The Development of Tactile Perception

Synchrony perception across senses: A systematic review of temporal binding window changes from infancy to adolescence in typical and atypical development

Sensory integration is increasingly acknowledged as being crucial for the development of cognitive and social abilities. However, its developmental trajectory is still little understood. This systematic review delves into the topic by investigating the literature about the developmental changes from infancy through adolescence of the Temporal Binding Window (TBW) - the epoch of time within which sensory inputs are perceived as simultaneous and therefore integrated. Following comprehensive searches across PubMed, Elsevier, and PsycInfo databases, only experimental, behavioral, English-language, peer-reviewed studies on multisensory temporal processing in 0-17-year-olds have been included. Non-behavioral, non-multisensory, and non-human studies have been excluded as those that did not directly focus on the TBW. The selection process was independently performed by two Authors. The 39 selected studies involved 2859 participants in total. Findings indicate a predisposition towards cross-modal asynchrony sensitivity and a composite, still unclear, developmental trajectory, with atypical development associated to increased asynchrony tolerance. These results highlight the need for consistent and thorough research into TBW development to inform potential interventions.

Cognitive potential of children and adolescents with CHARGE syndrome and deafblindness

BACKGROUND

The present study aimed to test the hypothesis stating that the cognitive potential of individuals with deafblindness is equal to those without a deafblind condition, an assumption that until now has been empirically unsubstantiated within the field of deafblindness.

METHODS

To explore the assumption, 15 children and adolescents with CHARGE underwent cognitive assessment with WISC-V using a sequential two-level assessment design. The 1st level involved standardized test conditions. The 2nd level was designed as a continuation of the performances obtained from the 1st level and involved accommodations to compensate for sensory motor impairment. Statistical procedures involved the sample as a whole and when divided into two subgroups: (i) participants with CHARGE without deafblindness; (ii) participants with CHARGE and deafblindness using the 1st level scores as base line.

RESULTS

Although results showed significantly lower scores in the deafblind subgroup with standardized procedures, they approximated the others after accommodating for their sensory deficits. This positive increase proved significant.

CONCLUSION

Findings supported the assumption of equal cognitive potential of individuals with and without deafblindness. Results indicated that the children and adolescents with deafblindness had most effect of the accommodations, enabling them to approximate the results of the subgroup without deafblindness. These gains were attributed enhanced accessibility endorsed by the accommodations and represented the participants latent cognitive dispositions only realized under certain circumstances.

Tactile discrimination as a diagnostic indicator of cognitive decline in patients with mild cognitive impairment: A narrative review

Background

Tactile discrimination, a cognitive task reliant on fingertip touch for stimulus discrimination, encompasses the somatosensory system and working memory, with its acuity diminishing with advancing age. Presently, the evaluation of cognitive capacity to differentiate between individuals with early Alzheimer's disease (AD) and typical older adults predominantly relies on visual or auditory tasks, yet the efficacy of discrimination remains constrained.

Aims

To review the existing tactile cognitive tasks and explore the interaction between tactile perception and the pathological process of Alzheimer's disease. The tactile discrimination task may be used as a reference index of cognitive decline in patients with mild cognitive impairment and provide a new method for clinical evaluation.

Methods

We searched four databases (Embase, PubMed, Web of Science and Google scholar). The reference coverage was from 1936 to 2023. The search terms included "Alzheimer disease" "mild cognitive impairment" "tactile" "tactile discrimination" "tactile test" and so on. Reviews and experimental reports in the field were examined and the effectiveness of different types of tactile tasks was compared.

Main results

Individuals in the initial phases of Alzheimer's spectrum disease, specifically those in the stage of mild cognitive impairment (MCI), exhibit notable impairments in tasks involving tactile discrimination. These tasks possess certain merits, such as their quick and straightforward comparability, independence from educational background, and ability to circumvent the limitations associated with conventional cognitive assessment scales. Furthermore, tactile discrimination tasks offer enhanced accuracy compared to cognitive tasks that employ visual or auditory stimuli.

Conclusions

Tactile discrimination has the potential to serve as an innovative reference indicator for the swift diagnosis of clinical MCI patients, thereby assisting in the screening process on a clinical scale.

Soft Sensors and Actuators for Wearable Human-Machine Interfaces

Haptic human-machine interfaces (HHMIs) combine tactile sensation and haptic feedback to allow humans to interact closely with machines and robots, providing immersive experiences and convenient lifestyles. Significant progress has been made in developing wearable sensors that accurately detect physical and electrophysiological stimuli with improved softness, functionality, reliability, and selectivity. In addition, soft actuating systems have been developed to provide high-quality haptic feedback by precisely controlling force, displacement, frequency, and spatial resolution. In this Review, we discuss the latest technological advances of soft sensors and actuators for the demonstration of wearable HHMIs. We particularly focus on highlighting material and structural approaches that enable desired sensing and feedback properties necessary for effective wearable HHMIs. Furthermore, promising practical applications of current HHMI technology in various areas such as the metaverse, robotics, and user-interactive devices are discussed in detail. Finally, this Review further concludes by discussing the outlook for next-generation HHMI technology.

Shaping the development of complex social behavior

Early life experiences can have an enduring impact on the brain and behavior, with implications for stress reactivity, cognition, and social behavior. In particular, the neural systems that contribute to the expression of social behavior are altered by early life social environments. However, paradigms that have been used to alter the social environment during development have typically focused on exposure to stress, adversity, and deprivation of species-typical social stimulation. Here, we explore whether complex social environments can shape the development of complex social behavior. We describe lab-based paradigms for studying early life social complexity in rodents that are generally focused on enriching the social and sensory experiences of the neonatal and juvenile periods of development. The impact of these experiences on social behavior and neuroplasticity is highlighted. Finally, we discuss the degree to which our current approaches for studying social behavior outcomes give insight into "complex" social behavior and how social complexity can be better integrated into lab-based methodologies.

Neural Circuit Transitions Supporting Developmentally Specific Social Behavior

Environmentally appropriate social behavior is critical for survival across the lifespan. To support this flexible behavior, the brain must rapidly perform numerous computations taking into account sensation, memory, motor-control, and many other systems. Further complicating this process, individuals must perform distinct social behaviors adapted to the unique demands of each developmental stage; indeed, the social behaviors of the newborn would not be appropriate in adulthood and vice versa. However, our understanding of the neural circuit transitions supporting these behavioral transitions has been limited. Recent advances in neural circuit dissection tools, as well as adaptation of these tools for use at early time points, has helped uncover several novel mechanisms supporting developmentally appropriate social behavior. This review, and associated Minisymposium, bring together social neuroscience research across numerous model organisms and ages. Together, this work highlights developmentally regulated neural mechanisms and functional transitions in the roles of the sensory cortex, prefrontal cortex, amygdala, habenula, and the thalamus to support social interaction from infancy to adulthood. These studies underscore the need for synthesis across varied model organisms and across ages to advance our understanding of flexible social behavior.

