Memory – the eyes have it.
Sighted people consume the world through their eyes; memories are created from what they see, hear, touch smell and feel emotionally, with visual impression being a key factor. While there’s no direct link between our eyes and the brain’s memory centre, the hippocampus, neuroscientists know that the brain uses a series of staging posts to transfer information from the eyes to the hippocampus. Recently there’s been a lot of interest in how our eyes move when we encode and retrieve memories. It’s been discovered that our eyes move in a particular way when we store and try to recall information. Research at Canada’s Baycrest health Sciences found that older adults use a particular series of eye movements to commit new things to memory and will repeat these movements when preparing to remember something, whereas younger people only use this strategy when they need to remember complex information. Researchers say they think this is a ‘rehearsal’ strategy, similar to repeating a telephone number aloud to try to remember it. They believe that older people are unconsciously moving their eyes in this way to compensate for memory deficits in ageing brains. This finding builds on previous research that showed our eyes move in the same way when we try to recall something and that this movement triggers activity in the hippocampus, whether the attempt at remembering is successful or not. Other studies have shown that people at risk of dementia appear to treat each scene they are shown as new – those without any cognitive impairment will spend more time looking at a new image than a familiar one when they’re presented side by side, whereas people developing a cognitive impairment will spend equal time looking at both images.
In some tests blind and visually impaired people have been shown to have superior recall and one theory is that they are not distracted by visual clutter that might distort memory. However this does not mean they are less likely to have a form of dementia in later life; research in Australia showed that blind or visually impaired people in care homes were more likely to have a form of dementia. Ageing is one of the highest risk factors for dementia and sight loss but research by the University of Michigan suggests that undiagnosed and untreated sight problems in earlier life leads to a higher risk of Alzheimer’s Disease, the most common form of dementia. There is also a form of dementia that affects the brain’s processing of visual cues, Posterior Cortical Atrophy, where a person is not able to see things that are present in reality at all. This often affects younger people and initially memory does not seem to be affected. It’s also well know that hallucinations are common with many forms of dementia.
There is so much we don’t yet understand about how memory works; the relationship between sight and remembering looks like it’s an exciting field with potential for new insights.