Tactile stimulation interventions: Influence of stimulation parameters on sensorimotor behavior and neurophysiological correlates in healthy and clinical samples

Enhancing touch sensibility with sensory electrical stimulation and sensory retraining

A large proportion of stroke survivors suffer from sensory loss, negatively impacting their independence, quality of life, and neurorehabilitation prognosis. Despite the high prevalence of somatosensory impairments, our understanding of somatosensory interventions such as sensory electrical stimulation (SES) in neurorehabilitation is limited. We aimed to study the effectiveness of SES combined with a sensory discrimination task in a well-controlled virtual environment in healthy participants, setting a foundation for its potential application in stroke rehabilitation. We employed electroencephalography (EEG) to gain a better understanding of the underlying neural mechanisms and dynamics associated with sensory training and SES. We conducted a single-session experiment with 26 healthy participants who explored a set of three visually identical virtual textures-haptically rendered by a robotic device and that differed in their spatial period-while physically guided by the robot to identify the odd texture. The experiment consisted of three phases: pre-intervention, intervention, and post-intervention. Half the participants received subthreshold whole-hand SES during the intervention, while the other half received sham stimulation. We evaluated changes in task performance-assessed by the probability of correct responses-before and after intervention and between groups. We also evaluated differences in the exploration behavior, e.g., scanning speed. EEG was employed to examine the effects of the intervention on brain activity, particularly in the alpha frequency band (8-13 Hz) associated with sensory processing. We found that participants in the SES group improved their task performance after intervention and their scanning speed during and after intervention, while the sham group did not improve their task performance. However, the differences in task performance improvements between groups only approached significance. Furthermore, we found that alpha power was sensitive to the effects of SES; participants in the stimulation group exhibited enhanced brain signals associated with improved touch sensitivity likely due to the effects of SES on the central nervous system, while the increase in alpha power for the sham group was less pronounced. Our findings suggest that SES enhances texture discrimination after training and has a positive effect on sensory-related brain areas. Further research involving brain-injured patients is needed to confirm the potential benefit of our solution in neurorehabilitation.

Toe stimulation improves tactile perception of the genitals

The human body is represented in a topographic pattern in the primary somatosensory cortex (S1), and genital representation is displaced below the toe representation. However, the relationship between the representation of the genitals and toe in S1 remains unclear. In this study, tactile stimulation was applied to the big toe in healthy subjects to observe changes in tactile acuity in the unstimulated genital area, abdomen, and metacarpal dorsal. Then tactile stimulation was applied to the right abdomen and metacarpal dorsal to observe changes in tactile acuity in bilateral genitals. The results revealed that tactile stimulation of the big toe led to a reduction in the 2-point discrimination threshold (2PDT) not only in the stimulated big toe but also in the bilateral unstimulated genitals, whereas the bilateral abdomen and metacarpal dorsal threshold remained unchanged. On the other hand, tactile stimulation of the abdomen and metacarpal dorsal did not elicit 2-point discrimination threshold changes in the bilateral genitals. Cortical and subcortical mechanisms have been proposed to account for the findings. One explanation involves the intracortical interaction between 2 adjacent representations. Another possible explanation is that the information content of a specific body part is broadly distributed across the S1. Moreover, exploring the links between human behaviors and changes in the cerebral cortex is of significant importance.

Less might be more: 1 mA but not 1.5 mA of tDCS improves tactile orientation discrimination

Background

Transcranial direct current stimulation (tDCS) is a frequently used brain stimulation method; however, studies on tactile perception using tDCS are inconsistent, which might be explained by the variations in endogenous and exogenous parameters that influence tDCS.

Objectives

We aimed to investigate the effect of one of these endogenous parameters-the tDCS amplitude-on tactile perception.

