Human neurologic function and the aging process

Association between dynapenia and cognitive decline in community-dwelling older Japanese adults: The IRIDE Cohort Study

AIM

Muscle mass and strength correlate with cognitive function; however, it remains unclear whether dynapenia (i.e., muscle weakness with preserved muscle mass) is relevant. This study aimed to explore whether dynapenia is associated with global cognitive function in community-dwelling older Japanese adults.

METHODS

This cross-sectional study used data from the Integrated Research Initiative for Living Well with Dementia Cohort Study, which pooled data from five community-based geriatric cohorts. Dynapenia was defined as muscle weakness without muscle mass loss according to the Asian Working Group for Sarcopenia criteria. Cognitive function was assessed using the Mini-Mental State Examination (MMSE). An ordered logistic regression analysis was conducted with dynapenia as the exposure and with cognitive decline stages, defined as an MMSE score of 27-30 for normal cognition, 24-26 for possible cognitive decline, and <24 for cognitive decline, as the outcome, stratified by sex and adjusted for age, muscle mass, education, alcohol consumption, smoking habits, living alone, and non-communicable diseases.

RESULTS

We analyzed data for 3338 participants (2162 female) with preserved muscle mass. Of these, 449 (13.5%) had dynapenia, and 79 (2.4%) exhibited cognitive decline. Multivariate odds ratios (95% confidence interval) for cognitive decline among those with dynapenia, compared with those without dynapenia, were 1.51 (1.02-2.24) for males and 2.08 (1.51-2.86) for females.

CONCLUSIONS

Muscle weakness is associated with cognitive decline, even in individuals with preserved muscle mass. Further studies are needed to better understand the association between muscle weakness and cognitive decline over time in order to develop dementia prevention strategies for those with dynapenia. Geriatr Gerontol Int 2024; 24: 123-129.

Clinically Measuring Orofacial Somatosensation in a Cohort of Healthy Aging Adults

PURPOSE

Humans experience the world through sensations of touch, taste, smell, vision, and audition. Alterations in sensory acuity occur across the adult life span in all types of sensation. The purpose of this study was to describe possible differences in lip and tongue somatosensation (sense of pressure) for healthy older adults using clinically available measurement tools as compared with previously published data using the same protocol.

METHOD

A total of 33 healthy adults (ages 60-93 years; M = 70.5 years; 19 women) completed bilateral assessment of lip and tongue pressure detection and discrimination using two-point discrimination discs and Von Frey hair monofilaments. Participants reported basic health information and completed a pure-tone hearing threshold assessment within the same session.

RESULTS

Descriptive results are presented for individual data points from healthy aging adults. Group data are compared with previously published data from a cohort of healthy young participants. Although there were no statistically significant differences between the two healthy groups, variations in standard deviations in older adults were observed.

CONCLUSIONS

Two-point discrimination and tactile detection and discrimination using Von Frey hair monofilaments can be used to assess labial and lingual pressure detection and discrimination in healthy aging adults. While not reaching statistical significance, on average, older adults demonstrated increased threshold estimates compared with younger adults with increases in standard deviations up to 11.5 times larger than the younger cohort. Subtle differences in somatosensation across the ages may be important for future comparisons with clinical populations across the life span. These assessment techniques can be used with an aging population to complete objective orofacial somatosensory testing.

Supplementary and Premotor Aspects of the Corticospinal Tract Show Links with Restricted and Repetitive Behaviors in Middle-Aged Adults with Autism Spectrum Disorder

Individuals with autism spectrum disorder (ASD) show motor impairment into adulthood and risk decline during aging, but little is known about brain changes in aging adults with ASD. Few studies of ASD have directly examined the corticospinal tract (CST)-the major descending pathway in the brain responsible for voluntary motor behavior-outside its primary motor (M1) connections. In 26 middle-aged adults with ASD and 26 age-matched typical comparison participants, we used diffusion imaging to examine the microstructure and volume of CST projections from M1, dorsal premotor (PMd), supplementary motor area (SMA), and primary somatosensory (S1) cortices with respect to age. We also examined relationships between each CST sub-tract (-cst), motor skills, and autism symptoms. We detected no significant group or age-related differences in tracts extending from M1 or other areas. However, sub-tracts of the CST extending from secondary (but not primary) motor areas were associated with core autism traits. Increased microstructural integrity of left PMd-cst and SMA-cst were associated with less-severe restricted and repetitive behaviors (RRB) in the ASD group. These findings suggest that secondary motor cortical areas, known to be involved in selecting motor programs, may be implicated in cognitive motor processes underlying RRB in ASD.

A Narrative Review of Handgrip Strength and Cognitive Functioning: Bringing a New Characteristic to Muscle Memory

BACKGROUND

Measures of handgrip strength have not only emerged as a clinically viable screening tool for determining risk for morbidity, functional disability, and early mortality, but also for helping to identify cognitive deficits. However, the phenomena that links low handgrip strength with cognitive decline remains unclear. The role of the muscular and neural systems, and their adaptations to muscle strengthening activities over the life course, may provide important information for how age-related changes to muscle mass, strength, and neural capacity influence cognition. Moreover, disentangling how handgrip strength and cognitive function are associated may help to inform healthcare providers working with aging adults and guide targeted interventions aiming to preserve muscle and cognitive functioning.

OBJECTIVE

To 1) highlight and summarize evidence examining the associations of handgrip strength and cognitive functioning, and 2) provide directions for future research in this area.

METHODS

Articles from the PubMed database were searched from November 2018-May 2019. The search term algorithm, inclusion and exclusion criteria were pre-specified by investigators.

RESULTS

Several cross-sectional and longitudinal studies have revealed that measures of handgrip strength were associated with cognitive declines regardless of age demographics and the presence of comorbidities.

CONCLUSION

Handgrip strength can be used in clinical and epidemiological settings for helping to determine the onset and progression of cognitive impairment. Future research should continue to examine how handgrip strength and cognitive function are linked.

