Group Of Healthy Older Adults Research Articles

The impact of hearing aids and age-related hearing loss on auditory plasticity across three months – An electrical neuroimaging study

The present study investigates behavioral and electrophysiological auditory and cognitive-related plasticity in three groups of healthy older adults (60–77 years). Group 1 was moderately hearing-impaired, experienced hearing aid users, and fitted with new hearing aids using non-linear frequency compression (NLFC on); Group 2, also moderately hearing-impaired, used the same type of hearing aids but NLFC was switched off during the entire period of study duration (NLFC off); Group 3 represented individuals with age-appropriate hearing (NHO) as controls, who were not different in IQ, gender, or age from Group 1 and 2. At five measurement time points (M1-M5) across three months, a series of active oddball tasks were administered while EEG was recorded. The stimuli comprised syllables consisting of naturally high-pitched fricatives (/sh/, /s/, and /f/), which are hard to distinguish for individuals with presbycusis. By applying a data-driven microstate approach to obtain global field power (GFP) as a measure of processing effort, the modulations of perceptual (P50, N1, P2) and cognitive-related (N2b, P3b) auditory evoked potentials were calculated and subsequently related to behavioral changes (accuracy and reaction time) across time.All groups improved their performance across time, but NHO showed consistently higher accuracy and faster reaction times than the hearing-impaired groups, especially under difficult conditions. Electrophysiological results complemented this finding by demonstrating longer latencies in the P50 and the N1 peak in hearing aid users. Furthermore, the GFP of cognitive-related evoked potentials decreased from M1 to M2 in the NHO group, while a comparable decrease in the hearing-impaired group was only evident at M5. After twelve weeks of hearing aid use of eight hours each day, we found a significantly lower GFP in the P3b of the group with NLFC on as compared to the group with NLFC off.These findings suggest higher processing effort, as evidenced by higher GFP, in hearing-impaired individuals when compared to those with normal hearing, although the hearing-impaired show a decrease of processing effort after repeated stimulus exposure. In addition, our findings indicate that the acclimatization to a new hearing aid algorithm may take several weeks.

Characterising omission errors in everyday task completion and cognitive correlates in individuals with mild cognitive impairment and dementia

ABSTRACTObjective: Functional ability declines with age and cognitive impairment. This study investigated errors of omission made by community-dwelling older adults completing everyday tasks in a naturalistic setting.Method: Sixty-five cognitively healthy older adults (HOA), 19 individuals with single domain mild cognitive impairment (sdMCI), 33 individuals with multi-domain MCI (mdMCI), and 13 individuals with dementia completed measures of memory, processing speed, working memory, and executive functioning, as well as eight different activities of daily living in a naturalistic environment. Task steps were divided into preparatory, action-oriented, and concluding steps.Results: For action-oriented steps, the number of omission errors increased with level of cognitive impairment beyond sdMCI (i.e., HOA = sdMCI < mdMCI < dementia). In contrast, for preparatory and concluding steps, the dementia group committed more omission errors than the HOA, sdMCI, and mdMCI groups, which did not differ.Conclusions: The results suggest that the more complex and integrative action-oriented steps may be the first type of everyday task step to be affected in the process of cognitive decline, with preparatory and concluding steps being preserved longer and only showing decline in later stages of impairment (i.e., dementia). Individuals with sdMCI may use other intact abilities to compensate for task omission errors.

Computerized Dual-Task Testing of Gait and Visuospatial Cognitive Functions; Test-Retest Reliability and Validity.

