Body Stimuli Research Articles

Neural Encoding of Bodies for Primate Social Perception.

Primates, as social beings, have evolved complex brain mechanisms to navigate intricate social environments. This review explores the neural bases of body perception in both human and nonhuman primates, emphasizing the processing of social signals conveyed by body postures, movements, and interactions. Early studies identified selective neural responses to body stimuli in macaques, particularly within and ventral to the superior temporal sulcus (STS). These regions, known as body patches, represent visual features that are present in bodies but do not appear to be semantic body detectors. They provide information about posture and viewpoint of the body. Recent research using dynamic stimuli has expanded the understanding of the body-selective network, highlighting its complexity and the interplay between static and dynamic processing. In humans, body-selective areas such as the extrastriate body area (EBA) and fusiform body area (FBA) have been implicated in the perception of bodies and their interactions. Moreover, studies on social interactions reveal that regions in the human STS are also tuned to the perception of dyadic interactions, suggesting a specialized social lateral pathway. Computational work developed models of body recognition and social interaction, providing insights into the underlying neural mechanisms. Despite advances, significant gaps remain in understanding the neural mechanisms of body perception and social interaction. Overall, this review underscores the importance of integrating findings across species to comprehensively understand the neural foundations of body perception and the interaction between computational modeling and neural recording.

Egocentric and Allocentric Spatial Memory for Body Parts: A Virtual Reality Study.

Extensive literature elucidated the mechanisms underlying the ability to memorize the positions of objects in space. However, less is known about the impact that objects' features have on spatial memory. The present study aims to investigate differences in egocentric and allocentric object-location memory between hand stimuli depicted in a first-person perspective (1PP) or in a third-person one (3PP). Fifty-two adults encoded spatial positions within a virtual museum environment featuring four square buildings. Each of these buildings featured eight paintings positioned along the walls, with two pictures displayed on each of the four walls. Thirty-two stimuli were employed, which represented pictures of the right hand performing various types of gestures. Half of the stimuli depicted the hand in the 1PP, while the other half depicted the hand in the 3PP. Both free and guided explorations served as encoding conditions. Immediately after that, participants underwent a two-step object-location memory task. Participants were provided with a map of the museum and asked to identify the correct building where the image was located (allocentric memory). Then, they were presented with a schematic representation of the exhibition room divided into four sections and instructed to select the section where they thought the picture was located (egocentric memory). Our findings indicate a memory performance boost associated with egocentric recall, regardless of the perspective of the bodily stimuli. The results are discussed considering the emerging literature on the mnemonic properties of body-related stimuli for spatial memory.

The role of identity priming on the (unconscious) bodily self-attribution

It has been recently demonstrated that hand stimuli presented in a first-, with respect to a third-, person perspective were prioritized before awareness independently from their identity (i.e., self, or other). This pattern would represent an unconscious advantage for self-related bodily stimuli rooted in spatial perspective. To deeper investigate the role of identity, we employed a breaking-Continuous Flash Suppression paradigm in which a self- or other-hand presented in first- or third-person perspective was displayed after a conscious identity-related prime (i.e., self or other face). We replicated the unconscious advantage of the first-person perspective but, crucially, we reported that within the first-person perspective, other-hand stimuli preceded by other-face priming slowed down the conscious access with respect to the other conditions. These findings demonstrate that a top-down conscious identity context modulates the unconscious self-attribution of bodily stimuli. Within a predictive processing framework, we suggest that, by adding ambiguous information, the prime forces a prediction update that slows conscious access.

Changes in spatial self-consciousness elicit grid cell–like representation in the entorhinal cortex

Grid cells in the entorhinal cortex (EC) encode an individual's location in space, integrating both environmental and multisensory bodily cues. Notably, body-derived signals are also primary signals for the sense of self. While studies have demonstrated that continuous application of visuo-tactile bodily stimuli can induce perceptual shifts in self-location, it remains unexplored whether these illusory changes suffice to trigger grid cell-like representation (GCLR) within the EC, and how this compares to GCLR during conventional virtual navigation. To address this, we systematically induced illusory drifts in self-location toward controlled directions using visuo-tactile bodily stimulation, while maintaining the subjects' visual viewpoint fixed (absent conventional virtual navigation). Subsequently, we evaluated the corresponding GCLR in the EC through functional MRI analysis. Our results reveal that illusory changes in perceived self-location (independent of changes in environmental navigation cues) can indeed evoke entorhinal GCLR, correlating in strength with the magnitude of perceived self-location, and characterized by similar grid orientation as during conventional virtual navigation in the same virtual room. These data demonstrate that the same grid-like representation is recruited when navigating based on environmental, mainly visual cues, or when experiencing illusory forward drifts in self-location, driven by perceptual multisensory bodily cues.

