Manual dexterity in young and healthy older adults. 1. Age- and gender-related differences in unimanual and bimanual performance

Age- and sex-related changes in motor functions: a comprehensive assessment and component analysis

Age-related motor impairments often cause caregiver dependency or even hospitalization. However, comprehensive investigations of the different motor abilities and the changes thereof across the adult lifespan remain sparse. We, therefore, extensively assessed essential basic and complex motor functions in 444 healthy adults covering a wide age range (range 21 to 88 years). Basic motor functions, here defined as simple isolated single or repetitive movements in one direction, were assessed by means of maximum grip strength (GS) and maximum finger-tapping frequency (FTF). Complex motor functions, comprising composite sequential movements involving both proximal and distal joints/muscle groups, were evaluated with the Action Research Arm Test (ARAT), the Jebsen-Taylor Hand Function Test (JTT), and the Purdue Pegboard Test. Men achieved higher scores than women concerning GS and FTF, whereas women stacked more pins per time than men during the Purdue Pegboard Test. There was no significant sex effect regarding JTT. We observed a significant but task-specific reduction of basic and complex motor performance scores across the adult lifespan. Linear regression analyses significantly predicted the participants' ages based on motor performance scores (R2 = 0.502). Of note, the ratio between the left- and right-hand performance remained stable across ages for all tests. Principal Component Analysis (PCA) revealed three motor components across all tests that represented dexterity, force, and speed. These components were consistently present in young (21-40 years), middle-aged (41-60 years), and older (61-88 years) adults, as well as in women and men. Based on the three motor components, K-means clustering analysis differentiated high- and low-performing participants across the adult life span. The rich motor data set of 444 healthy participants revealed age- and sex-dependent changes in essential basic and complex motor functions. Notably, the comprehensive assessment allowed for generating robust motor components across the adult lifespan. Our data may serve as a reference for future studies of healthy subjects and patients with motor deficits. Moreover, these findings emphasize the importance of comprehensively assessing different motor functions, including dexterity, force, and speed, to characterize human motor abilities and their age-related decline.

Older and younger adults differ in time course of skill acquisition but not in overall improvement in a bimanual visuomotor tracking task

Manual motor performance declines with age, but the extent to which age influences the acquisition of new skills remains a topic of debate. Here, we examined whether older healthy adults show less training-dependent performance improvements during a single session of a bimanual pinch task than younger adults. We also explored whether physical and cognitive factors, such as grip strength or motor-cognitive ability, are associated with performance improvements. Healthy younger (n = 16) and older (n = 20) adults performed three training blocks separated by short breaks. Participants were tasked with producing visually instructed changes in pinch force using their right and left thumb and index fingers. Task complexity was varied by shifting between bimanual mirror-symmetric and inverse-asymmetric changes in pinch force. Older adults generally displayed higher visuomotor force tracking errors during the more complex inverse-asymmetric task compared to younger adults. Both groups showed a comparable net decrease in visuomotor force tracking error over the entire session, but their improvement trajectories differed. Young adults showed enhanced visuomotor tracking error only in the first block, while older adults exhibited a more gradual improvement over the three training blocks. Furthermore, grip strength and performance on a motor-cognitive test battery scaled positively with individual performance improvements during the first block in both age groups. Together, the results show subtle age-dependent differences in the rate of bimanual visuomotor skill acquisition, while overall short-term learning ability is maintained.

Translation, Cross-Cultural Adaptation, and Feasibility of the NHPT-E of Manual Dexterity for the Spanish Population

The Nine-Hole Peg Test (NHPT) is considered a "gold standard" for the measurement of manual dexterity. The aim of this study was the translation and culturally adapting the original version of the NHPT.

MATERIALS AND METHODS

The adaptation was carried out following the standardized translation-retrotranslation guidelines and procedures referred to in the literature and in the International Test Commission (CIT). The final Spanish version of the NHPT (NHPT-E) was administered to 40 healthy adults. We evaluated its feasibility by means of a questionnaire elaborated according to Iraossi's checklist proposal for the pilot test process.

