Light therapy for ADHD, dyslexia and autism is a contentious area. How could spending twenty minutes sitting in front of a flashing light help children learn to read or control themselves? I was highly skeptical until I tried it myself (see Light Therapy Follow Up). Even having tried it I could only speculate on why it had the effect it did. Now some researchers have shown that light can effect your memory.
By exposing participants to a flashing light for one second, researchers in Oxford found that participants were better able to recall a list of trigrams (semi-random groups of three letters). Most importantly the improvements only happened when the lights were flashed at frequencies on or around 10.2 Hz. A frequency related to the brain’s alpha waves and believed to be relevant to memory functions.
Alpha waves normally span the 8 to 12 Hz range but this study was looking at older people with a mean age of 78. As the brain gets older its brain waves shift slightly and 10.2 Hz is the peak frequency for those aged 80 or above. The researchers tested flicker frequencies of 9.0 Hz, 9.5 Hz, 10.0 Hz, 10.2 Hz, 10.5 Hz, 11.0 Hz, 11.5 Hz and 500 Hz. Only those frequencies in the 9.5 – 10.5 Hz range improved participants recall.
This well designed study shows a clear link between flickering visual stimulus (sometimes called photic driving) and memory performance with strong evidence that the mechanism relates to brain wave activity. However this was a test of short exposure to flicker very quickly followed by the memory test. It provides no evidence as to what happens if the exposure to the flicker is longer or to how long the effects last. Both of these points are vital to understand what, if any, effect light therapy can have on people with learning disorders
Here we move into the field of speculation. It is clear that brain wave patterns do relate to cognitive abilities and behaviour. It also changes as we age, notably during childhood. Is it possible that children with learning problems that are related to poor short-term memory are stuck with the alpha wave patterns of a young child? If this is the case, could repeated exposure to photic driving train the brain to have strong, more consistent alpha waves? It is possible but much more research is needed.