Assessing the vibration perception threshold in a community sample of adult Ghanaians

BACKGROUND

The vibration perception threshold (VPT) helps evaluate human somatosensory function and diagnose peripheral neuropathy. To optimize its use as a primary neurologic tool, it is imperative to establish its typical values in healthy subjects and assess the factors affecting its variability in an individual to ensure consistency in its application.

METHODS

Demographic data and a brief medical history were collected from 391 non-diabetic adults aged 30-80 at Kpone-on-Sea in Ghana. The VPT was measured at the tip of the big toe, the medial malleolus, the tip of the middle finger, and the head of the ulna of each participant using a Horwell Neurothesiometer. The variability of VPT was assessed vis-à-vis the following factors: gender, age, fasting plasma sugar and body mass index.

RESULTS

The mean age of participants was 48.4 ± 0.7 years, and the female-to-male ratio was 1.46. The overall VPT values ranged from 5.74 ± 0.14 volts to 8.55 ± 0.18 volts in the lower limbs and 3.61 ± 0.06 volts to 5.00 ± 0.08 volts in the upper limbs. Age was found to be the only factor that could predict VPT for both the lower and upper limbs (P < 0.001). One-Way Analysis of Variance with Tukey's posthoc showed that the VPT in the feet was significantly higher than that in the hands.

CONCLUSIONS

Generally, the VPT was high on proximal sites and low on distal sites indicating that the vibration sensation increased from proximal to distal direction. Therefore, distal areas should be used for VPT testing with a Neurothesiomer. Age was found to be the only factor that affected VPT variability. Hence, the practical application of VPT will require age-specific reference ranges to cater for older adults.

The osteopath-parent-child triad in osteopathic care in the first 2 years of life: a qualitative study

Background

Enactivism and active inference are two important concepts in the field of osteopathy. While enactivism emphasizes the role of the body and the environment in shaping our experiences and understanding of the world, active inference emphasizes the role of action and perception in shaping our experiences and understanding of the world. Together, these frameworks provide a unique perspective on the practice of osteopathy, and how it can be used to facilitate positive change in patients. Since the neonatal period is a crucial time for development, osteopaths should aim to create a therapeutic relationship. Arguably, through participatory sense-making, osteopaths can help the baby build a generative model (with positive priors) to deal with stress and needs throughout their life.

Aim

Since the literature considers that interactions with the environment, which enact the patients' experiences, depending on contextual factors and communication between patient and caregiver, this research explored whether there is a correspondence between the indications in the literature and clinical practice in the management of the mother/parent-child dyad during osteopathic care on children aged 0 to 2 years old.

Methods

Semi-structured interviews were conducted with a purposive sample of nine osteopaths with experience in the field of pediatrics. Interviews were transcribed verbatim, and constructivist grounded theory was used to conceptualize, collect and analyze data. Codes and categories were actively constructed through an interpretive/constructionist paradigm.

Results

The core category was the idea of the pediatric osteopath as a support for the family, not only for the child. Four additional categories were identified: (1) Preparing a safe environment for both children and parents, (2) Communication, (3) Attachment and synchrony, and (4) Synchronization.

Conclusion

Through participatory sense-making, osteopaths manage contextual factors to establish an effective therapeutic alliance through the osteopath-parent-child triad to facilitate the construction of the child's internal generative model to promote healthy development. The therapeutic encounter is considered an encounter between embodied subjects, occurring within a field of affordances (ecological niche) that allows the interlocutors to actively participate in creating new meanings through interpersonal synchronization. Participatory sense-making and the establishment of a therapeutic alliance through the osteopath-parent-child triad are crucial to promote healthy development in the child.

The Effect of Yoga Practice on Cervical Tactile Acuity and Body Awareness

Body-mind-based holistic methods of relaxation and improved well-being, such as yoga and meditation, improve body awareness and have often been used to enhance quality of life and the ability to cope with pain. We aimed to compare tactile sensory acuity and body awareness in healthy sedentary individuals who practiced yoga regularly and in control participants who had not practiced yoga. Participants were 60 individuals, aged between 18 and 35 years who were divided into two groups according to whether they had previously practiced yoga. We used the two-point discrimination (TPD) test to determine participants' tactile acuity, as measured with a digital calliper at the C7, C5, C3, C1 and T1 spinal segments and with the Body Awareness Questionnaire (BAQ). The TPD measurements of individuals who practiced yoga and meditation had a lower discriminatory threshold compared to those who had not practiced yoga (p < .001), and the self-reported BAQ score of yoga practitioners was higher than that of the controls (p < .001). We found a positive correlation between the length of the prior duration of yoga experience and self-reported body awareness (r = .567, p < .001). There was a significant negative correlation (r = -.379, p = .015) between the C5 segment and the TPD measurements, but not for the other cervical spinal segments (p > .05). There was a negative correlation between the length of prior yoga practice and the TPD measurements in all cervical segments (p < .001). The most negative correlation was found at the C7 segment (r = -.844, p < .001) and the least negative correlation was found at the C3 segment (r = -.669, p < .001). These data suggest that yoga and meditation practices may improve well-being and diminish pain by increasing body awareness and tactile sensory acuity in the cervical region.

Feasibility, Validity, and Reliability of Lower Limb Tactile and Body Awareness Assessments in Children With Upper Motor Neuron Lesions

OBJECTIVE

To investigate the feasibility, discriminative and convergent validity, and inter-rater reliability of a lower limb tactile function and 2 body awareness assessments in children with upper motor neuron (UMN) lesions.

DESIGN

Cross-sectional psychometric study.

SETTING

Pediatric rehabilitation center.

PARTICIPANTS

Forty individuals with UMN lesions (mean age 11.7 years, SD 3.4 years; 27 girls) and 40 neurotypically developing children of the same age participated (N=80).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

We assessed the tactile threshold (TT) with monofilaments and body awareness with tactile localization tasks (TLTs) for structural (TLTaction) and spatial (TLTperception) body representation at the foot sole. We compared the test outcomes between children with UMN lesions and neurotypically developing children with the Wilcoxon signed-rank test. Furthermore, we quantified the relations between the 3 tests with Spearman correlations (rs) and the interrater reliability with quadratic weighted kappa (κQW).

RESULTS

About 80% of the children with UMN lesions perceived the tests easy to perform. The children with UMN lesions had significantly reduced somatosensory function compared with the neurotypically developing children. For the more affected leg, we found good relations between the TT and the TLTaction (rs=0.71; P<.001) and between the 2 TLTs (rs=0.66; P<.001), and a fair relation between the TT and the TLTperception (rs=0.31; P=.06). The inter-rater reliability analyses for the sum scores showed almost perfect agreement for the TT (κQW more affected leg 0.86; less affected leg 0.81), substantial agreement for TLTaction (κQW more affected leg 0.76; less affected leg 0.63), and almost perfect agreement for TLTperception (κQW more affected leg 0.88; less affected leg 0.74).

