Adrenaline and the Inner World: An Introduction to Scientific Integrative Medicine

6 Distress

Distress is a form of stress with additional characteristics: consciousness, aversiveness, observable signs, and adrenal gland activation. Characteristics of Distress Consciousness The occurrence of stress does not require consciousness. Selye would have agreed with this assertion, because he claimed that stress reactions can occur in anesthetized animals, in lower animals without nervous systems or undergoing mechanical damage to denervated limbs, and even in cells cultured outside the body. In contrast, distress does require consciousness, because distress involves not only a challenge to homeostasis but also a perception bytheorganismthathomeostaticmechanismsmaynotsuffice—thatis,consciousinterpretationof sensoryinformationandsimulationof futureevents. This is a more generalized statement of the concept of psychological stress as a consequence of a perceived inability to cope. The sense of an inability to cope or of a lack of controllability is basic to psychological theories about feelings associated with distress. An organism experiences distress when it perceives the inadequacy of compensatory adjustments to either a psychological or physiological stressor. Aversiveness Distressed organisms avoid situations that may produce the same experience .Distressthereforeisnegativelyreinforcing,motivatingescapeandavoidance learning. The experience of distress would be expected to enhance vigilance behavior and long-term memory of the distressing event. These adaptive neurological adjustments seem to involve catecholamines in the brain. Most animals can react instinctively not only to a stressor but also to 6 Distress symbolic substitutes that resemble the natural stimulus. Monkeys become visibly upset upon exposure to a snake, without ever having seen one before; rabbits freeze when a hawk-shaped shadow glides by; male stickleback fish attack any red object in their territory; and mallards scurry to the water in response to a foxlike piece of red-brown skin dragged along the edge of the pond. The plasticity afforded by learning decreases the likelihood of inappropriate instinctive responses to symbolic cues. One definition of learning is modification of behavior based on experience. According to this definition, learning requires memory. Even “primitive” animals have the capacity to learn to withdraw or escape from noxious stimuli or to habituate after prolonged or repeated exposure to a stimulus. These forms of learning mirror each other, the former a sensitization and the latter a desensitization. The fact that primitive animals have these capabilities indicates the remarkably ancient and durable survival advantage of learning. Classical (or Pavlovian) conditioning represents an important refinement of these responses (fig. 39). Habituation and sensitization exemplify nonassociative learning, where the organism learns about single stimuli. In contrast, classical conditioning (and operant conditioning, to be discussed shortly) involves learning associations among stimuli. In classical conditioning, repeated pairing of a neutral stimulus (e.g., a bell ringing) with an unconditioned stimulus (UCS) that elicits an instinctive unconditioned response (UCR—e.g., salivation at the presentation of meat powder to a hungry dog; limb withdrawal after a local shock) results eventually in the elicitation of the UCR (or components of it) by the previously neutral conditioned stimulus (CS). The CS elicits a conditioned response (CR). For instance, depending on the UCS with which the ringing is paired, a dog may salivate or withdraw its leg when the bell rings. Pavlov taught that the acquisition of conditioned reflexes requires cerebral cortices; however , even invertebrates such as the sea snail, Aplysia, have the capacity to learn by classical conditioning. Although most classical conditioning experiments involve an external UCS, such as an electric shock to the skin, this does not imply that the UCS must be external. For instance, rats can acquire hyperglycemia as a CR after repeated pairing of a previously neutral cue with injections of insulin. Pavlov himself demonstrated classically conditioned nausea and vomiting after repeated pairing of a CS (approach of the experimenter) with an internal UCS (evoked by injected morphine). 142 ADRENALINE AND THE INNER WORLD Instrumental,oroperant,conditioning,representsamoreadvancedform of learning that requires a cerebral cortex. In instrumental conditioning, the likelihood of a behavior increases when the behavior leads to positive reinforcement (reward) and decreases when the behavior leads to negative reinforcement (punishment). Conversely—but circularly—reinforcement can be defined as an event that strengthens the response it follows. The conditioning is “operant” in that the individual’s behavior operates on the environment , determining the occurrence of reinforcement; and the conditioning is “instrumental” in that the learning is a means to an end, with the occurrence of reinforcement contingent on the behavior. Operant conditioning therefore differs from Pavlovian conditioning, in which the delivery of the reinforcement occurs independently of the individual’s behavior...