Methods

We conducted this experiment on 28 undergraduates/graduates aged 18-36 years. In separate sessions, participants received 20 min of 1 mA or 1.5 mA current tDCS in a counterbalanced order. Half of the participants received anodal tDCS of the left SI coupled with cathodal tDCS of the right SI, and this montage was reversed for the other half. Pre- and post-tDCS tactile discrimination performance was assessed using the Grating Orientation Task (GOT). In this task, plastic domes with gratings of different widths cut into their surfaces are placed on the fingertip, and participants have to rate the orientation of the gratings.

Results

Linear modeling with amplitude, dome, and session as within factors and montage as between factors revealed the following: significant main effects of grating width, montage, and session and a marginally significant interaction effect of session and amplitude. Posthoc t-tests indicated that performance in GOT improved after 1 mA but not 1.5 mA tDCS independent of the montage pattern of the electrodes.

Conclusion

Increasing the stimulation amplitude from 1 mA to 1.5 mA does not facilitate the tDCS effect on GOT performance. On the contrary, the effect seemed more robust for the lower-current amplitude.

Effects of tactile stimulation on the sensory, motor and cognitive function in people with multiple sclerosis

OBJECTIVE

Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disease that causes demyelination in the brain and spinal cord. Repetitive sensory stimulation (RSS) can enhance sensory perception and motor function, improve inappropriate synaptic connections and adaptable malformations, and increase cognitive function. The purpose of this study was to specify the effect of RSS on the sensory, motor, and cognitive function in people with MS.

METHODS

RSS was applied to 50 people with MS. In this study, the following tests were used: two-point discrimination, 9-Hole Peg Test (9-HPT), Box and Block Test (BBT), hand mental rotation (HMR), Paced Auditory Serial Addition Test (PASAT), and Symbol Digit Modalities Test (SDMT). The tests were performed before and after the intervention.

RESULTS

The results of this study showed significant difference before and after the stimulation in intervention and control groups two-point discrimination threshold (both groups= 0.001), BBT score (both groups: P < 0.001) and 9-HPT score (both groups: P < 0.001), HMR ability (reaction time: both groups: P = 0.003; accuracy rate: intervention: P = 0.004, control: P < 0.001), PASAT score (intervention: P < 0.001, control: P = 0.012) and SDMT score (intervention: P = 0.008, control: P < 0.001), but there was no statistical difference observed between the two groups before and after the intervention in terms of the mentioned variables (P > 0.05).

CONCLUSION

The application of 30 min of RSS in the right index finger of people with MS could not improve the two-point discrimination threshold and the manual dexterity. In addition, this intervention did not improve cognitive function.

Experience-driven remodeling of S1 digit representation in awake monkeys: the challenge of comparing active and passive touch

Many studies have compared active and passive touch to understand how motor action shapes touch perception. Current views emphasize the difficulties in making such a comparison and promote investigating how motor strategies enable the filtering out of sensory inputs to reshape touch perception. Cybulska-Klosowicz et al. (Cybulska-Klosowicz A, Tremblay F, Jiang W, Bourgeon S, Meftah E-M, Chapman CE. J Neurophysiol 123: 1072-1089, 2020) suggest that primary somatosensory (S1) cortical remodeling of digit representation occurs during active touch. Here, alternative interpretations are proposed, and the relevance of studying multidigit scanning is emphasized.

Effects of tDCS on Tactile Perception Depend on Tactile Expertise in Both Musicians and Non-Musicians

Brain plasticity in the somatosensory cortex and tactile performance can be facilitated by brain stimulation. Here, we investigated the effects of transcranial direct current stimulation (tDCS) on tactile perception in musicians and non-musicians to elucidate how tDCS-effects might depend on tactile expertise. On three separate days, 17 semi-professional musicians (e.g., piano or violin players) and 16 non-musicians aged 18-27 years received 15 min of 1 mA anodal (a-tDCS), cathodal (c-tDCS) or sham tDCS in a pseudorandomized design. Pre and post tDCS, tactile sensitivity (Touch Detection Task; TDT) and discrimination performance (Grating Orientation Task; GOT) were assessed. For further analysis, the weekly hours of instrument-playing and computer-typing were combined into a "tactile experience" variable. For GOT, but not TDT, a significant group effect at baseline was revealed with musicians performing better than non-musicians. TDT thresholds were significantly reduced after a-tDCS but not c-tDCS or sham stimulation. While both musicians' and non-musicians' performance improved after anodal stimulation, neither musical nor tactile expertise was directly associated with the magnitude of this improvement. Low performers in TDT with high tactile experience profited most from a-tDCS. We conclude that tactile expertise may facilitate somatosensory cortical plasticity and tactile learning in low performers.