Integrated metabolomics and transcriptomics reveal the anti-aging effect of melanin from Sepiella maindroni ink (MSMI) on D-galactose-induced aging mice

Sepiella maindroni ink, a flavoring and coloring agent in food, has attracted considerable attention due to its various pharmacological activities. Our previous study showed that the melanin of Sepiella maindroni ink (MSMI) can alleviate oxidative damage and delay aging in D-galactose(D-gal)-induced aging mice. This study aimed to reveal the possible mechanisms of the anti-aging effect of MSMI. In this article, a comprehensive analysis of gas chromatography-mass spectrometry (GC-MS)-based metabolomics and microarray-based transcriptomics revealed that 221 mRNAs were differentially expressed and 46 metabolites were significantly changed in the anti-aging progress of MSMI. Integrated analysis of transcript and metabolic profiles indicated that MSMI mainly altered carbohydrate metabolism, lipid metabolism, and insulin signaling pathway. MSMI achieved anti-aging effects not only by reducing oxidative damage and sorbitol toxicity but also by regulating lipid metabolism, improving insulin sensitivity, and reducing the formation of advanced glycation end products (AGEs). Moreover, our findings firstly demonstrated that MSMI could increase the expression of interferon-induced proteins and might be a potential antiviral compound.

Association between single limb standing test results and healthcare costs among community-dwelling older adults

BACKGROUND AND OBJECTIVE

Identifying risks for older adults who will require healthcare resources is critical for the government, healthcare providers, and consumers. The objective of this study was to examine the relationship between the results of the single limb standing (SLS) test and healthcare costs among community-dwelling older adults.

METHODS

We used data obtained from a population-based prospective cohort study of the residents of Tadami town in Fukushima Prefecture, Japan. The participants were above 60 years of age and had undergone annual health check-ups, and data on their healthcare costs over the two-year study period were available. A censored regression model adjusted for potential confounders was used to estimate the mean difference in total healthcare costs between participants who could remain standing on a single limb for at least 30 s and those who could not.

RESULTS

Healthcare costs of participants who passed the SLS test were significantly lower than those who did not. The mean difference between the two groups' healthcare costs was 4064 USD (95 % confidence interval: 2661-5467 USD, p < 0.05). After adjusting for potential confounders, the mean difference between the two groups was smaller (1686 USD) but remained statistically significant (95 % confidence interval: 125-3246 USD, p < 0.05).

CONCLUSIONS

Among community-dwelling older adults, limited static balance (SLS time <30 s) was found to be associated with high healthcare costs in the two years after the SLS test. The SLS test may help identify individuals at high risk of becoming frequent users of healthcare services in the future.

Age-Dependent Control of Shoulder Muscles During a Reach-and-Lift Task

Aging affects fatigability and is a risk factor for incurring a fatigue-related injury in the neck/shoulder region. Age-related changes in the electromyographical features of motor control may be partly responsible. Young (N = 17) and older (N = 13) adults completed a reach-and-lift task at their self-selected speed, before and after a fatiguing task targeting the neck/shoulder. Electromyography amplitude (root mean square), amplitude variability (root mean square coefficient of variation [CV]), functional connectivity (normalized mutual information [NMI]), and functional connectivity variability (NMI CV) were extracted from several muscles and analyzed for effects and interactions of age using general estimating equation models. Root mean square CV and deltoid NMI CV increased from pre- to postfatigue (ps < .05). Upper trapezius-deltoid NMI decreased for young, but increased for older adults, while the opposite response was found for lower trapezius-deltoid NMI (ps < .05). Older adults seem to adapt to fatigue in reach-and-lift movement with a cranial shift in control of the scapula.

Impaired motor skills and atypical functional connectivity of the sensorimotor system in 40- to 65-year-old adults with autism spectrum disorders

Impairments in fine and gross motor function, coordination, and balance in early development are common in autism spectrum disorders (ASDs). It is unclear whether these deficits persist into adulthood and whether they may be exacerbated by additional motor problems that often emerge in typical aging. We assessed motor skills and used resting-state functional magnetic resonance imaging to study intrinsic functional connectivity of the sensorimotor network in 40- to 65-year-old adults with ASDs (n = 17) and typically developing matched adults (n = 19). Adults with ASDs scored significantly lower on assessments of motor skills compared with an age-matched group of typical control adults. In addition, functional connectivity of the sensorimotor system was reduced and the pattern of connectivity was more heterogeneous in adults with ASDs. A negative correlation between functional connectivity of the motor system and motor skills, however, was only found in the typical control group. Findings suggest behavioral impairment and atypical brain organization of the motor system in middle-age adults with ASDs, accompanied by pronounced heterogeneity.

Age Is a Greater Influence on Small Saccades Than Target Size in Normal Subjects on the Horizontal Video Head Impulse Test

Objective: This study sought to investigate whether the size of the target used in the horizontal vHIT has an effect on the saccade profile of healthy subjects, and to expand upon previous work linking age to the existence of small vHIT saccades.

Methods: Forty eight participants were recruited between 18 and 77 years of age, with no history of vestibular, oculomotor or neurological conditions and a visual acuity of at least 0.3 LogMAR. Participants underwent four consecutive horizontal vHIT trials using the standard target size and three smaller targets. VOR gain and metrics for saccadic incidence, peak eye velocity and latency were then extracted from results.

Results: Target size was a statistically significant influence on saccade metrics. As target size increased, saccadic incidence decreased while peak eye velocity and latency increased. However, a potential order effect was also discovered, and once this was corrected for the remaining effect of target size was small and is likely clinically insignificant. The effect of age was much stronger than target size; increasing age was strongly positively correlated with saccadic incidence and showed a medium size correlation with peak velocity, though not with saccadic latency.

Conclusion: While this study suggests that target size may have a statistically significant impact on the vHIT saccade profile of normal subjects, age has a greater influence on the incidence and size of small vHIT saccades.

Clinical Symptoms, Neurological Signs, and Electrophysiological Findings in Surviving Residents with Probable Arsenic Exposure in Toroku, Japan

Chronic arsenic intoxication is known to cause multisystem impairment and is still a major threat to public health in many countries. In Toroku, a small village in Japan, arsenic mines operated from 1920 to 1962, and residents suffered serious sequelae of arsenic intoxication. We have performed annual medical examinations of these residents since 1974, allowing us to characterize participants' long-term health following their last exposure to arsenic. The participants could not be described as having "chronic arsenic intoxication," because their blood arsenic levels were not measured. In this study, we defined them as having "probable arsenic intoxication." Symptoms frequently involved the sensory nervous system, skin, and upper respiratory system (89.1-97.8%). In an analysis of neurological findings, sensory neuropathy was common, and more than half of the participants complained of hearing impairment. Longitudinal assessment with neurological examinations and nerve conduction studies revealed that sensory dysfunction gradually worsened, even after exposure cessation. However, we could not conclude that arsenic caused the long-term decline of sensory function due to a lack of comparisons with age-matched healthy controls. This is the first study to characterize the longitudinal sequelae after probable arsenic exposure. Our study will be helpful to assess the prognosis of patients worldwide who still suffer from chronic arsenic intoxication.