RESULTS

Modifications of expression in the grammatical mode of the verbs were performed, as well as the adaptation of some terms used in the three sections of the original version of the test (General Information, Installation, and Application Instructions). In the pilot study, for 95% of the participants, the NHPT-E is a comfortable test to take, and, for 100% of the evaluators, the test includes all the necessary information, with clear instructions and interpretation of the results.

CONCLUSIONS

The cross-cultural adaptation and pilot study enabled the development of a suitable and viable version of the NHPT-E for use in the Spanish population.

Novel evaluation of upper-limb motor performance after stroke based on normal reaching movement model

BACKGROUND

Upper-limb rehabilitation robots provide repetitive reaching movement training to post-stroke patients. Beyond a pre-determined set of movements, a robot-aided training protocol requires optimization to account for the individuals' unique motor characteristics. Therefore, an objective evaluation method should consider the pre-stroke motor performance of the affected arm to compare one's performance relative to normalcy. However, no study has attempted to evaluate performance based on an individual's normal performance. Herein, we present a novel method for evaluating upper limb motor performance after a stroke based on a normal reaching movement model.

METHODS

To represent the normal reaching performance of individuals, we opted for three candidate models: (1) Fitts' law for the speed-accuracy relationship, (2) the Almanji model for the mouse-pointing task of cerebral palsy, and (3) our proposed model. We first obtained the kinematic data of healthy (n = 12) and post-stroke (n = 7) subjects with a robot to validate the model and evaluation method and conducted a pilot study with a group of post-stroke patients (n = 12) in a clinical setting. Using the models obtained from the reaching performance of the less-affected arm, we predicted the patients' normal reaching performance to set the standard for evaluating the affected arm.

RESULTS

We verified that the proposed normal reaching model identifies the reaching of all healthy (n = 12) and less-affected arm (n = 19; 16 of them showed an R² > 0.7) but did not identify erroneous reaching of the affected arm. Furthermore, our evaluation method intuitively and visually demonstrated the unique motor characteristics of the affected arms.

CONCLUSIONS

The proposed method can be used to evaluate an individual's reaching characteristics based on an individuals normal reaching model. It has the potential to provide individualized training by prioritizing a set of reaching movements.

Parameters to Consider for Successful Medication Use in Older Adults - an AGePOP Review

Older adults are the main users of medicine and due to their multimorbidity are often faced/confronted with a complex medication management. This review article provides a brief overview on aspects of medication management such as maintaining a stock of the required medicine, understanding and following the instructions for use, coping with the primary and secondary packaging as well as preparation prior to use. The main focus however is on the drug intake itself and provides an overview about the current understanding of real life dosing conditions of older adults and geriatric patients. Furthermore, it elaborates the acceptability of dosage forms, in particular solid oral dosage forms as they represent the majority of dosage forms taken by these patient populations. An improved understanding of the needs of older adults and geriatric patients, their acceptability of various dosage forms and the circumstances under which they manage their medications, will make the design of more patient-centric drug products possible.

A Sex-Specific Evaluation of Dental Students' Ability to Perform Subgingival Debridement: Randomized Trial

BACKGROUND

A successful periodontitis treatment demands good manual skills. A correlation between biological sex and dental students' manual dexterity is currently unknown.

OBJECTIVE

This study examines performance differences between male and female students within subgingival debridement.

METHODS

A total of 75 third-year dental students were divided by biological sex (male/female) and randomly assigned to one of two work methods (manual curettes n=38; power-driven instruments n=37). Students were trained on periodontitis models for 25 minutes daily over 10 days using the assigned manual or power-driven instrument. Practical training included subgingival debridement of all tooth types on phantom heads. Practical exams were performed after the training session (T1) and after 6 months (T2), and comprised subgingival debridement of four teeth within 20 minutes. The percentage of debrided root surface was assessed and statistically analyzed using a linear mixed-effects regression model (P<.05).