The common occurrence of age decline in mobility and cognition does cause a decrease in the level of physical activity and an increased falls risk. Consequently, dual -task (DT) assessment that simultaneously addresses both mobility skills and cognitive functions are important because, continued difficulties and fall injuries will have a sizable impact in this population. The first objective of the present study was to assess test-retest reliability of a computerized DT treadmill walking protocol and concurrent outcome measures of gait and visuospatial executive function in a group of healthy older adults. Secondly, discriminative validity was evaluated by examining the effect of DT conditions (single task vs. dual-task) on; (a) spatiotemporal gait measures (average and coefficient of variation) and (b) visuomotor and visuospatial executive performance measures. Twenty-five community-dwelling individuals median age 65 (range 61–67) were recruited from a Fitness Facility. Participants performed a computerized visuomotor tracking task and a visuospatial executive game task in standing and while treadmill walking. Testing was conducted on two occasions, 1 week apart. Moderate to high test-retest reliability (ICC values of 0.65–0.88) were observed for spatiotemporal gait variables. No significant differences between the group means were observed between test periods in any gait variable. Moderate test-retest reliability (ICC values of 0.6–0.65) was observed for measures of visuomotor and visuospatial executive performance during treadmill walking. Significant DT effects were observed for both spatiotemporal gait variables and visuospatial executive performance measures. This study demonstrates the reliability and reproducibility of the computer-based assessment tool for dual task treadmill walking. The high to moderate ICC values and the lack of systematic errors in the measures indicate that this tool has the ability to repeatedly record reliable data from community-dwelling older adults. The present computerized dual-task protocols broaden the types of standardized visuomotor and visuospatial executive activities for use with DT treadmill walking that has previously been reported.

P289 Induction of neuronal plasticity by transcranial direct current stimulation in healthy older adults

Introduction Transcranial direct current stimulation (tDCS) has emerged as an efficient tool to enhance cognitive functioning in young as well as older adults. The underlying neuronal mechanisms, however, are still insufficiently understood. Especially studies investigating neuronal correlates of tDCS-induced plasticity in healthy older adults are rare. Objectives The objective of the study was to investigate the mechanisms underlying tDCS-induced neuronal modulation in a group of healthy older adults. In particular, alterations in resting state functional connectivity within the motor network as well as GABA concentration within the primary motor cortex were examined. Materials and methods In this study, we assessed the effects of anodal, cathodal, and sham tDCS over the left primary motor cortex on functional connectivity of the motor network and GABA concentration in a group of healthy older adults. Stimulation of 1 mA was applied for 15 min with anodal or cathodal polarity; for 30 s in sham stimulation. The three stimulation conditions were separated by at least one week and their order was counterbalanced across the group. GABA concentration was assessed by MRS using MEGA-PRESS at 3 T before and after the stimulation interval. Resting-state fMRI scans were obtained twice during stimulation, separated by a break of 3 min. Results In line with previous studies with young adults, GABA concentration change was lower in the anodal tDCS condition as compared to the sham tDCS condition. Resting state motor networks showed a reduced inter-hemispheric functional connectivity between left and right primary motor cortices during anodal tDCS compared to cathodal and sham tDCS. This observation is consistent with results in young and older adults that have assessed tDCS-induced alterations of inter-hemispheric functional connectivity during resting-state fMRI. Conclusion Our study demonstrates tDCS-induced neuronal plasticity in healthy older adults. This observed reorganization of the functional architecture of the motor cortex is in line with recent tDCS studies in young adults, however, research results are still heterogeneous. In sum, our data suggests that anodal tDCS induced a functional decoupling of motor cortices, indicating a reversal of age-related effects on inter-hemispheric connectivity.

Frontal Structural Neural Correlates of Working Memory Performance in Older Adults.

Working memory is an executive memory process that allows transitional information to be held and manipulated temporarily in memory stores before being forgotten or encoded into long-term memory. Working memory is necessary for everyday decision-making and problem solving, making it a fundamental process in the daily lives of older adults. Working memory relies heavily on frontal lobe structures and is known to decline with age. The current study aimed to determine the neural correlates of decreased working memory performance in the frontal lobes by comparing cortical thickness and cortical surface area from two demographically matched groups of healthy older adults, free from cognitive impairment, with high versus low N-Back working memory performance (N = 56; average age = 70.29 ± 10.64). High-resolution structural T1-weighted images (1 mm isotropic voxels) were obtained on a 3T Philips MRI scanner. When compared to high performers, low performers exhibited significantly decreased cortical surface area in three frontal lobe regions lateralized to the right hemisphere: medial orbital frontal gyrus, inferior frontal gyrus, and superior frontal gyrus (FDR p < 0.05). There were no significant differences in cortical thickness between groups, a proxy for neurodegenerative tissue loss. Our results suggest that decreases in cortical surface area (a proxy for brain structural integrity) in right frontal regions may underlie age-related decline of working memory function.