CONCLUSION

The 3 tests are feasible to assess lower limb somatosensory function in children with UMN lesions. Discriminative and convergent validity and reliability of the 3 tests were confirmed. Further studies should investigate responsiveness and association with motor function of these outcome measures.

Developmental changes in audiotactile event perception

The fission and fusion illusions provide measures of multisensory integration. The sound-induced tap fission illusion occurs when a tap is paired with two distractor sounds, resulting in the perception of two taps; the sound-induced tap fusion illusion occurs when two taps are paired with a single sound, resulting in the perception of a single tap. Using these illusions, we measured integration in three groups of children (9-, 11-, and 13-year-olds) and compared them with a group of adults. Based on accuracy, we derived a measure of magnitude of illusion and used a signal detection analysis to estimate perceptual discriminability and decisional criterion. All age groups showed a significant fission illusion, whereas only the three groups of children showed a significant fusion illusion. When compared with adults, the 9-year-olds showed larger fission and fusion illusions (i.e., reduced discriminability and greater bias), whereas the 11-year-olds were adult-like for fission but showed some differences for fusion: significantly worse discriminability and marginally greater magnitude and criterion. The 13-year-olds were adult-like on all measures. Based on the pattern of data, we speculate that the developmental trajectories for fission and fusion differ. We discuss these developmental results in the context of three non-mutually exclusive theoretical frameworks: sensory dominance, maximum likelihood estimation, and causal inference.

Exploring maternal touch in the infant’s first 18 months of Life: A study on an Italian sample

Affective touch is a crucial component of caregiving in early life and constitutes a key factor with a significant impact on infant later-life outcomes. The Parent-Infant Caregiving Touch Scale (PICTS) allows to quantify and qualify the caregiver's self-perception of touch in the first months of an infant's life. In the current study, we contributed to validation of the PICTS in the Italian language in order to explore whether early maternal touch would be associated with maternal emotional state, maternal history of affective touch experiences throughout the lifespan, and infants' sex and age. Data analyses were run on a sample of 377 Italian mothers (mean age = 33.29; SD = 4.79) participating in an online survey. Confirmatory factor analysis was applied. A three-dimensional structure of PICTS (i.e., stroking, affective communication, and holding) after removing one item out resulted in the best model in our sample. Maternal emotional state did not affect PICTS factor scores while maternal comfort and amount of affective touch experienced during adulthood was significantly associated with the stroking, affective communication, and holding factors. Regarding infants' dimensions, infants' sex and age were not associated with PICTS factor scores. Findings suggest that the PICTS Italian version is a good measurement of caregiver's self-perception of touch in early infancy and that maternal history of touch is associated with a mother's current use of touch.

Mothers' use of touch across infants' development and its implications for word learning: Evidence from Korean dyadic interactions

Caregivers' touches that occur alongside words and utterances could aid in the detection of word/utterance boundaries and the mapping of word forms to word meanings. We examined changes in caregivers' use of touches with their speech directed to infants using a multimodal cross-sectional corpus of 35 Korean mother-child dyads across three age groups of infants (8, 14, and 27 months). We tested the hypothesis that caregivers' frequency and use of touches with speech change with infants' development. Results revealed that the frequency of word/utterance-touch alignment as well as word + touch co-occurrence is highest in speech addressed to the youngest group of infants. Thus, this study provides support for the hypothesis that caregivers' use of touch during dyadic interactions is sensitive to infants' age in a way similar to caregivers' use of speech alone and could provide cues useful to infants' language learning at critical points in early development.

Premature Triadic Music Therapy (PT-MT) for babies and their parents: a pilot study

OBJECTIVE

We aim to test the feasibility and effectiveness of Premature Triadic Music Therapy (PT-MT) in the premature baby unit.

METHODS

The design was a clinical pre-test-post-test trial with a convenience sample. Inclusion criteria were a gestational age higher than 28 weeks for preterm infants and the absence of shock or extreme distress for parents. Six preterm children (with a gestational age of 33 to 36 weeks) and their parents participated in the study. For the children, we measured heart rate, blood perfusion, and blood saturation at three different times (pre-PT-MT, during PT-MT, after PT-MT) as quantitative indicators of distress. Their parents completed the Edinburgh Postnatal Depression Scale (EPDS) before and after the PT-MT intervention.

RESULTS

We found a statistically significant lower heart rate and a marginally statistically significant higher blood perfusion during PT-MT, as compared to the baseline. However, these changes were not present at the end of PT-MT. The parents' EPDS scores were not statistically significantly lower at the post-test, although, the Medians of the scores did decrease.

CONCLUSIONS

PT-MT is a promising intervention for the reduction of distress in both parents and children. Further studies should include a higher number of sessions and participants.

Horses' Tactile Reactivity Differs According to the Type of Work: The Example of Equine-Assisted Intervention

Tactile perception in humans varies between individuals and could depend on extrinsic factors such as working activity. In animals, there is no study relating the influence of animals' work and their tactile reactivity per se. We investigated horses' tactile reactivity using von Frey filament in different body areas and compared horses working only in equine-assisted interventions (EAI), in riding school (RS) lessons, and in both activities (EAI-RS). We further compared tactile actions by people with or without mental and/or developmental disorders during brushing sessions. The results indicated that EAI horses showed higher tactile reactivity compared to EAI-RS and RS horses, both in terms of number of reactions overall, and especially when the test involved thin filaments. All horses showed high tactile reactivity when tested on the stifle, and this was particularly true for EAI horses. These differences could be related to humans' actions, as participants diagnosed with disorders brushed more the hindquarters and showed more fragmented actions. This study opens new lines of thought on the influence of EAI working activity on horses' tactile reactivity, and hence, on horses' sensory perception. Tactile reactivity outside work, may be directly (via tactile stimulations) or indirectly (via the welfare state), influenced by working conditions.

An integrative perspective on the role of touch in the development of intersubjectivity

Touch concerns a fundamental component of sociality. In this review, we examine the hypothesis that somatomotor development constitutes a crucial psychophysiological element in the ontogeny of intersubjectivity. An interdisciplinary perspective is provided on how the communication channel of touch contributes to the sense of self and extends to the social self. During gestation, the transformation of random movements into organized sequences of actions with sensory consequences parallels the development of the brain's functional architecture. Brain subsystems shaped by the coordinated activity of somatomotor circuits to support these first body-environment interactions are the first brain functional arrangements to develop. We propose that tactile self-referring behaviour during gestation constitutes a prototypic mode of interpersonal exchange that supports the subsequent development of intersubjective exchange. The reviewed research suggests that touch constitutes a pivotal bodily experience that in early stages builds and later filters self-other interactions. This view is corroborated by the fact that aberrant social-affective touch experiences appear fundamentally associated with attachment anomalies, interpersonal trauma, and personality disorders. Given the centrality of touch for the development of intersubjectivity and for psychopathological conditions in the social domain, dedicated research is urged to elucidate the role of touch in the evolution of subjective self-other coding.

