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Premotor-motor interhemispheric inhibition is released during movement initiation in older but not young adults.

Hinder MR, Fujiyama H, Summers JJ - PLoS ONE (2012)

Bottom Line: Neural interactions between contralateral motor regions are thought to be instrumental in the successful preparation, and execution, of volitional movements.Relative to the inhibitory interactions measured at rest, both young and older adults released LM1-RM1 inhibition beginning 250 ms after the warning signal, with no significant differences between groups.The results suggest a greater reliance on premotor regions during the preparation of simple motor actions with advancing age.

View Article: PubMed Central - PubMed

Affiliation: Motor Control Laboratory, School of Psychology, University of Tasmania, Tasmania, Australia. Mark.Hinder@utas.edu.au

ABSTRACT
Neural interactions between contralateral motor regions are thought to be instrumental in the successful preparation, and execution, of volitional movements. Here we investigated whether healthy ageing is associated with a change in functional connectivity, as indicated by the ability to modulate interhemispheric interactions during movement preparation in a manner that assists rapid movement responses. Thirteen young (mean age 22.2 years) and thirteen older (68.5 years) adults rapidly abducted their left index finger as soon as possible in response to a visual imperative signal, presented 500 ms after a visual warning signal.Interactions between left dorsal premotor cortex (LPMd) and right primary motor cortex (RM1) and between left primary motor cortex (LM1) and RM1 were investigated at six time points between the warning signal and the volitional response using paired-pulse transcranial magnetic stimulation. Relative to the inhibitory interactions measured at rest, both young and older adults released LM1-RM1 inhibition beginning 250 ms after the warning signal, with no significant differences between groups. LPMd-RM1 interactions became facilitatory (from the onset of the imperative signal onwards) in the older, but not the young, group. Regression analyses revealed that for the older adults, modulation of LPMd-RM1 interactions early in the preparation period was associated with faster responses, suggesting that specifically timed modulation of these pathways may be a compensatory mechanism to offset, at least in part, slowing of motor responses. The results suggest a greater reliance on premotor regions during the preparation of simple motor actions with advancing age.

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Related in: MedlinePlus

Interhemispheric interactions between LM1-RM1 (A) and LPMd-RM1 (B) for the young and older groups recorded at rest.Values <1 (horizontal dotted line) represent inhibitory interactions, while values >1 represent facilitatory interactions. Data are shown for the short and long ISIs and for both participant groups. Error bars represent 95% CIs.
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pone-0052573-g003: Interhemispheric interactions between LM1-RM1 (A) and LPMd-RM1 (B) for the young and older groups recorded at rest.Values <1 (horizontal dotted line) represent inhibitory interactions, while values >1 represent facilitatory interactions. Data are shown for the short and long ISIs and for both participant groups. Error bars represent 95% CIs.

Mentions: LM1-RM1 and LPMd-RM1 IHI ratios, assessed at rest, are presented in figure 3. For LM1-RM1, the main effects of ISI (F1,24 = 0.86; ηp2 = 0.04; p = 0.362) and age (F1,24 = 0.53; ηp2 = 0.01; p = 0.724), and the interaction between ISI and age (F1,24 = 0.06; ηp2<0.01; p = 0.815) were all non-significant. As Figure 3A indicates, both age groups exhibited qualitatively similar interactions (i.e., IHI<1) at both 10 ms ISI (SIHI) and 40 ms ISI (LIHI). In contrast, for the LPMd-RM1 interactions, ANOVA revealed a significant effect of ISI (F1,24 = 4.55; ηp2 = 0.16; p = 0.043), with substantial inhibition exhibited at the 40 ms ISI (IHI = 0.85), but not at the short 8 ms ISI (IHI = 1.03) (figure 3B). The main effect of age (F1,24 = 2.87; ηp2 = 0.11; p = 0.103) and the interaction between age and ISI (F1,24 = 0.28; ηp2 = 0.01; p = 0.602) were not statistically significant.