Rest-Activity Patterns in Older Adults with Heart Failure and Healthy Older Adults.

The purpose of this investigation is to examine differences in rest-activity patterns and sleep characteristics in older adults with heart failure (HF) and healthy older adults. The sample included older adults with HF (n = 20) and a reference group of healthy older adults (n = 20). Traditional cosinor analysis was used to assess three parameters of rest-activity from wrist actigraphy data: amplitude (range of activity), mesor (mean activity), and acrophase (time of peak activity). Traditional sleep characteristics were also determined from actigraphy data: total sleep time (TST), sleep latency (SL), sleep efficiency (SE), and wake after sleep onset (WASO). The HF group demonstrated significantly lower mesor and amplitude than the reference group (p < .01). The HF group had significantly greater TST (p < .01), but the groups had similar SE, SL, and WASO. Despite similar sleep characteristics to healthy older adults, overall rest-activity patterns were significantly dampened in those with HF.

Constraining eye movement in individuals with Parkinson's disease during walking turns.

Walking and turning is a movement that places individuals with Parkinson's disease (PD) at increased risk for fall-related injury. However, turning is an essential movement in activities of daily living, making up to 45% of the total steps taken in a given day. Hypotheses regarding how turning is controlled suggest an essential role of anticipatory eye movements to provide feedforward information for body coordination. However, little research has investigated control of turning in individuals with PD with specific consideration for eye movements. The purpose of this study was to examine eye movement behavior and body segment coordination in individuals with PD during walking turns. Three experimental groups, a group of individuals with PD, a group of healthy young adults (YAC), and a group of healthy older adults (OAC), performed walking and turning tasks under two visual conditions: free gaze and fixed gaze. Whole-body motion capture and eye tracking characterized body segment coordination and eye movement behavior during walking trials. Statistical analysis revealed significant main effects of group (PD, YAC, and OAC) and visual condition (free and fixed gaze) on timing of segment rotation and horizontal eye movement. Within group comparisons, revealed timing of eye and head movement was significantly different between the free and fixed gaze conditions for YAC (p<0.001) and OAC (p<0.05), but not for the PD group (p>0.05). In addition, while intersegment timings (reflecting segment coordination) were significantly different for YAC and OAC during free gaze (p<0.05), they were not significantly different in PD. These results suggest individuals with PD do not make anticipatory eye and head movements ahead of turning and that this may result in altered segment coordination during turning. As such, eye movements may be an important addition to training programs for those with PD, possibly promoting better coordination during turning and potentially reducing the risk of falls.

Alterations in whole-body arginine metabolism in chronic obstructive pulmonary disease1–3

Chronic obstructive pulmonary disease (COPD) is a condition characterized by systemic low-grade inflammation that could increase the production of nitric oxide (NO), of which arginine is the sole precursor. Arginine is derived from the breakdown of protein and through the conversion of citrulline to arginine (de novo arginine production). Our objective was to study whole-body arginine and citrulline and related metabolism in stable COPD patients. With the use of stable isotope methodology, we studied whole-body arginine and citrulline rates of appearance, de novo arginine (citrulline-to-arginine flux) and NO (arginine-to-citrulline flux) production, protein synthesis and breakdown rates, and plasma amino acid concentrations in a heterogeneous group of patients with moderate-to-severe COPD [n = 23, mean ± SE age: 65 ± 2 y, forced expiratory volume in 1 s (FEV1): 40% ± 2% of predicted], and a group of healthy older adults (n = 19, mean ± SE age: 64 ± 2 y, FEV1: 95% ± 4% of predicted). Although plasma arginine and citrulline concentrations were comparable between COPD patients and controls, whole-body arginine (P = 0.015) and citrulline (P = 0.026) rates of appearance were higher in COPD patients and related to a 57% greater de novo arginine production (P < 0.0001). Despite a higher whole-body arginine clearance in COPD patients (P < 0.0001), we found no difference in NO production. In stable patients with moderate-to-severe COPD, endogenous arginine production is upregulated to support a higher arginine utilization that is unrelated to whole-body NO production. This trial was registered at clinicaltrials.gov as NCT01173354 and NCT01172314.