Learning limb-specific contingencies in early infancy

Most research with the mobile paradigm has the underlying assumption that young infants can selectively move the limb causing the contingent feedback from the mobile while avoiding irrelevant motor responses. Contrary to this long-held belief, others have argued that such differentiation ability is not fully developed early in life. In the current study, we revisited the traditional mobile paradigm with a contemporary research approach (using high-precision motion capture techniques, a yoked-control design, and a large sample size) to investigate whether response differentiation ability emerges before 5 months of age. The data collected from 76 infants (aged between 115 and 159 days) revealed that infants can learn sensorimotor contingencies by increasing the movement of the connected leg relative to their baseline level. However, they did not differentially increase the movement of the leg causing an effect in the environment compared with that of other limbs. Our results illustrate that response differentiation ability emerges later than previously suggested.

Pleasant touch perception in borderline personality disorder and its relationship with disturbed body representation

BACKGROUND

Borderline personality disorder (BPD) is characterized by altered perception of affective stimuli, including abnormal evaluation of nociceptive input. However, whether or not perceptual alterations are present for its positive counterpart, i.e. pleasant touch (PT), has not yet been examined.

METHODS

In the present study, we applied standardized PT stimuli to the hands of 25 patients with BPD and 25 healthy controls (HC) and compared their perception. We used the affect-modulated acoustic startle response as a physiological correlate of affective processing. We further explored the effect of PT stimulation on dissociative experiences in BPD.

RESULTS

Compared to HC, BPD perceived PT as less pleasant and less intense. The effect on perceived valence of touch was large even after controlling for the effect of reduced perceived intensity of touch (ƞ² = .29). We further found qualitative alterations in touch perception in BPD, who rated the touch as significantly rougher and firmer compared to HC. There was a positive correlation between perceived valence of touch and changes in dissociative experiences in terms of body ownership of the stimulated body part from pre to post stimulation, suggesting that a more negative evaluation of touch is associated with an increase in body-related dissociative experiences, while a positive perception of touch might be related to a reduction of these dissociative experiences.

CONCLUSIONS

Our results confirm BPD-associated disturbances in the processing of affective somatosensory stimuli and indicate that not only pain perception but also pleasant touch perception is diminished in BPD. We discuss the role of altered touch perception for BPD psychopathology and its potential role for new treatment approaches.

Interpersonal Affective Touch in a Virtual World: Feeling the Social Presence of Others to Overcome Loneliness

Humans are by nature social beings tuned to communicate and interact from the very beginning of their lives. The sense of touch represents the most direct and intimate channel of communication and a powerful means of connection between the self and the others. In our digital age, the development and diffusion of internet-based technologies and virtual environments offer new opportunities of communication overcoming physical distance. It however, happens that social interactions are often mediated, and the tactile aspects of communication are overlooked, thus diminishing the feeling of social presence, which may contribute to an increased sense of social disconnection and loneliness. The current manuscript aims to review the extant literature about the socio-affective dimension of touch and current advancements in interactive virtual environments in order to provide a new perspective on multisensory virtual communication. Specifically, we suggest that interpersonal affective touch might critically impact virtual social exchanges, promoting a sense of co-presence and social connection between individuals, possibly overcoming feelings of sensory loneliness. This topic of investigation will be of crucial relevance from a theoretical perspective aiming to understand how we integrate multisensory signals in processing and making sense of interpersonal exchanges, this is important in both typical and atypical populations. Moreover, it will pave the way to promising applications by exploring the possibility to use technical innovations to communicate more interactively in the case of people who suffer from social isolation and disconnection from others.

The role of friction on skin wetness perception during dynamic interactions between the human index fingerpad and materials of varying moisture content

Mechanosensory inputs arising from dynamic interactions between the skin and moisture, such as when sliding a finger over a wet substrate, contribute to the perception of skin wetness. Yet, the exact relationship between the mechanical properties of a wet substrate, such as friction, and the resulting wetness perception remains to be established under naturalistic haptic interactions. We modeled the relationship between mechanical and thermal properties of substrates varying in moisture levels (0.49 × 10⁻⁴; 1.10 × 10⁻⁴; and 2.67 × 10⁻⁴ mL·mm⁻²), coefficient of friction (0.783, 0.848, 1.033, 0.839, 0.876, and 0.763), and maximum thermal transfer rate (Q_max, ranging from 511 to 1,260 W·m⁻²·K⁻¹), and wetness perception arising from the index finger pad’s contact with such substrates. Forty young participants (20M/20F) performed dynamic interactions with 21 different stimuli using their index finger pad at a controlled angle, pressure, and speed. Participants rated their wetness perception using a 100-mm visual analog scale (very dry to very wet). Partial least squares regression analysis indicated that coefficient of friction explained only ∼11% of the variance in wetness perception, whereas Q_max and moisture content accounted for ∼22% and 18% of the variance, respectively. These parameters shared positive relationships with wetness perception, such that the greater the Q_max, moisture content, and coefficient of friction, the wetter the perception. We found no differences in wetness perception between males and females. Our findings indicate that although the friction of a wet substrate modulates wetness perception, it is still secondary to thermal parameters such as Q_max.

NEW & NOTEWORTHY Our skin often interacts with wet materials, yet how their physical properties influence our experience of wetness remains poorly understood. We evaluated wetness perception following naturalistic haptic interactions with materials varying in moisture content, friction, optical profiles, and heat transfer rates. We show that although mechanical parameters can influence wetness perception, their role is secondary to that of thermal factors. These findings expand our understanding of multisensory integration and could guide innovation in healthcare product design.

Environment-Related and Body-Related Components of the Minimal Self

Perceptual changes that an agent produces by efferent activity can become part of the agent’s minimal self. Yet, in human agents, efferent activities produce perceptual changes in various sensory modalities and in various temporal and spatial proximities. Some of these changes occur at the “biological” body, and they are to some extent conveyed by “private” sensory signals, whereas other changes occur in the environment of that biological body and are conveyed by “public” sensory signals. We discuss commonalties and differences of these signals for generating selfhood. We argue that despite considerable functional overlap of these sensory signals in generating self-experience, there are reasons to tell them apart in theorizing and empirical research about development of the self.

