Hypohydration alters pre-frontal cortex haemodynamics, but does not impair motor learning

Figures

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  Fig. 1. Overview of the study design. Participants were pseudo-randomised into either the control (CON; black) or hypohydrated (HYPO; grey) groups and arrived at the laboratory at the respective time indicated above. The dehydration regime, accompanying data collection, and the rest period took ~ 240 min (120 min of cycling, ~ 60 min of ancillary data collection/intermittent rest periods during cycling, and ~ 46 min of rest following the cessation of exercise). Both the control and hypohydration group completed the discrete sequence production (DSP) task training trials (~ 90 min) and engaged in a retention interval of ~ 300 min. Participants then returned to the facilities to perform the delayed learning assessments (retention and transfer test; ~ 30 min). MHR is maximal heart rate

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  Fig. 2. An example trial of the discrete sequence production task used in this study. Ascending numerical values corresponded to the second to fifth digit (i.e. excluding the thumb) on the participant’s non-dominant (left) hand. Values remained visible until a key was depressed or the final key press was made. Feedback was provided to the participant on their performance at the conclusion of each trial

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  Fig. 3. Functional near-infrared spectroscopy channel placement using the International 10–20 EEG system. Emitter-optode pairs were positioned over the left and right PFC, denoted between Fp1 and F3 (red), and Fp2 and F4 (blue) respectively. Original image was published under creative commons licence (CC0 1.0)

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  Fig. 4. Response time during the training, retention, and the transfer test of the discrete sequence production task. Transparent circles and squares denote individual data for the control and hypohydration groups, respectively. A lower response time indicates faster performance

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  Fig. 5. Changes in pre-frontal cortex A oxyhaemoglobin and B deoxyhaemoglobin concentrations evoked from baseline, during training. Transparent circles and squares denote individual data from either hemisphere for the control and hypohydration groups respectively. The *symbol represents significant pairwise comparisons for consecutive blocks in CON (both P ≤ 0.03). †denotes a significant group × block interaction for HYPO (P = 0.02)

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  Fig. 6. Changes in pre-frontal cortex A oxyhaemoglobin and B deoxyhaemoglobin concentrations evoked from baseline, during the retention and transfer tests. Transparent circles and squares denote individual data from either hemisphere for the control and hypohydration groups, respectively