Grip force control during simple manipulation tasks in non-neuropathic diabetic individuals

Entropy in Electroencephalographic Signals Modulates with Force Magnitude During Grasping - A Preliminary Report

The ability to hold objects relies on neural processes underlying grip force control during grasping. Brain activity lateralized to contralateral hemisphere averaged over trials is associated with grip force applied on an object. However, the involvement of neural variability within-trial during grip force control remains unclear. We examined dependence of neural variability over frontal, central, and parietal regions of interest (ROI) on grip force magnitude using noninvasive electroencephalography (EEG). We utilized our existing EEG dataset comprised of healthy young adults performing an isometric force control task, cued to exert 5, 10, or 15% of their maximum voluntary contraction (MVC) across trials and received visual feedback of their grip force. We quantified variability in EEG signal via sample entropy (sequence-dependent) and standard deviation (sequence-independent measure) over ROI. We found lateralized modulation in EEG sample entropy with force magnitude over central electrodes but not over frontal or parietal electrodes. However, modulation was not observed for standard deviation in the EEG activity. These findings highlight lateralized and spatially constrained modulation in sequence-dependent, but not sequence-independent component of EEG variability. We contextualize these findings in applications requiring finer precision (e.g., prosthesis), and propose directions for future studies investigating role of neural entropy in behavior.

The effect of type 2 diabetes and diabetic peripheral neuropathy on predictive grip force control

This study investigated the impact of type 2 diabetes and diabetic peripheral neuropathy on grip force control during object manipulation. The study included three age-matched groups: type 2 diabetes alone (n = 11), type 2 diabetes with neuropathy (n = 13), and healthy controls (n = 12). Grip force control variables derived from lifting and holding an experimental cup were the ratio between grip force and load forces during lifting (GFR), latency 1 and latency 2, which represented the time between the object's grip and its lift-off from the table, and the period between object's lift-off and the grip force peak, respectively; time lag, which denoted the time difference between the grip and load force peaks during the lifting phase, and finally static force, which was the grip force average during the holding phase. Grip force control variables were compared between groups using one-way ANOVA and Kruskal-Wallis test. Post-hoc analysis was used to compare differences between groups. GFR and latency 1 showed significant differences between groups; the type 2 diabetes with neuropathy group showed larger GFR than the type 2 diabetes alone and healthy control groups. The latency 1was longer for the group with neuropathy in comparison with the health control group. There were no significant differences between groups for latency 2, time lag, and static force. Our results showed impaired GFR and latency 1 in participants with type 2 diabetes with neuropathy while the time lag was preserved. People with type 2 diabetes alone might not have any deficits in grip force control. Higher grip forces might expose people with type 2 diabetes and diabetic peripheral neuropathy to the risk of fatigue and injuring their hands. Future studies should investigate strategies to help people with type 2 diabetes with neuropathy adjust grip forces during object manipulation.

Lateralized Neural Entropy modulates with Grip Force during Precision Grasping

When holding a coffee mug filled to the brim, we strive to avoid spilling the coffee. This ability relies on the neural processes underlying the control of finger forces on a moment-to-moment basis. The brain activity lateralized to the contralateral hemisphere averaged over a trial and across the trials is known to be associated with the magnitude of grip force applied on an object. However, the mechanistic involvement of the variability in neural signals during grip force control remains unclear. In this study, we examined the dependence of neural variability over the frontal, central, and parietal regions assessed using noninvasive electroencephalography (EEG) on grip force magnitude during an isometric force control task. We hypothesized laterally specific modulation in EEG variability with higher magnitude of the grip force exerted during grip force control. We utilized an existing EEG dataset (64 channel) comprised of healthy young adults, who performed an isometric force control task while receiving visual feedback of the force applied. The force magnitude to be exerted on the instrumented object was cued to participants during the task, and varied pseudorandomly among 5, 10, and 15% of their maximum voluntary contraction (MVC) across the trials. We quantified neural variability via sample entropy (sequence-dependent measure) and standard deviation (sequence-independent measure) of the temporal EEG signal over the frontal, central, and parietal electrodes. The EEG sample entropy over the central electrodes showed lateralized, nonlinear, localized, modulation with force magnitude. Similar modulation was not observed over frontal or parietal EEG activity, nor for standard deviation in the EEG activity. Our findings highlight specificity in neural control of grip forces by demonstrating the modulation in sequence-dependent but not sequence-independent component of EEG variability. This modulation appeared to be lateralized, spatially constrained, and functionally dependent on the grip force magnitude. We discuss the relevance of these findings in scenarios where a finer precision is essential to enable grasp application, such as prosthesis and associated neural signal integration, and propose directions for future studies investigating the mechanistic role of neural entropy in grip force control.

The evaluation of tactile dysfunction in the hand in type 1 diabetes: a novel method based on haptics

AIMS

We present an innovative method based on haptics for the evaluation of the sense of touch in the hand, in people affected by type 1 diabetes.

METHODS

Forty individuals affected by diabetes and 20 healthy controls took part in the study; the diabetes group was further divided into two subgroups based on vibration sensitivity in the lower limb. By means of a novel haptic device, tactile sensitivity in the fingertip was measured as the ability of the participants to discriminate slip motion speed.

RESULTS

Tactile sensitivity was significantly lower in individuals affected by diabetes as compared to controls. Depending on the subgroup, the difference from the controls was equal to 0.11 (95% CI from 0.029 to 0.186) and to 0.267 (95% CI from 0.198 to 0.336). Within the diabetes group, tactile sensitivity correlated with vibration sensitivity in the upper (p = 0.001) and lower limb (p = 0.003). A significant relationship between nerve conduction parameters and tactile sensitivity was found (p = 0.03). Finally, we combined the different predictors (clinical, vibratory and electroneurography data) by using cluster analysis; tactile sensitivity was found to be significantly different between different clusters (p = 0.004).

CONCLUSIONS

Early signs of tactile dysfunction in the hand were found in individuals affected by diabetes, even in absence of diabetic neuropathy. The protocol presented in this study is a promising tool for the assessment of tactile dysfunction in the hand in people affected by type 1 diabetes.

Standardized translated instruction versus spontaneously translated instruction: Test-retest and interrater reliability of a hand function test

STUDY DESIGN

Cross-sectional study.

INTRODUCTION

Adhering to test administration and standardized instructions is important for attainment of accurate and reliable results in performance-based tests.

PURPOSE OF THE STUDY

To determine test-retest and interrater reliability of standardized translated instruction (St-TI) and spontaneously translated instruction (Sp-TI) of a hand function test.

METHODS

Four raters and seventy-two subjects were divided into 2 groups: St-TI group, direct administration of the Hong Kong Chinese version of the Jebsen Hand Function Test to subjects by raters; and Sp-TI group, spontaneously translating the Jebsen-Taylor Hand Function Test from English into Chinese by raters. Test-retest and interrater reliability were calculated based on instruction time by the rater and performance time by the subject.

RESULTS

Test-retest and interrater reliability of instruction time by rater for St-TI has intraclass correlation coefficient of 0.35 to 0.70 and 0.24 to 0.55, respectively, whereas that for Sp-TI was -0.50 to 0.18 and -0.09 to 0.51, respectively. Test-retest and interrater reliability of performance time by subject for St-TI was 0.56 to 0.84 and 0.33 to 0.78, respectively, whereas that for Sp-TI was 0.54 to 0.87 and 0.35 to 0.77, respectively. Sp-TI had two test-retest minimal detectable change percent values that fell within the acceptable range (subtest 3 = 21.9% and subtest 6 = 25.7%).

CONCLUSION

Instruction time by rater for Jebsen-Taylor Hand Function Test subtests had generally poor to moderate test-retest and interrater reliability for both St-TI and Sp-TI. Performance time by subject generally had moderate to good reliability, except for St-TI with poor to good interrater reliability.

Anticipatory and Reactive Grip Force Control in Patients with Alzheimer's Disease: A Pilot Study

BACKGROUND

Alzheimer's disease (AD) affects several cognitive functions and causes altered motor function. Fine motor deficits during object manipulation are evident in other neurological conditions, but have not been assessed in dementia patients yet.

OBJECTIVE

Investigate reactive and anticipatory grip force control in response to unexpected and expected load force perturbation in AD.

METHODS

Reactive and anticipatory grip force was investigated using a grip-device with force sensors. In this pilot study, fifteen AD patients and fourteen healthy controls performed a catching task. They held the device with one hand while a sandbag was dropped into an attached receptacle either by the experimenter or by the participant.

RESULTS

In contrast to studies of other neurological conditions, the majority of AD patients exerted lower static grip force levels than controls. Interestingly, patients who were slow in the Luria's three-step test produced normal grip forces. The timing and magnitude of reactive grip force control were largely preserved in patients. In contrast, timing and extent of anticipatory grip forces were impaired in patients, although anticipatory control was generally preserved. These deficits were correlated with decreasing Mini-Mental State Examination scores. Apraxia scores, assessed by pantomime of tool-use, did not correlate with performance in the catching task.

CONCLUSION

We interpreted the decreased grip force in AD in the context of loss of strength and lethargy, typical for patients with AD. The lower static grip force during object manipulation may emerge as a potential biomarker for early stages of AD, but more studies with larger sample sizes are necessary.

Grip and load force control and coordination in individuals with diabetes in different manipulation tasks

The study aimed to investigate the control and coordination of grip force (normal component) and load force (tangential component) in three different manipulation tasks in individuals with diabetes with and with no diagnosis of diabetic peripheral neuropathy (DPN) and healthy controls. Twenty-four individuals with type 2 diabetes mellitus, 12 with no (nDPN) and 12 with DPN (wDPN), and 12 healthy controls performed three manipulation tasks (static holding, lifting and holding, and oscillation) with the dominant hand, using an instrumented handle. Relative safety margin (% of GF exerted above the minimum GF needed to hold the object) was measured in all tasks. Individuals with diabetes from the nDPN and wDPN groups set lower relative safety margin than controls only in the static holding task. No other group effect was revealed, except a lower coefficient of friction between skin and object surface in individuals with DPN. The coordination between grip and load force and grip force control was not affected by the diabetes during dynamic manipulation tasks (lifting and holding and oscillation). However, when individuals with diabetes without and with DPN performed a manipulation task in which the inflow of cutaneous information was small and stable (static holding), grip force control was affected by the disease. This finding indicates that individuals with type 2 diabetes mellitus not diagnosed with DPN, already show mild impairments in the nervous system that could affect grip force control and that could be one of the first signs of neuropathy caused by the diabetes.

Brain and Body: A Review of Central Nervous System Contributions to Movement Impairments in Diabetes

Diabetes is associated with a loss of somatosensory and motor function, leading to impairments in gait, balance, and manual dexterity. Data-driven neuroimaging studies frequently report a negative impact of diabetes on sensorimotor regions in the brain; however, relationships with sensorimotor behavior are rarely considered. The goal of this review is to consider existing diabetes neuroimaging evidence through the lens of sensorimotor neuroscience. We review evidence for diabetes-related disruptions to three critical circuits for movement control: the cerebral cortex, the cerebellum, and the basal ganglia. In addition, we discuss how central nervous system (CNS) degeneration might interact with the loss of sensory feedback from the limbs due to peripheral neuropathy to result in motor impairments in individuals with diabetes. We argue that our understanding of movement impairments in individuals with diabetes is incomplete without the consideration of disease complications in both the central and peripheral nervous systems. Neuroimaging evidence for disrupted central sensorimotor circuitry suggests that there may be unrecognized behavioral impairments in individuals with diabetes. Applying knowledge from the existing literature on CNS contributions to motor control and motor learning in healthy individuals provides a framework for hypothesis generation for future research on this topic.

The impact of diabetic peripheral neuropathy on pinch proprioception

This study aims to investigate the impact of type 2 diabetes (T2D) and diabetic peripheral neuropathy (DPN) on pinch proprioception and to establish the correlations with sensory impairments. We collected data from a total of 36 participants (healthy, n = 12; T2D without DPN, n = 11; and T2D + DPN, n = 13), all matched for age, 60 ± 6 years. Pinch proprioception was determined through 3 trials of attempts to actively reproduce 15° of pinch position without visual feedback. Target accuracy and precision was compared between groups using Kruskal-Wallis test. Sensation was tested through the two-point discrimination and Semmes-Weinstein monofilaments applied on the fingers. Sensory measures were correlated with pinch proprioception measures via Spearman's rank test. The T2D + DPN group showed significant decrements in accuracy and precision as compared to the T2D-only (p = 0.003 and p = 0.006, respectively) and the healthy groups (both p = 0.002); no significant differences were found between T2D-only and healthy. Spearman's rank showed moderate (r = 0.45-0.66, p < 0.001) correlations between pinch proprioception and sensory measures. Our results showed pinch proprioception disruption in people with T2D + DPN, but not in people with T2D-only. The awareness of pinch proprioceptive deficits is paramount for the safety of individuals with T2D and DPN. Moderate correlations between sensory impairments and pinch proprioceptive deficits suggest that not only superficial/discriminative sensation is implicated in proprioceptive decrements. Other mechanisms such as damage to muscle spindles or central nervous system associated with T2D + DPN warrant further investigations.

