Scientists have claimed through a study that bigger brains do not necessarily result into better memory. Findings are published in journal Cerebral Cortex.
According to a new study led by Michigan State University, 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 has long been believed that a bigger hippocampus meant a better memory until a 2004 study showed that its size does not always matter for memory in older adults. But scientists are only now starting to understand why.
The study shows 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.
The study has potential implications for earlier diagnosis of aging-related memory disorders such as Alzheimer’s disease. Some older adults whose brain scans show a larger hippocampus – perhaps due to high levels of education, physical activity, or social and cognitive engagement – could have their cognitive decline overlooked or mischaracterized if physicians do not also consider their white matter connectivity.
Scientists analyzed two different types of MRI brain scans: one that evaluated hippocampal size and another that evaluated the white matter circuitry that connects the hippocampus with other brain regions involved in learning. The scans came from more than 330 older adults who are part of the Berlin Aging Study-II, or BASE-II, a large, population-based investigation of aging in Germany.
The BASE-II participants also took learning and memory tests in which they heard a list of 15 words and then had to record as many words as they could remember. Each participant repeated the exact same test five times to gauge how they learn through repetition.
Scientists then analyzed the relationships between how quickly the participants learned and the size of their hippocampus and white matter structure. They reported that faster learning was found only in older adults who had both a larger hippocampus and more uniform white matter circuitry connecting it to other parts of the brain.