Body postural sway analysis in older people with different fall histories

A cross-sectional study of postural sway analysis in older non-fallers, once-fallers and multiple-fallers using five common standing tests was conducted. Eighty-six older subjects with an average age of 80.4 years (SD ± 7.9) participated in the study. The angular rotation and velocity of the trunk of the participants in the roll (lateral) and pitch (sagittal) planes were recorded using an inertial sensor mounted on their lower backs. The Gaussian Mixture Models (GMM), Expectation-Maximisation (EM) and the Minimum Message Length (MML) algorithms were applied to the acquired data to obtain an index indicative of the body sway. The standing with feet together and standing with one foot in front, sway index distinguished older fallers from non-fallers with specificity of 75.7% and 77.7%, respectively, and sensitivity of 78.6% and 82.1%, respectively. This compares favourably with the Berg Balance Scales (BBS) with specificity of 70.5% and sensitivity of 75.3%. The results suggest that the proposed method has potential as a protocol to diagnose balance disorder in older people. Graphical abstract.

A randomized, double-blind, placebo-controlled crossover study of the effects of levetiracetam on cognition, mood, and balance in healthy older adults

OBJECTIVE

The cognitive and mood effects of levetiracetam (LEV) in older adults are not known. This study compared the cognitive and mood effects of LEV to placebo in healthy older adults.

METHODS

Cognitive, mood, and balance variables were compared between LEV and placebo using a randomized, double-blind, placebo-controlled crossover study with two 5-week treatment periods. Healthy volunteers (n = 20) aged 65-80 (mean age 72.4) received either LEV or placebo in which the LEV target dose was 1,000 mg/day. Volunteers, aged 65-80, were without epilepsy to limit potentially confounding the impact of seizures and/or underlying neuropathology on outcomes. LEV was initiated at 250 mg twice a day for 2 weeks, then increased to 500 mg twice a day for 2 weeks, and then tapered to 250 mg twice a day for 1 week. This was randomized with placebo for the two treatment arms. Measures included standardized neuropsychological, mood, and balance tests yielding 32 variables. Balance was assessed using subjective report (e.g., A-B neurotoxicity scale) and objective data (e.g., Berg Balance Scale).

RESULTS

Average LEV serum concentration was 16.9 (standard deviation [SD} 7.7). Repeated-measures analysis of variance (ANOVA) found no differences between LEV and placebo phases for 29 (90.6%) of 32 variables including no change in balance. Performance on LEV was better than placebo on a visual memory (MCG Complex Figure Recall; p = 0.007) and two attention tests (Trail Making Test, Part A, p = 0.009; Stroop Interference, p = 0.004). There was a trend for greater irritability and fatigue (POMS Anger and Fatigue) during the LEV phase (p = 0.029, p = 0.035). Effect-size changes were generally small (Cohen d < 0.5).

SIGNIFICANCE

LEV was well tolerated in this elderly population in terms of cognition, mood, and balance. When anticonvulsant medication is indicated for older adults, LEV has pharmacokinetic advantages, and these data indicate no adverse impact on cognition or balance.

The Balance Scale: Factor Analysis and Reliability

The purpose of this study was to determine the construct validity and reliability of the Balance Scale. This scale consisted of eight stances: bipedal stance with eyes open and closed, monopedal stance with eyes open and closed and these four stances repeated on a beam. These stances reflect the two factors related to balance, base of support and visual cues. The ability of subjects to maintain these stances was timed for a maximum of 30 sec. Using a nonprobability sample of 61 community living elders with a mean age of 71.9 yr., a forced four-factor principal components factor analysis was done. Simple structure was achieved with varimax rotation. The four factors extracted accounted for 79.2% of the total variance and were the monopedal factor, visual factor, bipedal nonvisual factor, and a beam factor. Standardized item coefficients for these factors ranged from .60 to .76.

Identifying Dimensions of Physical (Motor) Functional Capacity in Healthy Older Adults

This study addressed the dimensionality and construct validity of physical functional capacity within the context of performance-based measures. Sixty-two individuals (M= 70yrs), classified as "healthy" based on several screening procedures, completed a battery of standard neuromuscular and physical performance tests. Scores were submitted to a principal components factor analysis to examine and describe potential dimensions of physical functional capacity. Orthogonal and oblique rotations of axes were performed. Six interpretable and meaningful factors were extracted from the orthogonal rotation and identified as strength, unimanual dexterity, mobility/agility, static balance, general upper-extremity control, and movement planning speed. The results indicated that physical functioning in older persons is a multidimensional construct. Moreover, assessment techniques involving performance-based measures should be designed to diagnose physical functional status in separate motor dimensions and plan intervention approaches accordingly.

Labial Vibrotactile Somatosensory Perception: A Pilot Study in Healthy Aging versus Young Adult Participants

The purpose of this pilot study was to begin characterizing changes in labial vibrotactile somatosensation in healthy older adults as a foundational step in determining how changes in orofacial sensation can affect functional behaviors, such as speech and feeding. Labial vibrotactile perception capacity of healthy older adults ( n = 15) was compared to a cohort of healthy young adults ( n = 5). Vibrotactile inputs were delivered to the glabrous surface of the left lower lip at 5, 10, 50, and 150 Hz. A modified von Bekesy (staircase) method was used to identify participants' thresholds and response standard deviations for each test frequency. Consistent with findings in other body regions, a decrease in labial vibrotactile detection sensitivity was expected in healthy older adults. The threshold values for the 5 and 10 Hz test frequencies were higher in the older group and the differences in response standard deviations at these frequencies were statistically significant. This pilot study identified changes in labial perception among healthy older adults.

One-leg standing time and hip-fracture prediction

A hip fracture results in a lower quality of life and a cost of £30,000. In this study, one-leg standing time (OLST) had a negative linear relationship to the risk of a hip fracture. OLST could be a useful tool to assess the need for fracture-preventive interventions.

INTRODUCTION

A hip fracture immobilizes, restricts autonomy, shortens life expectancy, and results in a cost of £30,000 in the UK health care system. However, effective preventive treatments can be offered to high-risk individuals. Impaired postural balance is an important risk factor for hip fractures, and the aim of this study was to evaluate whether OLST can predict hip fractures in elderly women. FRAX is the most established fracture risk assessment tool worldwide and a secondary aim was to relate the predictive ability of OLST to that of FRAX in this population.

