BORED monkeys make stupid monkeys. That鈥檚 the possibility raised by a study in which Charles Gross of Princeton University showed that the richness of a primate鈥檚 environment affects its brain structure.
He housed pairs of adult marmosets in one of three types of cage for one month. The first was a bare cage with a food bowl, which met the minimum standards of the US National Institutes of Health. The second was a slightly larger cage with toys and structures that encouraged the monkeys to forage, such as branches that hid live worms. The third was twice as big with many more toys.
An examination of the monkeys鈥� brains showed that those housed in the second two types of cage developed denser neuron growth and almost double the amount of certain synaptic proteins that the brain uses to relay messages between neurons (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0508817102). 鈥淏oth of these reflect not only how much a monkey has learned, but also its ability to learn,鈥� Gross says.
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While he has not yet shown whether monkeys鈥� brains deteriorate when they are housed in basic conditions, Gross suggests that it may be necessary to house animals being used for cognitive studies in more stimulating environments than those specified by the NIH.
The study may also hold lessons for humans. 鈥淧eople are directly affected by what they do and what鈥檚 in their environments,鈥� says Gross. 鈥淲e鈥檙e just lucky that those are choices we get to make.鈥�
