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  • Writer's pictureEmine Topcu

Ageing and Memory – Part II

In my previous post, I briefly mentioned the theories behind what is happening to our brain that causes normal memory impairments and what could be the reason behind being a "super ager."


One important thing to point out is that there are different types of memories, and not all of them are impacted equally during ageing. Procedural and semantic memory, for example, the memory of how to do things and the memory of factual information, respectively, are less vulnerable to decline with ageing (1,2). On the other hand, episodic memory (the memory of experiences) is more prone to be impacted by age (2). The changes in the hippocampus during ageing may be behind the deficits in episodic memory (3). Hippocampus is also involved in spatial memory, and studies show a correlation between hippocampal atrophy and deficits in spatial memory as well (3).


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Regardless of the common results of many studies, it is not easy to draw clear lines on what type of memory is more affected by ageing. For example, even within the same type of memory, recognition is better than recall, which causes better test results when the participant is given a clue (4). Or, the memories that were initially thought to be less affected—like implicit, semantic, or picture memory—seem to be more vulnerable than thought if the experiments become demanding (4). The study design is a very important factor in the results achieved. There are even studies that claim there is no significant memory decline before the age of 60, but we have seen that the majority of the studies do not agree with this conclusion (1). Similarly, some studies claim that older people show similar performances as younger adults, only slower, but this is not supported widely either (3).


Another impairment observed with older age is the deficit in executive functions, like attention (2). With age, people seem to be more easily distracted, which can cause lower success in memory tests (2). One theory behind this loss of attention during working memory is the inability to suppress irrelevant thoughts (5,6). There may be more interference that lowers the memory performance.


Functional MRI (fMRI) is a great technology for neuroscience, as it allows for studying neural activity in the brain (2). fMRI studies show how older and younger people use their prefrontal cortex (PFC) differently (2). In general, more PFC activity is observed in older people. In tasks that require the activity on one side of the PFC region of the brain in younger people, both sides are active in older people. The timing of this activity can also be different. More aged people show activity during the later times of the processes, which the researchers termed "Reactive versus proactive" (2).


There are two main hypotheses about the higher activity that arises due to ageing. One of these hypotheses is the compensation: older adults use more neural resources than younger adults for the same task (2,4). Another school of thought behind the higher neural activity in older adults is the losing the ability to differentiate what is required (2). For example, in the studies that test implicit (unconscious) or explicit (conscious) memory, young adults showed higher activity in the hippocampus or striatum, respectively (2). On the other hand, older people did not show any differentiation. Instead, they showed increased activity in both regions in both memory tests. According to some studies, this loss of attention that is observed at the cellular level is called "dedifferentiation" and is believed to have detrimental effects rather than compensation (2).


Both at the cellular level and at the execution level, there are ways we compensate for the loss of memory that comes with ageing. The one mentioned above is higher neuronal activity. One other way is the presence of alternative pathways (4), the usage of different brain regions (2), or new strategy adaptations (2). It is also possible that older people use their background and experiences, their knowledge (4).


Further, it was also shown that relevant training allowed older people to score higher on memory tests (2). In a couple of studies, older people trained with digital photography or taught how to use a tablet showed better performance in episodic memory tests (4). So despite the unpreventable decline of memory throughout ageing, there are ways to make the best of what is left.


One of the components of successful ageing is the continuity of engagement with life (7). The fast technological advancements of our era may make older people stay behind and become less engaged and less productive. Catching up with the technology can work in both ways for ageing adults by helping to improve their memory and keeping them engaged more in life. We always hear that solving sudoku helps your memory. Maybe it is a better idea to solve those sudokus on a tablet!


 

Blog by Emine Topcu


References:

1. Nyberg L, Pudas S. Successful Memory Aging. Annu Rev Psychol. 2019;70:219–43.

2. Grady C. The cognitive neuroscience of ageing. Nat Rev Neurosci. 2012;13(7):491–505.

3. Li AWY, King J. Spatial memory and navigation in ageing: A systematic review of MRI and fMRI studies in healthy participants. Neurosci Biobehav Rev [Internet]. 2019;103(May):33–49. Available from: https://doi.org/10.1016/j.neubiorev.2019.05.005

4. Park DC, Festini SB. Theories of memory and aging: A look at the past and a glimpse of the future. Journals Gerontol - Ser B Psychol Sci Soc Sci. 2017;72(1):82–90.

5. Hasher L, Lustig C, Hacks R. Inhibitory Mechanisms and the Control of Attention. In: Conway ARA, editor. Variation in Working Memory. Oxford University Press; 2008. p. 227–40.

6. Hasher L, Zacks RT. Working memory, comprehension, and aging: A review and a new view BT - The psychology of learning and motivation. Psychol Learn Motiv [Internet]. 1988;22:193–225. Available from: https://books.google.com.tr/books?id=k6ufhxSYXe8C

7. Rowe JW, Kahn RL. Successful aging 2.0: Conceptual expansions for the 21st century. Journals Gerontol - Ser B Psychol Sci Soc Sci. 2015;70(4):593–6.


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