scholarly journals INTRINSIC MOTOR NEURONE EXCITABILITY IS REDUCED IN SOLEUS AND TIBIALIS ANTERIOR OF OLDER ADULTS

2021 ◽  
Author(s):  
Lucas B R Orssatto ◽  
David N Borg ◽  
Anthony J Blazevich ◽  
Raphael L Sakugawa ◽  
Anthony J Shield ◽  
...  
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Motor Unit ◽  
Tibialis Anterior ◽  
Motor Units ◽  
Motor Neurone ◽  
Age Related ◽  
Inward Currents ◽  
Motor Neurones ◽  
Intrinsic Motor

Age-related deterioration within both motor neurones and monoaminergic systems should theoretically reduce neuromodulation by weakening motor neuronal persistent inward current (PIC) strength. However, this assumption remains untested. Surface electromyographic signals were collected using two 32-channel electrode matrices placed on soleus and tibialis anterior of 25 older adults (70±4years) and 17 young adults (29±5 years) to investigate motor unit discharge behaviours. Participants performed triangular-shaped plantar and dorsiflexion contractions to 20% of maximum torque at a rise-decline rate of 2%/s of each participant's maximal torque. Pairwise and composite paired-motor unit analyses were adopted to calculate delta frequency (ΔF) and estimate PIC amplitudes. ΔF has been used to differentiate between the effects of synaptic excitation and intrinsic motor neuronal properties and is assumed to be proportional to PIC amplitude. The results show that soleus and tibialis anterior motor units in older adults had lower ΔFs when calculated with the pairwise (-0.99 and -1.29 pps, respectively) or composite (-1.65 and -2.26 pps, respectively) methods. Older adults' motor units discharged at lower rates (-2.14 and -2.03 pps, respectively) and were recruited at lower torque levels (-1.50 and -2.06% of maximum, respectively) than young adults. These results demonstrate reduced intrinsic motor neurone excitability during low-force contractions in older adults, likely mediated by decreases in the strength of persistent inward currents. Our findings might be explained by deterioration in the motor neurones or monoaminergic systems, and could contribute to the decline in motor function during ageing; these assumptions should be explicitly tested in future investigations.

scholarly journals Estimates of persistent inward currents are reduced in upper limb motor units of older adults

2021 ◽  
Author(s):  
Altamash S Hassan ◽  
Melissa E Fajardo ◽  
Mark Cummings ◽  
Laura Miller McPherson ◽  
Francesco Negro ◽  
...  
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Biceps Brachii ◽  
Gain Control ◽  
Motor Units ◽  
Older Individuals ◽  
Triceps Brachii ◽  
Persistent Inward Currents ◽  
Firing Rates ◽  
Inward Currents

Aging is a natural process that causes alterations in the neuromuscular system, which contribute to weakness and reduced quality of life. Reduced firing rates of individual motor units (MUs) likely contribute to weakness, but the mechanisms underlying reduced firing rates are not clear. Persistent inward currents (PICs) are crucial for the initiation, gain control, and maintenance of motoneuron firing, and are directly proportional to the level of monoaminergic input. Since the concentration of monoamines (i.e. serotonin and norepinephrine) are reduced with age, we sought to determine if estimates of PICs are reduced in older (>60 years old) compared to young adults (<35 years old). We decomposed MU spike trains from high-density surface electromyography over the biceps brachii and triceps brachii during isometric ramp contractions to 20% of maximum. Estimates of PICs (i.e. ΔF) were computed using the paired MU analysis technique. Regardless of the muscle, peak firing rates of older adults were reduced by ~1.6 pulses per second (pps) (P = 0.0292), and ΔF was reduced by ~1.9 pps (P < 0.0001), compared to young adults. We further found that age predicted ΔF in older adults (P = 0.0261), resulting in a reduction of ~1pps per decade, but there was no relationship in young adults (P = 0.9637). These findings suggest that PICs are reduced in older adults, and, further, age is a significant predictor of estimates of PICs in older adults. Reduced PIC magnitude represents one plausible mechanism for reduced firing rates and weakness in older individuals.

