GABA and primary motor cortex inhibition in young and older adults: a multimodal reliability study

Mooney, Ronan A.; Cirillo, John; Byblow, Winston D.

doi:10.1152/jn.00199.2017

Cited by 60 publications

(51 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…With aging, excitability and the capability to modulate excitability seems to decrease, causing motor deficits in older adults (Bhandari et al, ). Interestingly, current studies show that TMS measures of GABAergic inhibition are not correlated with GABA concentrations obtained by MRS (Dyke et al, ; Hermans et al, ; Mooney, Cirillo, & Byblow, ; Stagg et al, ; Tremblay et al, ). This appears to suggest that MRS and TMS investigate distinct mechanisms: whereas MRS is thought to reflect the inhibitory tone of a certain brain region, TMS targets the GABAergic synaptic transmission (Dyke et al, ; Stagg et al, ; Tremblay et al, ).…”

Section: Discussionmentioning

confidence: 87%

Age‐related differences in GABA levels are driven by bulk tissue changes

Maes

Hermans

Pauwels

et al. 2018

Human Brain Mapping

View full text Add to dashboard Cite

Levels of GABA, the main inhibitory neurotransmitter in the brain, can be regionally quantified using magnetic resonance spectroscopy (MRS). Although GABA is crucial for efficient neuronal functioning, little is known about age-related differences in GABA levels and their relationship with age-related changes in brain structure. Here, we investigated the effect of age on GABA levels within the left sensorimotor cortex and the occipital cortex in a sample of 85 young and 85 older adults using the MEGA-PRESS sequence. Because the distribution of GABA varies across different brain tissues, various correction methods are available to account for this variation. Considering that these correction methods are highly dependent on the tissue composition of the voxel of interest, we examined differences in voxel composition between age groups and the impact of these various correction methods on the identification of age-related differences in GABA levels. Results indicated that, within both voxels of interest, older (as compared to young adults) exhibited smaller gray matter fraction accompanied by larger fraction of cerebrospinal fluid. Whereas uncorrected GABA levels were significantly lower in older as compared to young adults, this age effect was absent when GABA levels were corrected for voxel composition. These results suggest that age-related differences in GABA levels are at least partly driven by the age-related gray matter loss. However, as alterations in GABA levels might be region-specific, further research should clarify to what extent gray matter changes may account for age-related differences in GABA levels within other brain regions.

show abstract

Section: Discussionmentioning

confidence: 87%

Age‐related differences in GABA levels are driven by bulk tissue changes

Maes

Hermans

Pauwels

et al. 2018

Human Brain Mapping

View full text Add to dashboard Cite

show abstract

“…A neurotransmitter system with strong influence on cortical inhibition and likely even motor control is the gamma aminobutyric acid system (GABA). The aging process may be responsible for a decrease in GABA tone in the neocortex (Gao et al, 2013 ; but see also Mooney et al ( 2017 ). However, this decrease may or may not be responsible for changes in motor performance in aging, as GABA receptors can change endogenous sensitivity levels over time (Rozycka and Liguz-Lecznar, 2017 ).…”

Section: Introductionmentioning

confidence: 99%

Influences of 12-Week Physical Activity Interventions on TMS Measures of Cortical Network Inhibition and Upper Extremity Motor Performance in Older Adults—A Feasibility Study

McGregor

Crosson

Mammino

et al. 2018

Front. Aging Neurosci.

