Reduced tactile sensitivity is associated with mild cognitive impairment

BACKGROUND

Sensory impairment has been related to age-associated cognitive decline. While these associations were investigated primarily in the auditory and visual domain, other senses such as touch have rarely been studied. Thus, it remains open whether these results are specific for particular sensory domains, or rather point to a fundamental role of sensory deficits in cognitive decline.

METHODS

Data from 31 participants with mild cognitive impairment (MCI), 46 participants with frailty, and 23 non-clinical control participants (NCCs) were included. We assessed sensory function using visual acuity and contrast sensitivity, hearing threshold, and mechanical detection threshold. Cognitive function in participants with MCI was assessed using associative memory performance. Group differences on sensory thresholds were tested using analyses of covariance with age, sex, and years of education as covariates. Associations between measures within participants with MCI were evaluated using Spearman correlations.

FINDINGS

We found a significant difference in mechanical detection threshold between the groups (p < 0.001, η2 = 0.18). Participants with MCI showed significantly reduced tactile sensitivity compared to participants with frailty and NCCs. In participants with MCI, lower associative memory performance was significantly related to reduced tactile sensitivity (rs = 0.39, p = 0.031) and auditory acuity (rs = 0.41, p = 0.022).

INTERPRETATION

Our results indicate that reduced tactile sensitivity is related to cognitive decline. Prospective studies should investigate the age-related alterations of multimodal sensory processes and their contribution to dementia-related processes.

FUNDING

Deutsche Forschungsgemeinschaft (FL 156/41-1) and a grant of the Hector-Stiftung II, Weinheim, Germany.

The perception of pain, discriminative touch and affective touch in patients suffering from Borderline Personality Disorder

Borderline Personality Disorder (BPD) is often characterized by self-injurious behaviors, with one-half to two-third of these patients reporting hypalgesic or analgesic phenomena during self-harming. Research on pain perception in BPD suggested abnormal processing of nociception either within the sensory-discriminative and/or motivational-affective systems of pain. Nevertheless, it is still unclear whether pain insensitivity could be generalized to other somatosensory submodalities. To investigate this question, 30 BPD patients and 30 matched healthy controls were enrolled in the current study and underwent a somatosensory battery composed of well-established psychophysical test assessing all the principal submodalities of somatosensation, namely pain perception (i.e., warm, cold and mechanical), discriminative touch (i.e., tactile acuity and tactile sensitivity) as well as affective touch. Results showed abnormal warm detection threshold, warm pain threshold, mechanical pain perception, and tactile sensitivity in BPD patients, but no differences emerged neither for tactile acuity nor for cold pain thresholds, cold tolerance, or for affective touch perception. Findings point to a deficit in nociception, as well as in tactile sensitivity in BPD individuals, and were discussed in relation to BPD clinical features including self-injurious behaviors.

Are foot deformity and plantar sensitivity impairment associated with physical function of community-dwelling older adults?

BACKGROUND

Foot deformities are highly prevalent in older adults and negatively impact their mobility and quality of life. However, the association between foot problems and physical function is still unclear.

OBJECTIVE

To investigate whether structural foot deformities and plantar tactile sensitivity are associated with lower extremity physical function impairment in community-dwelling older adults.

METHODS

We included 200 men and women aged 60 years and older from a community-based program. The foot assessment included toe deformities and calluses inspection and evaluation of plantar tactile sensitivity using monofilaments. The Short Physical Performance Battery (SPPB) was used to assess lower extremity physical function. We conducted a multivariate logistic regression analysis to investigate the association between foot problems and lower extremity physical function.

RESULTS

Hallux valgus was the most prevalent deformity among older adults. Those participants with reduced plantar tactile sensitivity (OR= 2.77; 95% CI: 1.38, 5.55) and a hallux valgus (OR= 2.23; 95% CI: 1.10, 4.52) were more likely to present poor lower extremity physical function.

CONCLUSION

Hallux valgus and impaired plantar sensitivity were associated with reduced lower extremity physical function in older adults. Further studies are necessary to identify this causality and to what extent management of these foot problems can improve general mobility and quality of life of older adults.