Inefficient Encoding as an Explanation for Age-Related Deficits in Recollection-Based Processing

2014 ◽  
Vol 28 (3) ◽  
pp. 148-161 ◽  
Author(s):  
David Friedman ◽  
Ray Johnson
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Cognitive Processes ◽  
Brain Activity ◽  
Memory Performance ◽  
Brain Regions ◽  
Semantic Retrieval ◽  
Age Related ◽  
The Face ◽  
Episodic Memories

A cardinal feature of aging is a decline in episodic memory (EM). Nevertheless, there is evidence that some older adults may be able to “compensate” for failures in recollection-based processing by recruiting brain regions and cognitive processes not normally recruited by the young. We review the evidence suggesting that age-related declines in EM performance and recollection-related brain activity (left-parietal EM effect; LPEM) are due to altered processing at encoding. We describe results from our laboratory on differences in encoding- and retrieval-related activity between young and older adults. We then show that, relative to the young, in older adults brain activity at encoding is reduced over a brain region believed to be crucial for successful semantic elaboration in a 400–1,400-ms interval (left inferior prefrontal cortex, LIPFC; Johnson, Nessler, & Friedman, 2013 ; Nessler, Friedman, Johnson, & Bersick, 2007 ; Nessler, Johnson, Bersick, & Friedman, 2006 ). This reduced brain activity is associated with diminished subsequent recognition-memory performance and the LPEM at retrieval. We provide evidence for this premise by demonstrating that disrupting encoding-related processes during this 400–1,400-ms interval in young adults affords causal support for the hypothesis that the reduction over LIPFC during encoding produces the hallmarks of an age-related EM deficit: normal semantic retrieval at encoding, reduced subsequent episodic recognition accuracy, free recall, and the LPEM. Finally, we show that the reduced LPEM in young adults is associated with “additional” brain activity over similar brain areas as those activated when older adults show deficient retrieval. Hence, rather than supporting the compensation hypothesis, these data are more consistent with the scaffolding hypothesis, in which the recruitment of additional cognitive processes is an adaptive response across the life span in the face of momentary increases in task demand due to poorly-encoded episodic memories.

scholarly journals Losing touch: age-related changes in plantar skin sensitivity, lower limb cutaneous reflex strength, and postural stability in older adults

2016 ◽  
Vol 116 (4) ◽  
pp. 1848-1858 ◽  
Author(s):  
Ryan M. Peters ◽  
Monica D. McKeown ◽  
Mark G. Carpenter ◽  
J. Timothy Inglis
Keyword(s):  
Older Adults ◽  
Lower Limb ◽  
Postural Stability ◽  
Tibialis Anterior ◽  
Tibialis Anterior Muscle ◽  
Quiet Standing ◽  
Detection Thresholds ◽  
Cutaneous Reflex ◽  
Age Related ◽  
Age Related Changes

Age-related changes in the density, morphology, and physiology of plantar cutaneous receptors negatively impact the quality and quantity of balance-relevant information arising from the foot soles. Plantar perceptual sensitivity declines with age and may predict postural instability; however, alteration in lower limb cutaneous reflex strength may also explain greater instability in older adults and has yet to be investigated. We replicated the age-related decline in sensitivity by assessing monofilament and vibrotactile (30 and 250 Hz) detection thresholds near the first metatarsal head bilaterally in healthy young and older adults. We additionally applied continuous 30- and 250-Hz vibration to drive mechanically evoked reflex responses in the tibialis anterior muscle, measured via surface electromyography. To investigate potential relationships between plantar sensitivity, cutaneous reflex strength, and postural stability, we performed posturography in subjects during quiet standing without vision. Anteroposterior and mediolateral postural stability decreased with age, and increases in postural sway amplitude and frequency were significantly correlated with increases in plantar detection thresholds. With 30-Hz vibration, cutaneous reflexes were observed in 95% of young adults but in only 53% of older adults, and reflex gain, coherence, and cumulant density at 30 Hz were lower in older adults. Reflexes were not observed with 250-Hz vibration, suggesting this high-frequency cutaneous input is filtered out by motoneurons innervating tibialis anterior. Our findings have important implications for assessing the risk of balance impairment in older adults.

Mechanism of Sequential Swallowing During Straw Drinking in Healthy Young and Older Adults

2004 ◽  
Vol 47 (1) ◽  
pp. 33-45 ◽  
Author(s):  
Stephanie K. Daniels ◽  
David M. Corey ◽  
Leslie D. Hadskey ◽  
Calli Legendre ◽  
Daniel H. Priestly ◽  
...  
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Movement Patterns ◽  
Leading Edge ◽  
Normal Aging ◽  
Significant Relation ◽  
Age Related ◽  
Laryngeal Penetration ◽  
Airway Invasion ◽  
Edge Location

Recent research has revealed differences between isolated and sequential swallowing in healthy young adults; however, the influence of normal aging on sequential swallowing has not been studied. Thus, the purpose of this investigation was to examine the effects of normal aging on deglutition during sequential straw drinking. Videofluoroscopic samples of two 10-s straw drinking trials were obtained for 20 healthy young men (age 29±3 years) and 18 healthy older men (age 69±7 years). Hyolaryngeal complex (HLC) movement patterns, leading edge of the bolus location at swallow onset, and occurrences of airway invasion were determined. Two HLC patterns were identified: (a) HLC lowering with the epiglottis returned to upright between swallows and (b) partially maintained HLC elevation with the epiglottis inverted between swallows. The bolus was frequently in the hypopharynx at swallow onset. Strong associations were identified between age and HLC pattern, age and leading edge of the bolus location, and HLC pattern and leading edge location. Laryngeal penetration was uncommon overall; however, it occurred more frequently in the older adults than in the young adults. A significant relation was identified between age and the average Penetration-Aspiration Scale score. Laryngeal penetration was associated with both HLC movement patterns and hypopharyngeal bolus location, particularly in older adults. Results indicate that subtle age-related differences are evident in healthy young and older adults with sequential straw drinking. These data suggest that specific inherent swallowing patterns may increase the risk of laryngeal penetration with normal aging.

