Differential Effects of Focused Attention and Open Monitoring Meditation on Autonomic Cardiac Modulation and Cortisol Secretion.

Mindfulness-based interventions (MBIs) have been used widely as a useful tool for the alleviation of various stress-related symptoms. However, the effects of MBIs on stress-related physiological activity have not yet been ascertained. MBIs primarily consist of focused-attention (FA) and open-monitoring (OM) meditation. Since differing effects of FA and OM meditation on brain activities and cognitive tasks have been mentioned, we hypothesized that FA and OM meditation have also differing effects on stress-related physiological activity. In this study, we examined the effects of FA and OM meditation on autonomic cardiac modulation and cortisol secretion. Forty-one healthy adults (aged 20-46 years) who were meditation novices experienced 30-min FA and OM meditation tasks by listening to instructions. During resting- and meditation-states, electrocardiogram transducers were attached to participants to measure the R-R interval, which were used to evaluate heart rate (HR) and perform heart rate variability (HRV) analyses. Saliva samples were obtained from participants pre- and post-meditation to measure salivary cortisol levels. Results showed that FA meditation induced a decrease in HR and an increase in the root mean square of successive differences (rMSDD). In contrast, OM meditation induced an increase in the standard deviation of the normal-to-normal interval (SDNN) to rMSSD ratio (SDNN/rMSSD) and a decrease in salivary cortisol levels. These results suggest that FA meditation elevates physiological relaxation, whereas OM meditation elevates physiological arousal and reduces stress.

Walking and talking independently predict interpersonal impressions.

When walking alongside someone, you may feel that your legs move in synchrony with theirs. Recent studies have shown that walk-in-synch behaviour observed in natural settings occurs at a rate significantly greater than would be expected by chance, and that the amount of this synchrony is related to interpersonal impressions. However, in such natural settings, the existence of verbal conversations between paired walkers should affect the interpersonal impressions and the effect is not distinguished from the effect of walk-in-synch on the impressions so far. In the current study, we used the analysis of conversation and path analysis to discriminate these two effects (i.e., the effects of synchronization of walking and conversation on interpersonal impressions). Analysis of conversation during the walk revealed that the amount of utterance overlap and the number of turn-takings between two walkers as well as the synchronization of steps predicted their positive interpersonal impression, while synchronization of steps and these two conversational indices were not correlated with each other. We propose that interpersonal synchronization of body movements, such as synchronization of steps itself in paired walking, plays a role in fostering the development of interpersonal relationships.

Investigating the Effects of Tactile Masking and Surface Texture on the Velvet Hand Illusion.

When we hold thin metallic bars between the palms of our hands and rub the palms against each other, the feeling of touching smooth velvet occurs. Previous studies have shown that tactile motion and pressure on the palms are important for this velvet hand illusion. Interestingly, when we experience this illusion, we cannot feel the texture of our palms as we usually do. In the present study, we investigated the possibility that tactile masking contributes to the occurrence of the velvet hand illusion. We measured vibrotactile detection performance on the palms of the hands during the occurrence of the velvet hand illusion. The detection performance was worse when the illusion occurred than when it did not. Moreover, the degradation of the detection performance correlated positively with the subjective magnitude of the illusion. We also examined whether additional surface texture could affect the occurrence of the illusion and found that the illusion became weaker as the roughness of the surface increased. These findings suggest that tactile motion and pressure information delivered by the bars of smooth surface mask tactile sensations on the palms of the hands, resulting in an illusory smooth, frictionless feeling on the palms.

Audio-tactile cues from an object's fall change estimates of one's body height.

When we drop an object from our hands, we use internal models of both our body height and object-motion to predict when it will hit the floor. What happens if the sensory feedback finally received from the impact conflicts with this prediction? The present study shows that such conflict results in changes in the internal estimates of our body height: When the object people dropped takes longer than expected to hit the floor, they report feeling taller and behave as if their legs were longer. This provides the first evidence of cross-modal recalibration of body-height representations as a function of changes in the distant environment. Crucially, the recalibration results from a mismatch between the predicted and actual outcome of an action, the ball's release and impact, which are causally-related but separated in space and time. These results suggest that implicit models of object-motion can interact with implicit and explicit models of one's body height.

Auditory-Somatosensory Temporal Sensitivity Improves When the Somatosensory Event Is Caused by Voluntary Body Movement.

