Why does losing sleep cost us memory?

Have you ever had a late night or had to stay up late to finish some work and found that the next day you are not quite at your usual perky self? After getting less sleep than normal you may notice that you are less focused, a bit fuzzy in your thinking and less able to recall things as easily as normal.

Some people (including myself!) know that drinking coffee late at night is a no-no because of its insomniac effect. What happens with coffee is that the caffeine competes with a naturally occurring brain chemical called adenosine. Our brain produces adenosine, which is taken up by specialized receptors to quieten down our brain in preparation for sleep. Drinking that cup of coffee at night allows the caffeine to compete for those same receptors as adenosine, allowing excess adenosine to remain circulating and we end up tossing and turning in bed, wishing we had had a cup of hot milk instead.

OK, so caffeine stops us from going to sleep, but why does lack of sleep affect our memory so much?

Researchers using mice studies seem to have found a biological explanation. In a study published in the Journal Of Neuroscience, researchers looked at the role of adenosine and memory in sleep deprivation. It turns out the effect is the same whether you are a fruit fly, a mouse or a human being. In sleep deprivation you end up with more adenosine floating around than normal, just in the same way as when caffeine blocks of adenosine uptake.

Glial cells, the brain cells that support neurons, produce adenosine. The receptors for the adenosine are located in the hippocampus the specialized area associate with memory and learning.

Losing the equivalent of half a night’s sleep for just for one night was shown to produce a significant impact on a mouse’s ability to form memory, and the neurons involved were less plastic than normal, meaning normal neuronal transmission was compromised.

Getting enough sleep is essential for us to think clearly and have normal memory function. This is true for both children at school and for adults in the workplace. We need enough shuteye to help our brain work at its best.

This was also discussed in relation to our children in a recent article in the New York Times. The author asked the question about how much do our children sleep and are they getting enough sleep.

This is especially pertinent for adolescents whose brains undergo some radical changes during their teens right up to the time when brain development is complete in their early twenties.

Sleep researchers report that this age group requires between 8 to 9+ hours sleep per night, yet many get far less than this, and trying to catch up on weekends doesn’t work. The result? Many high school students are in class already sleep deprived and in a less than perfect state in order to learn. Not only are they less efficient in taking in new information, they also need sleep to consolidate their learning and form memories. All of which adds up to a negative effect on those all important school grades.

When it comes to learning and memory, it boils down to the fact we really do need to get enough sleep.

Refs: C. Florian, C. G. Vecsey, M. M. Halassa, P. G. Haydon, T. Abel. Astrocyte-Derived Adenosine and A1 Receptor Activity Contribute to Sleep Loss-Induced Deficits in Hippocampal Synaptic Plasticity and Memory in Mice. Journal of Neuroscience, 2011; 31 (19): 6956 DOI: 10.1523/JNEUROSCI.5761-10.2011

http://www.nytimes.com/2011/05/24/health/24brody.html