Premotor-motor interhemispheric inhibition is released during movement initiation in older but not young adults.

Hinder MR, Fujiyama H, Summers JJ - PLoS ONE (2012)

Interhemispheric interactions between LM1-RM1 (A) and LPMd-RM1 (B) for the young and older groups recorded at rest.Values <1 (horizontal dotted line) represent inhibitory interactions, while values >1 represent facilitatory interactions. Data are shown for the short and long ISIs and for both participant groups. Error bars represent 95% CIs.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3526571&req=5

pone-0052573-g003: Interhemispheric interactions between LM1-RM1 (A) and LPMd-RM1 (B) for the young and older groups recorded at rest.Values <1 (horizontal dotted line) represent inhibitory interactions, while values >1 represent facilitatory interactions. Data are shown for the short and long ISIs and for both participant groups. Error bars represent 95% CIs.
Mentions: LM1-RM1 and LPMd-RM1 IHI ratios, assessed at rest, are presented in figure 3. For LM1-RM1, the main effects of ISI (F1,24 = 0.86; ηp2 = 0.04; p = 0.362) and age (F1,24 = 0.53; ηp2 = 0.01; p = 0.724), and the interaction between ISI and age (F1,24 = 0.06; ηp2<0.01; p = 0.815) were all non-significant. As Figure 3A indicates, both age groups exhibited qualitatively similar interactions (i.e., IHI<1) at both 10 ms ISI (SIHI) and 40 ms ISI (LIHI). In contrast, for the LPMd-RM1 interactions, ANOVA revealed a significant effect of ISI (F1,24 = 4.55; ηp2 = 0.16; p = 0.043), with substantial inhibition exhibited at the 40 ms ISI (IHI = 0.85), but not at the short 8 ms ISI (IHI = 1.03) (figure 3B). The main effect of age (F1,24 = 2.87; ηp2 = 0.11; p = 0.103) and the interaction between age and ISI (F1,24 = 0.28; ηp2 = 0.01; p = 0.602) were not statistically significant.

Bottom Line: Neural interactions between contralateral motor regions are thought to be instrumental in the successful preparation, and execution, of volitional movements.Relative to the inhibitory interactions measured at rest, both young and older adults released LM1-RM1 inhibition beginning 250 ms after the warning signal, with no significant differences between groups.The results suggest a greater reliance on premotor regions during the preparation of simple motor actions with advancing age.

View Article: PubMed Central - PubMed

Affiliation: Motor Control Laboratory, School of Psychology, University of Tasmania, Tasmania, Australia. Mark.Hinder@utas.edu.au

ABSTRACT
Neural interactions between contralateral motor regions are thought to be instrumental in the successful preparation, and execution, of volitional movements. Here we investigated whether healthy ageing is associated with a change in functional connectivity, as indicated by the ability to modulate interhemispheric interactions during movement preparation in a manner that assists rapid movement responses. Thirteen young (mean age 22.2 years) and thirteen older (68.5 years) adults rapidly abducted their left index finger as soon as possible in response to a visual imperative signal, presented 500 ms after a visual warning signal.Interactions between left dorsal premotor cortex (LPMd) and right primary motor cortex (RM1) and between left primary motor cortex (LM1) and RM1 were investigated at six time points between the warning signal and the volitional response using paired-pulse transcranial magnetic stimulation. Relative to the inhibitory interactions measured at rest, both young and older adults released LM1-RM1 inhibition beginning 250 ms after the warning signal, with no significant differences between groups. LPMd-RM1 interactions became facilitatory (from the onset of the imperative signal onwards) in the older, but not the young, group. Regression analyses revealed that for the older adults, modulation of LPMd-RM1 interactions early in the preparation period was associated with faster responses, suggesting that specifically timed modulation of these pathways may be a compensatory mechanism to offset, at least in part, slowing of motor responses. The results suggest a greater reliance on premotor regions during the preparation of simple motor actions with advancing age.

Show MeSH
Related in: MedlinePlus