Transient cAMP production drives rapid and sustained spiking in brainstem parabrachial neurons to suppress feeding

Brief stimuli can trigger longer-lasting brain states. G-protein-coupled receptors (GPCRs) could help sustain such states by coupling slow-timescale molecular signals to neuronal excitability. Brainstem parabrachial nucleus glutamatergic (PBNGlut) neurons regulate sustained brain states such as pain and express Gs-coupled GPCRs that increase cAMP signaling. We asked whether cAMP in PBNGlut neurons directly influences their excitability and effects on behavior. Both brief tail shocks and brief optogenetic stimulation of cAMP production in PBNGlut neurons drove minutes-long suppression of feeding. This suppression matched the duration of prolonged elevations in cAMP, protein kinase A (PKA) activity, and calcium activity invivo and exvivo, as well as sustained, PKA-dependent increases in action potential firing exvivo. Shortening this elevation in cAMP reduced the duration of feeding suppression following tail shocks. Thus, molecular signaling in PBNGlut neurons helps prolong neural activity and behavioral states evoked by brief, salient bodily stimuli.

Dream incorporation of three different bodily stimuli

Introduction Lucid dreaming opens the possibility to rehearse sport skills within a dream while sleeping (Peters et al. 2023; Stumbrys et al. 2016). But so far, no induction techniques have been developed to induce reliable lucid dreams. One potential technique is to apply external stimulation while a person is sleeping in order to send a hint into the dream which might enhance lucidity in the ongoing dream. Several studies have tested dream incorporation rates (DIR) with different stimuli and different results (Schredl, 2018), but none with a larger sample size and a within-design. Furthermore, in this study we wanted to explore body related stimulations to evoke in future studies lucid dreams. Methods 10-Channel polysomnography and three different bodily stimulation methods were combined during three consecutive test nights with each night using one stimulation method (plus adaptation night). The three stimulation methods consisted of electrical forearm muscle stimulation (EMS), galvanic vestibular stimulation (GVS), and haptic vibration stimulation (HS). During REM sleep, one of the three stimuli was presented or a sham condition was applied in a counterbalanced order. The stimuli were followed by REM awakenings, resulting in corresponding verbal dream reports. With the help of those reports, the translation from a physical arm movement, vestibular sensation and vibration into the dream environment was investigated using dream content analysis. Movement of the dream arm, balance related activity and tactile or somatosensory sensations targeted the dream incorporations of EMS, GVS and HS respectively. Results Movement of the arm was present in 23.2%, 8.1% and 23.5% of EMS, GVS and HS dreams respectively. Balance-related activity was present in 6.1%, 7.9% and 5.8% of EMS, GVS and HS dreams respectively. Finally, tactile and somatosensory sensations were present in 13.6%, 0% and 6.3% of the EMS, GVS and HS dreams respectively. After correcting for sham condition, tactile and somatosensory sensations on the EMS dreams seem to be the strongest incorporation effect upon stimulation. Discussion/Conclusion We tested dream incorporation of three different stimulation methods using a within-design on a larger sample size, a method that has never been attempted before. GVS appears unsuccessful in altering dream content, but this might be confounded due to challenges in methodology. EMS evokes the most dream incorporation in the scale of tactile and somatosensory dream content followed by HS. The investigation of the incorporation of external kinesthetic stimulation into dream content represents a fundamental contribution to various scientific fields and could foster future research on lucid dream induction, enabling the further exploration of sport practice in a sleep state.

Agreeableness modulates mental state decoding: Electrophysiological evidence.

