A new study on aging and the brain published in the Journal of Nature Communications looked at the hippocampus region of the brain.
“It's commonly accepted that aging negatively impacts most of our cognitive abilities, especially memory,” study author Zachariah M. Reagh told us. “While that is indeed the case, there might be more to the story.”
Reagh explains that a lot of ways we test memory involve really simplistic memorization tasks (such as learning arbitrary lists) that don't really reflect what we do in the real world. So, building on this, the memory deficits we often report in older adults can be pretty specific to laboratory tests.
“A lot of recent studies have focused on how we build and retrieve memories of naturalistic experiences, and a particular network of brain regions - which we call the Posterior Medial network - seems to be really important for this,” Reagh told us. “This network of brain regions is involved in certain aspects of memory, such as representing situations and contexts, and it's also vulnerable to certain age-related pathologies.”
One specific aspect of this network, alongside a part of the brain crucial for memory called the hippocampus, is that it is sensitive to moments where one event transitions to another, which researchers call event boundaries.
“Humans are pretty remarkably consistent about where they think these event boundaries occur, but that consistency seems to sometimes go down in older adults,” Reagh told us. “However, there isn't much data about what's going on in the aging brain during naturalistic events. So, the question arises: Does aging change the way the brain responds to event boundaries?”
The research team predicted that, in line with age-related vulnerability in the hippocampus and Posterior Medial network, older adults would show reduced activity at event boundaries compared to younger adults.
“There could not be a more important topic than understanding how we encode and retrieve information about the world around us,” Reagh told us. “Naturalistic studies are challenging, because the experimenter has to give up some control over what the participant is thinking and doing, but having a window into what the brain is normally doing in daily life is invaluable. Additionally, given the fact that we all age, and the fact that the world's proportion of older individuals is rapidly growing, we need to better understand the ways the brain and cognition change as we get older. This is important not only for understanding 'healthy' aging, but for being able to differentiate 'healthy' older adults from those who might go on to develop Alzheimer's disease.”
The research team tested their hypothesis by looking at brain activity during event boundaries across all of the participants, from 18 to 88 years old. Additionally, they looked at whether brain activity at event boundaries related to memory.
“In line with our predictions, we did find that activity at event boundaries was present throughout the Posterior Medial network, and that this activity tended to decline with age,” Reagh told us. “This was particularly pronounced in the posterior (i.e., back of the) hippocampus, a part of the brain crucial for making memories. However, not all Posterior Medial network regions showed this decline; some actually showed increased activity with age. One region where we saw this, the medial prefrontal cortex, is widely thought to be involved in representing coarse, gist-like information and memories.”
The research team also found that activity in the posterior hippocampus at event boundaries predicted memory for stories in the Logical Memory test, which assesses memory for short stories and is completely separate from the story depicted in the movie.
“This is really cool, because it suggests that hippocampal responses to event boundaries are memory-related, and moreover, that they may be memory-related in a broad sense that extends beyond memory for any one thing,” Reagh told us.
Reagh and the team were surprised to see different directionality of changes in the Posterior Medial network. The fact that some regions are showing declines across the age range while some are showing increases is a much more interesting story, because it could suggest that networks of brain regions responsible for encoding and retrieving information about events might be reorganizing or shifting duties rather than simply going downhill.
“It isn't uncommon in an aging study to see that virtually everything you measure just looks like a weaker, messier, or poorer version of what you see in younger adults, be it performance on a cognitive task or fMRI signal in a particular part of the brain,” Reagh told us. “That isn't what we saw here.”
Reagh believes the study points to the promise of using naturalistic research paradigms in studying older populations.
“For one, stories are engaging and enjoyable, which is all the more important when your participants may not have tons of experience with computerized tasks,” Reagh told us. “I think this could be a really interesting way of adding a tool to our box when it comes to clinical assessments, especially since we are coming to understand what the brain is doing during these complicated types of stimuli.”
Patricia Tomasi is a mom, maternal mental health advocate, journalist, and speaker. She writes regularly for the Huffington Post Canada, focusing primarily on maternal mental health after suffering from severe postpartum anxiety twice. You can find her Huffington Post biography here. Patricia is also a Patient Expert Advisor for the North American-based, Maternal Mental Health Research Collective and is the founder of the online peer support group - Facebook Postpartum Depression & Anxiety Support Group - with over 1500 members worldwide. Blog: www.patriciatomasiblog.wordpress.com