Hemodynamic response varies across tactile stimuli with different temporal structures

Tactile stimuli can be distinguished based on their temporal features (e.g., duration, local frequency, and number of pulses), which are fundamental for vibrotactile frequency perception. Characterizing how the hemodynamic response changes in shape across experimental conditions is important for designing and interpreting fMRI studies on tactile information processing. In this study, we focused on periodic tactile stimuli with different temporal structures and explored the hemodynamic response function (HRF) induced by these stimuli. We found that HRFs were stimulus‐dependent in tactile‐related brain areas. Continuous stimuli induced a greater area of activation and a stronger and narrower hemodynamic response than intermittent stimuli with the same duration. The magnitude of the HRF increased with increasing stimulus duration. By normalizing the characteristics into topographic matrix, nonlinearity was obvious. These results suggested that stimulation patterns and duration within a cycle may be key characters for distinguishing different stimuli. We conclude that different temporal structures of tactile stimuli induced different HRFs, which are essential for vibrotactile perception and should be considered in fMRI experimental designs and analyses.

Passive perceptual learning modulates motor inhibitory control in superior frontal regions

Response inhibition is of vital importance in the context of controlling inappropriate responses. The role of perceptual processes during inhibitory control has attracted increased interest. Yet, we are far from an understanding of the mechanisms. One candidate mechanism by which perceptual processes may affect response inhibition refers to “gain control” that is closely linked to the signal‐to‐noise ratio of incoming information. A means to modulate the signal‐to‐noise ratio and gain control mechanisms is perceptual learning. In the current study, we examine the impact of perceptual learning (i.e., passive repetitive sensory stimulation) on response inhibition combining EEG signal decomposition with source localization analyses. A tactile GO/NOGO paradigm was conducted to measure action restraint as one subcomponent of response inhibition. We show that passive perceptual learning modulates response inhibition processes. In particular, perceptual learning attenuates the detrimental effect of response automation during inhibitory control. Temporally decomposed EEG data show that stimulus‐related and not response selection processes during conflict monitoring are linked to these effects. The superior and middle frontal gyrus (BA6), as well as the motor cortex (BA4), are associated with the effects of perceptual learning on response inhibition. Reliable neurophysiological effects were not evident on the basis of standard ERPs, which has important methodological implications for perceptual learning research. The results detail how lower level sensory plasticity protocols affect higher‐order cognitive control functions in frontal cortical structures.

Sensory enhancement amplifies interlimb cutaneous reflexes in wrist extensor muscles

