When it comes to certain parts of the brain, bigger doesn’t necessarily mean better.
A larger hippocampus (a curved, seahorse-shaped structure embedded deep in the brain) does not always reliably predict learning and memory abilities in older adults.
It’s normal for the hippocampus to shrink as we age and scientists previously believed that a bigger hippocampus meant a better memory.
A 2004 study showed that its size does not always matter for memory in older adults and a new study sheds light on why.
It indicates that the size or volume of the hippocampus is only a meaningful marker of learning for older people with more intact limbic white matter – the neural circuitry that connects the hippocampus to the rest of the brain.
Andrew Bender, lead author of the paper, said: “Our findings highlight the need to measure not just the size of the hippocampus, but also how well it’s connected to the rest of the brain when we look for physical markers of memory decline in older adults.”
The study has potential implications for earlier diagnosis of ageing-related memory disorders, such as Alzheimer’s disease.
Some older adults whose brain scans show a larger hippocampus could have their cognitive decline overlooked or mischaracterised if physicians do not also consider their white matter connectivity.
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