RESULTS

The analysis is based on 68 students (both groups n=34). The percentage of cleaned surfaces was not significantly different (P=.40) between male (mean 81.6%, SD 18.2%) and female (mean 76.3%, SD 21.1%) students, irrespective of the instrument used. The use of power-driven instruments (mean 81.3%, SD 20.5%) led to significantly better results than the use of manual curettes (mean 75.4%, SD 19.4%; P=.02), and the overall performance decreased over time (T1: mean 84.5%, SD 17.5%; T2: mean 72.3%, SD 20.8%; P<.001).

CONCLUSIONS

Female and male students performed equally well in subgingival debridement. Therefore, sex-differentiated teaching methods are not necessary.

Influence of Solid Oral Dosage Form Characteristics on Swallowability, Visual Perception, and Handling in Older Adults

Swallowability, visual perception, and any handling to be conducted prior to use are all influence factors on the acceptability of an oral dosage form by the patient. Knowing the dosage form preferences of older adults, as the major group of medication end users, is needed for patient-centric drug development. This study aimed at evaluating the ability of older adults to handle tablets as well as to assess the anticipated swallowability of tablets, capsules, and mini tablets based on visual perception. The randomized intervention study included 52 older adults (65 to 94 years) and 52 younger adults (19 to 36 years). Within the tested tablets, ranging from 125 mg up to 1000 mg in weight and being of different shapes, handling was not seen as the limiting factor for the decision on appropriate tablet size. However, the smallest sized tablets were rated worst. According to visual perception, the limit of acceptable tablet size was reached at around 250 mg for older adults. For younger adults, this limit was shifted to higher weights and was dependent on the tablet shape. Differences in anticipated swallowability with respect to tablet shapes were most pronounced for tablets of 500 mg and 750 mg in weight, independent of the age category. Capsules performed worse compared to tablets, while mini tablets appeared as a possible alternative dosage form to tablets of higher weight. Within the deglutition part of this study, swallowability capabilities of the same populations were assessed and have been reported previously. Comparing the present results with the swallowing capabilities of the same populations with respect to tablets, it shows adults' clear self-underestimation of their ability to swallow tablets independent of their age.

Hand Dexterity Is Associated with the Ability to Resolve Perceptual and Cognitive Interference in Older Adults: Pilot Study

The relationship between hand dexterity and inhibitory control across the lifespan is underexplored. In this pilot study, we examined inhibitory control using a modified Simon task. During the task, participants were presented with right- and left-pointing arrows located either on the right or the left parts of the screen. In the congruent trials, the arrow location and direction matched. In the incongruent trials, they mismatched, thus creating cognitive interference. In 50% of trials, the arrow presentation was accompanied by a task-irrelevant but environmentally meaningful sound that created perceptual interference. Hand dexterity was measured with the 9-hole peg test. Significantly faster reaction time (RT) on the modified Simon task (p < 0.001) was observed in younger adults, trials with concurrent sound stimuli, and congruent trials. Older adults who reported recent falls had greater difficulty resolving cognitive interference than older adults without recent falls. Hand dexterity significantly moderated the effect of sound on RT, but only in the group of older individuals. Interestingly, older individuals with reduced hand dexterity benefited from concurrent sounds more than those with better hand dexterity. Our findings suggest that task-irrelevant but environmentally meaningful sounds may increase alertness and enhance stimulus perception and recognition, thus improving motor performance in older individuals.

