, and olfactory ability. We found that OB volume was significantly related to age of the patient, duration and etiology of olfactory loss, and olfactory ability (F(5, 172) = 11. 348, p < 0. 001, R2 = 0. 248). In conclusion, the results demonstrate that automatic segmentation of the OBs and subsequent computation of their volumes in MRI scans can be performed accurately and can be applied in clinical and research population studies. Automatic evaluation may lead to more insight in the role of OB volume in diagnosis, prognosis and treatment of olfactory loss.

YNIMG Journal 2022 Journal Article

Tractography indicates lateralized differences between trigeminal and olfactory pathways

Divesh Thaploo
Akshita Joshi
Charalampos Georgiopoulos
Jonathan Warr
Thomas Hummel

Odorous sensations are based on trigeminal and olfactory perceptions. Both trigeminal and olfactory stimuli generate overlapping as well as distinctive activations in the olfactory cortex including the piriform cortex. Orbitofrontal cortex (OFC), an integrative center for all senses, is directly activated in the presence of olfactory stimulations. In contrast, the thalamus, a very important midbrain structure, is not directly activated in the presence of odors, but rather acts as a relay for portions of olfactory information between primary olfactory cortex and higher-order processing centers. The aims of the study were (1) to examine the number of streamlines between the piriform cortex and the OFC and also between the piriform cortex and the thalamus and (2) to explore potential correlations between these streamlines and trigeminal and olfactory chemosensory perceptions. Thirty-eight healthy subjects were recruited for the study and underwent diffusion MRI using a 3T MRI scanner with 67 diffusion directions. ROIs were adapted from two studies looking into olfaction in terms of functional and structural properties of the olfactory system. The "waytotal number" was used which corresponds to number of streamlines between two regions of interests. We found the number of streamlines between the piriform cortex and the thalamus to be higher in the left hemisphere, whereas the number of streamlines between the piriform cortex and the OFC were higher in the right hemisphere. We also found streamlines between the piriform cortex and the thalamus to be positively correlated with the intensity of irritating (trigeminal) odors. On the other hand, streamlines between the piriform cortex and the OFC were correlated with the threshold scores for these trigeminal odors. This is the first studying the correlations between streamlines and olfactory scores using tractography. Results suggest that different chemosensory stimuli are processed through different networks in the chemosensory system involving the thalamus.

YNIMG Journal 2021 Journal Article

Individual odor hedonic perception is coded in temporal joint network activity

Paul Ruser
Carina J. Koeppel
Hagen H. Kitzler
Thomas Hummel
Ilona Croy

INTRO: The human sense of smell is highly individual and characterized by a strong variability in the perception and evaluation of olfactory stimuli, depending on cultural imprint and current physiological conditions. Since this individual perspective has often been neglected in fMRI studies on olfactory hedonic coding, this study focuses on the neuronal activity and connectivity patterns resulting from subject-specific olfactory stimulation. METHODS: Thirty-one normosmic participants took part in a fMRI block designed paradigm consisting of three olfactory stimulation sessions. The most pleasant and unpleasant odors were individually specified during a pre-test for each participant and validated in the main experiment. Mean activation and functional connectivity analysis focusing on the right and left piriform cortex were performed for the predefined olfactory regions-of-interest (ROIs) and compared between the three olfactory conditions. RESULTS: Individual unpleasant olfactory stimulation as compared to pleasant or neutral did not alter mean BOLD activation in the predefined olfactory ROIs but led to a change in connectivity pattern in the right piriform cortex. CONCLUSION: Our data suggests that the individual pleasantness of odors is not detectable by average BOLD magnitude changes in primary or secondary olfactory brain areas, but reflected in temporal patterns of joint activation that create a network between the right piriform cortex, the left insular cortex, the orbitofrontal cortex, and the precentral gyrus. This network may serve the evolutionary defense mechanism of olfaction by preparing goal-directed action.

