Saving New Brain Cells
It has long been thought that the ability of learning when young was due to the fact that as we aged no new brain cells developed. However in 1990 it was discovered that the mammalian brain continued making neurons into adulthood and in 1998 that this also occurred in humans. It is now known that substances such as alcohol can retard new brain cell formation while activity enhances development. The new neurons are formed in the hippocampus. Located in the brain this structure is involved in learning and memory. Though exercise increases the production of these it does not mean they survive. Most of the cells die in the first few days which creates the question: what is the point of creating these cells if they die soon after?
Professor Shors at Rutgers University has investigated the point of creating these cells. An experiment called the ‘trace eyeblink conditioning’ was carried out on rats whereby a tone is sounded and then around half a second later a puff of air directed at the eye is allowed causing the rat to blink. Eventually the animal makes the connection between the tone and the stimulation and so can anticipate what will occur therefore blinking before the stimulation. This experiment measures ‘anticipatory learning’ in animals. To see what part the new cells played the rats were injected with BrdU prior to the experiment so that any new brain cells could be identified.
It was found that after a length of time the rats who participated in the trace eyeblink conditioning retained more new brain cells then those that did not. However for simple tests to do with memory such as finding a platform in water the rats did not retain any additional new brain cells than usual. From this it was concluded that the new cells are needed ‘just in case’ for a particularly difficult challenge where the brain therefore needs the use of more cells. It was also found through these experiments that timing is important. The new cells will not be able to assist until they begin to differentiate into neurons – about one week after they are formed but they cannot be older than two weeks before learning begins as this is when the cells are too old and begin to die off. Further experiments where new cell production was inhibited in rats shows that with a lack of these cells the animal can function normally however cannot solve very complex problems.
Reference: Shors, TJ 2009, ‘Saving new brain cells’, American Scientific, vol. 300, no. 3, pp. 41-46
