Touch Conditions Research Articles

Sustained attention to spontaneous thumb sensations activates brain somatosensory and other proprioceptive areas

The present experiment was designed to test if sustained attention directed to the spontaneous sensations of the right or left thumb in the absence of any external stimuli is able to activate corresponding somatosensory brain areas. After verifying in 34 healthy volunteers that external touch stimuli to either thumb effectively activate brain contralateral somatosensory areas, and after subtracting attention mechanisms employed in both touch and spontaneous-sensation conditions, fMRI evidence was obtained that the primary somatosensory cortex (specifically left BA 3a/3b) becomes active when an individual is required to attend to the spontaneous sensations of either thumb in the absence of external stimuli. In addition, the left superior parietal cortex, anterior cingulate gyrus, insula, motor and premotor cortex, left dorsolateral prefrontal cortex, Broca’s area, and occipital cortices were activated. Moreover, attention to spontaneous-sensations revealed an increased connectivity between BA 3a/3b, superior frontal gyrus (BA 9) and anterior cingulate cortex (BA 32), probably allowing top-down activations of primary somatosensory cortex. We conclude that specific primary somatosensory areas in conjunction with other left parieto-frontal areas are involved in processing proprioceptive and interoceptive bodily information that underlies own body-representations and that these networks and cognitive functions can be modulated by top-down attentional processes.

Motion control, motion sickness, and the postural dynamics of mobile devices

Drivers are less likely than passengers to experience motion sickness, an effect that is important for any theoretical account of motion sickness etiology. We asked whether different types of control would affect the incidence of motion sickness, and whether any such effects would be related to participants' control of their own bodies. Participants played a video game on a tablet computer. In the Touch condition, the device was stationary and participants controlled the game exclusively through fingertip inputs via the device's touch screen. In the Tilt condition, participants held the device in their hands and moved the device to control some game functions. Results revealed that the incidence of motion sickness was greater in the Touch condition than in the Tilt condition. During game play, movement of the head and torso differed as a function of the type of game control. Before the onset of subjective symptoms of motion sickness, movement of the head and torso differed between participants who later reported motion sickness and those that did not. We discuss implications of these results for theories of motion sickness etiology.

Effect of fingertip touch on postural sway during static standing in patients with femoral neck or trochanteric fracture

Minami K, Nagatomi F, Watanabe S, Tsubahara A. Effect of fingertip touch on postural sway during static standing in patients with femoral neck or trochanteric fracture. Jpn J Compr Rehabil Sci 2014; 5:50-55. Objective: Patients with femoral neck or trochanteric fracture (hip fracture) are considered to be at high risk for falling. We investigated whether a light fingertip touch on a stable surface (LT) with a force insufficient to provide mechanical support of the body could stabilize static standing. We also investigated whether the effect differed between LT and heavy fingertip touch (HT) or between ipsilateral and contralateral fingertip touch (relative to the fracture). Methods: Eleven patients with hip fracture who were hospitalized in a kaifukuki (convalescence) rehabilitation ward participated in the study. The sway of the center of pressure (COP) during static standing was measured and compared under five fingertip touch conditions.

The effect of age on neural processing of pleasant soft touch stimuli

Tactile interactions with our environment stimulate afferent fibers within the skin, which deliver information about sensations of pain, texture, itch and other feelings to the brain as a comprehensive sense of self. These tactile interactions can stimulate brain regions involved in interoception and reward processing. This study examined subjective, behavioral, and neural processing as a function of age during stimulation of A-beta (Aβ) and C tactile (CT) afferents using a soft brush stroke task. 16 adolescents (ages 15–17), 22 young adults (ages 20–28), and 20 mature adults (ages 29–55) underwent a simple continuous performance task while periodically anticipating and experiencing a soft touch to the palm or forearm, during functional magnetic resonance imaging (fMRI). fMRI results showed that adolescents displayed greater bilateral posterior insula activation than young and mature adults across all conditions and stimulus types. Adolescents also demonstrated greater bilateral posterior insula activation than young and mature adults specifically in response to the soft touch condition. Adolescents also exhibited greater activation than mature adults in bilateral inferior frontal gyrus and striatum during the soft touch condition. However, mature adults showed greater striatum activation than adolescents and young adults during anticipation. In the left anterior cingulate cortex, mature adults exhibited greater activation than adolescents and young adults when anticipating the upcoming touch. These results support the hypothesis that adolescents show an exaggerated neural response to pleasant stimulation of afferents, which may have profound effects on how they approach or avoid social and risky situations. In particular, heightened interoceptive reactivity to pleasant stimuli might cause adolescents to seek experiences that are associated with pleasant stimulation.