When we actively interact with the environment, it is crucial that we perceive a precise temporal relationship between our own actions and sensory effects to guide our body movements. Thus, we hypothesized that voluntary movements improve perceptual sensitivity to the temporal disparity between auditory and movement-related somatosensory events compared to when they are delivered passively to sensory receptors. In the voluntary condition, participants voluntarily tapped a button, and a noise burst was presented at various onset asynchronies relative to the button press. The participants made either "sound-first" or "touch-first" responses. We found that the performance of temporal order judgment (TOJ) in the voluntary condition (as indexed by the just noticeable difference (JND)) was significantly better (M = 42.5 ms ± 3.8 SEM) than that when their finger was passively stimulated (passive condition: M = 66.8 ms ± 6.3 SEM). We further examined whether the performance improvement with voluntary action can be attributed to the prediction of the timing of the stimulation from sensory cues (sensory-based prediction), kinesthetic cues contained in voluntary action, and/or to the prediction of stimulation timing from the efference copy of the motor command (motor-based prediction). When three noise bursts were presented before the target burst with regular intervals (predictable condition) and when the participant's finger was moved passively to press the button (involuntary condition), the TOJ performance was not improved from that in the passive condition. These results suggest that the improvement in sensitivity to temporal disparity between somatosensory and auditory events caused by the voluntary action cannot be attributed to sensory-based prediction and kinesthetic cues. Rather, the prediction from the efference copy of the motor command would be crucial for improving the temporal sensitivity.

Corrigendum: Action Sounds Modulate Arm Reaching Movements.

[This corrects the article on p. 1391 in vol. 7, PMID: 27695430.].

Action Sounds Modulate Arm Reaching Movements.

Our mental representations of our body are continuously updated through multisensory bodily feedback as we move and interact with our environment. Although it is often assumed that these internal models of body-representation are used to successfully act upon the environment, only a few studies have actually looked at how body-representation changes influence goal-directed actions, and none have looked at this in relation to body-representation changes induced by sound. The present work examines this question for the first time. Participants reached for a target object before and after adaptation periods during which the sounds produced by their hand tapping a surface were spatially manipulated to induce a representation of an elongated arm. After adaptation, participants' reaching movements were performed in a way consistent with having a longer arm, in that their reaching velocities were reduced. These kinematic changes suggest auditory-driven recalibration of the somatosensory representation of the arm morphology. These results provide support to the hypothesis that one's represented body size is used as a perceptual ruler to measure objects' distances and to accordingly guide bodily actions.

Positive Emotion Facilitates Audiovisual Binding.

It has been shown that positive emotions can facilitate integrative and associative information processing in cognitive functions. The present study examined whether emotions in observers can also enhance perceptual integrative processes. We tested 125 participants in total for revealing the effects of emotional states and traits in observers on the multisensory binding between auditory and visual signals. Participants in Experiment 1 observed two identical visual disks moving toward each other, coinciding, and moving away, presented with a brief sound. We found that for participants with lower depressive tendency, induced happy moods increased the width of the temporal binding window of the sound-induced bounce percept in the stream/bounce display, while no effect was found for the participants with higher depressive tendency. In contrast, no effect of mood was observed for a simple audiovisual simultaneity discrimination task in Experiment 2. These results provide the first empirical evidence of a dependency of multisensory binding upon emotional states and traits, revealing that positive emotions can facilitate the multisensory binding processes at a perceptual level.

The pleasant heat? Evidence for thermal-emotional implicit associations occurring with semantic and physical thermal stimulation.

The association between thermal and emotional experiences in interpersonal relations is intuitively apparent and has been confirmed by previous studies. However, research has not yet elucidated whether such an association is grounded in mental processes occurring at an intrapersonal (internal) level. In two experiments we examined whether the thermal-emotional associations can be observed at an intrapersonal level. We looked at the speed and accuracy of stimuli categorization. Experiment 1 examined the implicit semantic association between temperature (warm versus cold) and emotional valence (positive versus negative). Experiment 2 examined the association between experience of physical temperature and emotional valence. In both experiments warm-positive/cold-negative associations were demonstrated. These results suggest a conceptual and perceptual mapping in the mental representation of emotion and temperature, which occurs at an intrapersonal level, and which might serve as the ground to the interpersonal thermal-emotional interactions.

Speech misperception: speaking and seeing interfere differently with hearing.

