Autonomic Adaptations to Hydration and Brain Functioning

Study Overview
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Brief Summary
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The influence of relatively small decreases in hydration status have been little studied. On two occasions subjects will be allowed to lose about 0,5% of their body weight and one occasion 300ml of water will be consumed. Functional MRI will be used to monitor brain functioning when performing a mental arithmetic task. Heart rate variability will be monitored and related to differences in brain functioning when water has and has not been drunk

Detailed Description
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On two mornings twelve male participants will be exposed to a temperature of 30oC for four hours and either drink or not drink two 150ml glasses of water during that time. The subjects the participate in an fMRI protocol during which they complete a modified version of the Paced Auditory Serial Addition Test (PASAT): a challenging arithmetic task designed to elicit autonomic arousal. Throughout the morning subjects will their heart rate variability (HRV) monitored. At periodic intervals subjects will rate their thirst and mood by visual analogue scales and at the end of the PASAT task they rate its difficulty. Changes in body temperature and fluid loss (perspiration and urine) and urine osmolality will be monitored.

Official Title
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Autonomic Adaptation to Hydration and Brain Functioning

Conditions
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Hydration

Intervention / Treatment
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* Biological: Water
* Other: No drink


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Self declared as healthy and not taking any medication Exclusion Criteria:

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 30 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Cross-over design where on one occasion subjects lost 0.5% body weight,and drank 300ml water and on another occasion nothing was consumed
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Water<br>Subjects consumed water | Biological: Water<br>* 150 mil of water was drunk on two occasions<br>|
| Experimental: No water<br>Subjects did not consume water | Other: No drink<br>* Although body weight lost no drink consumed<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| BOLD signal | Participants will be presented with an arithmetic task, modified for use in the scanner, similar to the Paced Auditory Serial Addition Task: a 'stressful' task that measures calculation ability and is known to elicit an autonomic response 35. Pairs of two digit numbers appeared on a screen in red and participants will be required to mentally add or subtract the numbers. After 2 seconds the screens will be removed and a second screen appeared containing a correct and an incorrect answer. Participants will be required to press either a left or right button to indicate which answer was correct ). The speed of presentation is designed to be just at the level that it is possible to perform the task although it required mental effort and was 'stressful'.This allows investigation of areas of the brain associated with working memory but also those associated with emotional arousal. | One hour in scanner (1300-1400 hours) | 
| Heart-rate variability | Differences in inter-beat intervals derived from RS800 Polar heart rate monitor with a sampling rate of 1000Hz. Profile to be analysed using the Kubios software | Differences on two testing occasions (0900 and 1300 hours) will be related to BOLD | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Ratings of ,mood and perceived effort | Using visual analogue scales mood and perceived effort will be rated. | Rated baseline (0830 hours), 30 mins later, 280 minutes later | 
| Change in body weight | Scales, sensitive to 5 grams, will be used to monitor changes in body weight | Measured at baseline (0830 hours), after 290 minutes (before urinating) and 300 mintues (after urinating) | 
| Osmolality | Using an Osmomat 300 freezing point osmometer the osmolality of urine will be measured at the beginning and end of testing sessions | Baseline (0830 hours) and after 300 minutes | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Hydration, Brain functioning, Heart-rate variability