Altered Bimanual Kinetic and Kinematic Motor Control Capabilities in Older Women

Older women may experience critical neuromuscular impairments interfering with controlling successful bimanual motor actions. Our study aimed to investigate altered bimanual motor performances in older women compared with younger women by focusing on kinetic and kinematic motor properties. Twenty-two older women and 22 younger women performed bimanual kinetic and kinematic motor tasks. To estimate bimanual kinetic functions, we calculated bimanual maximal voluntary contractions (i.e., MVC) and force control capabilities (i.e., mean force, accuracy, variability, and regularity of the total force produced by two hands) during bimanual hand-grip submaximal force control tasks. For bimanual kinematic performances, we assessed the scores of the Purdue Pegboard Test (i.e., PPT) in both hands and assembly tasks, respectively. For the bimanual MVC and PPT, we conducted an independent t-test between two groups. The bimanual force control capabilities were analyzed using two-way mixed ANOVAs (Group × Force Level; 2 × 2). Our findings revealed that the older women showed less bimanual MVC (p = 0.046) and submaximal force outputs (p = 0.036) and greater changes in bimanual force control capabilities as indicated by a greater force variability (p = 0.017) and regularity (p = 0.014). Further, the older women revealed lower scores of PPT in both the hands condition (p < 0.001) and assembly task condition (p < 0.001). The additional correlation analyses for the older women showed that lower levels of skeletal muscle mass were related to less bimanual MVC (r = 0.591; p = 0.004). Furthermore, a higher age was related to lower scores in the bimanual PPT assembly task (r = -0.427; p = 0.048). These findings suggested that older women experience greater changes in bimanual motor functions compared with younger women.

Reduction in manual asymmetry and decline in fine manual dexterity in right-handed older adults with mild cognitive impairment

Research in Parkinson's or Alzheimer's disease suggests that hand function is affected by neurodegenerative diseases. However, little is known about the relationship between hand function and mild cognitive impairment (MCI). Therefore, we conducted a kinematic analysis of unimanual hand movements in MCI patients to answer whether manual asymmetries and manual dexterity are affected or preserved in this condition. Forty-one MCI patients and fifty healthy controls were tested with the Purdue Pegboard test. All participants were right-handed. Kinematic analyses (by hand) were calculated for path length, angle, and linear and angular velocities during reaching, grasping, transport and inserting. Group differences were tested by with factorial MANOVAs and laterality indexes (LI) were assessed. Groups were compared on "Right-Left" hand correlations to identify kinematics that best single-out patients. Kinematics from grasping and inserting were significantly more deteriorated in the MCI group, while outcomes for reaching and transport denoted superior performance. LIs data showed symmetry of movements in the MCI group, during reaching and transport. Comparisons of "Right-Left" hand correlations revealed that kinematics in reaching and transport were more symmetrical in patients. This study showed a deterioration of fine manual dexterity, an enhancement in gross dexterity of upper-limbs, and symmetrical movements in MCI patients.

The reliability of neurobehavioral tests in a thai adult population

Early detection of decline in neurobehavioral (NB) performance requires reliable methods of testing. Although NB tests have been shown to be consistent and reliable in Western countries, there has been limited research in Asian populations.

Objective

The purpose of this study was to investigate the test-retest reliability of NB tests in a Thai adult population and examine the impact of demographic data on NB tests. The aspects of the tests chosen were memory, attention, hand-eye coordination, motor speed, and dexterity.

Methods

The three NB tests used were digit span, Purdue Pegboard, and visual-motor integration. All three were administered to a population of 30 Thai adults.

Results

The outcomes of all Pearson's correlation coefficient tests (r) were positive and greater than 0.60, and subtest-retest reliability correlation coefficients ranged from 0.63 (p<0.001) to 0.81 (p<0.001). Interestingly, the outcomes of all of these tests were not affected by demographic data, with the exception of the Purdue Pegboard test, in which performance on the preferred hand and both hands assessment was weakly associated with age (β=-0.09, p<0.001 and β=-0.08, p<0.05, respectively).

Conclusions

NB tests have adequate reliability and are useful for the evaluation of clinical memory, attention, hand-eye coordination, motor speed, and dexterity in Thai adults. These tests were not affected by demographic data. However, further studies to measure the validity of the digit span, Purdue Pegboard, and visual-motor integration tests are needed.

Is surgical subspecialization associated with hand grip strength and manual dexterity? A cross-sectional study

BACKGROUND

The aim of this study was to compare hand grip strength (HGS) and manual dexterity of academic, subspecialized surgeons.

