Australian scientists have made an important advance in understanding how the brain interprets the signals it receives from the eyes about how we view the orientation of the world we see about us.
Research by a team in The Vision Centre has found that while our brain has a natural tendency to view the world in terms of the vertical and horizontal, it has also developed an ability to override this to detect objects moving obliquely in the vision.
At its most basic, the skill might save us from a leaping lion or a speeding car or some other object that isn’t up/down or horizontal, says Professor Colin Clifford, of The Vision Centre and The University of Sydney.
“For a long time the prevailing view has been that our visual system responds to edges that are horizontal or vertical – and indeed there are many of these in the natural environment: trees, the horizon and so on,” he says. “Our latest research, however, indicates that the brain has a way of suppressing this dominant information flow enough to pick out objects that don’t conform.”
The discovery came as quite a surprise, he says. When the team put volunteers in a magnetic resonance imaging (MRI) machine and studied how the brain ‘lit up’ when confronted with visual signals at different angles, they expected to get a much stronger response to lines that were up, down or sideways – in line with the prevailing scientific theory.
Instead, they found the response to oblique lines was even stronger, suggesting the brain was carrying out some subtle extra processing to highlight these.
“We concluded that this probably was because oblique objects are likely to be of considerable interest to the brain – perhaps representing food or danger or some other important signal – and that we need to pay attention.
“The environment moulds our vision and the sensitivity of our visual neurons is mostly directed at edges that are up, down or sideways – but in this case it is somehow compensating for this natural tendency, to tell us something we really need to know.”
The results throw new light on how the brain performs the phenomenally complex task of making sense out of the avalanche of orientation, colour and movement signals fed to it via the nerve cells in the eye.
Understanding how the brain performs the miracle of sight holds more than just scientific interest, Prof. Clifford says. “If we can understand how these systems work, we have a better chance of understanding how and why they are not working properly – in cases of eye or even brain disease.
“The tests we used in our experiment could, in other words, become diagnostic tools to see if someone’s vision or their brain is performing as it should.
“They could also help us understand conditions such as amblyopia, in which a person with a strong squint manages to suppress the information coming from one of their eyes.”
The research may also reveal whether people with a greater ability to sense oblique visual signals may be better at certain tasks – such as cricket, driving or other highly visual activities.
The article ‘Orientation Anisotropies in Human Visual Cortex’ by Damien J. Mannion, J. Scott McDonald, and Colin W. G. Clifford appears in the Journal of Neurophysiology 103, April 2010.
The Vision Centre is funded by the Australian Research Council as the ARC Centre of Excellence in Vision Science.
Source:
The Vision Centre