Washington: Humans may have a sixth sense after all, scientists have suggested after finding that a protein in the human retina, when placed into fruit flies, has the ability to detect magnetic fields.
The researchers from the University of Massachusetts Medical School, however, cautioned that whether or not humans use it in that way is not known.
"It poses the question, `maybe we should rethink about this sixth sense,`" lead researcher Steven Reppert was quoted as saying by LiveScience.
"It is thought to be very important for how animals migrate. Perhaps this protein is also fulfilling an important function for sensing magnetic fields in humans."
Animals are known to have a magnetic sense that depends on special proteins called cryptochromes, which are also found in the human retina.
While past research has suggested humans can`t sense magnetic fields, with studies showing such a capability remaining controversial, there is evidence that geomagnetism affects the light system in our eyes.
To see if humans perhaps possessed this other sense, Reppert and his team carried out several experiments on wild fruit flies.
For their test, published in the journal Nature Communications, the team also replaced the cryptochromes of some fruit flies with the human version of the protein.
They placed the flies into a T-shaped maze, with each arm equipped with a coil wrapped in such a way that when a current was sent through it, the coil became magnetized.
The team varied which side was magnetised and its strength, which went up to eight times that of Earth`s magnetic field.
The flies with the human cryptochromes showed sensitivity to the magnetic fields ? either avoiding them as they might naturally do if not acclimated to the magnetism, or showing a preference for the magnetised arm of the maze when trained with sugar rewards to go toward the magnetic field.
The human protein only worked in the blue range of light, the researchers found.
Past research has suggested that in addition to helping animals such as sea turtles and migratory birds navigate, the ability to detect magnetic fields could help with visual spatial perception.
To picture a magnetic-field coordinate system overlaid on objects we view, Reppert said.
"It may aid how animals perceive how objects are in time and space in a way we haven`t thought about before," said the neurobiologist.