Comparison of 99 chimpanzee brains ranging from 10-51 years of age with 87 human brains ranging from 22-88 years of age has revealed that, unlike the humans, chimpanzee brains showed no sign of shrinkage with age. But the answer may be simple: we live much longer. In the wild, chimps rarely live past 45, and although human brains start shrinking as early as 25 (as soon as they reach maturity, basically!), it doesn’t become significant until around 50.
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Trying to learn two different things one after another is challenging. Almost always some of the information from the first topic or task gets lost. Why does this happen? A new study suggests the problem occurs when the two information-sets interact, and demonstrates that disrupting that interaction prevents interference. (The study is a little complicated, but bear with me, or skip to the bottom for my conclusions.)
What governs whether or not you’ll retrieve a memory? I’ve talked about the importance of retrieval cues, of the match between the cue and the memory code you’re trying to retrieve, of the strength of the connections leading to the code. But these all have to do with the memory code.
In a small study, 266 older adults with mild cognitive impairment (aged 70+) received a daily dose of 0.8 mg folic acid, 0.5 mg vitamin B12 and 20 mg vitamin B6 or a placebo for two years. Those treated with B vitamins had significantly lower levels of homocysteine at the end of the trial (high homocysteine is a known risk factor for age-related cognitive decline and dementia). Moreover, this was associated with a significantly slower rate of brain shrinkage.
I’ve always felt that better thinking was associated with my brain working ‘in a higher gear’ — literally working at a faster rhythm. So I was particularly intrigued by the findings of a recent mouse study that found that brainwaves associated with learning became stronger as the mice ran faster.
I’ve spoken often about the spacing effect — that it’s better to spread out your learning than have it all massed in a block. A study in which mice were trained on an eye movement task (the task allowed precise measurement of learning in the brain) compared learning durability after massed training or training spread over various spaced intervals (2.5 hours to 8 days, with 30 minute to one day intervals). In the case of massed training, the learning achieved at the end of training disappeared within 24 hours. However learning gained in spaced training did not.
In the first mouse study, when young and old mice were conjoined, allowing blood to flow between the two, the young mice showed a decrease in neurogenesis while the old mice showed an increase. When blood plasma was then taken from old mice and injected into young mice, there was a similar decrease in neurogenesis, and impairments in memory and learning.
In the experiment, rats learned which lever to press to receive water, where the correct lever depended on which lever they had pressed previously (the levers were retractable; there was a variable delay between the first and second presentation of the levers). Microelectrodes in the rats’ brains provided data that enabled researchers to work out the firing patterns of neurons in CA1 that resulted from particular firing patterns in CA3 (previous research had established that long-term memory involves CA3 outputs being received in CA1).
In the first study, undergraduates studied English-Lithuanian word pairs, which were displayed on a screen one by one for 10 seconds. After studying the list, the students practiced retrieving the English words — they had 8 seconds to type in the English word as each Lithuanian word appeared, and those that were correct went to the end of the list to be asked again, and those wrong had to be restudied. Each item was pre-assigned a "criterion level" from one to five — the number of times it needed to be correctly recalled during practice.
In my book on remembering what you’re doing and what you intend to do, I briefly discuss the popular strategy of asking someone to remind you (basically, whether it’s an effective strategy depends on several factors, of which the most important is the reliability of the person doing the reminding). So I was interested to see a pilot study investigating the use of this strategy between couples.