Evaluation of sterile glove usage on digital tactile sensitivity using the Grating Orientation Task.

Introduction: Surgical glove use may be associated with a decrease in tactile sensitivity, with thicker gloves or double-gloving techniques further altering sensation. This study evaluates digital tactile sensitivity by use of a Grating Orientation Task (GOT) with multiple sterile gloving techniques (no gloves, single standard gloving, double standard gloving, orthopedic gloves, and micro-thickness gloves). Methods: Each participant performed the GOT at increasing grating widths until correctly noting orientation in ≥8 of 10 trials with multiple glove types or double-gloving technique. Glove order was randomly assigned and participants were blinded to the orientation and dome size. Results: All gloves except micro-thickness gloves showed increased threshold sensitivity values (i.e. worse fingertip sensitivity) when compared to control (micro:control, p = 0.105, others:control, p < 0.05). Single-layer gloves showed no significant difference in sensitivity when compared to orthopedic (p = 0.06) or double-layer latex gloves (p = 0.26). Discussion: Standard latex gloves decreased fingertip sensitivity when evaluated with the GOT. Double-layer and orthopedic latex gloves do not decrease sensitivity when compared with single-layer gloving. Micro-thickness gloves may provide similar tactile sensitivity to no surgical glove.

A protocol for tactile function assessment using JVP domes: Feasibility study and preliminary results.

BACKGROUND: Touch is a crucial sense for perceiving the spatial characteristics of objects. The JVP dome was developed to evaluate tactile spatial acuity using a grating orientation task. There were few studies depicting sequences and details for the entire task, including practice, training, and testing sessions. Therefore, we proposed and elaborated a protocol for the grating orientation task using the staircase method, which required fewer testing trials compared with the method of constant stimuli. METHODS: Twenty-three healthy participants were enrolled in this experiment. The JVP domes with 11 different groove widths were used. Tactile discrimination thresholds were estimated using a two-down-one-up staircase method. The experiment comprised practice, training, and testing sessions, conducted by trained examiners who performed grating stimulation on participants' index fingerpads. RESULTS: All participants passed the required accuracy in the practice and training sessions. Eight transition points were obtained in the testing session for each participant. The tactile discrimination thresholds were determined from the last six transition points. We obtained the mean tactile discrimination threshold as 1.8 ± 0.75 mm (n = 23). The results demonstrated that the proposed protocol was successfully applied to assess tactile discrimination thresholds. CONCLUSIONS: The present study investigated the protocol of grating orientation tasks requiring a small number of testing trials with the assurance of the task quality. The feasibility study and preliminary results indicated the potentiality of this protocol for future clinical application.

Hand posture, but not vision of the hand, affects tactile spatial resolution in the grating orientation discrimination task.

The grating orientation discrimination task (GOT) is a sensitive and reliable measure of tactile spatial resolution, or acuity. We used the GOT in three experiments to investigate the effects of hand posture and hand visibility on spatial acuity. Participant sex and experimental design were also manipulated. Healthy adult participants received brief touches to their index fingertips of grated, domed objects. Their task was to decide whether the gratings ran 'along' or 'across' their finger. Measures of the smallest grating width for which participants could reliably discriminate between orientations were recorded as threshold. Experiment 1 evaluated the effect of two- versus one-interval discrimination, hand used and participant sex. Experiments 2 and 3 evaluated the effects of hand visibility (visible or covered) and hand posture (in front or to the side). Females were better than males; the two-interval task resulted in lower thresholds than the one-interval task; and left and right hand thresholds were not significantly different. Most importantly, while hand visibility did not have a significant effect on the task, thresholds were affected by hand posture-worse when the hand was oriented to the side of the body than in front. These results replicate previously reported effects of sex (or finger size), but failed to replicate the so-called 'visual enhancement of touch' (VET) effect. We also report a meta-analysis of 27 VET studies, finding a significant effect of 'non-informative' vision on tactile perception. Our novel finding is that hand posture affects tactile acuity.

You'd better think twice: post-decision perceptual confidence.

Current findings suggest that confidence emerges only after decision making. However, the temporal and neural dynamics of the emergence of post-decision confidence--a metacognitive judgement--are not fully explored. To gain insight into the dynamics of post-decision confidence processing and to disentangle the processes underlying confidence judgements and decision making, we applied a tactile discrimination task during functional magnetic resonance imaging (fMRI). Our results revealed that reaction times to post-decision confidence depend on the level of confidence, suggesting that post-decision confidence in a perceptual choice is not processed in parallel to perceptual decision making. Moreover, we demonstrated by the parametric analysis of fMRI data that post-decisionally modelled confidence processing can be distinguished from processes related to decision making through anatomical location and through the pattern of neural activity. In contrast to perceptual decision making, post-decision confidence appears to be strictly allocated to a prefrontal network of brain regions, primarily the anterior and dorsolateral prefrontal cortex, areas that have been related to metacognition. Moreover, the processes underlying decision making and post-decision confidence may share recruitment of the dorsolateral prefrontal cortex, although the former probably has distinct functions with regard to processing of perceptual choices and post-decision confidence. Thus, this is the first fMRI study to disentangle the processes underlying post-decision confidence and decision making on behavioural, neuroanatomical, and neurofunctional levels. With regard to the temporal evolution of post-decision confidence, results of the present study provide strong support for the most recent theoretical models of human perceptual decision making, and thus provide implications for investigating confidence in perceptual paradigms.

Transcranial direct current stimulation ameliorates tactile sensory deficit in multiple sclerosis.

BACKGROUND: Deficit of tactile sensation in patients with MS is frequent and can be associated with interference with daily life activities. Transcranial direct current stimulation (tDCS) showed to increase tactile discrimination in healthy subjects. OBJECTIVE: In the present study, we investigated whether tDCS may be effective in ameliorating tactile sensory deficit in MS patients. METHODS: Patients received sham or real anodal tDCS of the somatosensory cortex for 5 consecutive days in a randomized, double blind, sham-controlled study. Discrimination thresholds of spatial tactile sensation were measured using the grating orientation task (GOT). As secondary outcomes we also measured subjective perception of tactile sensory deficit through a visual analog scale (VAS), quality of life and overall disability to evaluate the impact of the treatment on patients daily life. Evaluations were performed at baseline and during a 4-week follow-up period. RESULTS: Following anodal but not sham tDCS over the somatosensory cortex, there was a significant improvement of discriminatory thresholds at the GOT and increased VAS for sensation scores. Quality of life, and disability changes were not observed. CONCLUSION: Our results indicate that a five day course of anodal tDCS is able to ameliorate tactile sensory loss with long-lasting beneficial effects and could thus represent a therapeutic tool for the treatment of tactile sensory deficit in MS patients.