Processing gender stereotypes in dementia patients and older healthy adults: a self-paced reading study

2019 ◽  
Vol 5 (s2) ◽  
Author(s):  
Daniel Müller-Feldmeth ◽  
Katharina Ahnefeld ◽  
Adriana Hanulíková
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Sentence Processing ◽  
Gender Stereotypes ◽  
Time Course ◽  
Healthy Adults ◽  
Control Group ◽  
Healthy Older Adults ◽  
Dementia Patients ◽  
Age Related

AbstractWe used self-paced reading to examine whether stereotypical associations of verbs with women or men as prototypical agents (e.g. the craftsman knits a sweater) are activated during sentence processing in dementia patients and healthy older adults. Effects of stereotypical knowledge on language processing have frequently been observed in young adults, but little is known about age-related changes in the activation and integration of stereotypical information. While syntactic processing may remain intact, semantic capacities are often affected in dementia. Since inferences based on gender stereotypes draw on social and world knowledge, access to stereotype information may also be affected in dementia patients. Results from dementia patients (n = 9, average age 86.6) and healthy older adults (n = 14, average age 79.5) showed slower reading times and less accuracy in comprehension scores for dementia patients compared to the control group. While activation of stereotypical associations of verbs was visible in both groups, they differed with respect to the time-course of processing. The effect of stereotypes on comprehension accuracy was visible for healthy adults only. The evidence from reading times suggests that older adults with and without dementia engage stereotypical inferences during reading, which is in line with research on young adults.

scholarly journals Systematic review and meta-analysis of age-related differences in instructed emotion regulation success

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e6051 ◽  
Author(s):  
Brooke Brady ◽  
Ian I. Kneebone ◽  
Nida Denson ◽  
Phoebe E. Bailey
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Emotion Regulation ◽  
Process Model ◽  
Meta Analysis ◽  
Cognitive Change ◽  
Emotional Behavior ◽  
Response Modulation ◽  
Age Related ◽  
Process Strategy

The process model of emotion regulation (ER) is based on stages in the emotion generative process at which regulation may occur. This meta-analysis examines age-related differences in the subjective, behavioral, and physiological outcomes of instructed ER strategies that may be initiated after an emotional event has occurred; attentional deployment, cognitive change, and response modulation. Within-process strategy, stimulus type, and valence were also tested as potential moderators of the effect of age on ER. A systematic search of the literature identified 156 relevant comparisons from 11 studies. Few age-related differences were found. In our analysis of the subjective outcome of response modulation strategies, young adults used expressive enhancement successfully (g = 0.48), but not expressive suppression (g = 0.04). Response modulation strategies had a small positive effect among older adults, and enhancement vs suppression did not moderate this success (g = 0.31 and g = 0.10, respectively). Young adults effectively used response modulation to regulate subjective emotion in response to pictures (g = 0.41) but not films (g = 0.01). Older adults were able to regulate in response to both pictures (g = 0.26) and films (g = 0.11). Interestingly, both age groups effectively used detached reappraisal, but not positive reappraisal to regulate emotional behavior. We conclude that, in line with well-established theories of socioemotional aging, there is a lack of evidence for age differences in the effects of instructed ER strategies, with some moderators suggesting more consistent effectiveness for older compared to younger adults.

scholarly journals Electrophysiological Evidence for Preserved Primacy of Lexical Prediction in Normative Aging

2017 ◽  
Author(s):  
Shruti Dave ◽  
Trevor A. Brothers ◽  
Matthew J. Traxler ◽  
Fernanda Ferreira ◽  
John M. Henderson ◽  
...  
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Prediction Accuracy ◽  
Predictive Accuracy ◽  
Accurate Prediction ◽  
Self Report ◽  
Clear Cut ◽  
Age Related ◽  
Contextual Support ◽  
Normative Aging