Agreeableness is one of the five personality traits which is associated with theory of mind (ToM) abilities. One of the critical processes involved in ToM is the decoding of emotional cues. In the present study, we investigated whether this process is modulated by agreeableness using electroencephalography (EEG) while taking into account task complexity and sex differences that are expected to moderate the relationship between emotional decoding and agreeableness. This approach allowed us to identify at which stage of the neural processing agreeableness kicks in, in order to distinguish the impact on early, perceptual processes from slower, inferential processing. Two tasks were employed and submitted to 62 participants during EEG recording: the reading the mind in the eyes (RME) task, requiring the decoding of complex mental states from eye expressions, and the biological (e)motion task, involving the perception of basic emotional actions through point-light body stimuli. Event-related potential (ERP) results showed a significant correlation between agreeableness and the contrast for emotional and non-emotional trials in a late time window only during the RME task. Specifically, higher levels of agreeableness were associated with a deeper neural processing of emotional versus non-emotional trials within the whole and male samples. In contrast, the modulation in females was negligible. The source analysis highlighted that this ERP-agreeableness association engages the ventromedial prefrontal cortex. Our findings expand previous research on personality and social processing and confirm that sex modulates this relationship.

Mirror Exposure Training for Adolescents With Anorexia Nervosa (MIRADAN): Cognitive Mechanisms of Body Disturbance - A Study Protocol.

Anorexia Nervosa (AN) is a severe mental illness, which typically develops in adolescence and, if left untreated, often becomes chronic. Body dissatisfaction is a core characteristic of AN. Mirror exposure (ME) is an effective therapeutic technique to tackle body dissatisfaction in adult patients with eating disorders, but there is limited evidence for the effects of ME in adolescence. One potential mechanism underlying effects of ME on body dissatisfaction is change in body-related attention bias. However, this mechanism remains to be empirically tested. Accordingly, the aim of the current study is twofold: primarily, we aim to test if ME can reduce body dissatisfaction and associated symptoms in adolescent patients with AN. Additionally, we aim to investigate whether change in biased body-related attention due to ME is a possible mechanism of action. Adolescent patients with AN are randomized to either 12 sessions of ME (3 ME-sessions/week) or wait-list within four weeks. Main outcomes include body dissatisfaction and associated symptoms of AN. Moreover, body-related attention bias is assessed at baseline and post-treatment by means of eye-tracking with two paradigms. Further, process variables are collected weekly. In addition, 12 weeks after end of the study, the acceptability of the ME is assessed. The main aim of the study is to evaluate high-frequency and high-intense ME for treating body dissatisfaction in adolescents with AN. In addition, we would like to clarify whether change in attentional bias for body stimuli is a mechanism underlying change in body dissatisfaction due to ME.

Anatomical predictors of mental rotation with bodily and non-bodily stimuli: A lesion-symptom study

Mental rotation (MR) is widely regarded as a quintessential example of an embodied cognitive process. This viewpoint stems from the functional parallels between MR and the physical rotation of tangible objects, as well as participants' inclination to employ motor-based strategies when tackling MR tasks involving bodily stimuli. These commonalities imply that MR may depend on brain regions crucial for the planning and execution of motor programs. However, there is disagreement regarding the anatomy of MR between findings from functional imaging and lesion studies involving brain-injured patients. The former indicate the involvement of the right-hemispheric parietal cortex, while the latter underscore the significance of posterior areas in the left hemisphere. In this study, we aimed to discern the neural underpinnings of MR using lesion-symptom mapping (LSM) for both bodily (hands) and non-bodily (letters) stimuli. Behavioral results from the two MR tasks revealed impaired MR of bodily stimuli in patients with left hemisphere damage. LSM results pinpointed the left primary motor and somatosensory cortices, along with the superior parietal lobule, as the anatomical substrates of MR for both bodily and non-bodily stimuli. Furthermore, damage to the left angular gyrus, supramarginal gyrus, supplementary motor area, and retrosplenial cortex was associated with MR of non-bodily stimuli. These findings support the causal involvement of the left hemisphere in MR and underscore the existence of a common anatomical substrate in brain regions pertinent to motor planning and execution.