METHODS

A single-center cross-sectional study was performed among 61 surgeons. HGS was analysed with a hand dynamometer and manual dexterity was extensively analysed with a Purdue Pegboard Test. Correlations between HGS and manual dexterity and specific characteristics of the surgeons were analysed using Pearson's correlation coefficient (r).

RESULTS

HGS and manual dexterity were comparable between surgeons from different specialities. HGS was positively correlated with male gender (r = 0.59, p < 0.001) and hand glove size (r = 0.61, p < 0.001), whereas manual dexterity was negatively correlated with male gender (r = -0.35, p = 0.006), age (r = -0.39, = 0.002), and hand glove size (r = -0.46, p < 0.001).

CONCLUSIONS

Surgical subspecialization was not correlated with HGS or manual dexterity. Male surgeons have greater HGS, whereas female surgeons have better manual dexterity. Manual dexterity is also correlated with age, showing better scores for younger surgeons.

What does hand motor function tell us about our aging brain in association with WMH?

Background

White matter hyperintensities (WMH) are a common cerebral finding in older people. WMH are usually asymptomatic, but excessive WMH are associated with cognitive decline and dementia. WMH are also among the neurological findings most consistently associated with declining motor performance in healthy ageing.

Aims

To determine if WMH load is associated with simple and complex motor movements in dominant and non-dominant hands in cognitively intact older subjects.

Methods

Hand motor performance was assessed with the Purdue Pegboard and Finger-tapping tests on 44 healthy right-handed participants, mean age 70.9 years (range 59–84 years). Participants also underwent magnetic resonance (MR) imaging, which were used to quantify WMH volume. The effect of WMH on the motor parameters was assessed via mediation analyses.

Results

WMH load increased significantly with age, while the motor scores decreased significantly with age. WMH load mediated only the relationship between age and left-hand pegboard scores.

Discussion

WMH mediated only the more complex Purdue Pegboard task for the non-dominant hand. This is likely because complex movements in the non-dominant hand recruit a larger cerebral network, which is more vulnerable to WMH.

Conclusions

Complex hand movements in the non-dominant hand are mediated by WMH. Subtle loss of motor movements of non-dominant hand might predict future excessive white matter atrophy.

Influence of visual feedback, hand dominance and sex on individuated finger movements

The ability to perform individual finger movements, highly important in daily activities, involves visual monitoring and proprioception. We investigated the influence of vision on the spatial and temporal control of independent finger movements, for the dominant and non-dominant hand and in relation to sex. Twenty-six healthy middle-aged to old adults (M age = 61 years; range 46–79 years; females n = 13) participated. Participants performed cyclic flexion–extension movements at the metacarpophalangeal joint of one finger at a time while keeping the other fingers as still as possible. Movements were recorded using 3D optoelectronic motion technique (120 Hz). The movement trajectory distance; speed peaks (movement smoothness); Individuation Index (II; the degree a finger can move in isolation from the other fingers) and Stationarity Index (SI; how still a finger remains while the other fingers move) were extracted. The main findings were: (1) vision only improved the II and SI marginally; (2) longer trajectories were evident in the no-vision condition for the fingers of the dominant hand in the female group; (3) longer trajectories were specifically evident for the middle and ring fingers within the female group; (4) females had marginally higher II and SI compared with males; and (5) females had fewer speed peaks than males, particularly for the ring finger. Our results suggest that visual monitoring of finger movements marginally improves performance of our non-manipulative finger movement task. A consistent finding was that females showed greater independent finger control compared with males.