YNIMG Journal 2020 Journal Article

Sensitivity to sweetness correlates to elevated reward brain responses to sweet and high-fat food odors in young healthy volunteers

Pengfei Han
Mohebbat Mohebbi
Han-Seok Seo
Thomas Hummel

Taste sensitivity relates to food preferences and macronutrients intake. The current study investigated whether the neural responses to food odors varied in sensory quality (sweet or non-sweet) and their associations with macronutrient content (high- or low-fat) in young healthy participants varied in sweet taste sensitivity. Thirty-eight participants were assessed for their sensitivity to sucrose solutions using a modified “taste strip” test. They were divided into high sweetness sensitive (HS, n = 15) and low sweetness sensitive (LS, n = 15) groups using the median split approach. Brain responses to four food-related odors (chocolate, peach, peanut, and bread) and one non-food odor (rose) were assessed using functional magnetic resonance imaging (fMRI). Preferences for tastes and macronutrients were measured using a computer-based task. Behavioral results showed that HS group, compared to LS group, had a higher preference for carbohydrate-dominated foods and liking for sweet foods, but a lower liking for protein-dominated foods. The food odors, in comparison to non-food odors, produced greater brain-activations in the gustatory and reward regions. Compared to LS group, the HS group showed a higher level of activation in the frontal inferior operculum in response to sweet vs. savory food odors, and stronger insular activations to high-fat vs. low-fat food odors. In addition, individual sweetness sensitivity was positively associated with activation of the insula in response to chocolate odor, suggesting an overlap of neural responses to food odor with high sugar and fat content. Our findings highlight that high sensitivity to sweetness can be associated with increased preference for carbohydrate-dominated or sweet foods, and elevated brain activations to sweet or high-fat food odors in the areas related to food reward processing.

YNIMG Journal 2020 Journal Article

Temporolimbic cortical volume is associated with semantic odor memory performance in aging

Janina Seubert
Grégoria Kalpouzos
Maria Larsson
Thomas Hummel
Lars Bäckman
Erika J. Laukka

Olfactory function, and specifically semantic olfactory memory (i. e. , odor identification), has frequently been shown to predict cognitive functioning across multiple domains in old age. This observation suggests that olfactory function can serve as a marker for the integrity of temporolimbic cortical networks, but a clear delineation of this association is still missing. To address this issue, the present study employed voxel-based morphometry in a region of interest-based design to determine the extent to which gray matter volumes of core olfactory and memory areas are associated with olfactory memory performance in an aging population free from neurodegenerative disease. We further aimed to determine potential overlap in structural anatomical correlates, and differences in association strength, for semantic and episodic olfactory memory. Structural magnetic resonance imaging (MRI), episodic and semantic odor memory and episodic and semantic verbal memory data were collected in 422 participants from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K), all aged ≥ 60 years. Controlling for age and education, semantic, but not episodic, olfactory memory was positively related to gray matter volume in a cluster extending from the anterior hippocampus and amygdala into the posterior piriform cortex. The observed associations remained even when verbal memory performance was controlled for, supporting a link between the olfactory memory domain and cortical volume over and above more generalized memory abilities. As such, our data provide evidence for distinct functional-structural associations for semantic odor memory, supporting the idea of temporolimbic integrity as a neurobiological substrate linking olfactory function to cognitive health in old age.

YNIMG Journal 2019 Journal Article

Olfactory loss is associated with reduced hippocampal activation in response to emotional pictures

Pengfei Han
Thomas Hummel
Claudia Raue
Ilona Croy

Emotional processing evolved within brain structures that were originally dedicated to olfactory function. Reduced olfactory function, absence of the olfactory bulb and the experimental removal of the olfactory bulb are associated with depressive behavior. Against this background, we hypothesized that olfactory dysfunction modifies the neural processing of non-olfactory emotion information. Using a functional magnetic resonance imaging design, we therefore tested whether people with and without impaired olfactory function differ in emotional perception and processing. Neural activity of 17 patients with acquired olfactory loss and 23 age- and sex-matched control participants were monitored in the MRI scanner, while they were presented with emotional and neutral pictures. Participants rated the valence and arousal for each picture after scanning. Patients showed reduced right hippocampal brain responses to emotional but not neutral pictures independent of their depressive symptoms. In addition, emotion-dependent activation in the hippocampus and insula was positively associated with the olfactory bulb (OB) volumes in healthy participants. Taken together, these findings suggest a disrupted neural processing of emotional pictures among patients with olfactory loss. This indicates a significant role of the neural olfactory trajectories for general emotion processing. Central emotion processing is reduced in olfactory disorders and relates to the OB volume in normosmic individuals.

