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BackgroundMotor imagery practice (MIP) and anodal transcranial direct current stimulation (a-tDCS) are innovative methods with independent positive influence on motor sequence learning (MSL) in older adults.ObjectiveThe present study investigated the effect of MIP combined with a-tDCS over the primary motor cortex (M1) on the learning of a finger tapping sequence of the non-dominant hand in healthy older adults.MethodsThirty participants participated in this double-blind sham-controlled study. They performed three MIP sessions, one session per day over three consecutive days and a retention test 1 week after the last training session. During training / MIP, participants had to mentally rehearse an 8-element finger tapping sequence with their left hand, concomitantly to either real (a-tDCS group) or sham stimulation (sham-tDCS group). Before and after MIP, as well as during the retention test, participants had to physically perform the same sequence as fast and accurately as possible.ResultsOur main results showed that both groups (i) improved their performance during the first two training sessions, reflecting acquisition/on-line performance gains, (ii) stabilized their performance from one training day to another, reflecting off-line consolidation; as well as after 7 days without practice, reflecting retention, (iii) for all stages of MSL, there was no significant difference between the sham-tDCS and a-tDCS groups.ConclusionThis study highlights the usefulness of MIP in motor sequence learning for older adults. However, 1.5 mA a-tDCS did not enhance the beneficial effects of MIP, which adds to the inconsistency of results found in tDCS studies. Future work is needed to further explore the best conditions of use of tDCS to improve motor sequence learning with MIP.

Due to population aging, elderly drivers nowadays represent a significant rate of car drivers. Yet, we do not know exactly how aging may alter sensorimotor functions and therefore, its actual impact on safety. This paper aimed to assess to which extent elderly drivers are sensitive to various task loads and how this could impact reaction time with application to driving. Old and middle-aged people completed reaction time tasks (RT) close to those drivers usually have to manage while driving. We requested the participants to detect and respond to traffic lights or a traffic light arrows as quickly as possible during three experimental conditions of increasing difficulty. We expected that decision-making should be impacted through RT by manipulating the number of cues to be processed in both groups. The first test was a simple RT-task. The second and third tests were choice reaction time tasks requiring the processing of three or five information respectively. Responses had to occur within a 2s time-window, otherwise the result was considered a no-response. We showed that RT, error rate and no-response rate increased as a function of task difficulty, in both groups. However, the middle-aged people group outperformed the elderly group. RT difference between the two groups increased drastically with task difficulty. In the third test, the rate of no-response suggested that old drivers need more than 2s to process complex information and respond accurately. Both prolonged RT and no-response rate, especially for difficult tasks, may attest impairment of cognitive abilities, related to aging. Therefore, usual driving conditions for young drivers could be complex and stressful for the elderly who should thus be informed about the effects of normal aging upon driving with simple recommendations and advices.