The effect of the menstrual cycle on the sense of touch, grip strength and manual dexterity of dental students

Objectives. This study aimed to evaluate through comparative tests the effect of the menstrual cycle on levels of depression, sleep quality and grip strength, fingertip touch and manual dexterity of students in the Dental Faculty. Methods. The study sample was formed from female students of the Dental Faculty. The total 70 participants comprised 31 from the first year and 39 from the final year. Evaluations were made in two different consecutive phases of the menstrual cycle. Data were collected using the Beck depression inventory (BDI), the Pittsburgh sleep quality index (PSQI), handgrip and lateral grip strength measurements, fingertip two-point discrimination sensory measurement, the Semmes-Weinstein monofilament test, the O'Connor tweezers skill test and the Purdue pegboard test. Results. A statistically significant difference was determined between the menstrual and ovulation phase measurements of the BDI, PSQI, Semmes-Weinstein monofilament test (right), the O'Connor tweezers skill test and Purdue pegboard test (right + left), and the Purdue Pegboard test (total and assembly) (p < 0.05). Conclusions. The menstrual cycle does not affect the sense of touch, grip strength and simple hand skills. However, task-focused skills requiring care and the manual dexterity needed for the use of instruments are affected.

Effect of Age on the Touchscreen Manipulation Ability of Community-Dwelling Adults

Assessment of touchscreen manipulation skills is essential for determining the abilities of older individuals and the extent to which they may benefit from this technology as a means to enhance participation, self-esteem, and quality of life. The aim of this study was to compare the touchscreen manipulation ability between community-dwelling older adults and middle-aged adults using a newly developed Touchscreen Assessment Tool (TATOO) and to determine the usability of this instrument. Convenience samples of two age groups were considered, one including 28 independent community-living older adults aged 81.9 ± 4.2 years with intact or corrected vision and with the abilities to walk independently with or without a walking aid and to understand and follow simple commands, and the other including 25 healthy middle-age adults aged 53.4 ± 5.9 years. The usability assessment was conducted during a single session using the System Usability Scale (SUS). Older adults demonstrated poorer touchscreen skills compared to middle-aged adults. Previous experience in manipulating a smartphone by the older adults did not affect their performance. The SUS results indicated good usability of the TATOO by both age groups. The TATOO shows promise as a user-friendly tool for assessing the specific skills needed to operate touchscreens. The outcomes of this study support the suitability of touchscreen devices and applications as well as the need for adapted accessibility for older adults. Researchers and clinicians will benefit from the availability of a rapid, low-cost, and objective tool to assess the skills required for touchscreen use.

Clip-On IMU System for Assessing Age-Related Changes in Hand Functions

Hand functions affect the instrumental activities of daily living. While functional outcome measures, such as a targeted box and block test, have been widely used in clinical settings and provide a useful measure of overall performance, the advent of a wearable Inertial Measurement Unit(IMU)-based system enables the examination of the specific performance and kinematic parameters of hand movements. This study proposed a novel clip-on IMU system to facilitate the clinically fitted measurements of fine-motor finger and wrist joint movements. Clinical validation was conducted with the aim of characterising age-related changes in hand functions, namely grasping, transporting, and releasing blocks. Eighteen young (age 20–31) and sixteen healthy older adults (age 75–89) were evaluated during the box and block test. The results demonstrated that an older age was characterized by slower movements and higher variations and kinematic alterations in the hand functions, such as a larger range of motions at the fingers as well as kinematic trajectories. The proposed IMU system and subsequent validations highlight the value of the performance and kinematics parameters for a more comprehensive understanding of fine-motor finger and wrist movements that could shed light on further implementations in clinical and practical settings.

Greater Sensorimotor Deficits and Abnormally Lower Globus Pallidus Fractional Anisotropy in HIV+ Women than in HIV+ Men

AIMS

Cognitive impairment may be greater in HIV-positive (HIV+) women than in HIV+ men. Whether sex-specific differences exist in brain microstructure of HIV+ individuals is unknown and was evaluated.

METHOD

39 HIV+ (21 men, 18 women) and 45 seronegative (SN, 20 men, 25 women) participants were assessed with brain diffusion tensor imaging and cognitive assessments (7 neuropsychological domains). Fractional anisotropy (FA) and mean diffusivity (MD) were measured with an automated atlas in selected brain regions. Group comparisons were assessed with linear mixed effects models, with sub-regions and hemisphere (left/right) as repeated factors for each region.