Tactile and Somatic Hallucinations in a Muslim Population of Psychotic Patients

Background: Tactile and somatic hallucinations are distressing phenomena that have hardly been researched. The few studies that have been published focus on their occurrence in neurodegenerative disorders and substance use, and, surprisingly, not on schizophrenia spectrum disorders. Objective: To fill this gap in our knowledge, we sought to explore the phenomenological characteristics of tactile and somatic hallucinations in a group of psychotic Muslim patients. Since many Muslims attribute such experiences to jinn (invisible spirits) and jinn are often perceived in multiple sensory modalities, we not only charted the involvement of the tactile and somatic modalities but also their interrelatedness with hallucinations in other sensory modalities. Methods: We performed a cross-sectional study using a semi-structured interview and dedicated questionnaire. Results: Of the 42 Muslim inpatients mostly diagnosed with a schizophrenia spectrum disorder, 62% reported to suffer from tactile and/or somatic hallucinations. Their phenomenological characteristics varied, with 96% being multimodal in nature and 38% taking the form of full-blown entity/jinn encounters. In comparison to other entity experiences, the involvement of the tactile and somatic modalities was exceptionally high, as was the level of ensuing distress. Regarding the order of recruitment of the various sensory modalities, we suggest the involvement of an underlying stochastic process. Conclusion: Muslim patients with severe psychosis can have tactile and somatic hallucinations, of which a large number are multimodal or full-blown entity/jinn encounters, which are almost invariably appreciated as harrowing. On the basis of our findings we make recommendations for further research and clinical practice.

Applicability of tactile memory examination as an option to visual- and verbal-based batteries

The validity and applicability of tactile battery tests for the diagnosis and medical follow-up of patients with Alzheimer's disease and other dementia syndromes do not have their usefulness well understood in clinical practice. While haptic abilities in older individuals receive less attention, in earlier stages of human life they are well focused on. There are even fewer studies on tactile memory, including episodic memory of demented individuals with or without sensorial limitations. The applicability of a new haptic memory battery was evaluated in patients with Alzheimer's disease with mild or moderate commitment.

Objective

The aim of this study is to apply a battery based on tactile perception, recognition, and recollection of everyday objects in patients with Alzheimer's disease, testing tactile delayed recall memory discrimination and late recognition to compare validated visual and verbal tests.

Methods

Tactile-, visual-, and verbal-based memory performance was registered in 21 patients diagnosed with Alzheimer's disease.

Results

Except for tactile identification, it showed that there was a close relationship between the three sensory modalities of memory, with an apparent better performance of tactile incidental memory and recognition compared with the test with pictures.

Conclusions

The haptic evaluation of memory demonstrated applicability in the evaluation of memory dysfunction in patients with Alzheimer's disease. Further studies are needed to establish the sensibility and specificity of the proposed test that had a small sample size and many limitations.

Pleasantness ratings in response to affective touch across hairy and glabrous skin: A meta-analysis

The processing of hedonic aspects of touch, namely affective touch, is associated with the activation of C-Tactile (CT) fibers. CTs were thought to be present only in hairy skin, with glabrous skin being often used as control site in affective touch studies. Nevertheless, several articles comparing pleasantness perception across hairy and glabrous skin reported no significant differences. Surprisingly, CT fibers have also been recently detected on the glabrous palm, further questioning whether affective touch perception across both hairy and glabrous skin is comparable. The present meta-analysis thus aimed to quantify pleasantness perception of affective tactile stimulations on both hairy and glabrous sites. Pooled effect sizes (Hedges' g) from 18 studies were analyzed using random effect models. No systematic preference towards affective stimulations on hairy or glabrous skin was observed. Moreover, studies were highly heterogeneous, suggesting high variance in the results of the retrieved articles. Results were not affected by publication bias nor by other moderators. Variables affecting affective touch perception on hairy and glabrous skin and methodological considerations were discussed.

Physical contact in parent-infant relationship and its effect on fostering a feeling of safety

The infant-caregiver relationship involves physical contact for feeding, moving, and other cares, and such contact also encourages the infant to form an attachment, an emotional bond with the caregivers. Physical contact always accompanies somatosensory perception, which is detected by mechanosensory neurons and processed in the brain. Physical contact triggers sensorimotor reflexes such as Transport Response in rodent infants, and calm human infants while being carried. Tactile sensation and deep pressure in physical interactions, such as hugging, can function as emotional communication between infant and caregiver, which can alter the behavior and mood of both the infant and caregiver. This review summarizes the findings related to physical contact between the infant and the caregiver in terms of pleasant, noxious, and neutral somatosensation and discusses how somatosensory perceptions foster a feeling of safety that is important for infant's psychosocial development.

Pupil Reactions to Tactile Stimulation: A Systematic Review

Pupil dynamics can represent an indirect measure of perception; thus, it has been broadly explored in the auditory and visual fields. Although it is crucial for experiencing the outside world, tactile perception is not well-explored. Considering that, we sought to answer the following question via a systematic review: does normal tactile perception processing modulate pupil dilation in mammals (human or not)? The review process was conducted according to PRISMA Statement. We searched on Periódicos CAPES (Brazil) for the following terms: [(touch) OR (cutaneous stimulation) OR (tactile perception) OR (somatosensory) AND (pupil OR pupillary) NOT blind NOT reflex NOT pain NOT fear NOT noxious NOT autism NOT nerve NOT (pupillary block) NOT glaucoma NOT cataract NOT aneurysm NOT syndrome NOT treatment NOT special education]. From the 6,488 papers found, 4,568 were duplicates, and nine fulfilled the inclusion criteria. All papers found a positive relationship between pupil diameter and tactile perception. We found that the pupil is a reliable indirect measure of brain states and can evaluate norepinephrine (NE)/locus coeruleus (LC) action, stimulus inhibition, arousal, cognitive processes, and affection independently of the stimuli category (visual, auditory, or tactile). We also found that the perceptual tactile processing occurs in similar ways as the other perceptual modalities. We verified that more studies should be done, mostly avoiding low sampling rate recording systems, confounders as cue signs, not automated stimulation, and concurrent stimulus and using more reliable equipment.

Behavioural and neural markers of tactile sensory processing in infants at elevated likelihood of autism spectrum disorder and/or attention deficit hyperactivity disorder

Backgrounds

Atypicalities in tactile processing are reported in autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) but it remains unknown if they precede and associate with the traits of these disorders emerging in childhood. We investigated behavioural and neural markers of tactile sensory processing in infants at elevated likelihood of ASD and/or ADHD compared to infants at typical likelihood of the disorders. Further, we assessed the specificity of associations between infant markers and later ASD or ADHD traits.

Methods

Ninety-one 10-month-old infants participated in the study (n = 44 infants at elevated likelihood of ASD; n = 20 infants at elevated likelihood of ADHD; n = 9 infants at elevated likelihood of ASD and ADHD; n = 18 infants at typical likelihood of the disorders). Behavioural and EEG responses to pairs of tactile stimuli were experimentally recorded and concurrent parental reports of tactile responsiveness were collected. ASD and ADHD traits were measured at 24 months through standardized assessment (ADOS-2) and parental report (ECBQ), respectively.

Results

There was no effect of infants’ likelihood status on behavioural markers of tactile sensory processing. Conversely, increased ASD likelihood associated with reduced neural repetition suppression to tactile input. Reduced neural repetition suppression at 10 months significantly predicted ASD (but not ADHD) traits at 24 months across the entire sample. Elevated tactile sensory seeking at 10 months moderated the relationship between early reduced neural repetition suppression and later ASD traits.

