The Hippocampus is a structure in the brain that is shaped like a seahorse and is essential for memory. The Hippocampus has been investigated in relation to conditions like Alzheimer’s Disease. At the Alzheimer’s Forum, there is a very interesting write-up on a study investigating the relationship of the Hippocampus to memory.
There are various lines of evidence that show the importance of the Hippocampus for memory, but the researchers here were interested in whether different parts of the Hippocampus were more or less important for memory. They investigated the question using structural Magnetic Resonance Imaging, a technique which enables them to image the Hippocampus in detail. The researchers investigated 18 subjects aged 21-34 years of age and then gave them two sets of language tasks. In these tasks, the subjects had to place words into one of two categories. They were then scored on how well they were able to recall which category they had placed the items into. The key finding from the study was that the volume of the posterior portion of the Hippocampus was significantly correlated with the memory performance, whilst the volume of the anterior portion was not. While a functional division of the Hippocampus is unsurprising, these findings raise interesting questions, the answers to which might shed light on conditions affecting memory. Many studies looking at a condition which affects memory – Amnestic Mild Cognitive Impairment have looked at a region of the brain known as the Medial Temporal Lobe or more specifically at the volume of the entire Hippocampus in understanding how the condition progresses. This new approach to dividing up the Hippocampus has been seen in at least one study in Amnestic Mild Cognitive Impairment (looking at the CA1 subfields) but these latest findings will no doubt encourage researchers to pursue this type of research when investigating both the pathology and physiology of memory.
A very well respected study – the Whitehall Study – has been going on for some time now. The researchers have been following Civil Servants over many decades. The researchers here report key findings with those aged 45-49 showing cognitive decline over the 10-year follow-up period for the current report.
Singh-Manoux and colleagues, BMJ 2012;344:d7622, Creative Commons 2.0 Attribution Non-Commercial License
The study has a large sample size and to quote from the study
‘For example, in men aged 45-49 at baseline, 10 year decline in reasoning was −3.6% (95% confidence interval −4.1% to −3.0%) ……. In women, the corresponding decline was −3.6% (−4.6% to −2.7%) in those aged 45-49‘
The deterioration in scores per decade increased with baseline age and was also reduced by exercise which again is shown as an important protective factor for cognition. This study supports the notion of Age Related Cognitive Decline at a much earlier stage than is thought of with Mild Cognitive Impairment. There is also R.Armstrong’s variation on the Amyloid Cascade Hypothesis which states that the multiple types of microtrauma to the brain may influence the build up of the plaques and tangles that are thought to lead to Alzheimer’s Disease.
R.Armstrong’s Modified Amyloid Cascade Hypothesis, Int J Alzheimer’s Disease, 2011, Creative Commons License
While this study does not provide direct evidence of this these findings would be consistent with the gradual and very subtle deterioration we might expect from the above hypothesis and the question of why this decline is occurring in middle-age needs to be investigated further with appropriately sensitive tests.
There is a very good piece in the New England Journal of Medicine (via @Dr Shock) which is well worth a look. The NEJM have produced a timeline of the past 200 years of developments in medicine (and culture) to celebrate their 200th Anniversary.
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