Interlimb neural connections support motor tasks such as locomotion and cross-education strength training. Somatosensory pathways that can be assessed with cutaneous reflex paradigms assist in subserving these connections. Many studies show that stimulation of cutaneous nerves elicits reflexes in muscles widespread across the body and induces neural plasticity after training. Sensory enhancement, such as long-duration trains of transcutaneous stimulation, facilitates performance during rehabilitation training or fatiguing motor tasks. Performance improvements due to sensory stimulation may be caused by altered spinal and corticospinal excitability. However, how enhanced sensory input regulates the excitability of interlimb cutaneous reflex pathways has not been studied. Our purpose was to investigate the effects of sensory enhancement on interlimb cutaneous reflexes in wrist extensor muscles. Stimulation to provide sensory enhancement (2-s trains at 150 Hz to median or superficial radial nerves) or evoke cutaneous reflexes (15-ms trains at 300 Hz to superficial radial nerve) was applied in different arms while participants (n = 13) performed graded isometric wrist extension. Wrist extensor electromyography and cutaneous reflexes were measured bilaterally. We found amplified inhibitory reflexes in the arm receiving superficial radial and median nerve sensory enhancement with net reflex amplitudes decreased by 709.5% and 695.3% repetitively. This suggests sensory input alters neuronal excitabilities in the interlimb cutaneous pathways. These findings have potential application in facilitating motor function recovery through alterations in spinal cord excitability enhancing sensory input during targeted rehabilitation and sports training.NEW & NOTEWORTHY We show that sensory enhancement increases excitability in interlimb cutaneous pathways and that these effects are not influenced by descending motor drive on the contralateral side. These findings confirm the role of sensory input and cutaneous pathways in regulating interlimb movements. In targeted motor function training or rehabilitation, sensory enhancement may be applied to facilitate outcomes.

Touch and Pain Sensations in Diadynamic Current (DD) and Transcutaneous Electrical Nerve Stimulation (TENS): A Randomized Study

The study investigated touch and pain sensations and the correlation between them in diadynamic current (DD) and transcutaneous electrical nerve stimulation (TENS), electrotherapies commonly applied in musculoskeletal disorders and occupational rehabilitation medicine. Forty healthy subjects were treated with either DD (n=20) or TENS (n=20). Each treatment consisted of three sessions with one-week interval. Touch sensation was determined with the JVP Domes esthesiometer, pain sensation with pressure pain threshold (PPT), and pressure pain tolerance threshold (PPTO) by an algometer. During each session the measurements were performed before the application of the procedure (T0), immediately after it (T1), and 30 minutes after the end of the procedure (T2). Both DD and TENS increased touch sensation (p<0.01) and did not significantly alter PPT and PPTO (p>0.05). No statistically significant differences in short-term effects, i.e., 3 weeks of the trial, were noted between DD and TENS in their influence on touch and pain sensations (p>0.05). There was a high significant correlation between touch and pain sensations in DD (r=0.86). TENS and DD caused similar analgesic effects. DD, which is shorter in the duration of the treatment, may comprise a realistic alternative to TENS in clinical practice of pain management.

Wearable Haptics and Immersive Virtual Reality Rehabilitation Training in Children With Neuromotor Impairments

The past decade has seen the emergence of rehabilitation treatments using virtual reality (VR) environments although translation into clinical practice has been limited so far. In this paper, an immersive VR rehabilitation training system endowed with wearable haptics is proposed for children with neuromotor impairments: it aims to enhance involvement and engagement of patients, to provide congruent multi-sensory afferent feedback during motor exercises and to benefit from the flexibility of VR in adapting exercises to the patient's need. An experimental rehabilitation session conducted with children with cerebral palsy (CP) and developmental dyspraxia (DD) has been performed to evaluate the usability of the system and proof of concept trial of the proposed approach. We compared CP/DD performance with both typically developing children and adult control group. Results show the system was compliant with different levels of motor skills and allowed patients to complete the experimental rehabilitation session, with performance varying according to the expected motor abilities of different groups. Moreover, a kinematic assessmentbased on the presented system has been designed. Obtained results reflected different motor abilities of patients and participants, suggesting suitability of the proposed kinematic assessment as a motor function outcome.

Rehabilitation modality and onset differentially influence whisker sensory hypersensitivity after diffuse traumatic brain injury in the rat

BACKGROUND

As rehabilitation strategies advance as therapeutic interventions, the modality and onset of rehabilitation after traumatic brain injury (TBI) are critical to optimize treatment. Our laboratory has detected and characterized a late-onset, long-lasting sensory hypersensitivity to whisker stimulation in diffuse brain-injured rats; a deficit that is comparable to visual or auditory sensory hypersensitivity in humans with an acquired brain injury.