Does the type of somatosensory information from the contralateral finger touch affect grip force control while lifting an object?

The magnitude of grip force used to lift and transport a hand-held object is decreased if a light finger touch from the contralateral arm is provided to the wrist of the target arm. We investigated whether the type of contralateral arm sensory input that became available with the finger touch to the target arm affects the way grip force is reduced. Nine healthy subjects performed the same task of lifting and transporting an instrumented object with no involvement of the contralateral arm and when an index finger touch of the contralateral arm was provided to the wrist, elbow, and shoulder. Touching the wrist and elbow involved movements of the contralateral arm; no movements were produced while touching the shoulder. Grip force was reduced by approximately the same amount in all conditions with the finger touch compared to the no touch condition. This suggests that information from the muscle and joint receptors of the contralateral arm is used in control of grip force when a finger touch is provided to the wrist and elbow, and cutaneous information is utilized when lifting an object while touching the shoulder. The results of the study provide additional evidence to support the use of a second arm in the performance of activities of daily living and stress the importance of future studies investigating contralateral arm sensory input in grip force control.

Interactions of touch feedback with muscle vibration and galvanic vestibular stimulation in the control of trunk posture

This study investigated the effect of touch on trunk sway in a seated position. Two touch conditions were included: touching an object with the index finger of the right hand (hand-touch) and maintaining contact with an object at the level of the spine of T10 on the mid back (back-touch). In both touch conditions, the exerted force stayed below 2N. Furthermore, the interaction of touch with paraspinal muscle vibration and galvanic vestibular stimulation (GVS) was studied. Thirteen healthy subjects with no history of low-back pain participated in this study. Subjects sat on a stool and trunk sway was measured with a motion capture system tracking a cluster marker on the trunk. Subjects performed a total of 12 trials of 60-s duration in a randomized order, combining the experimental conditions of no-touch, hand-touch or back-touch with no sensory perturbation, paraspinal muscle vibration or GVS. The results showed that touch through hand or back decreased trunk sway and decreased the effects of muscle vibration and GVS. GVS led to a large increase in sway whereas the effect of muscle vibration was only observed as an increase of drift and not of sway. In the current experimental set-up, the stabilizing effect of touch was strong enough to mask any effects of perturbations of vestibular and paraspinal muscle spindle afference. In conclusion, tactile information, whenever available, seems to play a dominant role in seated postural sway and therefore has important implications for studying trunk control.

Self-reported Pleasantness Ratings and Examiner-Coded Defensiveness in Response to Touch in Children with ASD: Effects of Stimulus Material and Bodily Location

Tactile defensiveness, characterized by behavioral hyperresponsiveness and negative emotional responses to touch, is a common manifestation of aberrant sensory processing in autism spectrum disorders (ASD) and other developmental disabilities (DD). Variations in tactile defensiveness with the properties of the stimulus and the bodily site of stimulation have been addressed in adults with self-report of perceived tactile pleasantness, but not in children. We presented three materials (pleasant, unpleasant, social) at three bodily sites and measured both examiner-coded defensiveness and self-reported pleasantness from a group of children with ASD and two comparison groups (one with DD, one with typical development (TD)). The main findings were: (1) children with ASD and DD showed significantly more defensiveness reactions and lower pleasantness ratings than the TD group, with higher variability, (2) there was a double dissociation for the effects of material and bodily site of stimulation: while bodily site predicted behavioral defensiveness, material predicted pleasantness rating. Additionally, it was noted that (3) the most pleasant material and the social touch conditions best distinguished ASD and DD from TD on defensiveness, and (4) within the ASD group, social impairment and defensiveness in bodily sites associated with social touch were positively correlated, suggesting a clinically relevant distinction between social and discriminative touch in ASD.

On the Edge: Haptic Discrimination of Edge Sharpness

The increasing ubiquity of haptic displays (e.g., smart phones and tablets) necessitates a better understanding of the perceptual capabilities of the human haptic system. Haptic displays will soon be capable of locally deforming to create simple 3D shapes. This study investigated the sensitivity of our haptic system to a fundamental component of shapes: edges. A novel set of eight high quality shape stimuli with test edges that varied in sharpness were fabricated in a 3D printer. In a two alternative, forced choice task, blindfolded participants were presented with two of these shapes side by side (one the reference, the other selected randomly from the remaining set of seven) and after actively exploring the test edge of each shape with the tip of their index finger, reported which shape had the sharper edge. We used a model selection approach to fit optimal psychometric functions to performance data, and from these obtained just noticeable differences and Weber fractions. In Experiment 1, participants performed the task with four different references. With sharpness defined as the angle at which one surface meets the horizontal plane, the four JNDs closely followed Weber’s Law, giving a Weber fraction of 0.11. Comparisons to previously reported Weber fractions from other haptic manipulations (e.g. amplitude of vibration) suggests we are sufficiently sensitive to changes in edge sharpness for this to be of potential utility in the design of future haptic displays. In Experiment 2, two groups of participants performed the task with a single reference but different exploration strategies; one was limited to a single touch, the other unconstrained and free to explore as they wished. As predicted, the JND in the free exploration condition was lower than that in the single touch condition, indicating exploration strategy affects sensitivity to edge sharpness.

