Reduced motor cortex plasticity following inhibitory rTMS in older adults.
OBJECTIVE
Ageing is accompanied by diminished practice-dependent plasticity. We investigated the effect of age on another plasticity inducing paradigm, repetitive transcranial magnetic stimulation (rTMS).


METHODS
Healthy young (n=15; 25+/-4 years) and old (n=15; 67+/-5 years) adults participated in two experiments. Motor evoked potentials (MEPs) were measured in the target muscle (first dorsal interosseus, FDI) and a remote muscle (abductor digiti minimi) during a set of single stimuli. Subjects then received real or sham inhibitory rTMS (intermittent subthreshold trains of 6Hz stimulation for 10min). MEPs were measured for 30min after rTMS.


RESULTS
In young adults, MEPs in the target FDI muscle were approximately 15% smaller in the real rTMS experiment than in the sham rTMS experiment (P<0.026). In old adults, FDI MEP size did not differ between experiments.


CONCLUSIONS
Advancing age is associated with reduced efficacy of inhibitory rTMS.


CONCLUSIONS
This work has important implications for the potential therapeutic use of rTMS in stroke and neurological disease.
Todd
Gabrielle
G
Discipline of Physiology, School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, SA, Australia. gabrielle.todd@adelaide.edu.au
Kimber
Thomas E
TE
Ridding
Michael C
MC
Semmler
John G
JG
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D004574:Electromagnetic Fields; D019054:Evoked Potentials, Motor / Q000502:physiology* / Q000528:radiation effects; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology* / Q000528:radiation effects; D009048:Motor Skills / Q000502:physiology / Q000528:radiation effects; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology / Q000528:radiation effects; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology* / Q000528:radiation effects; D009473:Neuronal Plasticity / Q000502:physiology* / Q000528:radiation effects; D011712:Pyramidal Tracts / Q000502:physiology / Q000528:radiation effects; D011930:Reaction Time / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology / Q000528:radiation effects; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D016896:Treatment Outcome; D055815:Young Adult