METHODS

Three hundred fifty-one women aged between 69 and 79 years were timed standing on one leg up to 30 s with eyes open and assessed with FRAX. Fracture data was obtained from registers.

RESULTS

The main outcome, a hip fracture, occurred in 40 of the 351 participants (11.4%). The age-adjusted risk of a hip fracture was 5% lower with 1 s longer OLST (Hazard ratio 0.95, 95% CI 0.927-0.978). The relation between OLST and hip fracture risk was linear. Harrell's c was 0.60 for FRAX and 0.68 for OLST adjusted for age.

CONCLUSION

With 1 s longer OLST, the risk of a hip fracture decreased significantly by 5%. This risk reduction was not explained by differences in the classic fracture risk factors included in FRAX. OLST had a predictive ability similar to FRAX. OLST is an easily performed balance test which may prove to be valuable in the assessment of hip fracture risk.

Beta oscillations reflect changes in motor cortex inhibition in healthy ageing

Beta oscillations are involved in movement and have previously been linked to levels of the inhibitory neurotransmitter GABA. We examined changes in beta oscillations during rest and movement in primary motor cortex (M1). Amplitude and frequency of beta power at rest and movement-related beta desynchronization (MRBD) were measured during a simple unimanual grip task and their relationship with age was explored in a group of healthy participants. We were able to show that at rest, increasing age was associated with greater baseline beta power in M1 contralateral to the active hand, with a similar (non-significant) trend in ipsilateral M1. During movement, increasing age was associated with increased MRBD amplitude in ipsilateral M1 and reduced frequency (in contralateral and ipsilateral M1). These findings would be consistent with greater GABAergic inhibitory activity within motor cortices of older subjects. These oscillatory parameters have the potential to reveal changes in the excitatory–inhibitory balance in M1 which in turn may be a useful marker of plasticity in the brain, both in healthy ageing and disease.

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Changes in motor cortex beta oscillations are linked with changes in GABA.

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Changes in GABA-related cortical inhibition are linked with plasticity.

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Older subjects had higher resting beta power and greater beta decrease during grip.

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Beta oscillations are useful markers of cortical inhibition and plasticity.

Age-related changes in cutaneous sensation in the healthy human hand

Cutaneous sensation deteriorates with age. It is not known if this change is consistent over the entire hand or if sensation is affected by changes in skin mechanics. Cutaneous perceptual thresholds were tested at eight sites in the glabrous skin and two in the hairy skin of both hands in 70 subjects (20-88 years), five male and five female per decade, using calibrated von Frey filaments, two-point discrimination, and texture discrimination. Venous occlusion at the wrist (40 ± 10 mmHg) and moisturizer were used to alter skin mechanics. Cutaneous thresholds increased significantly with age (p < 0.001); von Frey thresholds were 0.04 g [0.02-0.07] (median and interquartile range) in the 20s and 0.16 g [0.04-0.4] in the 80s, with differences between hands for older females (p = 0.044) but not males. The pattern of changes in cutaneous sensation varied according to the site tested with smaller changes on the fingers compared to the palm. Two-point discrimination deteriorated with age (p = 0.046), but with no interaction between sex, handedness, or changes in skin mechanics. There were no significant differences for texture discrimination. Changes in skin mechanics improved cutaneous thresholds in the oldest males after moisturizing (p = 0.001) but not otherwise. These results emphasize the complex pattern of age-related deterioration in cutaneous sensation with differences between sexes, the hands, sites on the hand, and the mode of testing. As the index fingertip is not a sensitive indicator of sensory decline, the minimum assessment of age-related changes in cutaneous sensation should include both hands, and sites on the palm.

Evaluation of the stability of normal subjects and patients with Perthes and spinal cord injury disorders during short and long periods of time

BACKGROUND

Stability during standing is achieved by a complex coordination process between various human systems. The stability of normal subjects and patients with various neuromuscular disorders has been evaluated by common methods based on force plate data analysis for one minute. However, most of the people frequently stand for a prolonged period during daily activities.

OBJECTIVES

This study aimed to evaluate the stability of subjects during a longer period of time. Moreover, the new method was introduced to analyze the stability of subjects with musculoskeletal disorders.

STUDY DESIGN

Experimental.

METHODS

Four groups of normal adults and children, individuals with spinal cord injury (SCI) and Perthes disease were recruited in this study. Stability of the subjects was evaluated by using parameters collected from centre of pressure (COP) sways obtained while subjects standing on force plate for one and then five minutes based on the old and new methods. Two sample t-test was used to compare the stability of the subjects by the commonly used method. The number of stable to unstable frames was selected for final analysis based on the new method.

RESULTS

Based on the traditional method, the SCI and Perthes patients were more stable than normal subjects (p < 0.05). Moreover, children were more unstable in the anteroposterior plane than adults. However, based on the new method, SCI and patients with Perthes disease were more unstable than normal adults. Moreover, in mediolateral direction the results of stability analysis with the new method differed from that of the traditional method.

CONCLUSION

The new method of stability analysis seems to be more sensitive and accurate than that of the traditional commonly used method. Based on the new method, stability is the ability of a subject to return from an unstable position to a stable one and to remain in a stable one for a certain period of time. Clinical relevance The results of this research can be used by most clinicians to evaluate the stability of subjects with various musculoskeletal disorders.

Frontal plane hip and ankle sensorimotor function, not age, predicts unipedal stance time

INTRODUCTION

Changes occur in muscles and nerves with aging. In this study we explore the relationship between unipedal stance time (UST) and frontal plane hip and ankle sensorimotor function in subjects with diabetic neuropathy.

METHODS

UST, quantitative measures of frontal plane ankle proprioceptive thresholds, and ankle and hip motor function were tested in 41 subjects with a spectrum of lower limb sensorimotor function ranging from healthy to moderately severe diabetic neuropathy.

RESULTS

Frontal plane hip and ankle sensorimotor function demonstrated significant relationships with UST. Multivariate analysis identified only composite hip strength, ankle proprioceptive threshold, and age to be significant predictors of UST (R(2) = 0.73), explaining 46%, 24%, and 3% of the variance, respectively.

CONCLUSIONS

Frontal plane hip strength was the single best predictor of UST and appeared to compensate for less precise ankle proprioceptive thresholds. This finding is clinically relevant given the possibility of strengthening the hip, even in patients with significant peripheral neuropathy.