OBJECTIVE

We hypothesize that the modality and onset of rehabilitation therapies will differentially influence sensory hypersensitivity in response to the Whisker Nuisance Task (WNT) as well as WNT-induced corticosterone (CORT) stress response in diffuse brain-injured rats and shams.

METHODS

After midline fluid percussion brain injury (FPI) or sham surgery, rats were assigned to one of four rehabilitative interventions: (1) whisker sensory deprivation during week one or (2) week two or (3) whisker stimulation during week one or (4) week two. At 28 days following FPI and sham procedures, sensory hypersensitivity was assessed using the WNT. Plasma CORT was evaluated immediately following the WNT (aggravated levels) and prior to the pre-determined endpoint 24 hours later (non-aggravated levels).

RESULTS

Deprivation therapy during week two elicited significantly greater sensory hypersensitivity to the WNT compared to week one (p < 0.05), and aggravated CORT levels in FPI rats were significantly lower than sham levels. Stimulation therapy during week one resulted in low levels of sensory hypersensitivity to the WNT, similar to deprivation therapy and naïve controls, however, non-aggravated CORT levels in FPI rats were significantly higher than sham.

CONCLUSION

These data indicate that modality and onset of sensory rehabilitation can differentially influence FPI and sham rats, having a lasting impact on behavioral and stress responses to the WNT, emphasizing the necessity for continued evaluation of modality and onset of rehabilitation after TBI.

Effect of somatosensory and neurofeedback training on balance in older healthy adults: a preliminary investigation

The aim of this study was to assess the effectiveness of balance training with somatosensory and neurofeedback training on dynamic and static balance in healthy, elderly adults. The sample group consisted of 45 healthy adults randomly assigned to one of the three test groups: somatosensory, neurofeedback, and a control. Individualization of the balance program started with pre-tests for static and dynamic balances. Each group had 15- and 30-min training sessions. All groups were tested for static (postural stability) and dynamic balances (Berg Balance Scale) in acquisition and transfer tests (fall risk of stability and timed up and go). Improvements in static and dynamic balances were assessed by somatosensory and neurofeedback groups and then compared with the control group. Results indicated significant improvements in static and dynamic balances in both test groups in the acquisition test. Results revealed a significant improvement in the transfer test in the neurofeedback and somatosensory groups, in static and dynamic conditions, respectively. The findings suggest that these methods of balance training had a significant influence on balance. Both the methods are appropriate to prevent falling in adults. Neurofeedback training helped the participants to learn static balance, while somatosensory training was effective on dynamic balance learning. Further research is needed to assess the effects of longer and discontinuous stimulation with somatosensory and neurofeedback training on balance in elderly adults.

Elucidating opportunities and pitfalls in the treatment of experimental traumatic brain injury to optimize and facilitate clinical translation

The aim of this review is to discuss the research presented in a symposium entitled "Current progress in characterizing therapeutic strategies and challenges in experimental CNS injury" which was presented at the 2016 International Behavioral Neuroscience Society annual meeting. Herein we discuss diffuse and focal traumatic brain injury (TBI) and ensuing chronic behavioral deficits as well as potential rehabilitative approaches. We also discuss the effects of stress on executive function after TBI as well as the response of the endocrine system and regulatory feedback mechanisms. The role of the endocannabinoids after CNS injury is also discussed. Finally, we conclude with a discussion of antipsychotic and antiepileptic drugs, which are provided to control TBI-induced agitation and seizures, respectively. The review consists predominantly of published data.