Body appearance values modulate risk aversion in eating restriction.

The understanding of eating disorders is hindered by the lack of integration between existing psychosocial and neurobiological approaches. We address this problem by developing a novel transdiagnostic and computational approach to eating restriction decisions. We first validated a novel paradigm which extends an established monetary risk task to involve body stimuli with psychosocial values. We used advanced behavioral data analysis of a large (total N = 539) sample of women from across the eating restraint spectrum, including those with anorexia nervosa (AN; n = 31), recovered from AN (n = 23), and subclinical women with varying levels of eating restraint (n = 485), obtained from an online experiment, public event, and laboratory-based study. We found that social and motivational values regarding body appearance have a significant effect on value-based, decision making in eating restriction. Subsequently, validated descriptive and predictive advanced computational modeling indicated that these behaviors are driven by an aversion to risk rather than loss, with desirable body outcomes being associated with less risk aversion, and undesirable body outcomes linked to greater risk aversion. These findings indicate that cognitive and social factors influence eating decisions by distinct mechanisms. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

A scoping review and index of body stimuli in psychological science.

Naturalistic body stimuli are necessary for understanding many aspects of human psychology, yet there are no centralized databases of body stimuli. Furthermore, there are a high number of independently developed stimulus sets lacking in standardization and reproducibility potential, and a general lack of organization, contributing to issues of both replicability and generalizability in body-related research. We conducted a comprehensive scoping review to index and explore existing naturalistic whole-body stimuli. Our research questions were as follows: (1) What sets of naturalistic human whole-body stimuli are present in the literature? And (2) On what factors (e.g., demographics, emotion expression) do these stimuli vary? To be included, stimulus sets had to (1) include human bodies as stimuli; (2) be photographs, videos, or other depictions of real human bodies (not computer generated, drawn, etc.); (3) include the whole body (defined as torso, arms, and legs); and (4) could include edited images, but still had to be recognizable as human bodies. We identified a relatively large number of existing stimulus sets (N = 79) which offered relative variability in terms of main manipulated factors and the degree of visual information included (i.e., inclusion of heads and/or faces). However, stimulus sets were demographically homogenous, skewed towards White, young adult, and female bodies. We identified significant issues in reporting and availability practices, posing a challenge to the generalizability, reliability, and reproducibility of body-related research. Accordingly, we urge researchers to adopt transparent and accessible practices and to take steps to diversify body stimuli.

Queues, crowds, and angry mobs: Face identification under distraction in a virtual airport.

In visual environments, selective attention must be employed to focus on task-relevant stimuli. A key question here concerns the extent to which other stimuli within the visual field influence target processing. In this study, we ask whether face identity matching is subject to similar effects from irrelevant stimuli in the visual field, specifically task-irrelevant people. Although most previous studies rely on highly controlled face and body stimuli presented in isolation, here we use a more realistic environment. Participants take the role of passport officers and must match a person's face to their photo-ID, while other people appear in the background, waiting to be processed. Presenting an interactive virtual environment on screen (Experiments 1 and 2) or in immersive VR (Experiment 3), we generally found no evidence for distraction from background people on face-matching accuracy. However, when immersed in VR, an angry crowd in the background delayed matching speed while not affecting accuracy. We discuss the theoretical implications of these results and their potential importance in practical settings.

Measuring implicit associations between food and body stimuli in anorexia nervosa: a Go/No-Go Association Task

PurposeThe present study aimed to explore the implicit associations between food and bodily stimuli in patients with anorexia nervosa (AN) and control subjects (HC).MethodsA Go/No-Go Association Task was administrated to 55 participants (28 AN and 27 HC), using food stimuli (low-calorie food vs. high-calorie food) and body stimuli (underweight vs. overweight bodies).ResultsWe evidenced an implicit association between food and body stimuli in the AN group, whereas the HC group only showed a tendency. AN and HC groups also exhibited different categorization strategies: the AN group tended to categorize stimuli as low-calorie foods and underweight bodies less than the HC group, and they tended to categorize stimuli as high-calorie foods and overweight bodies more than the HC group.ConclusionThe present study revealed for the first time specificities of the AN population’s implicit association between food and body stimuli in terms of association strength and categorization strategy. Furthermore, the results suggest that combining implicit methodologies with other methods could contribute to a better characterization of the physiopathology of AN.Level of evidenceLevel I, experimental study.