[Can a newly-established test for assessing standing and balance function be an alternative to the timed up-and-go test?--functional assessment of gait and balance in elderly patients for a comprehensive geriatric assessment initiative named 'Dr. SUPERMAN']

AIM

To identify elderly patients who are at high risk for falls, we used the timed up-and-go test (TUG) as an assessment tool for gait and balance function in a comprehensive geriatric assessment (CGA) initiative named 'Dr. SUPERMAN'. However, this test is difficult to perform in a small area because it requires at least 3 meters of movement space. Therefore, we investigated whether another, newly-developed test, based on the Berg balance test, could be an alternative to the TUG test.

METHODS

We enrolled a total of 99 eligible subjects out of 105 elderly patients with disorders such as Alzheimer disease, Parkinson disease, cerebral infarction, osteoporosis and vascular risk factors, and administered the TUG test and the newly-developed standing and balance test (SBT). Of these 99, 6 patients could not stand independently. While the time to accomplish TUG was determined, any unsteadiness during TUG was also recorded. The SBT consists of 3 components: standing up independently, standing on a narrow base for 15 seconds without any swaying of the trunk, and a timed one-leg standing test (TOLS) for 15 seconds on both sides. Taking more than 14 seconds to accomplish the TUG or abnormal unsteadiness during the test was defined as positive, and each cut-off point was measured on the TOLS, with or without swaying of the trunk.

RESULTS

The time to accomplish TUG significantly increased with age, and positive TUG findings were observed in 43 subjects. The mean TOLS time significantly and suddenly worsened at over 75 years of age, including among those subjects who showed swaying of the trunk and who could only perform the TOLS for less than 1 second. The receiver operating curve indicated that a TOLS cut-off point of less than 3 seconds, together with standing with help or swaying of the trunk during the SBT, most efficiently determined a positive TUG score, with high sensitivity (86%), high specificity (87.5%), and a high positive predictive value (84.1%).

CONCLUSION

In a narrow space, the SBT can adequately determine gait and balance abnormalities among elderly patients, indicating it to be an alternative to the TUG test. Subjects who could stand dependently, who showed swaying of the trunk in SBT, or who had a TOLS cut-off point of less than 3 seconds, were at high risk for falls. Further assessment of similar patients is necessary.

Age-related changes in the topological architecture of the brain during hand grip

Neuroanatomical changes in the aging brain are widely distributed rather than focal. We investigated age-related changes in large-scale functional brain networks by applying graph theory to functional magnetic resonance imaging data acquired during a simple grip task with either dominant or nondominant hand. We measured the effect of age on efficiency of information transfer within a series of hierarchical functional networks composed of the whole brain or component parts of the whole brain. Global efficiency was maintained with aging during dominant hand use, primarily due to increased efficiency in parietal-occipital-cerebellar-related networks. During nondominant hand use, global efficiency, as well as efficiency within ipsilateral hemisphere and between hemispheres declined with age. This was attributable largely to frontal-temporal-limbic-cerebellar-related networks. Increased efficiency with age was seen in networks involving parietal-occipital regions, but unlike for dominant hand use, this topological reconfiguration could not maintain the level of global efficiency. Here, graph theoretical approaches have demonstrated both compensatory and noncompensatory changes in topological configuration of large-scale networks during aging depending on the task.

Synergistic effects of age and stress in a rodent model of stroke

Ageing and stress represent critical influences on stroke risk and outcome. These variables are intricately linked, as ageing is frequently associated with gradual dysregulation of the hypothalamic-pituitary-adrenal axis. This study determined the effects of stress on motor function in aged rats, and explored possible interactions of age and stress on motor recovery following stroke in a rat model. Young adult (4 months) and aged (18 months) male Wistar rats were tested in skilled and non-skilled movement before and after focal ischemia in motor cortex. One group of each age received restraint stress starting seven days pre-lesion until three weeks post-lesion. Aged rats were less mobile and stress further diminished their overall exploratory activity. Aged rats were also less proficient in motor skill acquisition and slower to improve after lesion. Stress diminished post-lesion improvement and prevented recovery of endpoint measures. The larger functional loss in aged rats vs. young rats was accompanied by greater damage of cortical tissue and persistent elevations in corticosterone levels. The behavioural and physiological measures suggest limited ability of aged animals to adapt to chronic stress. These findings show that age or stress alone can modulate motor performance but may have greater influence by synergistically affecting stroke recovery.

Outcomes before and after total knee arthroplasty compared to healthy adults

STUDY DESIGN

Prospective cohort study.

OBJECTIVES

To measure changes in muscle strength, range of motion, and function from 2 weeks before to 6 months after total knee arthroplasty (TKA) and compare outcomes with data from a control group consisting of healthy adults.

BACKGROUND

Total knee arthroplasty successfully alleviates pain from knee osteoarthritis, but deficits in function can persist long term. How impairments and functional limitations change over the first 6 months after TKA, compared to data from healthy adults, has not been well reported in the literature.

METHODS

Twenty-four patients who underwent a primary unilateral TKA were compared to healthy adults (n = 17). All patients participated in a standardized rehabilitation program following surgery. Isometric quadriceps torque was assessed using an electromechanical dynamometer. Range of motion was measured actively and passively. Functional performance was assessed using the stair-climbing test, timed up-and-go test, 6-minute walk test, and single-limb stance time. Patients underwent testing at 2 weeks preoperatively and at 1, 3, and 6 months postoperatively.

RESULTS

Compared to healthy older adults, patients performed significantly worse at all times for all measures (P<.05), except for single-limb stance time at 6 months (P>.05). One month postoperatively, patients experienced significant losses from preoperative levels in all outcomes. Patients recovered to preoperative levels by 6 months postoperatively on all measures, except knee flexion range of motion, but still exhibited the same extent of limitation they did prior to surgery.

CONCLUSION

The persistent impairments and functional limitations 6 months after TKA with standard rehabilitation suggest that more intensive therapeutic approaches may be necessary to restore function of patients following TKA to the levels of healthy adults.

Screening for falls and osteoporosis: prevention practice for the hand therapist

Fractures of the upper extremity are considered a hallmark of underlying osteopenia or osteoporosis and strong predictors of subsequent fractures. Falling is the strongest single risk factor for fractures in older adults. Studies have shown that interventions to prevent falls can significantly reduce this risk factor. Hand therapists working with patients with an upper extremity injury from a fall cannot assume that screening for osteoporosis or the likelihood of falls has been addressed by other health care professionals. The purposes of this article are to 1) summarize osteoporosis and falls risk screening, 2) describe how fall prevention strategies can be integrated into hand therapy practice, and 3) present evidence for federal and professional organizational support of prevention practice.

