Self Comes to Mind

occur, the brain required a representation of (1) the current state of the living tissue, (2) the desirable state of the living tissue corresponding to the homeostatic goal, and (3) a simple comparison. Some kind of internal scale was developed for this purpose, signifying how far the goal was relative to the current state, while chemical molecules whose presence sped up certain responses were adopted to facilitate the correction. We are still sensing our organism states in terms of such a scale, something we do quite unconsciously, although the consequences of the measurement are made quite conscious when we feel hungry, very hungry, or not hungry at all.
    What we have come to perceive as feelings of pain or pleasure, or as punishments or rewards, corresponds directly to integrated states of living tissue within an organism, as they succeed one another in the natural business of life management. The brain mapping of states in which the parameters of tissues depart significantly from the homeostatic range in a direction not conducive to survival is experienced with a quality we eventually called pain and punishment. Likewise, when tissues operate in the best part of the homeostatic range, the brain mapping of the related states is experienced with a quality we eventually named pleasure and reward.
    The agents involved in orchestrating these tissue states are known as hormones and neuromodulators and were already very much present in simple organisms with only one cell. We know how these molecules operate. For example, in organisms with a brain, when a given tissue is risking its health due to a dangerously low level of nutrients, the brain detects the change and grades the need and the urgency with which the change must be corrected. This happens nonconsciously, but in brains with minds and consciousness, the state related to this information can become conscious. If and when it does, the subject experiences a negative feeling that may range from discomfort to pain. With or without consciousness of the process, a corrective chain of responses is engaged, in chemical and neural terms, helped by molecules that speed up the process. In the case of conscious brains, however, the consequence of the molecular process is not merely a correction of the imbalance: it is also a reduction of a negative experience such as pain and an experience of pleasure/reward. The latter comes, in part, from the life-conducive state the tissue may have now achieved. Eventually, the mere action of the incentive molecules is likely to place the organism in the functional configuration associated with pleasurable states.
    The appearance of brain structures capable of detecting the likely delivery of “goods” or “threats” to the organism was also important. Specifically, beyond sensing the goods or the threats in and of themselves, brains began to use cues to predict the delivery. They would signal the coming of goods with the release of a molecule, such as dopamine or oxytocin; or the coming of threats with cortisol-releasing hormone or prolactin. The release would in turn optimize the behavior required to obtain or avoid the delivery of the stimulus. Likewise, they would use molecules to signal a miscue (a prediction error) and behave accordingly; they would differentiate between the coming of an expected item and an unexpected one by degrees of neuron firing and the corresponding degree of release of a molecule (e.g., dopamine). Brains also became capable of using the pattern of stimuli—for example, the repetition or alternation of stimuli—to predict what might be happening next. When two stimuli happened close to each other, that spelled the possibility that a third stimulus might be coming.
    What did all this machinery achieve? First, a more or less urgent response depending on the circumstances—in other words, a differential response. Second, it achieved responses optimized by prediction.
    Homeostatic design and its associated incentive and prediction devices protected the integrity of the living tissue inside an organism. Curiously, much the same machinery was co-opted to ensure that the organism would engage in reproductive behaviors that favored the passing of genes. Sexual attraction, sexual desire, and mating rituals are examples. On the surface, the behaviors associated with life regulation and with reproduction became separate, but the deeper goal was the same, and it is thus not surprising that the mechanics are