Hand Grip and Load Force Coordination of the Ipsilesional Hand of Chronic Stroke Individuals

Object manipulation depends on a refined control of grip force (GF) and load force (LF). After a brain injury, the GF control is altered in the paretic hand but what happens with the non-paretic hand is still unclear. In this study, we compared the GF control and GF-LF coordination of the non-paretic hand of 10 stroke individuals who suffered right brain damage (RBD) and 10 who suffered left brain damage (LBD), with 20 healthy individuals during lifting and oscillation task, using an instrumented object. GF was recorded with a force transducer, and LF was estimated from the object weight and acceleration. Overall, the ipsilesional hand of stroke individuals, independent of the lesion side, presented similar GF control and GF-LF coordination. However, LBD individuals took longer to start lifting the object, which may be due to the need of more time to obtain somatosensory information from the contact with the object. The findings indicate that stroke individuals preserve their ability to control and coordinate GF and LF when using their ipsilesional hand for object manipulation and the left hemisphere may play an essential role in the processing of somatosensory information needed for the GF control.

External biomechanical constraints impair maximal voluntary grip force stability post-stroke

BACKGROUND

Grip strength is frequently measured as a global indicator of motor function. In clinical populations, such as hemiparesis post-stroke, grip strength is associated with upper-extremity motor impairment, function, and ability to execute activities of daily living. However, biomechanical configuration of the distal arm and hand may influence the magnitude and stability of maximal voluntary grip force and varies across studies. The influence of distal arm/hand biomechanical configuration on grip force remains unclear. Here we investigated how biomechanical configuration of the distal arm/hand influence the magnitude and trial-to-trial variability of maximal grip force performed in similar positions with variations in external constraint.

METHODS

We studied three groups of 20 individuals: healthy young, healthy older, and individuals post-stroke. We tested maximal voluntary grip force in 4 conditions: 1: self-determined/"free"; 2: standard; 3: fixed arm-rest; 4: gripper fixed to arm-rest, using an instrumented grip dynamometer in both dominant/non-dominant and non-paretic/paretic hands.

FINDINGS

Regardless of hand or group, maximal voluntary grip force was highest when the distal limb was most constrained (i.e., Condition 4), followed by the least constrained (i.e., Condition 1) (Cohen's f = 0.52, P's < 0.001). Coefficient of variation among three trials was greater in the paretic hand compared with healthy individuals, particularly in more (Conditions 3 and 4) compared to less (Conditions 1 and 2) constrained conditions (Cohen's f = 0.29, P's < 0.05).

INTERPRETATION

These findings have important implications for design of rehabilitation interventions and devices. Particularly in individuals post-stroke, external biomechanical constraints increase maximal voluntary grip force variability while fewer biomechanical constraints yield more stable performance.

Dynamical Coordination of Hand Intrinsic Muscles for Precision Grip in Diabetes Mellitus

This study investigated the effects of diabetes mellitus (DM) on dynamical coordination of hand intrinsic muscles during precision grip. Precision grip was tested using a custom designed apparatus with stable and unstable loads, during which the surface electromyographic (sEMG) signals of the abductor pollicis brevis (APB) and first dorsal interosseous (FDI) were recorded simultaneously. Recurrence quantification analysis (RQA) was applied to quantify the dynamical structure of sEMG signals of the APB and FDI; and cross recurrence quantification analysis (CRQA) was used to assess the intermuscular coupling between the two intrinsic muscles. This study revealed that the DM altered the dynamical structure of muscle activation for the FDI and the dynamical intermuscular coordination between the APB and FDI during precision grip. A reinforced feedforward mechanism that compensates the loss of sensory feedbacks in DM may be responsible for the stronger intermuscular coupling between the APB and FDI muscles. Sensory deficits in DM remarkably decreased the capacity of online motor adjustment based on sensory feedback, rendering a lower adaptability to the uncertainty of environment. This study shed light on inherent dynamical properties underlying the intrinsic muscle activation and intermuscular coordination for precision grip and the effects of DM on hand sensorimotor function.

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.