One-leg standing test for elderly populations

BACKGROUND

The one-leg standing (OLS) test is one of the balance tests used to diagnose musculoskeletal ambulation disability symptom complex (MARS), a condition newly defined by three professional Japanese medical societies in 2006 to help identify the symptoms of motor organ deterioration and establish preventive strategies. Although many studies have used the OLS test, none has shown conclusively that the test can be used as a practical marker of frailty among elderly people, especially in community settings. Based on the type of epidemiological study -- i.e., descriptive epidemiology and analytical epidemiology (observational and intervention studies) -- we reviewed evidence on three fundamental issues related to the OLS test: (1) testing procedures and reference values; (2) the associations between the OLS time and negative events; (3) improvement of the OLS time by intervention. These issues are key to any discussion of whether the OLS test can be used as a practical marker for predicting frailty in community-dwelling elderly populations.

METHODS

Articles were collected from MEDLINE databases using the search terms "one- leg standing" and the other names included in the same category.

RESULTS

Because various procedures are used to carry out the OLS test, the measured values for the OLS time varied widely from study to study. Some observational studies showed that the OLS time is related to negative events such as falls, declines in activity of daily living, and other morbidity. OLS times could be improved by several interventions.

CONCLUSIONS

This review suggests that the OLS test can be a tool for predicting frailty in community-dwelling elderly populations. However, our review should be interpreted with caution because we did not confirm the evidence level of each of the studies we selected. Further research on this topic is needed.

Frontal plane ankle proprioceptive thresholds and unipedal balance

Reliable unipedal balance is fundamental to safe ambulation. Accordingly, older persons with peripheral neuropathy (PN), who are at increased risk for falls, demonstrate impaired unipedal balance. To explore the relationship between afferent function and unipedal balance, frontal plane proprioceptive thresholds at the ankle were quantified in 22 subjects (72.5 +/- 6.3 years; 11 with PN and 11 matched controls) while they were standing using a foot cradle system and a staircase series of 100 rotational stimuli. PN subjects, as compared to controls, demonstrated shorter median unipedal balance times (3.4 +/- 2.7 vs. 14.3 +/- 8.9 s; P = 0.0017) and greater (less precise) combined ankle inversion/eversion proprioceptive thresholds (1.17 +/- 0.36 vs. 0.65 +/- 0.37 degrees ; P = 0.0055). Combined ankle inversion/eversion proprioceptive thresholds explained approximately half the variance in unipedal balance time (R2 = 0.5138; P = 0.0004). Given prior work demonstrating a similarly strong relationship between ankle torque generation and unipedal balance, neuropathy-associated impairments in ankle frontal plane afferent and efferent function appear to be equally responsible for the inability of older persons with PN to reliably balance on one foot. They therefore provide distinct targets for intervention.

Aging of the striatum: mechanisms and interventions

Motor function declines with increasing adult age. Proper regulation of the balance between dopamine (DA) and acetylcholine (ACh) in the striatum has been shown to be fundamentally important for motor control. Although other factors can also contribute to this age-associated decline, a decrease in the concentration and binding potential of the DA D(2) receptor subtype in the striatum, especially in the cholinergic interneurons, are involved in the mechanism. Our studies have shown that gene transfer of the DA D(2) receptor subtype with adenoviral vectors is effective in ameliorating age-associated functional decline of the striatal cholinergic interneurons. These achievements confirm that an age-associated decrease of D(2)R contributes functional alteration of the interaction of DA and ACh in the striatum and demonstrate that these age-associated changes indeed are modifiable.

Diabetic neuropathy in older adults

Diabetic neuropathy is a heterogeneous disease with diverse pathology. Recognition of the clinical homolog of these pathologic processes is necessary in achieving appropriate intervention. Treatment should be individualized so the particular manifestation and underlying pathogenesis of each patient's clinical presentation are considered. In older adults, special care should be taken to manage pain while optimizing daily function and mobility, with the fewest adverse medication side effects. Older adults are at great risk for falling and fractures because of instability and weakness, and require strength exercises and coordination training. Ultimately agents that address large fiber dysfunction will be essential to reduce the gross impairment of quality of life and activities of daily living that neuropathy visits older people who have diabetes.

Age-dependent changes in the neural correlates of force modulation: an fMRI study

Functional imaging studies in humans have demonstrated widespread age-related changes in cortical motor networks. However, the relative contribution of cortical regions during motor performance varies not only with age but with task parameters. In this study, we investigated whether motor system activity during a task involving increasingly forceful hand grips was influenced by age. Forty right-handed volunteers underwent functional magnetic brain imaging whilst performing repetitive isometric hand grips with either hand in separate sessions. We found no age-related changes in the average size and shape of the task-related blood oxygen level dependent (BOLD) signal in contralateral primary motor cortex (M1), but did observe reduced ipsilateral M1 deactivation in older subjects (both hands). Furthermore, task-related activity co-varied positively with force output in a number of brain regions, but was less prominent with advancing age in contralateral M1, cingulate sulcus (both hands), sensory and premotor cortices (right hand). These results indicate that a reduced ability to modulate activity in appropriate motor networks when required may contribute to age-related decline in motor performance.

Comparison of different structural foot types for measures of standing postural control

STUDY DESIGN

Matched group comparison of 3 subject groups with 3 different foot structures for force plate and clinical measures of postural control.

OBJECTIVES

To determine if subjects with different weight-bearing foot structure would demonstrate differences in static standing postural control, and to determine the reliability of study procedures.

BACKGROUND

Weight-bearing foot structure may influence postural control either because of a decreased base of support (supinated foot structure) or because of passive instability of the joints of the foot (pronated foot structure).

METHODS AND MEASURES

Young adults were categorized based on weight-bearing foot structure into neutral, pronated, or supinated groups (15 subjects per group). Postural control in single-limb stance with eyes closed was assessed using force plate measures and by measuring duration of single-limb stance on a firm floor and on a balance pad. Force plate measures were normalized center-of-pressure average speed; and standard deviation and maximum displacement in the anterior-posterior and medial-lateral directions.

RESULTS

Individuals in the supinated group had significantly greater center-of-pressure average speed, greater maximum displacement in the anterior-posterior direction, and greater SD and maximum displacement in the medial-lateral direction than individuals in the neutral group. The individuals in the pronated group had significantly greater SD and maximum displacement in the anterior-posterior direction, used more trials to complete force plate testing, and had shorter single-limb stance duration than those in the neutral group.

CONCLUSION

Individuals with pronated feet or supinated feet have poorer postural control than individuals with neutral feet, but perhaps through different mechanisms.

