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Combined Transcranial Magnetic Stimulation and Electroencephalography of the Dorsolateral Prefrontal Cortex
Published on: August 17, 2018
Threshold tracking transcranial magnetic stimulation: Effects of age and gender on motor cortical function
Kazumoto Shibuya1, Susanna B Park1, Nimeshan Geevasinga2
1Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW 2050, Australia.
Objective:
Recently, the utility of threshold tracking paired-pulse transcranial magnetic stimulation (TTTMS), to measure changes in cortical excitabilitability, has been established for diagnostic purposes across a range of neurological diseases. However, the impact of healthy aging on the GABA-ergic intracortical inhibitory system remains unclear. To improve the clinical applicability, TTTMS was performed across an age spectrum.
Methods:
TTTMS, single-pulse TMS and nerve conduction studies (NCS) were performed in 113 healthy subjects aged between 20 and 83years (57 male and 56 female).
Results:
Prolonged motor evoked potential (MEP) latency, increased central motor conduction time, decreased compound muscle action potential (CMAP) amplitude, prolonged F-wave latency and decreased neurophysiological index (NI), calculated from CMAP amplitude, latency and F-wave frequency, were observed as subjects aged. In contrast, short interval intracortical inhibition (SICI) and facilitation did not change. Compared to females, males exhibited a reduced SICI and NI along with longer MEP, CMAP with prolonged F-wave latencies. Multivariate analyses revealed similar results.
Conclusion:
Utilizing clinically applicable TTTMS protocols, findings suggest that GABA mediated intracortical inhibition may be greater in females but does not significantly change with age.
Significance:
These findings may better inform the interpretation of diagnostic TTTMS studies in the clinical setting.