Evidence for frequency-dependent cortical plasticity in the human brain

Frequency-dependent plasticity (FDP) describes adaptation at the synapse in response to stimulation at different frequencies. Its consequence on the structure and function of cortical networks is unknown. We tested whether cortical "resonance," favorable stimulation frequencies at which the sensory cortices respond maximally, influenced the impact of FDP on perception, functional topography, and connectivity of the primary somatosensory cortex using psychophysics and functional imaging (fMRI). We costimulated two digits on the hand synchronously at, above, or below the resonance frequency of the somatosensory cortex, and tested subjects' accuracy and speed on tactile localization before and after costimulation. More errors and slower response times followed costimulation at above- or below-resonance, respectively. Response times were faster after at-resonance costimulation. In the fMRI, the cortical representations of the two digits costimulated above-resonance shifted closer, potentially accounting for the poorer performance. Costimulation at-resonance did not shift the digit regions, but increased the functional coupling between them, potentially accounting for the improved response time. To relate these results to synaptic plasticity, we simulated a network of oscillators incorporating Hebbian learning. Two neighboring patches embedded in a cortical sheet, mimicking the two digit regions, were costimulated at different frequencies. Network activation outside the stimulated patches was greatest at above-resonance frequencies, reproducing the spread of digit representations seen with fMRI. Connection strengths within the patches increased following at-resonance costimulation, reproducing the increased fMRI connectivity. We show that FDP extends to the cortical level and is influenced by cortical resonance.

Superior non-specific motor learning in the blind

It is well established that blindness induces changes in cerebral function and structure, namely affecting the somatomotor regions. However, the behavioural significance of these changes on the motor system, and on motor learning in particular, remains elusive. In this study, we used a modified version of the serial reaction time task (SRTT) with auditory cues to assess sequence specific and non-specific motor learning in blind adults and sighted controls, and compare them with sighted controls performing the classic visual SRTT. Our results show that the auditory SRTT faithfully replicates the typical learning pattern obtained with the visual SRTT. On the auditory SRTT, blind individuals consistently showed faster reaction times than sighted controls, being at par with sighted individuals performing the visual SRTT. On the other hand, blind participants displayed a particular pattern of motor learning in comparison to both sighted groups; while controls improved prominently on sequence specific learning, blind individuals displayed comparable performance on both specific and non-specific learning, markedly outperforming the control groups on non-specific learning. These results show that blindness, in addition to causing long-term changes in cortical organisation, can also influence dynamic neuroplastic mechanisms in systems beyond those typically associated with compensatory sensory processing.

Shared somatosensory and motor functions in musicians

Skilled individuals are characterized by fine-tuned perceptual and motor functions. Here, we tested the idea that the sensory and motor functions of highly-trained individuals are coupled. We assessed the relationships among multifaceted somatosensory and motor functions of expert pianists. The results demonstrated a positive covariation between the acuity of weight discrimination and the precision of force control during piano keystrokes among the pianists but not among the non-musicians. However, neither the age of starting musical training nor the total amount of life-long piano practice was correlated with these sensory-motor functions in the pianists. Furthermore, a difference between the pianists and non-musicians was absent for the weight discrimination acuity but present for precise force control during keystrokes. The results suggest that individuals with innately superior sensory function had finer motor control only in a case of having undergone musical training. Intriguingly, the tactile spatial acuity of the fingertip was superior in the pianists compared with the non-musicians but was not correlated with any functions representing fine motor control among the pianists. The findings implicate the presence of two distinct mechanisms of sensorimotor learning elicited by musical training, which occur either independently in individual sensorimotor modalities or through interacting between modalities.

Plasticity and Recovery After Dorsal Column Spinal Cord Injury in Nonhuman Primates

Here, we review recent work on plasticity and recovery after dorsal column spinal cord injury in nonhuman primates. Plasticity in the adult central nervous system has been established and studied for the past several decades; however, capacities and limits of plasticity are still under investigation. Studies of plasticity include assessing multiple measures before and after injury in animal models. Such studies are particularly important for improving recovery after injury in patients. In summarizing work by our research team and others, we suggest how the findings from plasticity studies in nonhuman primate models may affect therapeutic interventions for conditions involving sensory loss due to spinal cord injury.