Original investigation correlated joint fluctuations can influence the selection of steady state gait patterns in the elderly

This investigation utilized a Markov model to investigate the relationship of correlated lower extremity joint fluctuations and the selection of a steady state gait pattern in the young and elderly. Our model simulated the neuromuscular system by predicting the behavior of the joints for the next gait cycle based on the behavior exhibited in the preceding gait cycles. Such dependencies in the joint fluctuations have been noted previously in the literature. We speculated that compared to the young model, the characteristics of the correlated fluctuations in the elderly model would result in the selection of a different steady state gait pattern. The results of our simulation support the notion that correlated fluctuations in the joint kinematics influence the selection of a steady state gait pattern. The steady state gait pattern for the elderly model was dependent the ankle and hip. Conversely, the steady state gait pattern for the young control model was dependent on the behavior of the knee and hip. Based on our model, we suggested that the altered steady state gait patterns observed in the elderly may be due to an altered neuromuscular memory of prior joint behaviors.

Quantitative measurement of handwriting in the assessment of drug-induced parkinsonism

Monitoring drug-induced side effects is especially important for patients who undergo treatment with antipsychotic medications, as these drugs often produce extrapyramidal side effects (EPS) resulting in movement abnormalities similar to parkinsonism. Scientists have developed several objective laboratory tests to measure and research drug-induced movement disorders, but equipment and tests are complex and costly and have not become accepted in large-scale, multi-site clinical trials. The goals of this study were to test whether a simple handwriting measure can discriminate between individuals with psychotropic-induced parkinsonism, Parkinson's disease, and healthy individuals, and to examine some of the psychometric properties of the measure. We examined pen movement kinematics during cursive writing of a standard word in 13 patients with idiopathic Parkinson's disease (PD), 10 schizophrenia patients with drug-induced parkinsonism (SZ), and 12 normal healthy control participants (NC). Participants were instructed to write the word "hello" in cursive twice, at three vertical height scales. Software was used for data acquisition and analysis of vertical stroke velocities, velocity scaling, and smoothness. There were four important results from this study: (1) both SZ patients with drug-induced EPS and PD participants exhibited impaired movement velocities and velocity scaling; (2) performance on the velocity scaling measure distinguished drug-induced EPS from normal with 90% accuracy; (3) SZ, but not PD participants displayed abnormalities in movement smoothness; and (4) there was a positive correlation between age and magnitude of the velocity scaling deficit in PD participants. This study demonstrates that kinematic analyses of pen movements during handwriting may be useful in detecting and monitoring subtle changes in motor control related to the adverse effects of psychotropic medications.

Compensatory mechanisms in the aging motor system

Motor functions decline with age due to a number of factors. There is interest in whether these changes are reflected in the organisation of the cerebral motor system in older subjects and whether such changes might be in some way compensatory. Most studies in humans have used functional brain imaging techniques to compare motor system activation in younger and older subjects. Interpretation of these results is made more difficult by potential neurovascular changes in older subjects. However, in general, there appears to be greater motor task-related brain activity in a wider network of brain regions in older compared to younger subjects. The evidence that these changes are compensatory in nature is less clear. Incorporation of behavioural and anatomical data will be required in order to fully interpret the functional imaging results.

Effects of aging and hormonal status on bimanual motor coordination in the rhesus monkey

Studies of age-related changes in motor function in nonhuman primates have been based exclusively on unimanual motor tasks. In this study, we examined whether aging affects bimanual motor coordination in the monkey model. In addition, we compared performance of ovariectomized and intact females on the task, to examine whether estrogen deficiency impairs motor function. The task required 29 rhesus monkeys (6-26 years old) to extract a maximum of 15 raisins from a testing hole-board. While the task could most efficiently be performed with two hands, other motor strategies were possible. The number of raisins extracted per minute was measured in each of eight sessions, the first and last of which were videotaped for analysis of motor patterns. The number of raisins retrieved per minute declined significantly with age. All monkeys improved with practice, but aged monkeys improved more slowly than young ones. The proportion of bimanual actions tended to increase between the first and the last sessions but was not significantly different between young and aged monkeys. Hormonal status did not affect performance. Finally, performance on the bimanual task was significantly correlated with performance on a previously administered unimanual motor test emphasizing speed, suggesting that age-related motor slowing may explain deficits in both tasks.

Morphometric evaluation of posterior funiculus nerve fibers in relation to aging

We morphologically evaluated the size of axons in the posterior funiculus in different age groups and examined the changes due to aging. In the past, such studies have been conducted at the cervical spinal cord (C6) level, and a decrease in the size and number of axons due to aging has been noted. The current study was conducted at the lower lumbar spinal cord (L2) level.

Relationship between hip abductor rate of force development and mediolateral stability in older adults

OBJECTIVE

To examine the relationship between hip abductor rate of force development (RFD) and performance of reactive and voluntary balance tasks in older adults.

DESIGN

Descriptive study using correlation and regression analyses.

SETTING

University research laboratory.

PARTICIPANTS

A volunteer sample of 30 community-dwelling men and women over the age of 65 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Measures of hip abductor RFD, center of pressure (COP) displacement during compensatory stepping, and scores on 1-leg standing (OLS), and tandem gait tests. Hip abductor RFD was defined as the time required to go from 10% of maximum force to 60% of maximum force (10%-60% RFD) or to 90% of maximum force (10%-90% RFD).

RESULTS

Hip abductor RFD did not correlate with COP displacement during compensatory stepping, but did correlate significantly with OLS and tandem gait variables (P<.05). In predicting OLS scores, age (beta=-.485, P<.05) and 10% to 60% RFD (beta=-.354, P<.05) were significant predictors. In predicting tandem gait scores, 10% to 90% RFD (beta=.384, P<.05) was the only significant predictor in the final regression model.

CONCLUSIONS

Hip abductor RFD, tested under voluntary conditions, correlated with performance of clinical tests that challenge lateral stability. Our results support the idea that voluntary and reactive balance tasks involve different types of neuromuscular control.

Norms for 15- to 34-year-olds for different versions of the finger-to-nose test

OBJECTIVES

To develop norms for the time to execute different versions of the finger-to-nose test (FNT) and to determine the effects of different testing procedures on performance in people aged 15 to 34 years.

DESIGN

Cross-sectional.

SETTING

Research center.