RESULTS

HIV+ women, but not HIV+ men, were slower than sex-matched SN controls on sensorimotor function (Dominant-hand: interaction-p = 0.007; Non-dominant hand: interaction-p = 0.039). Similarly, only HIV+ women had lower FA in the globus pallidus (GP, interaction-p = 0.011). Additionally, regardless of sex, the HIV+ group had poorer Fluency, Speed, and Attention than SN-controls (p = 0.006-0.008), as well as lower FA and higher MD in multiple brain regions (p = <0.001-0.044). Across all participants, performance on Attention was predicted by uncinate-FA (p < 0.001, r = 0.5) and corpus callosum (CC)-FA (p = 0.038, r = 0.23), while the Speed of Information Processing was predicted by CC-FA (p = 0.009, r = 0.3). Furthermore, faster sensorimotor function correlated with higher CC-FA and uncinate-FA in men but not in women (Sex*DTI-interaction-p = 0.03-0.06).

CONCLUSIONS

The relatively poorer sensorimotor function and abnormally lower GP_FA, suggesting lesser neuronal integrity, in HIV+ women demonstrate sex-specific effects from HIV-infection on these measures. These findings may be related to the greater immune activation and neuroinflammation in HIV+ women compared to HIV+ men. Graphical Abstract.

How Age, Cognitive Function and Gender Affect Bimanual Force Control

Coordinated bimanual control depends on information processing in different intra- and interhemispheric networks that differ with respect to task symmetry and laterality of execution. Aging and age-related cognitive impairments, but also sex can have detrimental effects on connectivity of these networks. We therefore expected effects of age, cognitive function and sex on bimanual force coordination. We furthermore expected these effects to depend on the characteristics of the task (i.e., difficulty and symmetry). 162 right handed participants (19 younger adults [YA], 21–30 years, 9 females; 52 cognitively healthy older adults [HOA], 80–91 years, 32 females; and 91 older adults with mild cognitive impairments [MCI] 80–91 years, 37 females) performed isometric bimanual force control tasks that required following constant or alternating (cyclic sine-wave) targets and varied in symmetry, i.e., (i) constant symmetric, asymmetric [with constant left and alternating right (ii) or vice versa (iii)], (iv) alternating in- and (v) alternating antiphase (both hands alternating with 0° or 180° relative phase, respectively). We analyzed general performance (time on target), bimanual coordination as coupling between hands (linear correlation coefficient) and structure of variability (i.e., complexity measured through detrended fluctuation analysis). Performance and coupling strongly depended on task symmetry and executing hand, with better performance in symmetric tasks and in asymmetric tasks when the left hand produced a constant and the right hand an alternating force. HOA and MCI, compared to YA, showed poorer performance (time on target) and reduced coupling in in- and antiphase tasks. Furthermore, both groups of OA displayed less complex structure in alternating force production tasks, a marker of reduced control. In addition, we found strong sex effects with females displaying reduced coupling during in- and antiphase coordination and less complex variably structure in constant force production. Results of this study revealed strong effects of age, but also sex on bimanual force control. Effects depended strongly on task symmetry and executing hand, possibly due to different requirements in interhemispheric information processing. So far, we found no clear relationship between behavioral markers of bimanual force control and age-related cognitive decline (compared to healthy aging), making further investigation necessary.

A comparison of the relationship between manual dexterity and postural control in young and older individuals with Parkinson's disease

