Researchers have described hour-by-hour changes in the amount of a protein believed to play a key role in Alzheimer's disease in the human brain.

A collaborative study by staff at Washington University in St Louis, USA and the University of Milan, Italy, made their report on amyloid beta in the journal Science.

Levels of the protein were measured using microdialysis, with a small catheter placed into brain tissue to sample fluid in the spaces between cells.

A total of 18 patients recovering from ruptured brain aneurysms or traumatic brain injuries took part in the study.

It was found that recovery from brain injury, rather than the wound itself, seemed to cause an increase in amyloid beta levels, contradicting the expectations of the scientists.

Commenting on the results, co-first author Dr David Brody states: "Proving that we can directly measure amyloid beta in the human brain is an important step forward for both clinical and basic research and that may be true not just in Alzheimer's disease but also in other serious neurological disorders."

He concluded by noting that the researchers' ultimate goal is to develop interventions which can be applied after a traumatic brain injury to enhance outcomes and reduce long-term Alzheimer's risk.

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