Enhanced early visual processing in response to snake and trypophobic stimuli

[Neural mechanisms of fear responses to emotional stimuli: a preliminary study combining early posterior negativity and electroencephalogram source network analysis]

Fear emotion is a typical negative emotion that is commonly present in daily life and significantly influences human behavior. A deeper understanding of the mechanisms underlying negative emotions contributes to the improvement of diagnosing and treating disorders related to negative emotions. However, the neural mechanisms of the brain when faced with fearful emotional stimuli remain unclear. To this end, this study further combined electroencephalogram (EEG) source analysis and cortical brain network construction based on early posterior negativity (EPN) analysis to explore the differences in brain information processing mechanisms under fearful and neutral emotional picture stimuli from a spatiotemporal perspective. The results revealed that neutral emotional stimuli could elicit higher EPN amplitudes compared to fearful stimuli. Further source analysis of EEG data containing EPN components revealed significant differences in brain cortical activation areas between fearful and neutral emotional stimuli. Subsequently, more functional connections were observed in the brain network in the alpha frequency band for fearful emotions compared to neutral emotions. By quantifying brain network properties, we found that the average node degree and average clustering coefficient under fearful emotional stimuli were significantly larger compared to neutral emotions. These results indicate that combining EPN analysis with EEG source component and brain network analysis helps to explore brain functional modulation in the processing of fearful emotions with higher spatiotemporal resolution, providing a new perspective on the neural mechanisms of negative emotions.

Excessive fear of clusters of holes, its interaction with stressful life events and the association with anxiety and depressive symptoms: large epidemiological study of young people in Hong Kong

BACKGROUND

Excessive and persistent fear of clusters of holes, also known as trypophobia, has been suggested to reflect cortical hyperexcitability and may be associated with mental health risks. No study, however, has yet examined these associations in representative epidemiological samples.

AIMS

To examine the prevalence of trypophobia in a population-representative youth sample, its association with mental health and functioning, and its interaction with external stress.

METHOD

A total of 2065 young people were consecutively recruited from a household-based epidemiological youth mental health study in Hong Kong. Trypophobia, symptoms of anxiety, depression and stress, and exposure to personal stressors were assessed. Logistic regression was used to assess the relationships between trypophobia and mental health. Potential additive and interaction effects of trypophobia and high stress exposure on mental health were also tested.

RESULTS

The prevalence of trypophobia was 17.6%. Trypophobia was significantly associated with severe symptoms of anxiety (odds ratio (OR) = 1.83, 95% CI = 1.32-2.53), depression (OR = 1.78, 95% CI = 1.24-2.56) and stress (OR = 1.68, 95% CI = 1.11-2.53), even when accounting for sociodemographic factors, personal and family psychiatric history, resilience and stress exposure. Dose-response relationships were observed, and trypophobia significantly potentiated the effects of stress exposure on symptom outcomes, particularly for depressive symptoms. Those with trypophobia also showed significantly poorer functioning across domains and poorer health-related quality of life.

CONCLUSIONS

Screening for trypophobia in young people may facilitate early risk detection and intervention, particularly among those with recent stress exposure. Nevertheless, the generally small effect sizes suggest that other factors have more prominent roles in determining recent mental health outcomes in population-based samples; these should be explored in future work.

A social media network analysis of trypophobia communication

Trypophobia has attracted scientific attention in recent years. Few related studies have recruited participants using online methods, and even less is known about health communication in an environment where trypophobia was first widely discussed (i.e., the Internet). This study describes communication patterns in a Facebook group for trypophobia by detecting frequent topics, top contributors, and their discourses. We identified key commenters and performed word frequency analysis, word co-occurrence analysis, topic modeling, and content analysis. Impactful users posted and replied more often when discussing peer-reviewed science. Triggering content was actively removed by the group administrators. A wide variety of triggers not discussed in trypophobia-related literature were frequently mentioned. However, there was a lack of discussion on peer-reviewed treatments. The combination of a few expert and many supportive amateur gatekeepers willing to understand trypophobia, along with active monitoring by administrators, might contribute to in-group trust and the sharing of peer-reviewed science by top users of the trypophobia Facebook group.