Conclusions

Reduced tactile neural repetition suppression is an early marker of later ASD traits in infants at elevated likelihood of ASD or ADHD, suggesting that a common pathway to later ASD traits exists despite different familial backgrounds. Elevated tactile sensory seeking may act as a protective factor, mitigating the relationship between early tactile neural repetition suppression and later ASD traits.

Hand size representation in healthy children and young adults

Whereas we experience our body as a coherent volumetric object, the brain appears to maintain highly fragmented representations of individual body parts. Little is known about how body representations of hand size and shape are built and evolve during infancy and young adulthood. This study aimed to investigate the effect of hand side, handedness, and age on the development of central hand size representation. The observational study with comparison groups was conducted with 90 typically developing Belgian school children and young adults (48 male and 42 female; age range = 5.0-23.0 years; 49 left-handed and 41 right-handed). Participants estimated their hand size and shape using two different tasks. In the localization task, participants were verbally cued to judge the locations of 10 anatomical landmarks of an occluded hand. An implicit hand size map was constructed and compared with actual hand dimensions. In the template selection task, the explicit hand shape was measured with a depictive method. Hand shape indexes were calculated and compared for the actual, implicit, and explicit conditions. Participants were divided into four age groups (5-8 years, 9-10 years, 11-16 years, and 17-23 years). Implicit hand maps featured underestimation of finger length and overestimation of hand width, which is already present in the youngest children. Linear mixed modeling revealed no influence of hand side on finger length underestimation; nonetheless, a significant main effect of age (p = .001) was exposed. Sinistrals aged 11 to 16 years showed significantly less underestimation (p = .03) than dextrals of the same age. As for the hand shape, the implicit condition differed significantly with the actual and explicit conditions (p < .001). Again, the implicit shape index was subjected to handedness and age effects, with significant differences being found between sinistrals and dextrals in the age groups of 9 and 10 years (p = .029) and 11 to 16 years (p < .001). In conclusion, the implicit metric component of the hand representation in children and young adults is misperceived, featuring shortened fingers and broadened hands since a very young age. Crucially, the finger length underestimation increases with age and shows a different developmental trajectory for sinistrals and dextrals. In contrast, the explicit hand shape is approximately veridical and seems immune from age and handedness effects. This study confirms the dual character of somatoperception and establishes a point of reference for children and young adults.

Affective touch experiences across the lifespan: Development of the Tactile Biography questionnaire and the mediating role of attachment style

The sense of touch develops early in life and becomes a determinant aspect of our personal narratives, providing crucial information about the world around us and playing a prominent role in affective and social interactions. In this study we aimed to explore whether individual differences in touch experiences across the lifespan are related to adult attachment styles and to perceived touch deprivation. For this we first developed an instrument, namely the Tactile Biography, to quantify individual differences in affective touch experiences throughout life. Secondly, we performed a set of regressions models and a mediation analysis to investigate the role of attachment in relation to both the tactile history and perceived touch deprivation. We found that experiences of affective touch during childhood and adolescence seem to be closely associated with adult attachment styles and adult social touch experiences. Avoidant attachment appears to serve as a mediator in the relationship between earlier (childhood/adolescent) and later (adult) affective touch experiences, as well as between earlier affective touch experiences and perceived touch deprivation. These findings offer further support to existing literature, providing novel insights for the fields of social affective touch and attachment research.

Sensory Feedback in Hand Prostheses: A Prospective Study of Everyday Use

Introduction

Sensory feedback in hand prostheses is lacking but wished for. Many amputees experience a phantom hand map on their residual forearm. When the phantom hand map is touched, it is experienced as touch on the amputated hand. A non-invasive sensory feedback system, applicable to existing hand prostheses, can transfer somatotopical sensory information via phantom hand map. The aim was to evaluate how forearm amputees experienced a non-invasive sensory feedback system used in daily life over a 4-week period.

Methods

This longitudinal cohort study included seven forearm amputees. A non-invasive sensory feedback system was used over 4 weeks. For analysis, a mixed method was used, including quantitative tests (ACMC, proprioceptive pointing task, questionnaire) and interviews. A directed content analysis with predefined categories sensory feedback from the prosthesis, agency, body ownership, performance in activity, and suggestions for improvements was applied.

Results

The results from interviews showed that sensory feedback was experienced as a feeling of touch which contributed to an experience of completeness. However, the results from the questionnaire showed that the sense of agency and performance remained unchanged or deteriorated. The ability to feel and manipulate small objects was difficult and a stronger feedback was wished for. Phantom pain was alleviated in four out of five patients.

Conclusion

This is the first time a non-invasive sensory feedback system for hand prostheses was implemented in the home environment. The qualitative and quantitative results diverged. The sensory feedback was experienced as a feeling of touch which contributed to a feeling of completeness, linked to body ownership. The qualitative result was not verified in the quantitative measurements.

Clinical Trial Registration

Name: Evaluation of a Non-invasive Sensory Feedback System in Hand Prostheses. Date of registration: March 15, 2019. Date the first participant was enrolled: April 1, 2015. ClinicalTrials.gov Identifier: NCT03876405 ORCID ID: https://orcid.org/0000-0002-4140-7478.

Body representation in infants: Categorical boundaries of body parts as assessed by somatosensory mismatch negativity

There is growing interest in developing and using novel measures to assess how the body is represented in human infancy. Various lines of evidence with adults and older children show that tactile perception is modulated by a high-level representation of the body. For instance, the distance between two points of tactile stimulation is perceived as being greater when these points cross a joint boundary than when they are within a body part, suggesting that the representation of the body is structured with joints acting as categorical boundaries between body parts. Investigating the developmental origins of this categorical effect has been constrained by infants’ inability to verbally report on the properties of tactile stimulation. Here we made novel use of an infant brain measure, the somatosensory mismatch negativity (sMMN), to explore categorical aspects of tactile body processing in infants aged 6–7 months. Amplitude of the sMMN elicited by tactile stimuli across the wrist boundary was significantly greater than for stimuli of equal distance that were within the boundary, suggesting a categorical effect in body processing in infants. We suggest that an early-appearing, structured representation of the body into ‘parts’ may play a role in mapping correspondences between self and other.

Disorganized Attachment pattern affects the perception of Affective Touch

Touch, such as affective caress, can be interpreted as being pleasant. The emotional valence that is assigned to touch is related to certain bottom-up factors, such as the optimal activation of C-tactile (CT) afferents. Tactile processing with a hedonic or emotional component has been defined as affective touch—a component that CT fibers are likely to convey. Tactile deficiencies are frequent in the psychiatric population but also in healthy people with disorganized attachment; accordingly, it is likely that affective difficulties in adults with disorganized attachment are reflected in altered perception of affective touch. To test this hypothesis, we combined methods from clinical psychology, psychophysics, and neuroimaging. We found that people with a history of traumatic parental bonds and a disorganized attachment pattern perceive a “caress-like” stimulus as being unpleasant, whereas participants with organized attachment consider the same tactile stimulation to be pleasant. Further, unlike in organized adults, the responses of disorganized adults to CT and non-CT stimulation activated limbic and paralimbic structures in a fight-or-flight manner, suggesting that early experiences with parental deficiencies shape the physiological responses of peripheral CT fibers and central nervous networks.

