Fri, Dec 13th, 2013

Light activates the brain in BLIND people: Scans reveals that those with no sight can still tell if a bulb is switched on


  • During tests, blind people identified when lights had been switched on
  • Scans also found the change in light activated parts of their brains
  • Researchers discovered light is registered by a part of the retina that is separate from the rods and cones that control sight
  • This suggests certain functions remain even when people lose their vision

In what has the potential to revolutionise how scientists and doctors treat blindness, researchers have discovered that light not only activates the brain, it does so even in people who can’t see.

Research from the University of Montreal found that even when vision is impaired and objects can no longer be seen, changes in light still register in the brain and blind people can tell when a light is switched on or off.

This is because the light is picked up by a part of the retina in the eye that is separate from the rods and cones that control overall vision.

‘We were stunned to discover that the brain still responded significantly to light in these rare three completely blind patients despite having absolutely no conscious vision at all,’ said study author Steven Lockley.

Researchers put three blind people in a room and asked them to say whether the light in the room was turned on or off. In all cases, the participants were able to identify changes in light.

‘We found the participants did indeed have a non-conscious awareness of the light – they were able to determine correctly when the light was on without being able to see it,’ said author Gilles Vandewalle.

The researchers then flashed lights directly at the participants’ eyes to study more closely what impact the light had on the brain.

‘The objective of this second test was to determine whether the light affected the brain patterns associated with attentiveness – and it did,’ said researcher Olivier Collignon.

Finally, the participants were put into a functional MRI (fMRI) brain scanner and each took part in a sound matching task while lights were flashed in their eyes.

‘The fMRI further showed that during an auditory working memory task, less than a minute of blue light activated brain regions important to performing the task,’ continued Vandewall. 

‘These regions are involved in alertness and cognition regulation as well being as key areas of the default mode network.’

Theses scans found the brain ‘sees,’ or detects light through a photoreceptor found in the ganglion cell layer of the retina. This receptor is separate from the rods and cones that control vision and help people see.

The study claims that the default network in the brain is linked so humans use ‘a minimal amount of resources’ when monitoring their surroundings.

‘If our understanding of the default network is correct, our results raise the intriguing possibility that light is key to maintaining sustained attention,’ said agreed the researchers.

‘This theory may explain why the brain’s performance is improved when light is present during tasks.’

Lockley concluded: ‘Light doesn’t just allow us to see, it tells the brain whether it’s night or day which in turn ensures our physiology, metabolism and behaviour are synchronised with environmental time’.

‘For diurnal species like ours, light stimulates day-like brain activity, improving alertness and mood, and enhancing performance on many cognitive tasks,’ explained researcher Julie Carrier.

The research could have far-reaching effects in the treatment of blind people, as well as in other cognitive disorders, because doctors can potentially use light to activate specific parts of the brain.

The researchers from University of Montreal also worked with teams at Boston’s Brigham and Women’s Hospital. Findings are reported in the Journal of Cognitive Neuroscience Science.

read more: www.dailymail.co.uk

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