PARTICIPANTS

Healthy subjects (149 men, 148 women; age range, 15-34 y) participated, and 36 men and 36 women were included in each of the 4 age categories studied (15-19 y, 20-24 y, 25-29 y, 30-34 y). Participants performed, in random order, 5 forms of the test in 2 positions (sitting, supine) with the right and left upper limbs (ULs).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

Time (in seconds) to complete 5 cycles of movement.

RESULTS

Test version and side of UL were found to affect performances; right-sided performances were faster than left-sided. Performances did not vary significantly (P>.001) with sex or among age categories; therefore, the results are presented for the group. Mean performances varied from 3.44 to 4.29 seconds. Subsequent analysis of variance (with data for each UL) showed main effects for testing position (sitting > lying) and eye condition (eyes open > eyes closed). Versions were strongly interrelated (.85<r<.98).

CONCLUSIONS

Norms for the time to execute different FNT versions were developed for both ULs for healthy people ages 15 to 34 years.

Differences in multi-joint kinematic patterns of repetitive hammering in healthy, fatigued and shoulder-injured individuals

BACKGROUND

Work-related musculo-skeletal disorders have been previously related to movement repetition, inadequate postures, non-ergonomic environments, muscular imbalance and fatigue. However, no direct link between fatigue and injury has been experimentally shown. To address this problem, we compared the effects of fatigue and injury on the kinematics of repetitive hammering.

METHODS

Healthy subjects (n=30) hammered repetitively both before and after fatigue. Fatigue was induced by a combination of static and dynamic procedures. Shoulder-injured subjects (n=15) hammered for 30s without fatigue. Kinematics of motion was recorded.

FINDINGS

The movement time and shoulder range of motion during hammering were not affected by either fatigue or shoulder injury. When fatigued, the healthy subjects displayed decreased range of joint motion, peak velocity and peak acceleration of elbow motion during hammering as well as reduced grip strength. Shoulder-injured individuals had a smaller hammer trajectory amplitude than healthy controls with or without fatigue. They also had lower wrist range of motion, elbow peak velocity, and peak wrist and elbow acceleration compared to healthy subjects hammering without fatigue but only lower wrist peak acceleration compared to healthy subjects hammering with fatigue.

INTERPRETATION

Results showed that fatigue affects elbow motion while shoulder injury affects both wrist and elbow motions during hammering. However, shoulder kinematics were not changed by either fatigue or shoulder injury. These changes at the wrist and elbow may reflect strategies used by individuals with shoulder injury to maintain constant movement duration and shoulder kinematics during movement.

Sex differences in age-related motor slowing in the rhesus monkey: behavioral and neuroimaging data

The nigrostriatal system is critical for fine motor function and its deterioration during aging is thought to underlie the decline in fine manual ability of old persons. Because estrogen has a neuroprotective effect on this system, one might expect women's motor function to be less vulnerable to the detrimental effects of aging than that of men. We examined this hypothesis in the rhesus monkey, which has been established as an excellent model of human age-related motor impairment. We tested 28 young and old rhesus monkeys of both sexes in a task involving the retrieval of a Life Saver candy from rods of different complexity to determine whether fine motor ability (1) is sexually dimorphic, (2) declines with age and (3) declines differently in males and females. In addition, we measured the whole brain volume, the volumes of the caudate, putamen, hippocampal formation and the area of the corpus callosum in a subset of the monkeys (n=15) for which magnetic resonance images of the brain were available. All monkeys performed similarly in the test with the simplest rod. In the test with complex rods; however, age-related slowing of motor function was evident in males, but not in females. Age-related decreases in the normalized caudate and putamen volumes were similar in males and in females. In addition, motor speed was not significantly correlated to any of the neuroanatomical measures under study. Further studies will be necessary to uncover the neurohormonal bases of the differential age-related motor decline between males and females.

The aging human neuromuscular system expresses less certainty for selecting joint kinematics during gait

This investigation quantitatively characterized the certainty of the aging neuromuscular system in selecting a joint range of motion during gait based on the statistical concept of entropy. Elderly and young control groups walked on a treadmill at a self-selected pace. Joint angles were calculated for the ankle, knee and hip. We hypothesized that the aging group would exhibit less certainty in selecting a joint range of motion during gait. Our results supported this hypothesis, and indicated that aged individuals demonstrated statistically less certainty for the knee (16.8%) and hip (24.6%). We suggest that neurophysiological changes associated with aging may result in less certainty of the neuromuscular system in selecting a stable gait.

Effects of estradiol and aging on fine manual performance in female rhesus monkeys

Aging is characterized by a progressive deterioration of motor function related to dysfunctions of the nigrostriatal system. Because estrogen has been reported to protect dopaminergic neurons and to improve the motor deficits associated with Parkinson's disease, we hypothesized that it would partially reverse the age-related decline of motor function in normal aging. We tested the effects of estrogen treatment and withdrawal on fine motor performance in five aged (21-24 years old) and five young (6-9 years old) ovariectomized female rhesus monkeys. The tests required the monkeys to use each hand to retrieve a Life Saver candy from metal rods bent in shapes of different complexity. Monkeys were tested twice a week for 8 consecutive weeks, during treatment with placebo or ethinyl estradiol (EE(2)) in alternating 14-day blocks. Each behavioral test was videotaped and subsequently scored for the duration and the success of the first trial on each shape. Both groups of monkeys improved rapidly with practice in speed and success of retrieval. The older monkeys were slower but as successful as the young monkeys in retrieving the candy. The left hand was faster than the right hand for both the aged and young females. We failed to detect any effect of EE(2) treatment on speed or success of retrieval in either group. These results confirm the slowing of fine motor performance with aging in female rhesus monkeys. They also indicate that estradiol, at least as administered in this study, does not benefit fine manual performance.

Age-related changes in grip force and dynamics of hand movement

The authors investigated whether older adults (n = 16; mean age = 65 years) increased grip force to compensate for load force fluctuations during up and down movements more than young adults did (n = 16; mean age = 24 years) and whether older and young adults exhibited similar adaptation of grip force to alterations in friction associated with changes in object surface texture. As previously reported, older adults used a higher level of grip force than young adults during static holding. Increased grip force was observed in the older group during movement. The increase was appropriate to the lower coefficient of friction estimated for the older group. In both groups, grip force was greater with a smooth than with a rough surface (the latter having the higher coefficient of friction) during static holding and during movement. Moreover, grip force modulation was equally well synchronized with load force fluctuation during movement in the two groups. The authors concluded that changes in organization of grip force with age are well adapted to change in hand-object interface properties. Elevated grip force in older adults does not necessarily signify a fundamental change in synchronizing grip force modulation with load force fluctuation.