Infants Show Physiological Responses Specific to Parental Hugs

Caregivers hug their infants to express affection and joy. However, it remains unknown how infants react to being hugged. Here we examined heart rate responses in first-year infants during a hug, hold, and tight hug from parents. Infants older than four months showed an increased R-R interval (RRI) during a hug, indicating reduced heart rates and pronounced parasympathetic activity. Few head movements predicted a higher RRI increase in infants during a parental hug compared with that during a hold and tight hug. Infants did not show an increased RRI during a hug from a female stranger. Infants younger than four months did not show RRI increase during parental hug but exhibited a decreased RRI correlated with contact pressure. Parents showed an increased RRI during hugging their infants. These results suggest the parent-infant hug underlies the parent-infant bonding and psychophysiological development of infants.

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We examined heart rate responses in first-year infants during hugs from parents

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Infants showed an RRI increase when hugged by parents but not by strangers

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Few head movements predicted higher RRI increase during a parental hug

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Parents also showed an increased RRI when hugging their infants

The body comes first. Embodied reparation and the co-creation of infant bodily-self

During infancy relational experiences of body-to-body exchanges (i.e., embodied interactions) contribute to the infant's bodily perception. Early embodied interactions are based on countless multimodal reciprocal exchanges, in which mother and infant contribute to interpersonal rhythmic cycles of co-regulation (i.e., attunement). However, it remains unclear how infants and their mothers actually accomplish attunement in their exchanges. Interactions between mothers and their infants typically fluctuate between attuned and misattuned states and recovery attunement states by a process called 'reparation'. Here, we discuss recent neuroscientific evidence that provides insight into the mechanisms underpinning the concepts of attunement and misattunement in early embodied interactions. We propose that a process of embodied reparation might be achieved within the dyad through tactile contact behaviors (e.g., skin-to-skin, affectionate touch) and maternal interoceptive sensitivity (i.e., ability to perceive internal input about the state of one's own body). We describe how these elements that mothers provide during embodied interactions with their infants, might contribute not only to bodily attunement, but also to co-create the infant bodily-self.

Hand size underestimation grows during childhood

Cortical body size representations are distorted in the adult, from low-level motor and sensory maps to higher levels multisensory and cognitive representations. Little is known about how such representations are built and evolve during infancy and childhood. Here we investigated how hand size is represented in typically developing children aged 6 to 10. Participants were asked to estimate their hand size using two different sensory modalities (visual or haptic). We found a distortion (underestimation) already present in the youngest children. Crucially, such distortion increases with age and regardless of the sensory modality used to access the representation. Finally, underestimation is specific for the body as no bias was found for object estimation. This study suggests that the brain does not keep up with the natural body growth. However, since motor behavior nor perception were impaired, the distortion seems functional and/or compensated for, for proper interaction with the external environment.

Rethinking Intrusiveness: Exploring the Sequential Organization in Interactions Between Infants and Mothers

To date, studies investigating maternal postpartum depression (PPD) have mainly focused on identifying failures in interactions of postpartum depressed mothers and their infants, often attributed to single dysfunctional maternal behaviors. Intrusiveness has been identified as a dysfunctional behavior characterizing mothers suffering from PPD. However, this research does not consider the co-constructed and sequential nature of social interactions, in which single behaviors cannot be conceived as isolated or disconnected units. The aim of the work presented in this paper was to explore the interactional dynamics underlying maternal behaviors previously identified as intrusive by mainstream literature on postpartum depression. Through a conversation analytical approach, we analyzed filmed interactions between mothers with and without postpartum depression and their 3-months-old infants. The analyses of 4 selected episodes illustrate similar dyadic activities, yet presenting different levels of mutuality and affective attunement. Results showed two normative features of social interactions that contributed to the different quality in the mutual adjustment of the partners: interactional rhythm and preliminaries. Interactional rhythm refers to the structuring of infants' spontaneous activity into a turn sequence, whereas preliminaries consist of verbal or nonverbal moves that anticipate following action. As evident from our analytical observations, what seems to be hindering the mutual coordination (previously labeled as “intrusive”) is not based on specific individual behaviors but on the absence or violation of such interactional norms. Adopting an interactive and dynamical framework, we shifted the focus from maternal behaviors considered as dysfunctional to observing the unfolding of interactional aspects contributing to better or poorer sequential structuring. We argue that these aspects shape the possibilities for the infant's participation. Finally, we discuss the theoretical and methodological implications of adopting a conversation analytical approach for a better understanding of the relational dynamics related to clinical and non-clinical interactions.

Reaching to the Self: The Development of Infants' Ability to Localize Targets on the Body

This study focused on the development of infants' sensorimotor knowledge about the layout of their bodies. Little is known about the development of the body as a reaching space, despite the importance of this skill for many self-directed adaptive behaviors, such as removing foreign stimuli from the skin or scratching an itch. A new method was developed in which vibrating targets were placed on the heads and arms of 7- to 21-month-old infants (N = 78) to test reaching localization of targets. Manual localization improved with age, and visual localization was associated with successful reaching. Use of the ipsilateral or contralateral hand varied with body region: Infants primarily used the ipsilateral hand for head targets but the contralateral hand for arm targets, for which ipsilateral reaches were not biomechanically possible. The results of this research highlight a previously understudied form of self-knowledge involving a functional capacity to reach to tactile targets on the body surface.

Infants discriminate the source of social touch at stroking speeds eliciting maximal firing rates in CT-fibers

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Infants’ cardiac response to touch varies depending on its social source.

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This effect occurs only for velocities yielding maximal firing rates in CTs.

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Infants’ responses to touch do not just depend upon its mechanical properties.

The evaluation of interpersonal touch is heavily influenced by its source. For example, a gentle stroke from a loved one is generally more pleasant than the same tactile stimulation from a complete stranger. Our study tested the early ontogenetic roots of humans’ sensitivity to the source of interpersonal touch. We measured the heart rate of three groups of nine-month-olds while their legs were stroked with a brush. The participants were stroked at a different speed in each group (0.3 cm/s, 3 cm/s, 30 cm/s). Depending on the Identity condition (stranger vs. parent), the person who acted as if she was stroking the infant’s leg was either an unfamiliar experimenter or the participant’s caregiver. In fact, the stimulation was always delivered by a second experimenter blind to the Identity condition. Infants’ heart rate decreased more in reaction to strokes when their caregiver rather than a stranger acted as the source of the touch. This effect was found only for tactile stimulations whose velocity (3 cm/s) is known to elicit maximal mean firing rates in a class of afferents named C-tactile fibers (CTs). Thus, the infants’ reaction to touch is modulated not just by its mechanical properties but also by its social source.

