Hindawi Publishing Corporation Neural Plasticity Volume 2013, Article ID 396865, 9 pages http://dx.doi.org/10.1155/2013/396865 Research Article Time of Day Does Not Modulate Improvements in Motor Performance following a Repetitive Ballistic Motor Training Task Martin V. Sale, 1 Michael C. Ridding, 2 and Michael A. Nordstrom 3 1 Queensland Brain Institute, he University of Queensland, St Lucia, Brisbane, QLD 4072, Australia 2 he Robinson Institute, School of Paediatrics and Reproductive Health, he University of Adelaide, Adelaide, SA 5005, Australia 3 Discipline of Physiology, School of Medical Sciences, he University of Adelaide, Adelaide, SA 5005, Australia Correspondence should be addressed to Martin V. Sale; m.sale@uq.edu.au Received 18 December 2012; Accepted 18 February 2013 Academic Editor: Clive Bramham Copyright © 2013 Martin V. Sale et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Repetitive performance of a task can result in learning. he neural mechanisms underpinning such use-dependent plasticity are inluenced by several neuromodulators. Variations in neuromodulator levels may contribute to the variability in performance outcomes following training. Circulating levels of the neuromodulator cortisol change throughout the day. High cortisol levels inhibit neuroplasticity induced with a transcranial magnetic stimulation (TMS) paradigm that has similarities to use-dependent plasticity. he present study investigated whether performance changes following a motor training task are modulated by time of day and/or changes in endogenous cortisol levels. Motor training involving 30 minutes of repeated maximum let thumb abduction was undertaken by twenty-two participants twice, once in the morning (8 AM) and once in the evening (8 PM) on separate occasions. Saliva was assayed for cortisol concentration. Motor performance, quantiied by measuring maximum let thumb abduction acceleration, signiicantly increased by 28% following training. Neuroplastic changes in corticomotor excitability of abductor pollicis brevis, quantiied with TMS, increased signiicantly by 23% following training. Training-related motor performance improvements and neuroplasticity were unafected by time of day and salivary cortisol concentration. Although similar neural elements and processes contribute to motor learning, training-induced neuroplasticity, and TMS-induced neuroplasticity, our indings suggest that the inluence of time of day and cortisol difers for these three interventions. 1. Introduction Learning a new motor task is associated with an improvement in performance. he neural adaptations to training that contribute to performance improvements depend on the type and duration of training. For example, learning to juggle daily for six weeks leads to structural changes in white matter density that persist for four weeks following cessation of training [1]. Shorter periods of training (30 mins) also lead to neural changes [2], but these changes are less enduring. Irrespective of the duration and type of training, motor learning can be divided into fast and slow learning phases, but the time involved in acquiring the performance gains in the diferent phases of learning is very much task speciic [3]. Fast learning occurs ater a single session of training, whilst slow learning occurs ater several sessions, and involves “of-line” consolidation [4]. he relatively short time course involved in inducing training-related changes in cortical activity with fast learning makes these types of protocols particularly suitable for studying the neural adaptations to training, and is the type of learning involved in the present study. he neural changes associated with training also vary considerably between individuals. Some of the factors that inluence an individual’s neural response to training include genetic polymorphisms (e.g., brain-derived neurotrophic factor) [5, 6], attention [7], and age [8]. A key goal of neurorehabilitation research is to understand the mechanisms involved in mediating the efectiveness of training, thereby allowing for better targeted interventions. In this context, although repetitive training of tasks or movements is most obviously associated with rehabilitation for motor disorders, such as those induced