The motor symptoms of Parkinson's disease (PD) cause deterioration in manual dexterity. This deterioration affects independence in activities of daily living negatively. The loss of postural control, which occurs more frequently with disease progression, restricts physical functions and reduces mobility in patients with PD. Impaired postural control may affect distal mobility of an individual. The aim of this study was to investigate postural control and manual dexterity in individuals ≤ 65 and >65 years with PD and analyze the relationship between these variables according to age. Sixty-six individuals with PD participated in the study. The participants were categorized according to age (n = 29 for 65 years of age or younger and n = 37 for older). Manual dexterity (Dominant and Non-dominant hand) was assessed by the Nine Hole Peg Test (NHPT). Postural control was evaluated by the Limit of Stability Test (LoS) using a computerized balance measuring instrument. There was no statistically significant difference between the age groups on the combined dependent variables after controlling for disability, gender, weight, and height; F(7, 54) = 0.804, p = 0.587. Only LoS-Maximum Excursion was higher in the individuals ≤ 65 years (p = 0.035). Significant correlations were found between NHPT-Dominant and LoS-Reaction Time, LoS-Maximum Excursion; NHPT-Non-dominant and LoS-Reaction Time, LoS-Endpoint Excursion, LoS-Maximum Excursion in the older group (p < 0.05). There was no difference manual dexterity and postural control according to age except for LoS-Maximum Excursion. LoS-Maximum Excursion was higher in the young group. The manual dexterity was associated with postural control in individuals over 65 years of age with PD; however, not associated in younger individuals.

Motor Imagery Training With Neurofeedback From the Frontal Pole Facilitated Sensorimotor Cortical Activity and Improved Hand Dexterity

To develop a real-time neurofeedback system from the anterior prefrontal cortex (aPFC) using functional near-infrared spectroscopy (fNIRS) for motor rehabilitation, we investigated the effects of motor imagery training with neurofeedback from the aPFC on hand dexterity and cerebral hemodynamic activity during a motor rehabilitation task. Thirty-one right-handed healthy subjects participated in this study. They received motor imagery training six times for 2 weeks under fNIRS neurofeedback from the aPFC, in which they were instructed to increase aPFC activity. The real group subjects (n = 16) were shown real fNIRS neurofeedback signals from the aPFC, whereas the sham group subjects (n = 15) were shown irrelevant randomized signals during neurofeedback training. Before and after the training, hand dexterity was assessed by a motor rehabilitation task, during which cerebral hemodynamic activity was also measured. The results indicated that aPFC activity was increased during the training, and performance improvement rates in the rehabilitation task after the training was increased in the real group when compared with the sham group. Improvement rates of mean aPFC activity across the training were positively correlated with performance improvement rates in the motor rehabilitation task. During the motor rehabilitation task after the training, the hemodynamic activity in the left somatosensory motor-related areas [premotor area (PM), primary motor area (M1), and primary somatosensory area (S1)] was increased in the real group, whereas the hemodynamic activity was increased in the supplementary motor area in the sham group. This hemodynamic activity increases in the somatosensory motor-related areas after the training correlated with aPFC activity during the last 2 days of motor imagery training. Furthermore, improvement rates of M1 hemodynamic activity after the training was positively correlated with performance improvement rates in the motor rehabilitation task. The results suggest that the aPFC might shape activity in the somatosensory motor-related areas to improve hand dexterity. These findings further suggest that the motor imagery training using neurofeedback signals from the aPFC might be useful to patients with motor disability.

The effects of speed of execution on upper-limb kinematics in activities of daily living with respect to age

In this study, 26 young, 16 older adults ≤ 66a, and 22 older adults ≥ 67a were examined in a set of neuropsychological tests and the kinematics in two different activities of daily living (ADL) were assessed. Half of the participants performed the ADL in a natural speed, the other half as fast as possible. The performance in the Trail Making Task B revealed an increased slope after 67 years of age. When executed in a natural speed, ADL kinematics were comparable. When executed as fast as possible, almost all kinematic parameters showed significant group and speed differences and revealed group × speed interactions. Models of multiple linear regression predicting ADL trial durations showed similar strategies in the young and older adults < 67a. Factors were the general movement speed, the travelled path lengths, and the simultaneous use of both hands. In the older adults ≥ 67a, factors were the general movement speed, the travelled path length, and the activity level (during the task execution). A principal component analysis supported these findings by revealing two underlying components: movement strategy and age-dependent decline in primarily executive functions, where the ADL trial duration had comparable loadings on both components. These results in association with the accelerated decline in executive functions found in the oldest group suggest that deterioration of ADL with age is particularly caused by specific age-dependent changes in cognitive capacities.