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"Touch Perception - physiology"
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Touch : the science of hand, heart, and mind
\"The New York Times bestselling author examines how our sense of touch and emotion are interconnected Johns Hopkins neuroscientist and bestselling author of The Compass of Pleasure, David J. Linden presents an engaging and fascinating examination of how the interface between our sense of touch and our emotional responses affects our social interactions as well as our general health and development. Accessible in its wit and clarity, Touch explores scientific advances in the understanding of touch that help explain our sense of self and our experience of the world. From skin to nerves to brain, the organization of the body's touch circuits powerfully influences our lives-affecting everything from consumer choice to sexual intercourse, tool use to the origins of language, chronic pain to healing. Interpersonal touch is crucial to social bonding and individual development. Linden lucidly explains how sensory and emotional context work together to distinguish between perceptions of what feels good and what feels bad. Linking biology and behavioral science, Linden offers an entertaining and enlightening answer to how we feel in every sense of the word\"-- Provided by publisher.
Book
Attention and control of posture: the effects of light touch on the center-of-pressure time series regularity and simple reaction time task
The stabilizing influence of a light touch (LT) on a postural sway has been consistently shown in the literature, however there is still no consensus in what way attentional resources are used when adopting LT during standing. To better elucidate the underlying mechanisms we introduced additional feedback (LT), which seems to distracts from postural control, and verified it by center of pressure (COP) regularity level and simple reaction time task. 25 healthy students randomly performed eight postural tasks, four without (NoRT)/ four with simple reaction task (RT). COP displacements were measured on a force plate in two visual conditions: eyes open/closed and two sensory conditions: without (NoLT)/with light touch (LT). Participants were asked to consider the postural task as the primary task. Although simple reaction time did not differ between postural conditions (
p
> 0.05), LT decreased postural sway velocity in anteroposterior direction (
p
< 0.001, η2 = 0.86) and decreased standard deviation (
p
< 0.001, η2 = 0.91) in both, reaction and visual conditions. Interestingly, RT task modified subjects behavior in NoLT conditions and caused slower COP velocity (
p
< 0.001, η2 = 0.53) without changes in signal regularity. Results also showed a significant increase in irregularity during standing with LT (
p
< 0.001, η2 = 0.86) in both vision and reaction conditions, suggesting that the signal was more random. Current results suggests that providing LT enhance postural steadiness and also seem to redirect attention externally, as shown by increased signal irregularity. Hence, LT possibly reduce the attention invested in the postural task itself. A RT task can be not sensitive enough to detect such subtle changes.
Journal Article
Ketamine reduces the neural distinction between self- and other-produced affective touch: a randomized double-blind placebo-controlled study
A coherent sense of self is crucial for social functioning and mental health. The N-methyl-D-aspartate antagonist ketamine induces short-term dissociative experiences and has therefore been used to model an altered state of self-perception. This randomized double-blind placebo-controlled cross-over study investigated the mechanisms for ketamine’s effects on the bodily sense of self in the context of affective touch. Thirty healthy participants (15 females/15 males, age 19–39) received intravenous ketamine or placebo while performing self-touch and receiving touch by someone else during functional MRI – a previously established neural measure of tactile self-other-differentiation. Afterwards, tactile detection thresholds during self- and other-touch were assessed, as well as dissociative states, interoceptive awareness, and social touch attitudes. Compared to placebo, ketamine administration elicited dissociation and reduced neural activity associated with self-other-differentiation in the right temporoparietal cortex, which was most pronounced during other-touch. This reduction correlated with ketamine-induced reductions in interoceptive awareness. The temporoparietal cortex showed higher connectivity to somatosensory cortex and insula during other- compared to self-touch. This difference was augmented by ketamine, and correlated with dissociation strength for somatosensory cortex. These results demonstrate that disrupting the self-experience through ketamine administration affects neural activity associated with self-other-differentiation in a region involved in touch perception and social cognition, especially with regard to social touch by someone else. This process may be driven by ketamine-induced effects on top-down signaling, rendering the processing of predictable self-generated and unpredictable other-generated touch more similar. These findings provide further evidence for the intricate relationship of the bodily self with the tactile sense.