YNICL Journal 2016 Journal Article

Brain lesion-pattern analysis in patients with olfactory dysfunctions following head trauma

Jörn Lötsch
Alfred Ultsch
Maren Eckhardt
Caroline Huart
Philippe Rombaux
Thomas Hummel

The presence of cerebral lesions in patients with neurosensory alterations provides a unique window into brain function. Using a fuzzy logic based combination of morphological information about 27 olfactory-eloquent brain regions acquired with four different brain imaging techniques, patterns of brain damage were analyzed in 127 patients who displayed anosmia, i.e., complete loss of the sense of smell (n = 81), or other and mechanistically still incompletely understood olfactory dysfunctions including parosmia, i.e., distorted perceptions of olfactory stimuli (n = 50), or phantosmia, i.e., olfactory hallucinations (n = 22). A higher prevalence of parosmia, and as a tendency also phantosmia, was observed in subjects with medium overall brain damage. Further analysis showed a lower frequency of lesions in the right temporal lobe in patients with parosmia than in patients without parosmia. This negative direction of the differences was unique for parosmia. In anosmia, and also in phantosmia, lesions were more frequent in patients displaying the respective symptoms than in those without these dysfunctions. In anosmic patients, lesions in the right olfactory bulb region were much more frequent than in patients with preserved sense of smell, whereas a higher frequency of carriers of lesions in the left frontal lobe was observed for phantosmia. We conclude that anosmia, and phantosmia, are the result of lost function in relevant brain areas whereas parosmia is more complex, requiring damaged and intact brain regions at the same time.

YNIMG Journal 2016 Journal Article

Olfactory modulation of affective touch processing — A neurophysiological investigation

Ilona Croy
Edda Drechsler
Paul Hamilton
Thomas Hummel
Håkan Olausson

Touch can be highly emotional, and depending on the environment, it can be perceived as pleasant and comforting or disgusting and dangerous. Here, we studied the impact of context on the processing of tactile stimuli using a functional magnetic resonance imaging (fMRI) paradigm. This was achieved by embedding tactile stimulation in a variable olfactory environment. Twenty people were scanned with BOLD fMRI while receiving the following stimulus blocks: Slow stroking Touch, Civette odor (feces like), Rose odor, Touch+Civette, and Touch+Rose. Ratings of pleasantness and intensity of tactile stimuli and ratings of disgust and intensity of olfactory stimuli were collected. The impact of the olfactory context on the processing of touch was studied using covariance analyses. Coupling between olfactory processing and somatosensory processing areas was assessed with psychophysiological interaction analysis (PPI). A subjectively disgusting olfactory environment significantly reduced the perceived pleasantness of touch. The touch fMRI activation in the secondary somatosensory cortex, operculum 1 (OP1), was positively correlated with the disgust towards the odors. Decreased pleasantness of touch was related to decreased posterior insula activity. PPI analysis revealed a significant interaction between the OP1, posterior insula, and regions processing the disgust of odors (orbitofrontal cortex and amygdala). We conclude that the disgust evaluation of the olfactory environment moderates neural reactivity in somatosensory regions by upregulation of the OP1 and downregulation of the posterior insula. This adaptive regulation of affective touch processing may facilitate adaptive reaction to a potentially harmful stimulus.

YNIMG Journal 2014 Journal Article

Human olfactory lateralization requires trigeminal activation

Ilona Croy
Max Schulz
Anna Blumrich
Cornelia Hummel
Johannes Gerber
Thomas Hummel

Rats are able to lateralize odors. This ability involves specialized neurons in the orbitofrontal cortex which are able to process the left, right and bilateral presentation of stimuli. However, it is not clear whether this function is preserved in humans. Humans are in general not able to differentiate whether a selective olfactory stimulant has been applied to the left or right nostril; however exceptions have been reported. Following a screening of 152 individuals with an olfactory lateralization test, we identified 19 who could lateralize odors above chance level. 15 of these “lateralizers” underwent olfactory fMRI scanning in a block design and were compared to 15 controls matched for age and sex distribution. As a result, both groups showed comparable activation of olfactory eloquent brain areas. However, subjects with lateralization ability had a significantly enhanced activation of cerebral trigeminal processing areas (somatosensory cortex, intraparietal sulcus). In contrast to controls, lateralizers furthermore exhibited no suppression in the area of the trigeminal principal sensory nucleus. An exploratory study with an olfactory change detection paradigm furthermore showed that lateralizers oriented faster towards changes in the olfactory environment. Taken together, our study suggests that the trigeminal system is activated to a higher degree by the odorous stimuli in the group of “lateralizers”. We conclude that humans are not able to lateralize odors based on the olfactory input alone, but vary in the degree to which the trigeminal system is recruited.