A Practical Training Program for Peripheral Radial Artery Catheterization in Adult Patients: A Prospective, Randomized Controlled Trial

BACKGROUND

The main cause of unsuccessful peripheral radial artery catheterization using traditional palpation is imprecisely locating the arterial center. The authors evaluated factors causing disparities between the arterial centers determined by palpation versus ultrasound. The authors applied them to create and test a novel catheterization training program.

METHODS

The arterial central axis was determined by ultrasound and palpation in 350 adults. Potential independent predictors of disparity included sex, body mass index, pulse pressure, transverse arterial diameter, subcutaneous arterial depth, chronic hypertension, and experience as an anesthesiologist (less than 3 vs. greater than or equal to 3 yr). Using the results, the authors developed a radial artery catheterization training program. It was tested by enrolling 20 first-year interns, randomized to a training or control group. The time to successful insertion was the primary outcome measure. The success rate and time required for catheterization by palpation were evaluated in 100 adult patients per group.

RESULTS

Independent predictors of central axis disparity were pulse pressure, subcutaneous radial artery depth, years of experience, and chronic hypertension. Training improved the catheterization time (training group 56 ± 2 s vs. control group 109 ± 2 s; difference -53 ± 3 s; 95% CI, -70 to -36 s; P < 0.0001) and total success rate (training group 83 of 100 attempts, 83%; 95% CI, 75 to 90 vs. control group 57 of 100, 57%; 95% CI, 47 to 66; odds ratio, 3.7; 95% CI, 2.7 to 5.1).

CONCLUSIONS

Misjudging the central axis position of the radial artery is common with a weak pulse and/or deep artery. The authors' program, which focused on both these issues, shortened the time for palpation-guided catheterization and improved success.

Neuromagnetic correlates of adaptive plasticity across the hand-face border in human primary somatosensory cortex

It is well established that permanent or transient reduction of somatosensory inputs, following hand deafferentation or anesthesia, induces plastic changes across the hand-face border, supposedly responsible for some altered perceptual phenomena such as tactile sensations being referred from the face to the phantom hand. It is also known that transient increase of hand somatosensory inputs, via repetitive somatosensory stimulation (RSS) at a fingertip, induces local somatosensory discriminative improvement accompanied by cortical representational changes in the primary somatosensory cortex (SI). We recently demonstrated that RSS at the tip of the right index finger induces similar training-independent perceptual learning across the hand-face border, improving somatosensory perception at the lips (Muret D, Dinse HR, Macchione S, Urquizar C, Farnè A, Reilly KT.Curr Biol24: R736-R737, 2014). Whether neural plastic changes across the hand-face border accompany such remote and adaptive perceptual plasticity remains unknown. Here we used magnetoencephalography to investigate the electrophysiological correlates underlying RSS-induced behavioral changes across the hand-face border. The results highlight significant changes in dipole location after RSS both for the stimulated finger and for the lips. These findings reveal plastic changes that cross the hand-face border after an increase, instead of a decrease, in somatosensory inputs.

Development of a new haptic perception instrument: a pilot study

OBJECTIVE

Hand sensory tests do not consider distinct physiological receptors, nor detect normal range variations concerning developmental or pathological changes. We developed an instrument with a set of tests with timing and scoring for assessing haptic perception, which is the interaction between sensory and motor systems, in surfaces exploration, by moving hands.

METHOD

Firstly, group meetings were set for test/manual conception and materials testing. The test/manual were submitted to 30 reviewers in 3 stages (10 reviewers on each stage).

RESULTS

The Hand Haptic Perception Instrument (HHPI) evaluates hand sensorimotor performance on six domains: depression, elevation, texture, compressibility, weight (barognosis) and form perception. Each domain requires specific materials. Score ranges from 0 to 57, being 0 the worst rating.

CONCLUSION

This methodological process allowed the development of six domains and instructions to assess haptic perception. This version of HHPI is a pilot model. Further studies will determine reliability and normality ranges.