Do you see what I see?

A Southern Cross University psychology researcher has, along with a team of national and international researchers, discovered an important new link between what people see and the way their minds process that visual information.

For more than a century, scientists have hypothesised, but been unable to prove, that what is being seen by a person depends on the level of activity in the brain that is processing the visual stimulation.

Now for the first time, Professor Robert O'Shea, from the School of Health and Human Sciences at the Coffs Harbour campus, and his colleagues have been able to demonstrate that the level of activity of the neurons in the brain determines what a person sees.

"Until now, evidence for such a mechanism has been lacking. In fact, prior to our study, all the previous experiments showed there was no relationship. But our experiments also show why the previous experiments were unsuccessful," Professor O'Shea said.

The study, 'Visual sensitivity underlying changes in visual consciousnesses' has been published in the scientific journal Current Biology.

Visual consciousness has received much interest in recent years because it is thought to be the key to understanding the brain processes that support the conscious experience we have every moment of our waking lives.

The increased understanding of visual consciousness delivered by this research is important for such things as predicting how artificial eyes might be used by blind people, and for understanding disorders such as colour blindness, motion blindness and face blindness.

The method used by the researchers tested a remarkable phenomenon of visual consciousness in which what someone sees flips, every few seconds or so, between two incompatible images continuously presented to each eye.

The researchers used a set of horizontal lines as one image for one eye, and a complex chequerboard pattern as the image for the other eye. They briefly changed some of the horizontal lines while their participants were either seeing the lines or seeing the chequerboard and asked their participants to detect the change.

The researchers found that when people were seeing the lines, the change was easy to see but when they were seeing the chequerboard, the change was difficult to see. Critically, they found that just before consciousness flipped from the lines to the chequerboard, the change was quite difficult to see.

"It is as though the neurons in the brain processing the image we see get tired out," Professor O'Shea said.

The researchers also found that just before consciousness flipped from the chequerboard to the lines, the change was quite easy to see.

"It is as though the neurons in the brain processing the image we do not see have been resting, recovering their energies."

Professor O'Shea said that this confirmed, for the first time, a theory proposed in 1901 that the level of activity of the neurons in the brain processing the images is responsible for the changes in visual consciousness.

"From 1967 to the 1990s there was this glaring inconsistency with this theory. What we have done is remove that inconsistency and found the final piece of evidence to support the theory," he said.

Professor O'Shea joined Southern Cross University in May 2009. He is recognised nationally and internationally for his research and extensive publication in perception and in cognitive neuroscience. A central research theme for Professor O'Shea is his ongoing investigation into the mechanisms of visual consciousness, which underlies virtually all aspects of everyday behaviour and cognition.

Professor O'Shea's colleagues were Associate Professor David Alais from The University of Sydney, Dr John Cass from University of Western Sydney and Professor Randolph Blake from Vanderbilt University in the USA.