Desire to eat and intake of 'insect' containing food is increased by a written passage: The potential role of familiarity in the amelioration of novel food disgust

Over two studies we investigated the effect of various written interventions (passages) on the disgust response towards a food (falafels) which supposedly contained mealworm (insect) flour. Actually, participants (Study 1 N = 80, Study 2 N = 78) were given the same non-mealworm containing food in all conditions. Disgust was measured using: tactile sensitivity, food intake, liking and desire to eat. Results of Study 1 showed that a sustainability passage (sustainability advantages of entomophagy), but not a delicacy passage (oro-sensory qualities of insects), was effective in reducing disgust. In Study 2, contrary to prediction, a passage describing the sustainability and nutritional advantages entomophagy failed to reduce disgust - falafel intake, liking and desire to eat were decreased. However, a passage which described how mealworm flour is produced, did significantly reduce disgust. Taken together, these studies demonstrate that written passages can alter the disgust response, notably resulting in a maintenance of food intake. Interventions that increase the perception of familiarity of a novel food, but not logic-based arguments, may be a key driver of the amelioration of disgust. These results also support the suggestion that altering the ideational component of disgust can result in changes of distaste perception.

Non-informative vision improves spatial tactile discrimination on the shoulder but does not influence detection sensitivity

Vision of the body has been reported to improve tactile acuity even when vision is not informative about the actual tactile stimulation. However, it is currently unclear whether this effect is limited to body parts such as hand, forearm or foot that can be normally viewed, or it also generalizes to body locations, such as the shoulder, that are rarely before our own eyes. In this study, subjects consecutively performed a detection threshold task and a numerosity judgment task of tactile stimuli on the shoulder. Meanwhile, they watched either a real-time video showing their shoulder or simply a fixation cross as control condition. We show that non-informative vision improves tactile numerosity judgment which might involve tactile acuity, but not tactile sensitivity. Furthermore, the improvement in tactile accuracy modulated by vision seems to be due to an enhanced ability in discriminating the number of adjacent active electrodes. These results are consistent with the view that bimodal visuotactile neurons sharp tactile receptive fields in an early somatosensory map, probably via top-down modulation of lateral inhibition.

Comparison of tactile sensitivity measured with a new digital esthesiometer (Beam Test) relative to Semmes-Weinstein monofilament analog esthesiometer

The assessment of tactile sensitivity uses many tests, of which monofilaments are considered the best. The aim of this study was to develop a tactile sensitivity test, similar to the monofilament test, which eliminates the error risk related to manipulations by the observer, and to establish a correspondence scale. We studied 29 healthy subjects (18 women and 11 men) with a mean age of 27.8 years. The Semmes-Weinstein monofilament (SWM) analog esthesiometer and a digital beam esthesiometer (DBE) were used. We evaluated the tactile sensitivity threshold on the fingertip of each subject's dominant index using the SWM and the DBE. The DBE test consisted of applying the index against the tip of the beam. During a cycle of four elevations/depressions, the subject would press a button each time he/she felt pressure. The test was repeated three times. The screen displayed an average force value between 0 and 200 allowing the result to be expressed in grams (g). The minimum perceived force was 0.06656g (0.023, 0.166) on average with the SWM test and 0.51773g (0.4824, 0.8062) with the DBE test. Our results confirm the DBE test suppresses the observer's manipulations and that a SWM correspondence scale can be established. With the DBE test, the normal sensation ranged from 0.4824g to 0.757g and light touch decreased from 0.758g to 0.8062g. The threshold value of pathological tactile sensitivity was 0.8063g. The DBE test could therefore be used for preventive diagnosis of carpal tunnel syndrome in occupational medicine.

Effects of age and individual experiences on tactile perception over the life span in women