Depersonalization affects self-prioritization of bodily, but not abstract self-related information.

Depersonalization is a common and distressing experience characterized by a feeling of estrangement from one's self, body, and the world. In order to examine the relationship between depersonalization and selfhood we conducted an experimental study comparing processing of three types of self-related information between nonclinical groups of people experiencing high and low levels of depersonalization. Using a sequential matching task, we compared three types of biases for processing of self-related information: prioritization of one's name, of self-associated abstract stimuli (geometrical shapes), and of self-associated bodily stimuli (avatar faces). We found that both groups demonstrated the standard pattern of results for self-prioritization of one's name and geometrical shapes, but they differed with regard to avatar faces. While people with low depersonalization showed the standard prioritization of avatar faces, people with high depersonalization showed overall better response accuracy with avatar faces, and faster response times for stranger-associated avatar faces. These results were complemented by the additional finding that people with high depersonalization reported being more likely to use avatars of a different gender to their own outside of the experimental context. Finally, in this large sample (N = 180) we investigated the relationships between different measures of self-related processing and self-identification, finding no correlation between explicit reports of self-identification with self-associated avatar faces and geometrical shapes, self-prioritization of these stimuli, and prioritization of one's name. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

How embodied is cognition? fMRI and behavioral evidence for common neural resources underlying motor planning and mental rotation of bodily stimuli.

Functional neuroimaging shows that dorsal frontoparietal regions exhibit conjoint activity during various motor and cognitive tasks. However, it is unclear whether these regions serve several, computationally independent functions, or underlie a motor "core process" that is reused to serve higher-order functions. We hypothesized that mental rotation capacity relies on a phylogenetically older motor process that is rooted within these areas. This hypothesis entails that neural and cognitive resources recruited during motor planning predict performance in seemingly unrelated mental rotation tasks. To test this hypothesis, we first identified brain regions associated with motor planning by measuring functional activations to internally-triggered vs externally-triggered finger presses in 30 healthy participants. Internally-triggered finger presses yielded significant activations in parietal, premotor, and occipitotemporal regions. We then asked participants to perform two mental rotation tasks outside the scanner, consisting of hands or letters as stimuli. Parietal and premotor activations were significant predictors of individual reaction times when mental rotation involved hands. We found no association between motor planning and performance in mental rotation of letters. Our results indicate that neural resources in parietal and premotor cortex recruited during motor planning also contribute to mental rotation of bodily stimuli, suggesting a common core component underlying both capacities.

Spatial perspective and identity in visual awareness of the bodily self-other distinction

Spatial perspective and identity of visual bodily stimuli are two key cues for the self-other distinction. However, how they emerge into visual awareness is largely unknown. Here, self- or other-hands presented in first- or third-person perspective were compared in a breaking-Continuous Flash Suppression paradigm (Experiment 1) measuring the time the stimuli need to access visual awareness, and in a Binocular Rivalry paradigm (Experiment 2), measuring predominance in perceptual awareness. Results showed that, irrespectively of identity, first-person perspective speeded up the access, whereas the third-person one increased the dominance. We suggest that the effect of first-person perspective represents an unconscious prioritization of an egocentric body coding important for visuomotor control. On the other hand, the effect of third-person perspective indicates a conscious advantage of an allocentric body representation fundamental for detecting the presence of another intentional agent. Summarizing, the emergence of self-other distinction into visual awareness would strongly depend on the interplay between spatial perspectives, with an inverse prioritization before and after conscious perception. On the other hand, identity features might rely on post-perceptual processes.

Red biases sex categorization of human bodies.

