A new study suggests that even subtle differences in blood sodium levels within the normal healthy range are associated with changes in brain excitability, offering fresh insight into how basic physiology may shape neural function. Researchers reported that individuals with slightly lower sodium concentrations tended to show signs of increased brain electrical responsiveness — a measure of how easily nerve cells fire.
The research, published in Scientific Reports, analysed data from 42 healthy adults who underwent blood tests and non‑invasive transcranial magnetic stimulation (TMS) — a technique that measures resting motor threshold, an indicator of cortical excitability. Scientists found a significant correlation: lower plasma sodium levels within the typical clinical range were linked to a lower resting motor threshold, meaning the brain’s motor circuits were more easily activated.
Sodium ions play a critical role in generating the electrical signals that allow neurons to communicate. Even small shifts in their concentration subtly influence the ionic gradients that underlie action potentials — the electrical impulses neurons use to transmit information. While severe imbalances are well known to cause neurological crises like seizures, this study highlights that even normal‑range variations could be part of what makes individual brains function differently.
Researchers emphasised that their findings do not prove cause and effect — the study shows an association rather than direct proof that lower sodium alters brain excitability. They also found no similar links with other electrolytes such as potassium or calcium. Future work will need larger samples and experimental manipulation to determine whether and how sodium changes directly influence neural activity.
Experts say this research could have implications for understanding subtle inter‑individual differences in cognition, motor control, and susceptibility to neurological conditions. The findings also raise questions about how dietary sodium and electrolyte balance might intersect with brain function, although scientists caution that sticking to well‑established nutritional and medical guidance remains crucial.
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