Evaluating the 'skin disease-avoidance' and 'dangerous animal' frameworks for understanding trypophobia

ABSTRACTTrypophobia refers to the extreme negative reaction when viewing clusters of circular objects. Two major evolutionary frameworks have been proposed to account for trypophobic visual discomfort. The skin disease-avoidance (SD) framework proposes that trypophobia is an over-generalised response to stimuli resembling pathogen-related skin diseases. The dangerous animal (DA) framework posits that some dangerous organisms and trypophobic stimuli share similar visual characteristics. Here, we performed the first experimental manipulations which directly compare these two frameworks by superimposing trypophobic imagery onto multiple image categories to evaluate changes in comfort. Participants from two countries (United States and Croatia) were evaluated on several measures, including general trypophobia levels, perceived vulnerability to disease, and generalised anxiety. Several analyses showed stronger changes in comfort in the human skin condition (hand, feet, and chest images) compared to the dangerous animal condition (snake and spider images). Furthermore, participants with higher levels of trypophobia showed significantly stronger changes in comfort in the skin condition than the dangerous animal condition, with comparable effects obtained across nationalities. Several variables entered as covariates failed to significantly account for this effect. The present work is the first to experimentally test both evolutionary frameworks of trypophobia, with results supporting the skin disease-avoidance framework.

Neural processing of emotional facial stimuli in specific phobia: An fMRI study

BACKGROUND

Patients with specific phobia (SP) show altered brain activation when confronted with phobia-specific stimuli. It is unclear whether this pathogenic activation pattern generalizes to other emotional stimuli. This study addresses this question by employing a well-powered sample while implementing an established paradigm using nonspecific aversive facial stimuli.

METHODS

N = 111 patients with SP, spider subtype, and N = 111 healthy controls (HCs) performed a supraliminal emotional face-matching paradigm contrasting aversive faces versus shapes in a 3-T magnetic resonance imaging scanner. We performed region of interest (ROI) analyses for the amygdala, the insula, and the anterior cingulate cortex using univariate as well as machine-learning-based multivariate statistics based on this data. Additionally, we investigated functional connectivity by means of psychophysiological interaction (PPI).

RESULTS

Although the presentation of emotional faces showed significant activation in all three ROIs across both groups, no group differences emerged in all ROIs. Across both groups and in the HC > SP contrast, PPI analyses showed significant task-related connectivity of brain areas typically linked to higher-order emotion processing with the amygdala. The machine learning approach based on whole-brain activity patterns could significantly differentiate the groups with 73% balanced accuracy.

CONCLUSIONS

Patients suffering from SP are characterized by differences in the connectivity of the amygdala and areas typically linked to emotional processing in response to aversive facial stimuli (inferior parietal cortex, fusiform gyrus, middle cingulate, postcentral cortex, and insula). This might implicate a subtle difference in the processing of nonspecific emotional stimuli and warrants more research furthering our understanding of neurofunctional alteration in patients with SP.

Emotion-Attention Interaction in the Right Hemisphere

Hemispheric asymmetries in affective and cognitive functions have been extensively studied. While both cerebral hemispheres contribute to most affective and cognitive processes, neuroscientific literature and neuropsychological evidence support an overall right hemispheric dominance for emotion, attention and arousal. Emotional stimuli, especially those with survival value such as threat, tend to be prioritized in attentional resource competition. Arousing unpleasant emotional stimuli have prioritized access, especially to right-lateralized attention networks. Interference of task performance may be observed when limited resources are exhausted by task- and emotion-related processing. Tasks that rely on right hemisphere-dependent processing, like attending to the left visual hemifield or global-level visual features, are especially vulnerable to interference due to attention capture by unpleasant emotional stimuli. The aim of this review is to present literature regarding the special role of the right hemisphere in affective and attentional brain processes and their interaction. Furthermore, clinical and technological implications of this interaction will be presented. Initially, the effects of focal right hemisphere lesion or atrophy on emotional functions will be introduced. Neurological right hemisphere syndromes including aprosodia, anosognosia and neglect, which further point to the predominance of the intact right hemisphere in emotion, attention and arousal will be presented. Then there will be a brief review of electrophysiological evidence, as well as evidence from patients with neglect that support attention capture by emotional stimuli in the right hemisphere. Subsequently, experimental work on the interaction of emotion, attention and cognition in the right hemispheres of healthy subjects will be presented. Finally, clinical implications for better understanding and assessment of alterations in emotion-attention interaction due to brain disorder or treatment, such as neuromodulation, that impact affective brain functions will be discussed. It will be suggested that measuring right hemispheric emotion-attention interactions may provide basis for novel biomarkers of brain health. Such biomarkers allow for improved diagnostics in brain damage and disorders and optimized treatments. To conclude, future technological applications will be outlined regarding brain physiology-based measures that reflect engagement of the right hemisphere in affective and attentional processes.