Speech perception is thought to be linked to speech motor production. This linkage is considered to mediate multimodal aspects of speech perception, such as audio-visual and audio-tactile integration. However, direct coupling between articulatory movement and auditory perception has been little studied. The present study reveals a clear dissociation between the effects of a listener's own speech action and the effects of viewing another's speech movements on the perception of auditory phonemes. We assessed the intelligibility of the syllables [pa], [ta], and [ka] when listeners silently and simultaneously articulated syllables that were congruent/incongruent with the syllables they heard. The intelligibility was compared with a condition where the listeners simultaneously watched another's mouth producing congruent/incongruent syllables, but did not articulate. The intelligibility of [ta] and [ka] were degraded by articulating [ka] and [ta] respectively, which are associated with the same primary articulator (tongue) as the heard syllables. But they were not affected by articulating [pa], which is associated with a different primary articulator (lips) from the heard syllables. In contrast, the intelligibility of [ta] and [ka] was degraded by watching the production of [pa]. These results indicate that the articulatory-induced distortion of speech perception occurs in an articulator-specific manner while visually induced distortion does not. The articulator-specific nature of the auditory-motor interaction in speech perception suggests that speech motor processing directly contributes to our ability to hear speech.

Serotonin transporter gene-linked polymorphism affects detection of facial expressions.

Previous studies have demonstrated that the serotonin transporter gene-linked polymorphic region (5-HTTLPR) affects the recognition of facial expressions and attention to them. However, the relationship between 5-HTTLPR and the perceptual detection of others' facial expressions, the process which takes place prior to emotional labeling (i.e., recognition), is not clear. To examine whether the perceptual detection of emotional facial expressions is influenced by the allelic variation (short/long) of 5-HTTLPR, happy and sad facial expressions were presented at weak and mid intensities (25% and 50%). Ninety-eight participants, genotyped for 5-HTTLPR, judged whether emotion in images of faces was present. Participants with short alleles showed higher sensitivity (d') to happy than to sad expressions, while participants with long allele(s) showed no such positivity advantage. This effect of 5-HTTLPR was found at different facial expression intensities among males and females. The results suggest that at the perceptual stage, a short allele enhances the processing of positive facial expressions rather than that of negative facial expressions.

Separability and commonality of auditory and visual bistable perception.

It is unclear what neural processes induce individual differences in perceptual organization in different modalities. To examine this issue, the present study used different forms of bistable perception: auditory streaming, verbal transformations, visual plaids, and reversible figures. We performed factor analyses on the number of perceptual switches in the tasks. A 3-factor model provided a better fit to the data than the other possible models. These factors, namely the "auditory," "shape," and "motion" factors, were separable but correlated with each other. We compared the number of perceptual switches among genotype groups to identify the effects of neurotransmitter functions on the factors. We focused on polymorphisms of catechol-O-methyltransferase (COMT) Val(158)Met and serotonin 2A receptor (HTR2A) -1438G/A genes, which are involved in the modulation of dopamine and serotonin, respectively. The number of perceptual switches in auditory streaming and verbal transformations differed among COMT genotype groups, whereas that in reversible figures differed among HTR2A genotype groups. The results indicate that the auditory and shape factors reflect the functions of the dopamine and serotonin systems, respectively. Our findings suggest that the formation and selection of percepts involve neural processes in cortical and subcortical areas.

Influence of the body on crossmodal interference effects between tactile and two-dimensional visual stimuli.

We investigated how tactile discrimination performance was interfered with by irrelevant two-dimensional visual stimuli using the crossmodal interference task. Participants made speeded discrimination responses to the location of vibrotactile targets presented to either tip or base of their forefinger, while trying to ignore simultaneously presented visual distractors presented to either side of the central fixation on a front display. The array of visual distractors was presented at four different angles, and the participants rested their stimulated hand on a desk in either a forward-pointing or inward-pointing posture. Although there was apparently no specific spatial relationship between the tactile and two-dimensional visual stimuli arrays and the spatial response requirement was controlled, visuotactile interference effects occurred between them. Moreover, we found that the spatial relationships between the arrays depended on the potential range of movement and the current posture of the vibrotactile-stimulated hand and possibly the stored orientation of our hand representation, even without any explicit cue referring to hands. Our results suggest that the visuotactile spatial interactions involve multiple mechanisms regarding our bodily perception and our internal body representation.

Serotonin transporter gene and inhibition of conflicting emotional information.

Genetic variation of the serotonin-transporter-linked promoter region has been reported to be associated with susceptibility to mood disorders. However, little is known about the behavioral characteristics that mediate this genetic variation and susceptibility to depression. We examined whether the serotonin-transporter genotype modulates inhibition of facial expressions and emotional words in the emotional 'face-word' Stroop task. Although negative word distractors interfered with the valence identification of positive faces among carriers of two short alleles, positive word distractors interfered with that of negative faces among carriers of one or two long alleles. We discuss a possible role of the reduced inhibitory control over semantic negative information in carriers of two short alleles in the risk of developing depressive mental state.