The Contribution of Prospective Memory Performance to the Neuropsychological Assessment of Mild Cognitive Impairment

Objective: Prospective memory difficulties are a feature of the amnestic form of mild cognitive impairment (aMCI). Although comprehensive test batteries of prospective memory are suitable for clinical practice, they are lengthy, which has detracted from their widespread clinical use. Our aim was to investigate the utility of a brief screening measure of prospective memory, which can be incorporated into a clinical neuropsychological assessment. Methods: Seventy-seven healthy older adults (HOA) and 77 participants with aMCI were administered a neuropsychological test battery, including a prospective memory screening measure (Envelope Task), a retrospective memory measure (CVLT-II), and a multi-item subjective memory questionnaire (Prospective and Retrospective Memory Questionnaire; PRMQ) and a single-item subjective memory scale. Results: Compared with HOA participants, participants with aMCI performed poorly on the Envelope Task (η2 = .38), which provided good discrimination of the aMCI and HOA groups (AUC = .83). In the aMCI group, there was a small but significant relationship between the Envelope Task and the single-item subjective rating of memory, with the Envelope Task accounting for 5–6% of the variance in subjective memory after accounting for emotional status. This relationship of prospective memory and subjective memory was not significant for the multi-item questionnaire (PRMQ); and, retrospective memory was not a significant predictor of self-rated memory, single-item, or multi-item. Conclusion: A brief screening measure of prospective memory, the Envelope Task, provides useful support to traditional memory measures in detecting aMCI.

Recovery of slow-5 oscillations in a longitudinal study of ischemic stroke patients.

Functional networks in resting-state fMRI are identified by characteristics of their intrinsic low-frequency oscillations, more specifically in terms of their synchronicity. With advanced aging and in clinical populations, this synchronicity among functionally linked regions is known to decrease and become disrupted, which may be associated with observed cognitive and behavioral changes. Previous work from our group has revealed that oscillations within the slow-5 frequency range (0.01–0.027 Hz) are particularly susceptible to disruptions in aging and following a stroke. In this study, we characterized longitudinally the changes in the slow-5 oscillations in stroke patients across two different time-points. We followed a group of ischemic stroke patients (n = 20) and another group of healthy older adults (n = 14) over two visits separated by a minimum of three months (average of 9 months). For the stroke patients, one visit occurred in their subacute window (10 days to 6 months after stroke onset), the other took place in their chronic window (> 6 months after stroke). Using a mid-order group ICA method on 10-minutes eyes-closed resting-state fMRI data, we assessed the frequency distributions of a component's representative time-courses for differences in regards to slow-5 spectral power. First, our stroke patients, in their subacute stage, exhibited lower amplitude slow-5 oscillations in comparison to their healthy counterparts. Second, over time in their chronic stage, those same patients showed a recovery of those oscillations, reaching near equivalence to the healthy older adult group. Our results indicate the possibility of an eventual recovery of those initially disrupted network oscillations to a near-normal level, providing potentially a biomarker for stroke recovery of the cortical system. This finding opens new avenues in infra-slow oscillation research and could serve as a useful biomarker in future treatments aimed at recovery.

Strategies for improving memory: a randomized trial of memory groups for older people, including those with mild cognitive impairment.