Cortical signatures of vicarious tactile experience in four-month-old infants

The human brain recruits similar brain regions when a state is experienced (e.g., touch, pain, actions) and when that state is passively observed in other individuals. In adults, seeing other people being touched activates similar brain areas as when we experience touch ourselves. Here we show that already by four months of age, cortical responses to tactile stimulation are modulated by visual information specifying another person being touched. We recorded somatosensory evoked potentials (SEPs) in 4-month-old infants while they were presented with brief vibrotactile stimuli to the hands. At the same time that the tactile stimuli were presented the infants observed another person's hand being touched by a soft paintbrush or approached by the paintbrush which then touched the surface next to their hand. A prominent positive peak in SEPs contralateral to the site of tactile stimulation around 130 ms after the tactile stimulus onset was of a significantly larger amplitude for the "Surface" trials than for the "Hand" trials. These findings indicate that, even at four months of age, somatosensory cortex is not only involved in the personal experience of touch but can also be vicariously recruited by seeing other people being touched.

Feel-Good Robotics: Requirements on Touch for Embodiment in Assistive Robotics

The feeling of embodiment, i.e., experiencing the body as belonging to oneself and being able to integrate objects into one's bodily self-representation, is a key aspect of human self-consciousness and has been shown to importantly shape human cognition. An extension of such feelings toward robots has been argued as being crucial for assistive technologies aiming at restoring, extending, or simulating sensorimotor functions. Empirical and theoretical work illustrates the importance of sensory feedback for the feeling of embodiment and also immersion; we focus on the the perceptual level of touch and the role of tactile feedback in various assistive robotic devices. We critically review how different facets of tactile perception in humans, i.e., affective, social, and self-touch, might influence embodiment. This is particularly important as current assistive robotic devices – such as prostheses, orthoses, exoskeletons, and devices for teleoperation–often limit touch low-density and spatially constrained haptic feedback, i.e., the mere touch sensation linked to an action. Here, we analyze, discuss, and propose how and to what degree tactile feedback might increase the embodiment of certain robotic devices, e.g., prostheses, and the feeling of immersion in human-robot interaction, e.g., in teleoperation. Based on recent findings from cognitive psychology on interactive processes between touch and embodiment, we discuss technical solutions for specific applications, which might be used to enhance embodiment, and facilitate the study of how embodiment might alter human-robot interactions. We postulate that high-density and large surface sensing and stimulation are required to foster embodiment of such assistive devices.

Neural measures of anticipatory bodily attention in children: Relations with executive function

The ability to selectively direct attention to a certain location or modality is a key neurocognitive skill. One important facet of selective attention is anticipation, a foundational biological construct that bridges basic perceptual processes and higher-order cognition. The current study focuses on the neural correlates of bodily anticipation in 6- to 8-year-old children using a task involving tactile stimulation. Electroencephalographic (EEG) activity over sensorimotor cortex was measured after a visual cue directed children to monitor their right or left hand in anticipation of tactile stimulation. Prior to delivery of the tactile stimulus, a regionally-specific desynchronization of the alpha-range mu rhythm occurred over central electrode sites (C3/C4) contralateral to the cue direction. The magnitude of anticipatory mu rhythm desynchronization was associated with children's performance on two executive function tasks (Flanker and Card Sort). We suggest that anticipatory mu desynchronization has utility as a specific neural marker of attention focusing in young children, which in turn may be implicated in the development of executive function.

Fragility of haptic memory in human full-term newborns

BACKGROUND

Numerous studies have established that newborns can memorize tactile information about the specific features of an object with their hands and detect differences with another object. However, the robustness of haptic memory abilities has already been examined in preterm newborns and in full-term infants, but not yet in full-term newborns. This research is aimed to better understand the robustness of haptic memory abilities at birth by examining the effects of a change in the objects' temperature and haptic interference.

METHODS

Sixty-eight full-term newborns (mean postnatal age: 2.5 days) were included. The two experiments were conducted in three phases: habituation (repeated presentation of the same object, a prism or cylinder in the newborn's hand), discrimination (presentation of a novel object), and recognition (presentation of the familiar object). In Experiment 1, the change in the objects' temperature was controlled during the three phases.

RESULTS AND CONCLUSION

Results reveal that newborns can memorize specific features that differentiate prism and cylinder shapes by touch, and discriminate between them, but surprisingly they did not show evidence of recognizing them after interference. As no significant effect of the temperature condition was observed in habituation, discrimination and recognition abilities, these findings suggest that discrimination abilities in newborns may be determined by the detection of shape differences. Overall, it seems that the ontogenesis of haptic recognition memory is not linear. The developmental schedule is likely crucial for haptic development between 34 and 40 GW.

Social touch and human development

Social touch is a powerful force in human development, shaping social reward, attachment, cognitive, communication, and emotional regulation from infancy and throughout life. In this review, we consider the question of how social touch is defined from both bottom-up and top-down perspectives. In the former category, there is a clear role for the C-touch (CT) system, which constitutes a unique submodality that mediates affective touch and contrasts with discriminative touch. Top-down factors such as culture, personal relationships, setting, gender, and other contextual influences are also important in defining and interpreting social touch. The critical role of social touch throughout the lifespan is considered, with special attention to infancy and young childhood, a time during which social touch and its neural, behavioral, and physiological contingencies contribute to reinforcement-based learning and impact a variety of developmental trajectories. Finally, the role of social touch in an example of disordered development –autism spectrum disorder—is reviewed.

Feel-Good Robotics: Requirements on Touch for Embodiment in Assistive Robotics

The feeling of embodiment, i.e., experiencing the body as belonging to oneself and being able to integrate objects into one's bodily self-representation, is a key aspect of human self-consciousness and has been shown to importantly shape human cognition. An extension of such feelings toward robots has been argued as being crucial for assistive technologies aiming at restoring, extending, or simulating sensorimotor functions. Empirical and theoretical work illustrates the importance of sensory feedback for the feeling of embodiment and also immersion; we focus on the the perceptual level of touch and the role of tactile feedback in various assistive robotic devices. We critically review how different facets of tactile perception in humans, i.e., affective, social, and self-touch, might influence embodiment. This is particularly important as current assistive robotic devices - such as prostheses, orthoses, exoskeletons, and devices for teleoperation-often limit touch low-density and spatially constrained haptic feedback, i.e., the mere touch sensation linked to an action. Here, we analyze, discuss, and propose how and to what degree tactile feedback might increase the embodiment of certain robotic devices, e.g., prostheses, and the feeling of immersion in human-robot interaction, e.g., in teleoperation. Based on recent findings from cognitive psychology on interactive processes between touch and embodiment, we discuss technical solutions for specific applications, which might be used to enhance embodiment, and facilitate the study of how embodiment might alter human-robot interactions. We postulate that high-density and large surface sensing and stimulation are required to foster embodiment of such assistive devices.