Minute organs hidden deep within the ear appear to directly alter blood flow to the brain, scientists have revealed.
Until now, experts thought the inner ear's job was to control balance alone. But the Harvard Medical School team, working with Nasa, found the balance organs also affect brain blood flow in their study involving 24 people.
They told BMC Neuroscience journal that the connection probably evolved to enable man to stand upright and still get enough blood up to the brain. The organs of balance are deep within the ear, inside a maze of bony chambers.
Two sacs, called the utricle and saccule, make up the inner ear's vestibule and three fluid-filled loops, known as the semi-circular canals, detect the rotation and tilting movements of the head.
Dr Jorge Serrador and his team from Harvard Medical School asked 24 healthy people to undergo a range of tests normally used on astronauts. These included a tilt test where the individual sits strapped to a chair that is then tilted to different angles, plus a ride inside a giant, spinning centrifuge.