Governments are promoting the importance of maintaining cognitive health into older age to minimize risk of cognitive decline and dementia. Older people with amnestic mild cognitive impairment (aMCI) are particularly vulnerable to memory challenges in daily activities and are seeking ways to maintain independent living. To evaluate the effectiveness of memory groups for improving memory strategies and memory ability of older people, especially those with aMCI. 113 healthy older adults (HOA) and 106 adults with aMCI were randomized to a six-week memory group or a waitlist control condition. Outcome was evaluated through knowledge and use of memory strategies, memory ability (self-report and neuropsychological tests), and wellbeing. Assessments included a six-month follow-up. Using intention to treat analyses, there were intervention effects for HOA and aMCI groups in strategy knowledge (HOA: η2= 0.20; aMCI: η2= 0.06), strategy use (HOA: η2= 0.18; aMCI: η2= 0.08), and wellbeing (HOA: η2= 0.11; aMCI: η2= 0.05). There were also intervention effects in the HOA group, but not the aMCI group, in self-reported memory ability (η2= 0.06) and prospective memory tests (η2= 0.02). By six-month follow-up, gains were found on most HOA outcomes. In the aMCI group gains were found in strategy use, and by this stage, gains in prospective memory were also found. Memory groups can engage older people in techniques for maintaining cognitive health and improve memory performance, but more modest benefits are seen for older adults with aMCI.

Is Trunk Posture in Walking a Better Marker than Gait Speed in Predicting Decline in Function and Subsequent Frailty?

BackgroundMany recent guidelines and consensus on sarcopenia have incorporated gait speed and grip strength as diagnostic criteria without addressing early posture changes adopted to maintain gait speed before weakness is clinically evident. ObjectivesOlder adults are known to compensate well for declining physiological reserve through environmental modification and posture adaptation. This study aimed to analyze and identify significant posture adaptation in older adults that is required to maintain gait speed in the face of increasing vulnerability. This would be a useful guide for early posture correction exercise interventions to prevent further decline, in addition to traditional gait, balance, and strength training. DesignA community-based cross-sectional study. Setting and ParticipantsThe participants comprised 90 healthy community-dwelling Chinese men between the ages of 60 and 80 years and 20 Chinese adults between the ages of 21 and 50 years within the normal BMI range as a comparison group. MeasurementsAll the participants underwent handgrip strength testing, 6-minute walk, timed up-and-go (TUG), and motion analysis for gait characteristics. Low function was characterized by slow walking speed (<1.0 m/s) and/or slow TUG (>10 seconds), whereas low strength was determined by hand grip dynamometer testing (<26 kg). The degree of frailty was classified using the Canadian Study for Health and Ageing Clinical Frailty Scale (CSHA-CFS) to differentiate between healthy and vulnerable older adults. ResultsAs expected, the vulnerable older adults had lower functional performance and strength compared with the healthy older adults group. However, a significant number demonstrated posture adaptations in walking in all 3 groups, including those who maintained a good walking speed (>1.0 m/s). The extent of such adaptation was larger in the vulnerable group as compared with the healthy group. ConclusionAlthough gait speed is a robust parameter for screening older adults for sarcopenia and frailty, our data suggest that identifying trunk posture adaptation before the onset of decline in gait speed will help in planning interventions in the at-risk community-dwelling older adults even before gait speed declines.

Efficacy of a computerized cognitive training application on cognition and depressive symptomatology in a group of healthy older adults: A randomized controlled trial

ObjectiveThe purpose of this study was to evaluate the efficacy of a multimedia and interactive cognitive program on cognition and depressive symptomatology in healthy older adults. MethodsAdults aged ≥65 years were randomly assigned to two groups: the experimental group in which the participants received a computerized cognitive training application; and the control group in which the participants received no intervention during the protocol. Performance on the mini-mental state examination (MMSE) and the short-form of the geriatric depression scale (GDS-SF) were analysed using a three-way repeated-measure analysis of variance. ResultsTo determine cognition after the training, the cognitive program was used and the results were assessed using the MMSE, indicating that the significant time effects within the groups reflected the score for cognitive assessment that was significantly better after the intervention in the experimental group. No significant differences were observed with regard to the depressive symptomatology or between the groups according to sex or educational level on the two dimensions previously established (cognition and depressive symptomatology). ConclusionThe development of technological applications for intervention in older adults is increasing. Based on the established objective, we can conclude that the computerized intervention may constitute a good alternative to enhance the cognitive status in older people.

Visual Priming and Visual Hallucinations in Parkinson's Disease. Evidence for Normal Top-Down Processes.