Color is associated with gender information (e.g., red-female). However, little has been known on the effect of color on sex recognition of human bodies. This study aimed to investigate whether the color red could influence the categorization of human bodies by sex, and the effect of contextual information. Visual stimuli were created using body silhouettes varying along the waist-to-hip ratio from female to male shapes. These stimuli were presented in conjunction with red, green, and gray colors, which were used either as body color (Experiment 1) or background color (Experiment 2). Participants were instructed to categorize the sex of the body stimuli as either male or female by pressing labeled keys. The results showed that when red was used as a body color, it induced a bias toward feminine body perception, while when used as a background color, it induced a bias toward masculine body perception. Thus, the color red influenced the sex categorization of human bodies, which being modulated by contextual information. These findings provided novel insights into the effect of contextual color cues in sex recognition of human bodies.

The relationship between body dissatisfaction and attentional bias to thin bodies in Malaysian Chinese and White Australian women: a dot probe study.

Studies suggest that an attentional bias to thin bodies is common among those with high levels of body dissatisfaction, which is a risk factor for, and symptom of, various eating disorders. However, these studies have predominantly been conducted in Western countries with body stimuli involving images of White people. In a preregistered study, we recruited 150 Malaysian Chinese women and 150 White Australian women for a study using standardized images of East Asian and White Australian bodies. To measure attentional bias to thin bodies, participants completed a dot probe task which presented images of women who self-identified their ethnicity as East Asian or as White Australian. Contrary to previous findings, we found no evidence for an association between body dissatisfaction and attentional bias to thin bodies. This lack of association was not affected by participant ethnicity (Malaysian Chinese versus White Australian) or ethnic congruency between participants and body stimuli (own-ethnicity versus other-ethnicity). However, the internal consistency of the dot probe task was poor. These results suggest that either the relationship between body dissatisfaction and attentional bias to thin bodies is not robust, or the dot probe task may not be a reliable measure of attentional bias to body size.

Infants’ representations of the infant body in the first year of life: a preferential looking time study

Representing others’ bodies is of fundamental importance for interacting with our environment, yet little is known about how body representations develop. Previous research suggests that infants have expectations about the typical structure of human bodies from relatively early in life, but that these expectations are dependent on how closely the stimuli resemble the bodies infants are exposed to in daily life. Yet, all previous studies used images of adult human bodies, and therefore it is unknown whether infants’ representations of infant bodies follow a similar developmental trajectory. In this study we investigated whether infants have expectations about the relative size of infant body parts in a preferential looking study using typical and disproportional infant bodies. We recorded the looking behaviour of three groups of infants between 5 and 14 months of age while they watched images of upright and inverted infant bodies, typical and proportionally distorted, and also collected data on participants’ locomotor abilities. Our results showed that infants of all ages looked equally at the typical and proportionally distorted infant body stimuli in both the upright and inverted conditions, and that their looking behaviour was unrelated to their locomotor skills. These findings suggest that infants may need additional visual experience with infant bodies to develop expectations about their typical proportions.

Autopilot functionality and self-destructive behavior in patients with complex dissociative disorders-A qualitative study.

Dissociative disorders are common in psychiatric patients and severely impact patients' lives. They are, however, underdiagnosed, thus preventing patients from accessing timely and adequate therapy. Identifying how patients with dissociative disorders relate to themselves could improve diagnostics. However, this question has not been explored in detail. The aim of the study was to gain insights into how people with complex dissociative disorders relate to themselves. We conducted semistructured qualitative interviews with ten women diagnosed with complex dissociative disorders who had previously completed trauma-focused therapy. Data were analyzed through reflexive thematic analysis. Participants described their behavior toward themselves before the start of the therapy as "autopilot-functional" and "self-destructive." The "autopilot functionality" was characterized by being outward-oriented and ignoring one's own needs. Hence, participants only appeared to be functional. "Self-destructive behavior" was described as a spectrum of various destructive behaviors (e.g., eating disorders, self-harm, excessive exercise, and substance abuse) that participants perceived as a cohesive complex. The participants illustrated that both behaviors were driven by a lack of self-empathy and connected to suppression and poor perception of bodily stimuli. "Autopilot functionality" seems to be a hallmark in patients with complex dissociative disorders. With patients hiding their self-destructive behavior, health personnel may misjudge the severity of these patients' mental illness. Neither "autopilot functionality" nor "self-destructive behavior" should be judged (neither negatively nor positively), but one should understand both as a coping mechanism for trauma-related disorders. (PsycInfo Database Record (c) 2023 APA, all rights reserved).