Never Enough: The Neuroscience and Experience of Addiction

by Judith Grisel

The fundamental role of the brain is to be a contrast detector. As experiences are distinguished from monotony, they spark neurochemical changes in specific brain circuits, informing us of all we care to know: opportunities for food, drink, or sex; danger or pain; beauty and pleasure, for example. The process of actively maintaining the stable baseline critical for conducting the brain’s business of contrast detection is called homeostasis, and it depends on having a set point, a comparator, and a mechanism for adjustment. It is easy to appreciate this principle in terms of body temperature, which is maintained around ninety-nine degrees Fahrenheit. If you become much warmer or colder than this, your body feels it, and there are mechanisms to return you to baseline, such as sweating or shivering. Feelings are also constrained within tight bounds under normal conditions. What we generally experience is our personal neutral okayness; otherwise we’d be incapable of detecting “good” or “bad” events. We’ll return to homeostasis later. For now we’ll consider what makes abused drugs remarkable—their ability to hijack the contrast detector for pleasure.