Visual hallucinations (VH) are common in Parkinson's disease (PD) and are associated with increased morbidity and mortality. Current explanations for VH in PD suggest combined impairments in top-down attentional and bottom-up perceptual processes, which allow the passive "release" of stored images. Alternative models in other disorders have suggested that top-down factors may actively encourage hallucinations. In order to explore the interaction between top-down and bottom-up visual processing in PDVH, we developed novel experimental priming tasks in which top-down verbal cues were used to prime the bottom-up recognition of partial or ambiguous pictures. Two groups of PD participants with (PD + VH, n = 16), and without VH (PD - VH, n = 20) were compared to a group of healthy older adults (NC, n = 20) on 3 novel measures of visual priming. All tasks showed significant priming effects. The PD + VH group was more impaired at accurately identifying silhouette and fragmented images compared to the PD - VH group. There were no differences in priming between the 2 PD groups. The study showed that VH in PD are not associated with relatively greater top-down activation, and that the interaction between top-down and bottom-up processes is intact.

Qi-gong training reduces basal and stress-elicited cortisol secretion in healthy older adults

IntroductionQi-gong, a mind–body practice combining meditation, physical movement and controlled breathing, is reported to improve psychological well-being and physical function in older adults. However, the effects of Qi-gong on hypothalamic–pituitary–adrenal (HPA) axis activity and reactivity to stress in older people are elusive. An uncontrolled, before-and-after study in a group of healthy older adults was conducted to investigate the possible benefits of 12-week Qi-gong training on self-rated distress symptoms and cortisol secretion under basal and stimulated conditions. MethodsBefore (T0) and after (Tf) Qi-gong training, participants (n=28), men and women, mean age 65 years;(smokers, obese subjects, persons with chronic diseases and oral pathologies, and subjects reporting major stressful events in their recent past were excluded) answered the PSS-10 questionnaire. Salivary samples were collected for cortisol detection at various times of the day during a challenging mental task. ResultsQi-gong training reduced basal cortisol output across the day, notably in the morning. In subjects who responded to the stressor at T0 (n=16, baseline-to-peak increment >1.5nmol/l), cortisol response to cognitive challenge was markedly blunted after training, accompanied by a decreasing trend of PSS-10 score. ConclusionQi-gong practice in elderly people appears to improve control on HPA axis activity, reducing daytime cortisol levels and attenuating cortisol responses to mental stress. Ameliorating the profile of basal and stimulated HPA activity, may reflect better adaptation to stress, and may favor successful aging and positive health outcomes. Present findings encourage the implementation of programs aimed at further disseminating Qi-gong practice among the older population.

The Influence of Parkinson's Disease Motor Symptom Asymmetry on Hand Performance: An Examination of the Grooved Pegboard Task.

This study examined the influence of motor symptom asymmetry in Parkinson's disease (PD) on Grooved Pegboard (GP) performance in right-handed participants. The Unified Parkinson's Disease Rating Scale was used to assess motor symptoms and separate participants with PD into two groups (right-arm affected, left-arm affected) for comparison with a group of healthy older adults. Participants completed the place and replace GP tasks two times with both hands. Laterality quotients were computed to quantify performance differences between the two hands. Comparisons among the three groups indicated that when the nonpreferred hand is affected by PD motor symptoms, superior preferred hand performance (as seen in healthy older adults) is further exaggerated in tasks that require precision (i.e., place task). Regardless of the task, when the preferred hand is affected, there is an evident shift to superior left-hand performance, which may inevitably manifest as a switch in hand preference. Results add to the discussion of the relationship between handedness and motor symptom asymmetry in PD.

