In a recent post I guessed that it would be better to begin to study the effects of omega-3 and other fats on the brain with healthy subjects than with “unhealthy” ones — that is, persons with obvious brain dysfunction. So far, almost all behavioral studies of omega-3 have used unhealthy subjects — adults with bipolar disorder or depression, children with coordination problems, autism, or ADHD. My guess was based on three things: 1. A thought experiment. Imagine trying to learn how cars work. You’d rather experiment with working cars than broken cars. 2. Healthy subjects are far more available and easier to study. 3. The work of Saul Sternberg, who pioneered the study of memory using tests on which subjects are very accurate (e.g., 95% correct). The main measure of performance on these tasks was speed (called reaction time) rather than accuracy. After his work, reaction-time experiments became far more popular. In my study of the effects of flaxseed oil, I had directly compared high- and low-accuracy tasks. I had measured the effects of flaxseed oil using two high-accuracy tasks (arithmetic and memory-scanning) and a low-accuracy task (digit span). The effects were much clearer (smaller p values) with the high-accuracy tasks.
I asked Sternberg what he thought of my guess. He wrote, “I certainly agree that it is worth studying the effects of X on “normal” brains, where X can be many things” and later added:
I suspect my decision to measure [reaction] time under conditions of high accuracy was multiply determined, and that the determinants included some speculative notions. E. g. I may have thought that the variety of strategies is greater when the system is overloaded and errors are occurring than when it is functioning smoothly, so one was more likely to get clear answers about an underlying mechanism. Also, there was something of a tradition of measuring RT in experiments on “information processing” that weren’t normally described as memory experiments, but could be. Another reason was probably that I felt that RT – a continuous measure – probably contained more “information” than errors, with a few discrete possibilities, did.
It is possible that the emphasis in memory experiments on studying accuracy when the relevant brain system is failing was influenced by the study of sensory processes, where the experimental and analytic techniques (e.g., for measuring discriminability and detectability) were well worked out, and where it is believed that the enterprise has been highly successful. Also, sensory detectability and discriminability may be more intrinsically interesting and more closely related to actual situations of practical concern than accurate performance.
In the case of Andrew Stoll’s research on omega-3s and bipolar disorder, he did not begin with the question “What is the effect of omega-3s on mood?” He began this way:
“Several years ago, we were searching for alternatives to mood stabilizers, such as lithium and Depakote, used to treat bipolar. We began investigating what we knew about the chemical mechanisms of lithium and valproate (Depakote) on the brain and discovered that these drugs are not working on the receptors, or re-uptake sites, that Prozac and similar drugs do. They work inside the cell in a process called signal transduction.
“In our search, we began looking for compounds that had a similar mechanism in the brain but had never been tested before. Omega-3s, along with other compounds, came up in our search. But omega-3s had a whole list of mechanisms that certainly appeared to have mood effects in people. This discovery was very surprising, because no one had ever looked at using omega-3s in adult psychiatric disorders. Later in our research, we discovered that we are all depleted of these essential fattyacids.
“When individuals consume a diet rich in omega3s, their brain cell membranes become more fluid, allowing for smoother flow of chemical messengers, such as serotonin, in the brain.”
(Source: UMI, THE SATURDAY EVENING POST, 09/2001)
Thanks, that’s good to know.