Is an animal's agility affected by the position of its eyes?

Feb 22, 2010

New research from scientists in Liverpool has revealed the relationship between agility and vision in mammals. The study, published today in the Journal of Anatomy, sampled 51 species to compare the relationship between agility and vision between frontal eyed species, such as cats, to lateral-eyed mammals such as rabbits, to establish if the positioning of the eyes resulted in limitations to speed and agility.

"Footballers do it, cheetahs do it, and even sedentary academics can do it. We all have the ability to visually track an object whilst on the move and you don't give a second thought to the effort involved," explained co-author Dr Nathan Jeffery from the University of Liverpool. "As you walk or run your head swings up and down, tilts from side to side and rotates. Three semicircular canals of fluid found on each side of the skull sense these movements, one for each direction. These then send signals via the brain to three pairs of muscles that move the eyeball in the opposite direction and ensure that you can keep your eye on the ball, gazelle or the beer in your hand."

This process, known as the vestibulo-ocular reflex, is affected by the directions sensed by the canals and the pull directions of the eye muscles. In mammals, the eyes can be on the side of the head, as with rabbits, or at the front of the head like in cats, however the position of the canals is basically the same. In some the brain must do extra calculations to adjust the signal from the canals to match the different pull directions of the eye muscles.

"In our study we wanted to find out if these extra calculations placed any limitations on how fast an animal could move," said co-author Phillip Cox. "We asked if there could be a point whereby, if an animal moves too quickly it could result in the brain being unable to adjust the signals from canal to muscle planes, which in turn would result in blurred vision." The work was funded by the Biotechnology and Biological Sciences Research Council.

The team used MRI scanners to analyse the arrangement of canals and eye muscles in 51 species of mammal including giraffes, camels and zebra, tree shrews, bats and sloths. Astonishingly, the team found that the position of canals and eye muscles had no effect on the ability to see clearly at speed. In theory, a Sloth could travel as fast as a Cheetah without blurring its vision.

The team also found evidence suggesting that the role of the extraocular muscles switches with changes of eye position. For instance, muscles that make up-down compensatory movements in frontal-eyed species appear aligned for torsional movements in lateral-eyed species. Before this, scientists had assumed that major rewiring of the connections was essential to adapt the reflex to changes of eye position.

"Switching between muscles offers an economical way of adapting the vestibulo-ocular reflex to changes of eye position without major rewiring of the connections or changes of canal orientations," concluded Dr Jeffery. "The mammalian brain can apparently cope with the extra demands placed on it whether the eyes are at the front, side or almost at the back of the head."

Explore further: World's first microbe 'zoo' opens in Amsterdam

More information: Jeffery.N, Cox.P,“Do agility and skull architecture influence geometry of the mammalian vestibule-ocular reflex?” Journal of Anatomy, Wiley-Blackwell, February 2010, DOI:10.1111/j.1469-7580.2010.01211.x

Related Stories

Streamlining brain signals for speed and efficacy

Oct 22, 2008

Life exists at the edge of chaos, where small changes can have striking and unanticipated effects, and major stimuli may go unheard. But there is no space for ambiguity when the brain needs to transform head motion into precise ...

Here's venom in your eye: Spitting cobras hit their mark

Jan 22, 2009

Spitting cobras have an exceptional ability to spray venom into eyes of potential attackers. A new study published in Physiological and Biochemical Zoology reveals how these snakes maximize their chances of hitting the ta ...

Recommended for you

World's first microbe 'zoo' opens in Amsterdam

1 hour ago

The world's first "interactive microbe zoo" opened in Amsterdam on Tuesday, shining new light on the tiny creatures that make up two-thirds of all living matter and are vital for our planet's future.

Study shows how chimpanzees share skills

2 hours ago

Evidence of new behaviour being adopted and transmitted socially from one individual to another within a wild chimpanzee community is publishing on September 30 in the open access journal PLOS Biology. This i ...

Little blue penguin back at sea after hospital stint

7 hours ago

Wildbase Recovery Community Trust ambassador and Rangitikei MP Ian McKelvie joined Massey University veterinary staff to release a little blue penguin back into the sea at Himatangi Beach this morning.

User comments : 0