Intra-individual variability (IIV) refers to within-person variability in behavioural task responses. Several factors can influence IIV, including aging and cognitive demands. The present study investigated effects of aging on IIV of response times during executive functioning tasks. Known age-related differences in cognitive control and emotion processing motivated evaluating how varying the design of emotional response inhibition tasks would influence IIV in older and younger adults. We also tested whether IIV predicted inhibitory control across task designs and age groups. Older and (...) younger adults (N = 237) completed one of three versions of a stop-signal task, which all displayed happy, fearful, or neutral faces in Stop trials. An independent group of older and younger adults (N = 80) completed a go/no-go task also employing happy, fearful and neutral faces. Results showed older adults had more consistent responses (lower IIV) than younger adults in the stop-signal task, but not the go/no-go task. Lower IIV predicted more efficient emotional response inhibition for fear faces in the stop-signal task, but only when attention to emotion was task-relevant. Collectively, this study clarifies effects of aging and task design on IIV and illustrates how task design impacts the relationship between IIV and emotional response inhibition in younger and older adults. (shrink)

Short-term limb immobilization results in skeletal muscle decline, but the underlying mechanisms are incompletely understood. This study aimed to determine the neurophysiologic basis of immobilization-induced skeletal muscle decline, and whether repetitive Transcranial Magnetic Stimulation could prevent any decline. Twenty-four healthy young males underwent unilateral limb immobilization for 72 h. Subjects were randomized between daily rTMS using six 20 Hz pulse trains of 1.5 s duration with a 60 s inter-train-interval delivered at 90% resting Motor Threshold, or Sham rTMS throughout immobilization. (...) Maximal grip strength, EMG activity, arm volume, and composition were determined at 0 and 72 h. Motor Evoked Potentials were determined daily throughout immobilization to index motor excitability. Immobilization induced a significant reduction in motor excitability across time. The rTMS intervention increased motor excitability at 0 h. Despite daily rTMS treatment, there was still a significant reduction in motor excitability, loss in EMG activity, and a loss of maximal grip strength after immobilization. Interestingly, the increase in biceps and posterior forearm skinfold thickness with immobilization in Sham treatment was not observed following rTMS treatment. Reduced MEPs drive the loss of strength with immobilization. Repetitive Transcranial Magnetic Stimulation cannot prevent this loss of strength but further investigation and optimization of neuroplasticity protocols may have therapeutic benefit. (shrink)