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Aging, aerobic activity and interhemispheric communication.

McGregor KM, Heilman KM, Nocera JR, Patten C, Manini TM, Crosson B, Butler AJ - Brain Sci (2012)

Bottom Line: However, higher levels of physical fitness are associated with improved dexterity and fitness may mitigate the loss of both inhibitory and excitatory communication in aging adults.Our results show that the middle-aged adults who were physically fit had better dexterity of their right hand (finger tapping and peg-board).We found that better dexterity correlated with ipsilateral silent period duration (greater inhibition) thereby supporting the postulate that fitness improves interhemispheric motor communication.

View Article: PubMed Central - PubMed

Affiliation: Atlanta Rehabilitation Research and Development Center of Excellence, Department of Veteran's Affairs, Decatur, GA 30033, USA. keith.mcgregor@emory.edu.

ABSTRACT
Recent studies have shown that during unimanual motor tasks, aging adults show bilateral recruitment of primary motor cortex (M1), while younger adults show a suppression of the ipsilateral motor cortex. Additional work has indicated that increased bilateral M1 recruitment in older adults may be deleterious when performing some motor tasks. However, higher levels of physical fitness are associated with improved dexterity and fitness may mitigate the loss of both inhibitory and excitatory communication in aging adults. The goal of this study was to assess dexterity and interhemispheric motor communication in physically fit and sedentary middle-age (40-60 years) right handed participants using tests of hand deftness and transcranial magnetic stimulation (TMS). To behaviorally assess the influence of interhemispheric communication on motor performance, participants also perform the coin rotation deftness task while maintaining pinch force with the opposite hand (bimanual condition). We correlated these behavioral measures with the ipsilateral silent period using TMS to assess interhemispheric inhibition. Our results show that the middle-aged adults who were physically fit had better dexterity of their right hand (finger tapping and peg-board). When performing the coin rotation task the fit group had no between hand differences, but the sedentary group's left hand performance was inferior to the their right hand. We found that better dexterity correlated with ipsilateral silent period duration (greater inhibition) thereby supporting the postulate that fitness improves interhemispheric motor communication.

No MeSH data available.


Related in: MedlinePlus

Illustration of ipsilateral silent period. Rectified EMG across multiple trials within a single participant while holding isometric force at 35%–50% MVC. Highlighted (dark) area delineates EMG depression. Motor evoked potential and subsequent silent period occurs at ~38 ms. iSP duration for this participant was 45 ms.
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brainsci-02-00634-f001: Illustration of ipsilateral silent period. Rectified EMG across multiple trials within a single participant while holding isometric force at 35%–50% MVC. Highlighted (dark) area delineates EMG depression. Motor evoked potential and subsequent silent period occurs at ~38 ms. iSP duration for this participant was 45 ms.

Mentions: The TMS protocol is similar to that used in our previous work [12]. Two single-pulse TMS measures were considered for the current study: LMT value and ipsilateral silent period (iSP) duration (ms). To assess the iSP duration, the participant produced isometric pinch grip at 30%–50% maximal voluntary contraction (MVC), determined by grip dynamometer while TMS was delivered concurrently at 150% LMT to the left primary motor area FDI hotspot. EMG was monitored from the right FDI. Twenty consecutive trials were performed for the iSP assessment. After every five trials, the participant was given a brief rest to allay fatigue. During iSP assessment, the participant was instructed to maintain the non-active hand in a prone, resting position. Two TMS measures were analyzed: lowest motor threshold (LMT) and duration of ipsilateral silent period (iSP). Scope 4.0, JMP 9.0 and Microsoft Excel 2007 software were used to complete this analysis. This procedure was modified from related literature [34]. EMG data were rectified prior to analysis. EMG baseline was taken as mean of the EMG signal 20 ms pre-stimulus during pinch grip. MEP latency was measured from the onset of the stimulus presentation to the onset of the MEP. The first of five consecutive datapoints after MEP that evidenced a minimum decrease of 50% from mean EMG values from the 20 ms prestimulus recording period were taken as the silent period onset. Conversely, the first of five consecutive data points evidencing a return to greater than 50% of prestimulus mean levels identified termination of the silent period. A sample participant’s iSP is illustrated in Figure 1. Group comparisons of TMS measures were analyzed using between-subjects Student’s t-test and p-values < 0.05 were considered statistically significant.