Young adults show consistent neural benefits of predictable contexts when processing upcoming words, but these benefits are less clear-cut in older adults. Here we conduct two ERP experiments to examine whether aging uniquely affects neural correlates of prediction accuracy, as compared to contextual support independent of accuracy. In Experiment 1, readers were asked to predict sentence-final words and self-report prediction accuracy, allowing for separation of ERP effects of accurate prediction and contextual support. While N250 and N400 effects of accurate prediction were reduced in older readers, both temporal primacy and relative amplitudes of predictive compared to contextual processing were similar across age. In Experiment 2, participants read for comprehension without an overt prediction task and showed similar age-related declines in N400 amplitude across experiments. In both studies, older adults showed relatively larger frontal post-N400 positivities (PNPs) than young adults, suggesting age-graded differences in revision following unexpected items. Previous research suggests the production system may be linked to lexical prediction, but here we found that verbal fluency modulated PNP effects of contextual support, but not predictive accuracy. Taken together, our findings suggest that normative aging does not result in specific declines or boosts of lexical prediction.

scholarly journals Directed connectivity between primary and premotor areas underlying ankle force control in young and older adults

2019 ◽  
Author(s):  
Meaghan Elizabeth Spedden ◽  
Mikkel Malling Beck ◽  
Mark Schram Christensen ◽  
Martin Jensen Dietz ◽  
Anke Ninija Karabanov ◽  
...  
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Force Control ◽  
Coupling Strength ◽  
Empirical Bayes ◽  
Premotor Cortex ◽  
Force Production ◽  
Age Group ◽  
Compensatory Mechanisms ◽  
Age Related

AbstractThe control of ankle muscle force is an integral component of walking and postural control. Aging impairs the ability to produce force steadily and accurately, which can compromise functional capacity and quality of life. Here, we hypothesized that reduced force control in older adults would be associated with altered cortico-cortical communication within a network comprising the primary motor area (M1), the premotor cortex (PMC), parietal, and prefrontal regions. We examined electroencephalographic (EEG) responses from fifteen younger (20-26 yr) and fifteen older (65-73 yr) participants during a unilateral dorsiflexion force-tracing task. Dynamic Causal Modelling (DCM) and Parametric Empirical Bayes (PEB) were used to investigate how directed connectivity between contralateral M1, PMC, parietal, and prefrontal regions was related to age group and precision in force production. DCM and PEB analyses revealed that the strength of connections between PMC and M1 were related to ankle force precision and differed by age group. For young adults, bidirectional PMC-M1 coupling was negatively related to task performance: stronger backward M1-PMC and forward PMC-M1 coupling was associated with worse force precision. The older group exhibited deviations from this pattern. For the PMC to M1 coupling, there were no age-group differences in coupling strength; however, within the older group, stronger coupling was associated with better performance. For the M1 to PMC coupling, older adults followed the same pattern as young adults - with stronger coupling accompanied by worse performance - but coupling strength was lower than in the young group. Our results suggest that bidirectional M1-PMC communication is related to precision in ankle force production and that this relationship changes with aging. We argue that the observed age-related differences reflect compensatory mechanisms whereby older adults maintain performance in the face of declines in the sensorimotor system.

Kinematic Analysis of Dance-Based Exergaming: A Cross-Sectional Study

2021 ◽  
Author(s):  
Ernest K. Ofori ◽  
Savitha Subramaniam ◽  
Shuaijie Wang ◽  
Tanvi Bhatt
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Postural Stability ◽  
Center Of Mass ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Healthy Older Adults ◽  
Age Related ◽  
Aging Populations ◽  
Cortical Pathology

Background: Recent studies demonstrate improvements in both postural stability and mobility among aging populations and those with stroke who are exposed to dance-based exergaming (DBExG). However, age-related deficits and aging with cortical pathology may lead to distinct movement adaptation patterns during DBExG, which could impact therapeutic outcomes.Aim: The aim of this study was to examine the movement kinematics (postural stability and mobility) of healthy older adults, older adults with stroke, and young adults for different paces of dance during DBExG. Method: The study included 33 particpants (11 participant from each group of healthy older adults, older adults with chronic stroke, and healthy young adults) who performed the DBExG using slow- (SP), medium- (MP), and fast-paced (FP) songs with movements in the anteroposterior (AP) and mediolateral (ML) directions. Center of mass (CoM) sway area, excursion (Ex), and peaks as well as hip, knee, and ankle joint excursions were computed. Results: Results of the study revealed that CoM sway areas and Exs were greater for healthy young adults than for older adults with stroke for the SP dance (p < 0.05) and that there were significantly more AP CoM peaks for young adults than for healthy older adults and those with stroke for the FP dance (p < 0.05). Young adults also exhibited greater hip and ankle Exs than older adults with stroke (p < 0.05) for all song paces. Similarly, knee and ankle Exs were greater for healthy older adults than for older adults with stroke for all song paces (p < 0.05). Conclusion: The quantitative evaluation and comparison of the movement patterns presented for the three groups could provide a foundation for both assessing and designing therapeutic DBExG protocols for these populations.

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