The tactile continuity illusion.

We can perceive the continuity of an object or event by integrating spatially/temporally discrete sensory inputs. The mechanism underlying this perception of continuity has intrigued many researchers and has been well documented in both the visual and auditory modalities. The present study shows for the first time to our knowledge that an illusion of continuity also occurs with vibrotactile stimulation. We found that when the brief temporal gaps inserted into a vibrotactile target were filled with vibrotactile noise, the target vibration was perceived to continue through the noise if the target vibration was sufficiently weak relative to the noise. It is important that the illusory continuity of the vibration cannot be distinguished from the physically continuous vibration. These results therefore suggest that the continuity illusion is common to multiple sensory modalities and that it reflects a fundamental principle of perception.

Auditory-somatosensory multisensory interactions are spatially modulated by stimulated body surface and acoustic spectra.

Previous research has provided inconsistent results regarding the spatial modulation of auditory-somatosensory interactions. The present study reports three experiments designed to investigate the nature of these interactions in the space close to the head. Human participants made speeded detection responses to unimodal auditory, somatosensory, or simultaneous auditory-somatosensory stimuli. In Experiment 1, electrocutaneous stimuli were presented to either earlobe, while auditory stimuli were presented from the same versus opposite sides, and from one of two distances (20 vs. 70 cm) from the participant's head. The results demonstrated a spatial modulation of auditory-somatosensory interactions when auditory stimuli were presented from close to the head. In Experiment 2, electrocutaneous stimuli were delivered to the hands, which were placed either close to or far from the head, while the auditory stimuli were again presented at one of two distances. The results revealed that the spatial modulation observed in Experiment 1 was specific to the particular body part stimulated (head) rather than to the region of space (i.e. around the head) where the stimuli were presented. The results of Experiment 3 demonstrate that sounds that contain high-frequency components are particularly effective in eliciting this auditory-somatosensory spatial effect. Taken together, these findings help to resolve inconsistencies in the previous literature and suggest that auditory-somatosensory multisensory integration is modulated by the stimulated body surface and acoustic spectra of the stimuli presented.

Contrast and depth perception: effects of texture contrast and area contrast.

Many objects in natural scenes have textures on their surfaces. Contrast of the texture surfaces (the texture contrast) reduces when the viewing distance increases. Similarly, contrast between the surfaces of the objects and the background (the area contrast) reduces when the viewing distance increases. The texture contrast and the area contrast were defined by the contrast between random dots, and by the contrast between the average luminance of the dot pattern and the luminance of the background, respectively. To examine how these two types of contrast influence depth perception, we ran two experiments. In both experiments two areas of random-dot patterns were presented against a uniform background, and participants rated relative depth between the two areas. We found that the rated depth of the patterned areas increased with increases in texture contrast. Furthermore, the effect of the texture contrast on depth judgment increased when the area contrast became low.

Assessing the influence of schematic drawings of body parts on tactile discrimination performance using the crossmodal congruency task.

Seeing one's own body (either directly or indirectly) can influence visuotactile crossmodal interactions. Recently, it has been shown that even viewing a simple line drawing of a hand can also modulate such crossmodal interactions, as if the picture of the hand somehow corresponds to (or primes) the participants' own hand. Alternatively, however, it could be argued that the modulatory effects of viewing the picture of a hand on visuotactile interactions might simply be attributed to cognitive processes such as the semantic referral to the relevant body part or to the orientation cues provided by the hand picture instead. In the present study, we evaluated these various different interpretations of the hand picture effect. Participants made speeded discrimination responses to the location of brief vibrotactile targets presented to either the tip or base of their forefinger, while trying to ignore simultaneously-presented visual distractors presented to either side of central fixation. We compared the modulatory effect of the picture of a hand with that seen when the visual distractors were presented next to words describing the tip and base of the forefinger (Experiment 1), or were superimposed over arrows which provided another kind of directional cue (Experiment 2). Tactile discrimination performance was modulated in the hand picture condition, but not in the word or arrow conditions. These results therefore suggest that visuotactile interactions are specifically modulated by the image of the hand rather than by cognitive cues such as simply semantic referral to the relevant body sites and/or any visual orientation cues provided by the picture of a hand.