Dehydration occurs when a person loses more fluids than they are incorporating into their body . It usually occurs in very hot situations, in which you sweat more than usual, or after performing sports activities that require great effort and without adequate rest . Lack of fluids can cause feelings of dizziness or disorientation , in addition to making it difficult for the body’s functions to function properly. Although it is especially dangerous in young children and the elderly, dehydration can affect anyone and have greater consequences than is believed. A new study has investigated how a lack of fluids in the body affects brain function .
A team from the Georgia Institute of Technology has used brain scans and simple, repetitive tasks designed to assess the responsiveness of subjects who had lost a lot of fluids and had not rehydrated. Dehydration caused study subjects to make more mistakes and certain areas of their brains showed significant changes. The thirteen volunteers performed the assigned tasks in three different scenarios: at rest and hydrated , after prolonged heat, exercise and sweating but drinking water during exercise or after prolonged heat, exercise and sweating without water . All subjects completed the tasks in air-conditioned rooms and with a rest after strenuous activity.
The tests they had to carry out consisted of pressing a button for 20 minutes each time a yellow square appeared on the screen , and this could happen according to regular or random patterns. The intention was to avoid cognitive complexity so that the neural process was as similar as possible to that normally used in repetitive movements . Other studies have shown that these types of neural responses are those that occur in repetitive motor functions such as manual work or military exercises . The monotony of these processes can cause inattention that is accentuated in situations of heat, stress or loss of fluids.
Heat, stress, accident
During the experiment, when participants exercised, sweated and drank water, spaces in the center of their brain that fill with fluid, called ventricles , contracted. In contrast, exercise and dehydration caused the ventricles to expand . Functional magnetic resonance imaging ( fMRI ) revealed these differences, but better or worse task performance cannot be explained by this change in the size of the brain ventricles.
However, during dehydration other alterations in neuronal activation patterns were observed, activating with greater intensity the areas necessary to complete the task and others that are not necessary . Researchers believe that the latter is due to a response from the body’s physiological state saying ” I am dehydrated .” Mindy Millard-Stafford , project leader, states that “even when hydrated, heat and exercise also affected subjects during the task, but to a lesser extent than dehydration.”
The study also decided to test the effects of over-hydration in the subjects. Hyponatremia or water intoxication occurs when the blood plasma is too dilute and the sodium concentration in the blood drops excessively, being decompensated in the face of an increasing amount of water.
Citation: Melinda L. Millard-Stafford, Matthew T. Wittbrodt & team. Institute of Technology of Georgia. ‘Exercise ‐ heat stress with and without water replacement alters brain structures and impairs visuomotor performance’. Physiological Reports (2018). DOI: https://doi.org/10.14814/phy2.13805