Tactile perception results from the interplay of peripheral and central mechanisms for detection and sensation of objects and the discrimination and evaluation of their size, shapes, and surface characteristics. For different tasks, we investigated this interaction between more bottom-up stimulus-driven and rather top-down attention-related and cognitive processes in tactile perception. Moreover, we were interested in effects of age and tactile experiences on this interaction. 299 right-handed women participated in our study and were divided into five age groups: 18-25 years (N = 77), 30-45 years (N = 76), 50-65 years (N = 62), 66-75 years (N = 63) and older than 75 years (N = 21). They filled a questionnaire on tactile experiences and rated their skin as either very dry, dry, normal, or oily. Further they performed three tactile tests with the left and right index fingers. Sensitivity for touch stimuli was assessed with von Frey filaments. A sand paper test was used to examine texture discrimination performance. Spatial discrimination was investigated with a tactile Landolt ring test. Multivariate ANOVA confirmed a linear decline in tactile perceptual skills with age (F(3, 279) = 76.740; p < .000; pEta² = 0.452), starting in early adulthood. Largest age effects were found for the Landolt ring test and smallest age effects for the Sand paper test, indicating different aging slopes. Tactile experiences had a positive effect on tactile performance (F (3,279) = 4.450; p = .005; pEta² = 0.046) and univariate ANOVA confirmed this effect for the sand paper and the Landolt ring test, but not for the von Frey test. Using structural equation modelling, we confirmed two dimensions of tactile performance; one related to more peripheral or early sensory cortical (bottom-up) processes (i.e., sensitivity) and one more associated with cognitive or evaluative (top-down) processes (i.e., perception). Interestingly, the top-down processes were stronger influenced by age than bottom-up ones, suggesting that age-related deficits in tactile performance are mainly caused by a decline of central perceptive-evaluative capacities rather than by reduced sensitivity.

The tactile detection threshold changes when a visual stimulus is presented with a short temporal gap

[Purpose] The interaction between the visual and tactile modalities influences on different levels from neural activity, perception, higher cognition to behavior. The aim of this study was to examine how a visual stimulus influences tactile sensitivity depending on temporal asynchrony. [Subjects and Methods] In total, 15 participants took part in this study. They were required to perform a two-alternative forced-choice task regarding whether a tactile pulse was felt. The individual participants’ tactile thresholds were estimated using a repetitive stepwise method. Visual stimuli were simultaneously presented with various temporal gaps (0 ms, ± 50 ms, ± 100 ms, and ± 300 ms), whereas no visual stimulus was presented in the tactile only condition. The tactile thresholds in eight conditions were compared using analysis of variance. [Results] Of the participants, 53.5% showed the most sensitive tactile threshold when presented with a visual stimulus with a short temporal gap, especially when the visual stimulus preceded the tactile one by 50 ms. [Conclusion] The preceding visual stimulus facilitates the perceptual sensitivity of the tactile sensation. Providing sensory stimuli in a multisensory mode benefits perceptual encoding. A pre-attentional mechanism led by a particular sensory modality might work as a perceptual advantage for another modality.

Grip force control and hand dexterity are impaired in individuals with diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) affects the sensory function of the hands and, consequently, may negatively impact hand dexterity, maximum grip strength (GS_Max), and hand grip force (GF) control during object manipulation. The aims of this study were to examine and compare the GF control during a simple holding task as well as GS_Max and hand dexterity of individuals with DPN and healthy controls. Ten type 2 diabetic individuals diagnosed with DPN and ten age- and gender-matched healthy controls performed two traditional timed hand dexterity tests (i.e., nine-hole peg test and Jebsen-Taylor hand function test), a GS_Max test, and a GF control test (i.e., hold a instrumented handle). The results indicated that individuals with DPN and controls produced similar GS_Max. However, individuals with DPN took longer to perform the hand dexterity tests and set lower safety margin (exerted lower GF) than controls when holding the handle. The findings showed that mild to moderate DPN did not significantly affect maximum hand force generation, but does impair hand dexterity and hand GF control, which could impair the performance of daily living manipulation tasks and put them in risk of easily dropping handheld objects.

Effects of monochromatic infrared phototherapy in patients with diabetic peripheral neuropathy: a systematic review and meta-analysis of randomized controlled trials

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MIRE is an adjunctive phototherapy source approved by FDA to improve blood perfusion and reduce pain.

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MIRE was associated with a modest short-term improvement in plantar tactile sensitivity, not sustained over time.

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MIRE resulted in a less decrease in pain relief, possibly associated with initial improvement in plantar sensitivity.

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Current quality of evidence is low and further studies are likely to change the estimated effect.

Background

Monochromatic infrared energy (MIRE) or phototherapy has been used to improve plantar sensitivity and pain in lower limbs of patients with diabetic sensorimotor peripheral neuropathy (DSPN), but the available primary results are inconsistent.

