Saturday, February 28, 2009
I have discussed elsewhere a new idea for treating unpleasant memories, such as post-traumatic stress syndrome. The latest treatment being investigated by some researchers is based on using a common blood pressure drug, propranolol, which has a side effect of blocking the re-consolidation of emotions associated with old memories when those memories are recalled.
The original idea was first confirmed in rats. Now a study indicates that the approach can work in humans and might become a clinically valuable treatment. In this human study, subjects were given a mild shock when shown pictures of spiders on the first day of the study. Their fear response was measured as the eyeblink startle reflex to a loud noise. On day 2 of the study, the memory reactivation phase, the study volunteers exhibited the same response to the fearful stimuli (the spider pictures) as on day 1. On day 3, 20 of the subjects were given 40 mg of propranolol, and the remaining 20 were given a placebo. Next, the entire group was exposed to the fearful stimuli. The propranolol group did not exhibit the same startle response as on previous days. The placebo group showed no change in startle response compared to days 1 or 2. In other words, the drug reduced the emotional response, yet did not reduced the memory of the learned event.
Thus, it seems that if propranolol is in the body at the time when one recalls a bad memory, the emotional impact of the memory can diminish without impairing the ability to remember the item. Psychiatric treatment protocols remain to be worked out. Notice that in this situation the learned fear response was recent. Nobody knows if this effect occurs with old, well-entrenched fear memories. Another issue that nobody seems to be asking is the possibility that people on this kind of blood pressure medication might be suffering impairments of emotional memories that they don't want to lose. Does this drug cause a general dulling of emotions?
Merel Kindt, Marieke Soeter, Bram Vervliet (2009). Beyond extinction: erasing human fear responses and preventing the return of fear Nature Neuroscience DOI: 10.1038/nn.2271
Wednesday, February 25, 2009
Biological reward comes from the release of the neurotransmitter, dopamine. Performing working memory tasks promotes dopamine release. In the study of human subjects by Fiona McNab and colleagues in Stockholm, human males (age 20-28) were trained on working memory tasks with a difficulty level close to their individual capacity limit for 35 minutes per day for 5 weeks. After such training, all subjects showed increased working memory capacity. Functional MRI scans also showed that the memory training increased the cerebral cortex density of dopamine D1 receptors, the receptor subtype that mediates feelings of euphoria and reward.
Students who make good grades feel good about their success. Likewise, people who are "life-long learners" have discovered that learning lots of new things makes them feel good. Though this present study did not rigorously test the idea, it is possible that learning how to improve your working memory capacity can also make you feel good.
Source: McNab, F. et al. 2009. Changes in cortical dopamine D1 receptor binding associated with cognitive training. Science. 323: 800-802.
Wednesday, February 11, 2009
I have reported earlier on a study indicating that blueberries are good for memory. Actually, there are several studies indicating that blueberries are good for mental function in general. Blueberries contain polyphenolics, the levels of which are indicated by the amount of two compounds, ferulic acid and caffeic acid. Ferulic acid helps to stabilize cell walls and protects the nervous system. It lowers blood pressure. Caffeic acid also protects neurons and may even prevent neural degeneration. Both compounds are powerful antioxidants.
Blueberries are potent anti-inflammatory agents. One study in rats fed a diet including a non-steroidal anti-inflammatory drug or a 2% blueberry diet showed that within just two weeks the blueberry supplement activated anti-inflammatory genes in the brain much more than did the anti-inflammatory drug.
Now, a recent report indicates that the health benefits of blueberries are blocked by milk. Phenolics have a high affinity for protein, and the binding to milk protein prevents phenolics from accessing body cells. The study that demonstrated this effect involved measuring blood levels of the blueberry phenolics at various times after human volunteers consumed 200 gms of blueberries with 200 ml of either water or milk. Levels of phenolics rose sharply when water was consumed, but there was no increase when milk was consumed.
Heat destroys blueberry phenolics. So even though blueberry pie tastes great, it won't help your health. Only fresh blueberries provide useful levels of phenolics.
So, the recommendation is to consume blueberries without proteins. It should suffice to eat blueberries either one hour before eating other foods or two hours afterwards. For me, I will eat my blueberries alone an hour before my milk and cereal.
Serafini, M. et al. 2009. Antioxidant activity of blueberry fruit is impaired by association with milk. Free Radical Biology and Medicine. doi:10.1016/j.freeradbiomed.2008.11.023
Shukitt-Hale, B. et al. 2008. Blueberry polyphenols attenuate kainic acid-induced decrements in cognition and alter inflammatory gene expression in rat hippocampus. Nutr. Neuroscience. 11 (4): 172-182.