The brain makes up l/50th of our body mass but consumes a staggering 1/5th of the calories we burn for energy. If your brain were a car, in terms of gas mileage, it’d be a Hummer. Most of our conscious activity is happening in our prefrontal cortex, the part of our brain responsible for focus, handling short-term memory, solving problems, and moderating impulse control. It’s at the heart of what makes us human and the center for our executive control and willpower. The “last in, first out” theory is very much at work inside our head. The most recent parts of our brain to develop are the first to suffer if there is a shortage of resources. Older, more developed areas of the brain, such as those that regulate breathing and our nervous responses, get first helpings from our blood stream and are virtually unaffected if we decide to skip a meal. The prefrontal cortex, on the other hand, feels the impact. Unfortunately, being relatively young in terms of human development, it’s the runt of the litter come feeding time.
As a consequence of natural analgesic actions or as a result of the administration of drugs that interfere with body signaling (painkillers, anesthetics), the brain receives a distorted view of what the body state really is at the moment. We know that in situations of fear in which the brain chooses the running option rather than freezing, the brain stem disengages the part of the pain-transmission circuitry, a bit like pulling the plug. The periqueductal gray, which controls these responses, can also command the secretion of natural opioids and achieve precisely what taking an analgesic would achieve -- elimination of pain signals.In the strict sense, we are dealing here with a hallucination of the body because what the brain registers in its maps and the conscious mind feels do not correspond to the reality that might be perceived. Whenever we ingest molecules the have the power to modify the transmission or mapping of body signals, we play on this mechanism. Alcohol does it; so do analgesics and anesthetics, as well as countless drugs of abuse. It is patently clear that, other than out of curiousity, humans are drawn to such molecules because of their desire to generate feelings of well-being, feelings in which pain signals are obliterated and pleasure signals induced.