Objective

To review systematically the effects of MIRE on plantar sensitivity and neuropathic pain in patients with DSPN.

Methods

Medline, EMBASE, Cochrane CENTRAL, and Google Scholar were searched up to September 2016. Randomized controlled trials addressing the effects of MIRE on plantar sensitivity and neuropathic pain in patients with DSPN were selected. Study inclusion, risk of bias and quality assessment, and data extraction were completed by two independent reviewers.

Results

Of 2549 records identified, six studies met the selection criteria, with 304 patients (594 feet) randomized. MIRE was not associated with improvement in plantar tactile sensitivity (SMD = 0.22, 95%CI −0.07 to 0.51, low quality of evidence). Subgroups of studies with short-term (up to 2 weeks) follow-up showed significant improvement in plantar sensitivity (SMD = 0.41, 95% CI 0.18–0.64). Neuropathic pain increased significantly in patients who received MIRE (MD = 0.49, 95% CI 0.30–0.68, low quality of evidence).

Conclusions

There was limited evidence that MIRE results in short-term improvement of tactile sensitivity probably not sustained over time. Limited evidence also suggested that MIRE does not provide relief for neuropathic pain. As quality of evidence is low, further studies are likely to change the estimated effect.

The effect of hair density on the coupling between the tactor and the skin of the human head

The purpose of this study was to determine the effect of hair density on vibration detection thresholds associated with the perception of low frequency vibration stimuli applied to the head. A host of tactile sensitivity information exists for other parts of the body, however the same information is lacking for the head. Thirty-three college students, age 18-35, were recruited for the study. A mixed design was used to evaluate the effect of hair density, head location, and frequency on vibration detection thresholds. Results suggest that hair density might slightly impede vibration signals from reaching the scalp and reduce vibration sensitivity, for the least sensitive locations on the head. This research provides design recommendations for head-mounted tactile displays for women and those with hair that can be used to convey directional cues for navigation and as alerts to critical events in the environment.

Hypoesthesia of the malleolus as a soft sign in depression

BACKGROUND

Physical signs often are present in many psychiatric conditions, making up a fundamental part of them and accompanying the psychiatric manifestations themselves. Identifying minor neurological signs is especially of interest due to they are easily accessible through simple neurological examination and could be a useful if underused tool for the diagnostic process and patient therapy.

METHOD

A group of depressed patients (n=85) and group of healthy individuals (n=101) that served as control were examined using the Wartenberg wheel, a medical device for neurological use, in order to determine the presence of hypoesthesia on both sides of their ankles.

RESULTS

The data revealed: (i) patients with depression are generally more likely to present malleolar hypoesthesia than healthy participants; and (ii) participants who presented malleolar hypoesthesia presented greater depressive symptomatology as well as greater anxiety symptomatology at the time of assessment.

LIMITATIONS

Although all patients in this study were taking psychotropic medication, anxiolytics and antidepressants are not associated with skin sensitivity. As is usual, the categorization of hypoesthesia is based on participant subjectivity. However, this subjectivity cannot explain the differences between depressed patients and healthy individuals.

CONCLUSIONS

The present findings corroborate that localized tactile sensitivity is altered in depression and correlates with anxiety-depressive symptomatology, even on a subclinical level. The observation of neurological soft signs such as the detection of malleolar hypoesthesia in patients with depressive symptomatology is easily accessible using a simple neurological examination, and it could became a powerful tool that could provide objective information on affective disorders.

Feel your food. The influence of tactile sensitivity on picky eating in children

Children who are very picky in eating frequently refuse the intake of foods. This rejection is not only based on the evaluation of taste, but also on tactile qualities of foods. It matters whether food is crispy or slimy, consistent, or with bits and pips. It is hypothesised that children who are more sensitive to touch and dislike the feel of various tactile stimuli in general, are also more dismissive of tactile stimulation in their mouth and therefore more selective in their eating. In the present study, 44 children between the ages of 4 and 10 were asked to feel different tactile stimuli with their hands and to taste different foods. Results showed a significant positive correlation between the evaluations of the two modalities, especially for the younger subjects. This suggests that tactile sensitivity might play a role in the acceptance of food. Future research could explore if training children to tolerate more tactile stimuli would also increase their appreciation of a wider variety of foods.