YNIMG Journal 2014 Journal Article

Olfactory short-term memory encoding and maintenance — An event-related potential study

Steffen Lenk
Annet Bluschke
Christian Beste
Emilia Iannilli
Veit Rößner
Thomas Hummel
Stephan Bender

This study examined whether the memory encoding and short term maintenance of olfactory stimuli is associated with neurophysiological activation patterns which parallel those described for sensory modalities such as vision and auditory. We examined olfactory event-related potentials in an olfactory change detection task in twenty-four healthy adults and compared the measured activation to that found during passive olfactory stimulation. During the early olfactory post-processing phase, we found a sustained negativity over bilateral frontotemporal areas in the passive perception condition which was enhanced in the active memory task. There was no significant lateralization in either experimental condition. During the maintenance interval at the end of the delay period, we still found sustained activation over bilateral frontotemporal areas which was more negative in trials with correct – as compared to incorrect – behavioural responses. This was complemented by a general significantly stronger frontocentral activation. Summarizing, we were able to show that olfactory short term memory involves a parallel sequence of activation as found in other sensory modalities. In addition to olfactory-specific frontotemporal activations in the memory encoding phase, we found slow cortical potentials over frontocentral areas during the memory maintenance phase indicating the activation of a supramodal memory maintenance system. These findings could represent the neurophysiological underpinning of the ‘olfactory flacon’, the olfactory counter-part to the visual sketchpad and phonological loop embedded in Baddeley's working memory model.

YNIMG Journal 2013 Journal Article

Brain structure is changed in congenital anosmia

Johannes Frasnelli
Therese Fark
Jacqueline Lehmann
Johannes Gerber
Thomas Hummel

Olfactory function in healthy people correlates with structural features of both the olfactory bulb and higher order olfactory processing areas, but we do not yet know how congenital anosmia affects these latter structures. In order to examine this question closer, we acquired T1 weighted magnetic resonance images from 17 subjects with congenital anosmia and from 17 age- and sex-matched controls. We compared white and gray matter volumes as well as cortical thickness between both groups. We found subjects with congenital anosmia to exhibit larger gray matter volumes in the left entorhinal and piriform cortices. Further, they had thicker orbitofrontal cortices bilaterally. Their left piriform cortex was also thicker than that of controls. These findings are in contrast to those observed in acquired anosmia, where reduced olfactory function is associated with reduced volumes and thickness. However, they fit well with observations from other sensory systems, e. g. , vision, where congenital sensory loss is associated with a thicker primary cortex. This finding has been attributed to reduced or absent synaptic pruning as a result of missing peripheral sensory input. Our findings suggest that similar mechanisms take place in the olfactory system.

YNIMG Journal 2012 Journal Article

Taste laterality studied by means of umami and salt stimuli: An fMRI study

Emilia Iannilli
P. Bano Singh
Benno Schuster
Johannes Gerber
Thomas Hummel

Aim of the present study was to investigate laterality of the gustatory system in the human brain for the taste qualities elicited by MSG (monosodium glutamate) and NaCl (sodium chloride). A total of 23 subjects participated in a block-design functional magnetic resonance imaging (fMRI) study. Liquid stimuli were presented at supra-threshold concentrations and delivered by means of a computer controlled gustometer. Left and right sides of the mouth were stimulated separately in order to correlate statistical parametrical maps to both the site of the stimulus and the specific taste quality. Following the effects of the site of stimulation through primary and secondary gustatory cortices an effort was made to explore the laterality of the gustatory pathways. Our results showed for both tastants a predominance of ipsilateral connections at the thalamus level. Insula left and right regions were both involved for both tastants. In these regions we found a high proportion of ipsilateral connection again for both the tastants. Considering orbitofrontal/prefrontal cortex, left-sided stimulation with NaCl or MSG produced left-sided activation of the orbito-frontal cortex clearly indicating the presence of an ipsilateral path. Finally, the hypothesis of frontal operculum as primary gustatory cortex and lateral prefrontal cortex as secondary was also supported by the results from dynamic causal modeling.