View full text Add to dashboard Cite

Objective: Data from previous cross-sectional studies have shown that an increased level of physical fitness is associated with improved motor dexterity across the lifespan. In addition, physical fitness is positively associated with increased laterality of cortical function during unimanual tasks; indicating that sedentary aging is associated with a loss of interhemispheric inhibition affecting motor performance. The present study employed exercise interventions in previously sedentary older adults to compare motor dexterity and measure of interhemispheric inhibition using transcranial magnetic stimulation (TMS) after the interventions.Methods: Twenty-one community-dwelling, reportedly sedentary older adults were recruited, randomized and enrolled to a 12-week aerobic exercise group or a 12-week non-aerobic exercise balance condition. The aerobic condition was comprised of an interval-based cycling “spin” activity, while the non-aerobic “balance” exercise condition involved balance and stretching activities. Participants completed upper extremity dexterity batteries and estimates of VO2max in addition to undergoing single (ipsilateral silent period—iSP) and paired-pulse interhemispheric inhibition (ppIHI) in separate assessment sessions before and after study interventions. After each intervention during which heart rate was continuously recorded to measure exertion level (load), participants crossed over into the alternate arm of the study for an additional 12-week intervention period in an AB/BA design with no washout period.Results: After the interventions, regardless of intervention order, participants in the aerobic spin condition showed higher estimated VO2max levels after the 12-week intervention as compared to estimated VO2max in the non-aerobic balance intervention. After controlling for carryover effects due to the study design, participants in the spin condition showed longer iSP duration than the balance condition. Heart rate load was more strongly correlated with silent period duration after the Spin condition than estimated VO2.Conclusions: Aging-related changes in cortical inhibition may be influenced by 12-week physical activity interventions when assessed with the iSP. Although inhibitory signaling is mediates both ppIHI and iSP measures each TMS modality likely employs distinct inhibitory networks, potentially differentially affected by aging. Changes in inhibitory function after physical activity interventions may be associated with improved dexterity and motor control at least as evidence from this feasibility study show.

show abstract

“…With conventional paired‐pulse TMS, IHI is quantified as the decrease in motor‐evoked potential (MEP) amplitude elicited by the contralaterally conditioned test stimulus relative to the test stimulus alone (Ferbert et al., ). Threshold hunting paired‐pulse TMS has previously been used to assess intracortical inhibition in both young (Amandusson, Flink, & Axelson, ; Awiszus, Feistner, Urbach, & Bostock, ; Cirillo & Byblow, ) and older adults (Mooney, Cirillo, & Byblow, ) and may provide a useful alternative for examining IHI. In contrast to the conventional approach, threshold hunting maintains a target MEP amplitude in the presence of the conditioning stimulus by adjusting the test stimulus intensity (Awiszus et al., ).…”

Section: Introductionmentioning

confidence: 99%

Adaptive threshold hunting reveals differences in interhemispheric inhibition between young and older adults

Mooney

Cirillo

Byblow

2018

Eur J of Neuroscience

Self Cite

View full text Add to dashboard Cite

Interhemispheric inhibition between bilateral motor cortices is important for the performance of unimanual activities and may be compromised with advancing age. Conventionally, interhemispheric inhibition is assessed using paired-pulse transcranial magnetic stimulation (TMS) with constant conditioning and test stimulation parameters. Adaptive threshold hunting TMS, whereby a target motor-evoked potential amplitude is maintained in the presence of the conditioning, may provide an alternative means of assessment. Furthermore, interhemispheric inhibition may suppress late indirect-waves more so than early indirect-waves which can be preferentially elicited using anterior-posterior (AP) and posterior-anterior (PA) induced currents, respectively. The aim of this study was to assess age-related effects on interhemispheric inhibition using both conventional and threshold hunting techniques with PA- and AP-induced current. In 15 young and 15 older adults, short (10 ms) and long (40 ms) interval interhemispheric inhibition was examined in the nondominant extensor carpi radialis muscle at rest and during voluntary extension of the contralateral wrist. With the conventional technique, there were no age-related differences in short-interval interhemispheric inhibition. With threshold hunting and AP-induced current, young adults exhibited greater short-interval interhemispheric inhibition during contralateral activation compared with rest and compared with older adults. Furthermore, long-interval interhemispheric inhibition was greater in older adults compared with young for both conventional and threshold hunting techniques. Age-related differences in interhemispheric inhibition are evident with threshold hunting using PA- and AP-induced current.

show abstract

GABA and primary motor cortex inhibition in young and older adults: a multimodal reliability study

Cited by 60 publications

References 57 publications

Age‐related differences in GABA levels are driven by bulk tissue changes

Age‐related differences in GABA levels are driven by bulk tissue changes

Influences of 12-Week Physical Activity Interventions on TMS Measures of Cortical Network Inhibition and Upper Extremity Motor Performance in Older Adults—A Feasibility Study

Adaptive threshold hunting reveals differences in interhemispheric inhibition between young and older adults

Contact Info

Product

Resources

About