Journal Article
An Oxytocin-Induced Facilitation of Neural and Emotional Responses to Social Touch Correlates Inversely with Autism Traits
Social communication through touch and mutual grooming can convey highly salient socio-emotional signals and has been shown to involve the neuropeptide oxytocin (OXT) in several species. Less is known about the modulatory influence of OXT on the neural and emotional responses to human interpersonal touch. The present randomized placebo (PLC)-controlled within-subject pharmaco-functional magnetic resonance imaging (fMRI) study was designed to test the hypothesis that a single intranasal dose of synthetic OXT (24 IU) would facilitate both neural and emotional responses to interpersonal touch in a context- (female vs male touch) and trait- (autistic trait load) specific manner. Specifically, the experimental rationale was to manipulate the reward value of interpersonal touch independent of the intensity and type of actual cutaneous stimulation administered. Thus, 40 heterosexual males believed that they were touched by either a man or a woman, although in fact an identical pattern of touch was always given by the same female experimenter blind to condition type. Our results show that OXT increased the perceived pleasantness of female, but not male touch, and associated neural responses in insula, precuneus, orbitofrontal, and pregenual anterior cingulate cortex. Moreover, the behavioral and neural effects of OXT were negatively correlated with autistic-like traits. Taken together, this is the first study to show that the perceived hedonic value of human heterosexual interpersonal touch is facilitated by OXT in men, but that its behavioral and neural effects in this context are blunted in individuals with autistic traits.
Journal Article
Humans flexibly use visual priors to optimize their haptic exploratory behavior
Humans can use prior information to optimize their haptic exploratory behavior. Here, we investigated the usage of visual priors, which mechanisms enable their usage, and how the usage is affected by information quality. Participants explored different grating textures and discriminated their spatial frequency. Visual priors on texture orientation were given each trial, with qualities randomly varying from high to no informational value. Adjustments of initial exploratory movement direction orthogonal to the textures’ orientation served as an indicator of prior usage. Participants indeed used visual priors; the more so the higher the priors’ quality (Experiment 1). Higher task demands did not increase the direct usage of visual priors (Experiment 2), but possibly fostered the establishment of adjustment behavior. In Experiment 3, we decreased the proportion of high-quality priors presented during the session, hereby reducing the contingency between high-quality priors and haptic information. In consequence, even priors of high quality ceased to evoke movement adjustments. We conclude that the establishment of adjustment behavior results from a rather implicit contingency learning. Overall, it became evident that humans can autonomously learn to use rather abstract visual priors to optimize haptic exploration, with the learning process and direct usage substantially depending on the priors’ quality.
Journal Article
Oxytocin administration enhances pleasantness and neural responses to gentle stroking but not moderate pressure social touch by increasing peripheral concentrations
Social touch constitutes a key component of human social relationships, although in some conditions with social dysfunction, such as autism, it can be perceived as unpleasant. We have previously shown that intranasal administration of oxytocin facilitates the pleasantness of social touch and activation of brain reward and social processing regions, although it is unclear if it influences responses to gentle stroking touch mediated by cutaneous C-touch fibers or pressure touch mediated by other types of fibers. Additionally, it is unclear whether endogenous oxytocin acts via direct entry into the brain or by increased peripheral blood concentrations.
In a randomized controlled design, we compared effects of intranasal (direct entry into the brain and increased peripheral concentrations) and oral (only peripheral increases) oxytocin on behavioral and neural responses to social touch targeting C-touch (gentle-stroking) or other (medium pressure without stroking) cutaneous receptors.
Although both types of touch were perceived as pleasant, intranasal and oral oxytocin equivalently enhanced pleasantness ratings and responses of reward, orbitofrontal cortex, and social processing, superior temporal sulcus, regions only to gentle-stroking not medium pressure touch. Furthermore, increased blood oxytocin concentrations predicted the pleasantness of gentle stroking touch. The specificity of neural effects of oxytocin on C-touch targeted gentle stroking touch were confirmed by time-course extraction and classification analysis.
Increased peripheral concentrations of oxytocin primarily modulate its behavioral and neural responses to gentle social touch mediated by C-touch fibers. Findings have potential implications for using oxytocin therapeutically in conditions where social touch is unpleasant.
Key Technological Projects of Guangdong Province grant 2018B030335001.
NCT05265806.