Methamphetamine dependent individuals show attenuated brain response to pleasant interoceptive stimuli

BackgroundMechano-receptive C-fiber (MR-CF) stimulation via slow stroking of C-fiber rich skin areas can be used to probe the relationship between reward and interoception. Individuals with substance use disorders show impaired reward processing, and dysfunctional interoceptive processing of MR-CF may contribute to this dysfunction. This study predicted that methamphetamine dependent (MD) individuals would exhibit altered responses to MR-CF stimulation in brain regions important for interoception. MethodsRecently abstinent MD (n=25) and comparison (CTL, n=17) subjects received a pleasant interoceptive stimulus (“Soft Touch” consisting of a slow brush stroke) to the palm or forearm during functional magnetic resonance imaging. Subjects were provided with cues signaling stimulation to examine anticipatory and stimulus-related processing. Subjective responses were measured using visual analog scales (VAS). ResultsGroups were similar on behavioral performance and ratings of the interoceptive stimuli, yet MD exhibited lower anterior insula, dorsal striatum, and thalamus activation than CTL, across anticipation and soft touch conditions. The lower the anterior insula activation, the faster the reaction time across conditions in MD, whereas the opposite pattern was evident in CTL. Striatal activation in MD was greater than CTL during anticipation, but lower during soft touch. Greater striatal attenuation was associated with higher VAS pleasantness ratings of soft touch. ConclusionsMD expend fewer brain processing resources during soft touch, a form of positively-valenced interoceptive stimuli, in brain areas that are important for both interoception and reward. Future studies will ascertain if sustained abstinence from methamphetamine use can normalize aberrant neural interoceptive processing.

Uso da informação somatossensorial adicional no controle postural: efeito da dominância manual

Buscamos com o presente estudo investigar o efeito da dominância manual e da visão no uso da informação somatossensorial adicional fornecida pelo toque suave no controle postural. Quinze adultos jovens e destros permaneceram em pé sobre uma plataforma de força com a) olhos abertos ou fechados e b) braços ao lado do corpo ou o dedo indicador direito ou esquerdo tocando a barra fixa. A área do centro de pressão (CP), amplitude e velocidade médias do CP nas direções anteroposterior e médio-lateral foram avaliadas. Os resultados indicaram uma redução nas medidas nas condições de toque e aumento com os olhos fechados, exceto quando o toque foi realizado com dedo indicador direito. A força máxima foi maior para a mão direita, enquanto a sensibilidade cutânea e as forças aplicadas à barra foram similares entre os hemicorpos. Esses resultados sugerem um efeito da dominância manual e visão no uso da informação somatossensorial adicional no controle postural.

Trust during retail encounters: A touchy proposition

Adopting an interpersonal communication perspective, this study examines the propositions that a salesperson's touch increases trust, which increases product evaluations and purchase intention. These relationships are evaluated in a contact and non-contact culture, with need for touch (NFT) examined as an additional moderator. An exploratory series of in-depth interviews provides an initial understanding of these relationships, followed by a 2 (touch/no touch condition)×2 (consumers in France/Germany) experiment with wine serving as the example category. The findings indicate that touch does not uniformly instill trust in customers. Instead a salesperson's touch relates to greater trust only when consumers have an inherent NFT or when they are from a culture where personal touching behavior is less prevalent. Trust, in turn, relates positively to evaluations of product attractiveness, quality, and to purchase intention.