Trypophobia: Heart rate, heart rate variability and cortical haemodynamic response

BACKGROUND

Trypophobia is a common condition in which sufferers are averse to images of small holes arranged in clusters.

METHODS

We used photo-plethysmography to examine cardiovascular correlates and near infrared spectroscopy to examine cortical correlates of the phenomenon in order to validate the Trypophobia Questionnaire and explore the several interlinked explanations of the disorder.

RESULTS

Trypophobic images were found to increase both heart rate and heart rate variability, but only in individuals with high scores on the Trypophobia Questionnaire. Trypophobic images were also found to elicit larger haemodynamic responses in posterior cortical areas, but again only in individuals with high scores.

LIMITATIONS

The results are consistent with a contribution from both parasympathetic and sympathetic systems.

CONCLUSION

The data demonstrate the validity of the Trypophobia Questionnaire and show an involvement not only of the autonomic system but cortical mechanisms including cortical hyperexcitability.

Pattern matters: Snakes exhibiting triangular and diamond-shaped skin patterns modulate electrophysiological activity in human visual cortex

The neural and perceptual mechanisms that support the efficient visual detection of snakes in humans are still not fully understood. According to the Snake Detection Theory, selection pressures posed by snakes on early primates have shaped the development of the visual system. Previous studies in humans have investigated early visual electrophysiological activity in response to snake images vs. various alternative dangerous or non-dangerous stimuli. These studies have shown that the Early Posterior Negativity (EPN) component is selectively elicited by snake or snake-like images. Recent findings yielded the complementary/alternative hypothesis that early humans (and possibly other primates) evolved an aversion especially for potentially harmful triangular shapes, such as teeth, claws or spikes. In the present study we investigated the effect of triangular and diamond-shaped patterns in snake skins on the ERP correlates of visual processing in humans. In the first experiment, we employed pictures of snakes displaying either triangular/diamond-shaped patterns or no particular pattern on their skins, and pictures of frogs as control. Participants observed a random visual presentation of these pictures. Consistent with previous studies, snakes elicited an enhanced negativity between 225 and 300 ms (EPN) compared to frogs. However, snakes featuring triangular/diamond-shaped patterns on their skin produced an enhanced EPN compared to the snakes that did not display such patterns. In a second experiment we used pictures displaying only skin patterns of snakes and frogs. Results from the second experiment confirmed the results of the first experiment, suggesting that triangular snake-skin patterns modulate the activity in human visual cortex. Taken together, our results constitute an important contribution to the snake detection theory.

Trypophobic images gain preferential access to early visual processes

Trypophobia is a common but unusual phobia that is induced by viewing many clustered objects. Previous studies suggested that this trypophobia is caused by the specific power spectrum of the images; this idea has not been fully investigated empirically. In the present study, we used breaking continuous flash suppression (b-CFS) to clarify whether the trypophobic images affect access to visual awareness, and what features of trypophobic images contribute to rapid access of awareness. In the b-CFS paradigms, a dynamic masking pattern presented to one eye suppresses the target images shown to the other eye. The participants' task was to indicate where the target image appeared in a dichoptic display through a mirror stereoscope. The target images consisted of trypophobic, fear-related, clusters or neutral images. The trypophobic images emerged into awareness faster than the other types of images. However, the phase-scrambled versions of the trypophobic images did not show any differences across the image types, suggesting that the trypophobic power spectra themselves did not affect access to awareness. Moreover, the phase-scrambled trypophobic images without CFS tended to be detected earlier than the phase-scrambled fearful and neutral images. These findings indicate that trypophobic power spectra might affect post-perceptual processing, such as response production.