That's an interesting question. The brain is 60% fat, a large part of that being DHA, a polyunsaturated oil that can go rancid very easily. So wouldn't it stand to reason that the brain could go "rancid" as well? Rancidity means that the fats have become oxidized or turned into lipid peroxides in a process called "oxidative rancidity." Oxygen molecules make their way into the structure of the fatty acid, profoundly changing its shape, function, and structure. The more unsaturated a fat is, the more easily it goes rancid when exposed to heat or light. That's why it's advised not to cook with polyunsaturated fats or leave them on the shelf in a clear bottle. Once the structure of the fat...