Aging, aerobic activity and interhemispheric communication.

McGregor KM, Heilman KM, Nocera JR, Patten C, Manini TM, Crosson B, Butler AJ - Brain Sci (2012)

Illustration of ipsilateral silent period. Rectified EMG across multiple trials within a single participant while holding isometric force at 35%–50% MVC. Highlighted (dark) area delineates EMG depression. Motor evoked potential and subsequent silent period occurs at ~38 ms. iSP duration for this participant was 45 ms.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061818&req=5

brainsci-02-00634-f001: Illustration of ipsilateral silent period. Rectified EMG across multiple trials within a single participant while holding isometric force at 35%–50% MVC. Highlighted (dark) area delineates EMG depression. Motor evoked potential and subsequent silent period occurs at ~38 ms. iSP duration for this participant was 45 ms.
Mentions: The TMS protocol is similar to that used in our previous work [12]. Two single-pulse TMS measures were considered for the current study: LMT value and ipsilateral silent period (iSP) duration (ms). To assess the iSP duration, the participant produced isometric pinch grip at 30%–50% maximal voluntary contraction (MVC), determined by grip dynamometer while TMS was delivered concurrently at 150% LMT to the left primary motor area FDI hotspot. EMG was monitored from the right FDI. Twenty consecutive trials were performed for the iSP assessment. After every five trials, the participant was given a brief rest to allay fatigue. During iSP assessment, the participant was instructed to maintain the non-active hand in a prone, resting position. Two TMS measures were analyzed: lowest motor threshold (LMT) and duration of ipsilateral silent period (iSP). Scope 4.0, JMP 9.0 and Microsoft Excel 2007 software were used to complete this analysis. This procedure was modified from related literature [34]. EMG data were rectified prior to analysis. EMG baseline was taken as mean of the EMG signal 20 ms pre-stimulus during pinch grip. MEP latency was measured from the onset of the stimulus presentation to the onset of the MEP. The first of five consecutive datapoints after MEP that evidenced a minimum decrease of 50% from mean EMG values from the 20 ms prestimulus recording period were taken as the silent period onset. Conversely, the first of five consecutive data points evidencing a return to greater than 50% of prestimulus mean levels identified termination of the silent period. A sample participant’s iSP is illustrated in Figure 1. Group comparisons of TMS measures were analyzed using between-subjects Student’s t-test and p-values < 0.05 were considered statistically significant.

Bottom Line: However, higher levels of physical fitness are associated with improved dexterity and fitness may mitigate the loss of both inhibitory and excitatory communication in aging adults.Our results show that the middle-aged adults who were physically fit had better dexterity of their right hand (finger tapping and peg-board).We found that better dexterity correlated with ipsilateral silent period duration (greater inhibition) thereby supporting the postulate that fitness improves interhemispheric motor communication.

View Article: PubMed Central - PubMed

Affiliation: Atlanta Rehabilitation Research and Development Center of Excellence, Department of Veteran's Affairs, Decatur, GA 30033, USA. keith.mcgregor@emory.edu.

ABSTRACT
Recent studies have shown that during unimanual motor tasks, aging adults show bilateral recruitment of primary motor cortex (M1), while younger adults show a suppression of the ipsilateral motor cortex. Additional work has indicated that increased bilateral M1 recruitment in older adults may be deleterious when performing some motor tasks. However, higher levels of physical fitness are associated with improved dexterity and fitness may mitigate the loss of both inhibitory and excitatory communication in aging adults. The goal of this study was to assess dexterity and interhemispheric motor communication in physically fit and sedentary middle-age (40-60 years) right handed participants using tests of hand deftness and transcranial magnetic stimulation (TMS). To behaviorally assess the influence of interhemispheric communication on motor performance, participants also perform the coin rotation deftness task while maintaining pinch force with the opposite hand (bimanual condition). We correlated these behavioral measures with the ipsilateral silent period using TMS to assess interhemispheric inhibition. Our results show that the middle-aged adults who were physically fit had better dexterity of their right hand (finger tapping and peg-board). When performing the coin rotation task the fit group had no between hand differences, but the sedentary group's left hand performance was inferior to the their right hand. We found that better dexterity correlated with ipsilateral silent period duration (greater inhibition) thereby supporting the postulate that fitness improves interhemispheric motor communication.

No MeSH data available.


Related in: MedlinePlus