Attention capacity and self-report of subjective cognitive decline: A P3 ERP study

Subjective cognitive decline (SCD) has recently been proposed as the earliest stage of pathologic cognitive decline in older adults. Longitudinal research suggests that many individuals with SCD go on to develop mild cognitive impairment or Alzheimer's disease. However, those with SCD typically appear normal on standardized neuropsychological testing, and as of yet there are no reliable objective measures discriminating those with SCD from healthy peers. Two groups of healthy older adults (ages 65–80), who self-identified as being with (n=17) or without SCD (n=23), completed self-report measures and objective measures of cognition. Groups did not differ on demographic variables, estimated cognitive reserve, or clinical neuropsychological testing. However, self-identifying as having SCD predicted clear differences in the P3 event-related potential in response to an attention control task, over and above any contributions from mood, anxiety, or neuroticism. Results suggest that using direct neural measures of information processing might be useful where standardized clinical tools are insensitive in those with SCD.

Corticospinal and intracortical excitability of the quadriceps in patients with knee osteoarthritis.

Deficits in voluntary activation of the quadriceps muscle are characteristic of knee osteoarthritis (OA), contributing to the quadriceps weakness that is also a hallmark of the disease. The mechanisms underlying this central activation deficit (CAD) are unknown, although cortical mechanisms may be involved. Here, we utilize transcranial magnetic stimulation (TMS) to assess corticospinal and intracortical excitability in patients with knee OA and in a comparably aged group of healthy older adults, to quantify group differences, and to examine associations between TMS measures and pain, quadriceps strength, and CAD. Seventeen patients with knee OA and 20 healthy controls completed testing. Motor evoked potentials were measured at the quadriceps by superficial electromyographic recordings. Corticospinal excitability was assessed by measuring resting motor threshold (RMT) to TMS stimulation of the quadriceps representation at primary motor cortex, and intracortical excitability was assessed via paired-pulse paradigms for short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). No statistically significant differences between patients with knee OA and healthy controls were found for RMT, SICI or ICF measures (p > 0.05). For patients with knee OA, there were significant associations observed between pain and RMT, as well as between pain and ICF. No associations were observed between CAD and measures of corticospinal or intracortical excitability. These data suggest against direct involvement of corticospinal or intracortical pathways within primary motor cortex in the mechanisms of CAD. However, pain is implicated in the neural mechanisms of quadriceps motor control in patients with knee OA.

Quantifying saccades while walking: validity of a novel velocity-based algorithm for mobile eye tracking.

We validate a novel algorithm to detect saccades from raw data obtained during walking from a mobile infra-red eye-tracking device. The algorithm was based on a velocity threshold detection method, which excluded artefacts such as blinks and flickers using specific criteria. Mobile infra-red eye-tracking was performed with a group of healthy older adults (n=5) and Parkinson's disease (n=5) subjects. Saccades determined from raw eye tracker data obtained during walking using the algorithm were compared to a ground truth dataset defined as frame-by-frame visual inspection of raw eye-tracking videos. 100 trials from 10 subjects were analyzed and compared. The algorithm was highly reliable when compared to the ground truth (ICC(2,1) = 0.94), with an overall correct saccade detection percentage of 85%. This provides a simple yet robust algorithm for the analysis of mobile eye-tracking data.

Load-induced changes in older individual's hand-finger tremor are ameliorated with targeting

The purpose of this study was to investigate hand–finger tremor dynamics when a load was applied to the finger in a group of healthy older adults. Moreover, we sought to determine if projecting a representation of the subject's finger tremor on a target was capable of overcoming the effects of loading so that hand–finger interactions returned to a state that was similar to normal tremor. Eight healthy older males (67±1year) performed a postural pointing task, where tremor was assessed using lightweight accelerometers attached to the hand and finger. Tremor was then assessed when a laser pointer was attached to the finger and switched off (the load), and then with the laser pointer attached and switched on pointing at targets of 40mm and 20mm in diameter. The main findings of this study were that 1) loading the finger resulted in a reduction in finger tremor amplitude and increased finger tremor regularity, but no change in hand tremor, 2) loading caused increased hand–finger 8–12Hz cross wavelet coherence and phase synchrony, and 3) pointing at different targets while the finger was loaded resulted in an increase in finger tremor amplitude, and changes in inter-segmental coupling to the extent that hand–finger dynamics reflected normal unloaded conditions. Overall, these results illustrate that the damping effects of limb loading can be offset, in part, by altering the accuracy demands of the task to make the pointing action more challenging.