Coefficient of Friction at the Fingertips in Type II Diabetics Compared to Healthy Adults

Clinical observations suggest that type II diabetes patients are more susceptible to skin changes, which may be associated with reduced coefficient of friction at the fingertips. Reduced coefficient of friction may explain recent reports of fine motor dysfunction in diabetic patients. Coefficient of friction was evaluated using slip force evaluation in a cross-sectional cohort of diabetic patients and age- and sex-matched healthy controls. Covariates of tactile sensation, disease duration, glycated hemoglobin, and clinical diagnosis of peripheral neuropathy were also assessed. A significant decrease in fingertip coefficient of friction in the diabetic group was found as compared to controls. Health state covariates did not alter the strength of between-group differences in statistical analyses. This finding of between-group differences for fingertip frictional properties suggests that causative factors of reported manual motor dysfunction lie in both the distal and proximal portions of the nervous system.

Simultaneous assessment of hand function and neuromuscular quickness through a static object manipulation task in healthy adults

Both hand function [as seen through the coordination between grip force (GF) and load force (LF)] and the ability to produce a submaximal force quickly (i.e., neuromuscular quickness) are two important qualities of motor function that could be seriously affected by the presence of neurological diseases. Therefore, their quantitative assessment is very important in clinical settings. Within this study, we aimed to develop, standardize, and measure the within-session reliability of a clinically meaningful test that assesses both hand function and neuromuscular quickness simultaneously. Thirteen healthy young adults produced around 90 rapid isometric LF pulses to varying submaximal magnitudes by either pulling down or pulling up on an externally fixed GF- and LF-measuring device. Results revealed high indices of force coordination (i.e., GF scaling as assessed by GF/LF and GF coupling as assessed by maximum cross-correlation between GF and LF) in both force directions, while GF coupling was higher in downward than in upward direction (p < 0.001). Regarding the indices of neuromuscular quickness (i.e., the regression parameters obtained from the relationship between peak force and it's rate of development and half-relaxation time), results, in general, revealed a higher slope (named as rate of force development scaling factor; p < 0.01), similar R ² (p > 0.05), and shorter half-relaxation time (p < 0.05) for LF than for GF. Furthermore, all of the selected variables showed moderate to excellent within-session reliability with only 45 pulses. Findings suggest that brief force production tasks should be further evaluated as clinical tests of hand function and neuromuscular quickness in various populations.

Contribution of tactile dysfunction to manual motor dysfunction in type II diabetes

INTRODUCTION

Changes in sensory and motor functions of the hand in type II diabetes (T2D) patients have been reported; there is speculation that these changes are driven by tactile dysfunction. The purpose of this study was to evaluate the effects of tactile feedback on manual function in T2D patients.

METHODS

T2D patients and healthy controls underwent median nerve blocks at the wrist and elbow. All participants underwent traditional timed motor evaluations, force dynamometry, laboratory-based kinetic evaluations, and sensory evaluation.

RESULTS

Tactile sensation in the T2D group at baseline was found to be equivalent to tactile function of the control group after median nerve block. Traditional timed evaluation results were negatively impacted by anesthesia, but more sensitive kinetic measures were not impacted.

CONCLUSIONS

These data suggest that mechanisms outside of tactile dysfunction play a significant role in motor dysfunction in T2D. Muscle Nerve 54: 895-902, 2016.

Cross-Cultural Adaptation and Validation of the Jebsen-Taylor Hand Function Test in an Italian Population

Objective. This paper describes the Italian translation and adaptation to the Italian culture of the original version of the Jebsen-Taylor hand function test and conveys the procedure for testing its validity and reliability. Design. The cultural adaptation process and validation were based on data from a group of people with no clinical evidence of disease or impairment of the upper limbs. The process required a forward and reverse translation in its original language. The scale obtained was reviewed by 8 experts in the field of psychometrics dealing with statistical methods that are useful for the behavioral and social sciences. The Italian adapted version of the JTHFT was then produced and validated. Participants. The test was submitted to 320 people with no clinical evidence of disease in order to test its acceptability and consistency. Results. The total time required to perform each subtest was 80.16 ± 43.13 seconds for the nondominant hand (NDH) and 49.97 ± 27.28 seconds for the dominant hand (DH). The internal consistency (assessed with Pearson's r) and the reliability or the construct validity (assessed with Cronbach's alpha) are significative. Conclusions. This is the first study reporting the result of the translation, cultural adaptation, and validation protocols of the JTHFT in Italian. It provides a new tool for Italian professionals to measure the functionality of the hand in participants with various upper limb pathologies.