Journal Article
Acute tryptophan depletion alters affective touch perception
RationaleAffiliative tactile interactions help regulate physiological arousal and confer resilience to acute and chronic stress. C-tactile afferents (CTs) are a population of unmyelinated, low threshold mechanosensitive cutaneous nerve fibres which respond optimally to a low force stimulus, moving at between 1 and 10 cm/s. As CT firing frequencies correlate positively with subjective ratings of touch pleasantness, they are hypothesised to form the first stage of encoding affiliative tactile interactions. Serotonin is a key modulator of social responses with known effects on bonding.ObjectivesThe aim of the present study was to determine the effect of acutely lowering central serotonin levels on perceptions of CT-targeted affective touch.MethodsIn a double blind, placebo-controlled design, the effect of acute tryptophan depletion (ATD) on 25 female participants’ ratings of directly and vicariously experienced touch was investigated. Psychophysical techniques were used to deliver dynamic tactile stimuli; some velocities were targeted to optimally activate CTs (1–10 cm/s), whereas other, faster and slower strokes fell outside the CT optimal range. Discriminative tactile function, cold pain threshold and tolerance were also measured.ResultsATD significantly increased pleasantness ratings of both directly and vicariously experienced affective touch, increasing discrimination of the specific hedonic value of CT targeted velocities. While ATD had no effect on either tactile or cold pain thresholds, there was a trend for reduced tolerance to cold pain.ConclusionsThese findings are consistent with previous reports that depletion of central serotonin levels modulates neural and behavioural responsiveness to appetitive sensory signals.
Journal Article
Hierarchical unimodal processing within the primary somatosensory cortex during a bimodal detection task
Do sensory cortices process more than one sensory modality? To answer these questions, scientists have generated a wide variety of studies at distinct space-time scales in different animal models, and often shown contradictory conclusions. Some conclude that this process occurs in early sensory cortices, but others that this occurs in areas central to sensory cortices. Here, we sought to determine whether sensory neurons process and encode physical stimulus properties of different modalities (tactile and acoustic). For this, we designed a bimodal detection task where the senses of touch and hearing compete from trial to trial. Two Rhesus monkeys performed this novel task, while neural activity was recorded in areas 3b and 1 of the primary somatosensory cortex (S1). We analyzed neurons’ coding properties and variability, organizing them by their receptive field’s position relative to the stimulation zone. Our results indicate that neurons of areas 3b and 1 are unimodal, encoding only the tactile modality in both the firing rate and variability. Moreover, we found that neurons in area 3b carried more information about the periodic stimulus structure than those in area 1, possessed lower response and coding latencies, and had a lower intrinsic time scale. In sum, these differences reveal a hidden processing-based hierarchy. Finally, using a powerful nonlinear dimensionality reduction algorithm, we show that the activity from areas 3b and 1 can be separated, establishing a clear division in the functionality of these two subareas of S1.
Journal Article
Individual differences in cognitive processing for roughness rating of fine and coarse textures
Previous studies have demonstrated that skin vibration is an important factor affecting the roughness perception of fine textures. For coarse textures, the determining physical factor is much less clear and there are indications that this might be participant-dependent. In this paper, we focused on roughness perception of both coarse and fine textures of different materials (glass particle surfaces and sandpapers). We investigated the relationship between subjective roughness ratings and three physical parameters (skin vibration, friction coefficient, and particle size) within a group of 30 participants. Results of the glass particle surfaces showed both spatial information (particle size) and temporal information (skin vibration) had a high correlation with subjective roughness ratings. The former correlation was slightly but significantly higher than the latter. The results also indicated different weights of temporal information and spatial information for roughness ratings among participants. Roughness ratings of a different material (sandpaper versus glass particles) could be either larger, similar or smaller, indicating differences among individuals. The best way to describe our results is that in their perceptual evaluation of roughness, different individuals weight temporal information, spatial information, and other mechanical properties differently.
Journal Article
Cross‐Modal Transfer Effects of the Go/No‐Go Training With Visual Stimuli
Introduction Motor task performance guided by one sensory modality (e.g., visual stimuli) can be improved by training; however, whether this training can also improve performance on the same task guided by another sensory modality remains uncertain (e.g., tactile stimuli). This study examined the effects of Go/No‐go task training using visual stimulus cues on Go/No‐go task performance using tactile cues and whether training also influences the dominance of the sensory modality. Methods Go/No‐go tasks and a temporal order judgment (TOJ) task were performed by 24 right‐handed, healthy adults on days 1 and 5 of the 5‐day experiment. Furthermore, a subpopulation (the training group) practiced the Go/No‐go task with visual stimulus cues on days 2–4, whereas the remaining control group did not practice the task. Results The training group demonstrated significantly reduced reaction times (RTs) on both the visual and tactile Go/No‐go tasks by day 5, whereas the control group demonstrated significantly reduced RTs only on the tactile Go/No‐go task. The RT change was also significantly greater in the training group than in the control group for both modalities. Conversely, no significant change in the TOJ for visual and tactile stimuli was observed between the groups. Conclusion These results indicate that motor training with visual guidance can improve performance on the same task guided by tactile stimuli, possibly due to neuroplastic changes in the multimodal association cortices. Visual modality training reduced reaction time. The rate of change was greater in the visual modality training group.
Journal Article