An fMRI study on cortical responses during active self-touch and passive touch from others

Active, self-touch and the passive touch from an external source engage comparable afferent mechanoreceptors on the touched skin site. However, touch directed to glabrous skin compared to hairy skin will activate different types of afferent mechanoreceptors. Despite perceptual similarities between touch to different body sites, it is likely that the touch information is processed differently. In the present study, we used functional magnetic resonance imaging (fMRI) to elucidate the cortical differences in the neural signal of touch representations during active, self-touch and passive touch from another, to both glabrous (palm) and hairy (arm) skin, where a soft brush was used as the stimulus. There were two active touch conditions, where the participant used the brush in their right hand to stroke either their left palm or arm. There were two similar passive, touch conditions where the experimenter used an identical brush to stroke the same palm and arm areas on the participant. Touch on the left palm elicited a large, significant, positive blood-oxygenation level dependence (BOLD) signal in right sensorimotor areas. Less extensive activity was found for touch to the arm. Separate somatotopical palm and arm representations were found in Brodmann area (BA) 3 of the right primary somatosensory cortex (SI) and in both these areas, active stroking gave significantly higher signals than passive stroking. Active, self-touch elicited a positive BOLD signal in a network of sensorimotor cortical areas in the left hemisphere, compared to the resting baseline. In contrast, during passive touch, a significant negative BOLD signal was found in the left SI. Thus, each of the four conditions had a unique cortical signature despite similarities in afferent signaling or evoked perception. It is hypothesized that attentional mechanisms play a role in the modulation of the touch signal in the right SI, accounting for the differences found between active and passive touch.

Pleasant human touch is represented in pregenual anterior cingulate cortex

Touch massage (TM) is a form of pleasant touch stimulation used as treatment in clinical settings and found to improve well-being and decrease anxiety, stress, and pain. Emotional responses reported during and after TM have been studied, but the underlying mechanisms are still largely unexplored. In this study, we used functional magnetic resonance (fMRI) to test the hypothesis that the combination of human touch (i.e. skin-to-skin contact) with movement is eliciting a specific response in brain areas coding for pleasant sensations. The design included four different touch conditions; human touch with or without movement and rubber glove with or without movement. Force (2.5 N) and velocity (1.5 cm/s) were held constant across conditions. The pleasantness of the four different touch stimulations was rated on a visual analog scale (VAS-scale) and human touch was rated as most pleasant, particularly in combination with movement. The fMRI results revealed that TM stimulation most strongly activated the pregenual anterior cingulate cortex (pgACC). These results are consistent with findings showing pgACC activation during various rewarding pleasant stimulations. This area is also known to be activated by both opioid analgesia and placebo. Together with these prior results, our finding furthers the understanding of the basis for positive TM treatment effects.

Unperceivable noise to active light touch effects on fast postural sway

Human postural sway during quiet standing is reduced when a fingertip lightly touches a stable surface. The tactile feedback information from the fingertip has been considered responsible for this effect of light touch. Studies have shown that a noise-like minute stimulation to the sensory system can improve the system's weak signal detection. In the present study, we investigated whether a noise-like unperceivable vibration on the fingertip enhances its tactile sensation and facilitates the effect of light touch during quiet standing. Thirteen volunteers maintained quiet standing while lightly touching a touch surface with the index fingertip. Based on each subject's vibrotactile threshold (VT), a noise-like vibration was applied to the touch surface at amplitudes under (0.5VT) or at VT (1.0VT), in addition to the normal light touch condition (no vibration, 0VT). The results showed that the mean velocities of the foot center of pressure (CoP) in both the anteroposterior (AP) and mediolateral (ML) directions were significantly reduced at 0.5VT compared to 0VT and 1.0VT ( P < 0.05), while there was no significant difference between 1.0VT and 0VT ( P > 0.05). Frequency analysis of CoP revealed that the power of high-frequency fluctuation (1–10 Hz) was significantly reduced at 0.5VT ( P < 0.05), whereas no significant change was observed in that of low-frequency sway (below 1 Hz) ( P > 0.05). These results indicate that an unperceivable noise-like vibration can facilitate the effect of light touch on postural stability, by further reducing fast postural sway.

Programmable tactile pattern presentations operational under MRI to investigate neural mechanisms of tactile shape discrimination

We have developed a novel tactile presentation system for assessing and training cognitive function on tactile senses. The device is operational in magnetic resonance imaging (MRI) environment and capable of investigating the underlying neural mechanisms of tactile pattern discrimination. The primary components of the system include a finger movement control unit (FCU), a disk for multiple tactile pattern delivery (DPD), and a force-sensing unit (FSU). An ultrasonic motor rotates the DPD to deliver different tactile patterns for cognitive sensitivity test. We evaluated the operational reliability and the performance of the system in a MRI environment. The results showed that the system performance was not affected by the magnetic field, nor did the system operation interfere with the magnetic field either. The results from the two functional MRI experiments also indicated that the brain activation can be reliably detected with the present system. Furthermore, a tactile pattern discrimination experiment was conducted using the system to investigate cognitive characteristics of shape discrimination under active and passive touch conditions. We found that the mean accuracy of discrimination under active touch was significantly higher than that under passive touch. The high accuracy and magnetic field compatibility of the device suggest that the device provides a powerful means of investigating the neural mechanisms of perception and cognitive function for touch discrimination.