YNIMG Journal 2008 Journal Article

Thresholds and chemosensory event-related potentials to malodors before, during, and after puberty: Differences related to sex and age

Anita Chopra
Arianne Baur
Thomas Hummel

A sex-related difference in olfactory sensitivity to androstadienone and androstenone has been reported to occur during puberty. The study reported here extends this work to investigate whether sex and age differences exist before, during, and after puberty for 2-methyl, 3-mercapto-butanol (2M3M; a malodorous component of human sweat), carbon disulfide/hydrogen sulfide (H2S), and androstadienone. A total of 121 participants took part in the study (58 females, 63 males; age range 9–20 years). Participants were divided into 3 groups (i) pre-puberty, (ii) puberty and (iii) post-puberty. Threshold measurements for (i) androstadienone, (ii) 2M3M and (iii) carbon disulfide were recorded. Chemosensory event-related potentials (CSERPs) were recorded using air-dilution olfactometry. The results revealed that female thresholds for the three odorants were stable between the three age groups. Pubescent males had higher thresholds (less sensitive) for all three odorants. In the post-puberty group, sex differences were only observed for 2M3M. These differences are mirrored by significant sex differences for CSERP latencies. The latency increase in male pubescents may be due to the production of sweat by the apocrine glands resulting in increased levels of 2M3M and androstadienone, resulting in adaptation. To conclude, based on the present study performed in a relatively large sample, the processing of malodors in males is different from that of females during puberty. This observation not only relates to a reduced sensitivity towards odors typially found in axillary sweat but also extends towards other malodors. While the underlying cause may be partly due to specific adaptation towards malodors present in axillary sweat it might also reflect hormonal changes modifying the perception of odors.

YNIMG Journal 2007 Journal Article

Influence of chemosensory pain-expectancy on olfactory event-related potentials

Patricia J. Bulsing
Monique A.M. Smeets
Thomas Hummel
Marcel A. van den Hout

Health symptoms attributed to environmental odor exposure are not well understood. Cognitive factors seem to play a significant role in odor-related illness. In the present study, we investigated whether such influences are predominantly interpretational (i. e. best understood as interpretations of perceived odors), or also perceptual (i. e. affect perceptions of the characteristics of the odor). To investigate the neuronal activation behind such processes olfactory ERPs were recorded. The experiment consisted of two conditions: one where participants expected just several administrations of one odor (labelled as the “non-painful” condition), and one where they also expected, in between the odor administrations, to feel irritation in the nose (labelled as the “painful” condition). Participants received painless H2S stimuli during both conditions. To reinforce pain-expectancy, a CO2 pulse was given occasionally during the “painful” condition. Crucial comparisons were made between reactions to H2S, under the two expectancy conditions. Detection sensitivity (reflected by amplitudes and latencies of the early N1 peak) and stimulus salience (reflected by amplitudes and latencies of the late “cognitive” positivity) were examined. Peak amplitudes were unaffected by expectancy condition. However, a significant main effect of expectancy on the N1 latency was found, which suggests that expecting a painful stimulus reduces the time to detect a harmless odor. In conclusion, expectancies seem to alter early aspects of odor perception.

YNIMG Journal 2006 Journal Article

A putative social chemosignal elicits faster cortical responses than perceptually similar odorants

Johan N. Lundström
Mats J. Olsson
Benoist Schaal
Thomas Hummel

Social chemosignals, so-called pheromones, have recently attracted much attention in that effects on women's psychophysiology and cortical processing have been reported. We here tested the hypothesis that the human brain would process a putative social chemosignal, the endogenous steroid androstadienone, faster than other odorants with perceptually matched intensity and hedonic characteristics. Chemosensory event-related potentials (ERP) were recorded in healthy women. ERP analyses indicate that androstadienone was processed significantly faster than the control odorants. Androstadienone elicited shorter latencies for all recorded ERP components but most so for the late positivity. This finding indicates that androstadienone is processed differently than other related odorants, suggesting the possibility of a specific neuronal subsystem to the main olfactory pathway akin to the one previously reported in Old-world monkeys and emotional visual stimuli in humans.