As it is pumped through blood vessels and delivers oxygen to brain cells, blood may actually help us think.
Research done by scientists at MIT suggests that in addition to providing nutrients and oxygen to the body's cells, blood may affect the activity of neurons in the brain as it flows through, changing how they transmit signals to each other and regulating the flow of information through the brain.
"We hypothesize that blood actively modulates how neurons process information," said researcher Christopher Moore in an invited review in the Journal of Neurophysiology. "Many lines of evidence suggest that blood does something more interesting than just delivering supplies. If it does modulate how neurons relay signals, that changes how we think the brain works."
This relationship between blood flow and brain function has implications for understanding neurological diseases, such as Alzheimer's disease, schizophrenia, multiple sclerosis and epilepsy.
"Most people assume the symptoms of these diseases are a secondary consequence of damage to the neurons. But we propose that they may also be a causative factor in the disease process," Moore said.
For example, epileptics often have abnormal blood vessels in the regions of the brain where seizures occur, which suggests that abnormal blood flow could trigger the seizure.
Moore has a few theories that could explain just how blood affects neural activity, based on studies in his lab. Blood contains diffusible elements that could leak out of blood vessels and affect brain activity, and changes in blood volume could affect the concentrations of these factors. Neurons may also react to the mechanical forces applied to them when the blood vessels expand and contract.
Blood also influences the temperatures of the brain tissue, which affects the activity of the cells.
The research was funded by Thomas F. Peterson, the Mitsui Foundation and the McGovern Institute for Brain Research at MIT.