P‐190: High SNR Multi‐Touch Capacitance Touch‐screen Controller with Haptics Support

AbstractA high performance multi‐touch capacitive touch‐screen controller has been developed which is capable of supporting multiple sensor types, gloves, small‐tipped conductive stylus, and low‐latency haptics. The controller improves the user experience through high signal‐to‐noise ratio (SNR) which allows supporting a wider range of touch conditions and better combats noisy environments.

Research on Influence of Longitudinal Gradient to Rigid Base Composite Road of Cross River (Sea) Tunnel under Large Longitudinal Slope

The influences of longitudinal gradient on the large longitudinal slope rigid base composite road of cross river(sea) tunnel are concerned recently. Then the relationships between sheering stresses versus slope angle, load, pavement depth, interlayer touch condition and modulus are discussed separately by a three dimensional FEM model. Calculation and analysis showed: gradient had great influence on the surface tangent load and little influence on design deflection, the base and surface.The maximum tension and sheer on surface were increased with the gradient. On general, the gradient and surface tangent load should be considered in structure analysis for the large longitudinal slope road.

Scenario-based touching: on the influence of top-down processes on tactile and visual appreciation

The aim was to propose a testing procedure that allows measuring ecological valid judgments as a tool for selecting e.g. surface materials in the design process. Precise measures are essential for evaluation processes for example in design research and applied studies. Contextual effects in form of top-down processes often lead to biases in measures such as quality or liking judgments. We examined contextual effects of such factors by varying specific instructions, which were based on everyday life scenarios. We also investigated the stability and ecological validity of evaluations with the focus on a multisensory approach involving vision plus touch, touch-only and vision-only conditions. Participants evaluated the materials, for preference in experiment 1, and for perceived material properties (thermal conductivity, hardness and roughness) in experiment 2—either with or without specific instructions. Results showed higher consistency in the vision plus touch condition than in the unimodal conditions. Moreover, preferences and perceived material properties strongly varied according to the presence and the content of instruction (scenarios). These results demonstrate the strong impact of top-down processes on tactile as well as visual judgments.

Haptic touch reduces sway by increasing axial tone

It is unclear how haptic touch with a stable surface reduces postural sway. We hypothesized that haptic input enhances postural stability due to alterations in axial postural tone. We measured the influence of heavy and light touch (LT) of the hands on a stable bar on axial postural tone and postural sway during stance in 14 healthy adults. A unique “Twister” device measured hip torque by fixing the upper body in space while oscillating the surface in yaw ±10 at 1 deg/s. Subjects were tested while: (1) standing quietly with their arms at their sides, (2) lightly touching a rigid bar in front of them and (3) firmly gripping the bar. Horizontal and vertical sway was not restricted by the device's yaw fixation, therefore, the subjects remained in a state of active postural control during the three touch conditions. Haptic touch significantly increased hip postural tone by 44% during light touch, from 2.5±0.9 to 3.6±1.0 Nm ( P=0.005), and by 40% during firm grip to 3.5±0.8 Nm ( P=0.005). Increases in hip postural tone were associated with a reduction in postural sway ( r=−0.55, P=0.001). This is the first study showing that axial postural tone can be modified by remote somatosensory input and provides a potential explanation for how light touch improves postural stability. Changes in subjects' perception from trunk to surface rotation when changing from no touch (NT) to haptic touch, suggests that the CNS changes from using a global, to a local, trunk reference frame for control of posture during touch. The increase of hip postural tone during touching and gripping can be explained as a suppression of hip muscle shortening reactions that normally assist axial rotation.

Surface texture can bias tactile form perception

The sense of touch is believed to provide a reliable perception of the object's properties; however, our tactile perceptions could be illusory at times. A recently reported tactile illusion shows that a raised form can be perceived as indented when it is surrounded by textured areas. This phenomenon suggests that the form perception can be influenced by the surface textures in its adjacent areas. As perception of texture and that of form have been studied independently of each other, the present study examined whether textures, in addition to the geometric edges, contribute to the tactile form perception. We examined the perception of the flat and raised contact surface (3.0 mm width) with various heights (0.1, 0.2, 0.3 mm), which had either textured or non-textured adjacent areas, under the static, passive and active touch conditions. Our results showed that texture decreased the raised perception of the surface with a small height (0.1 mm) and decreased the flat perception of the physically flat surface under the passive and active touch conditions. We discuss a possible mechanism underlying the effect of the textures on the form perception based on previous neurophysiological findings.