Evolution The modern era dawned with Darwin, whose exposition

of biological evolution through natural selection has recently come to the fore in psychiatric thinking. Darwin’s conclusion that emotions were adaptive evolutionary products had been obscured by Freud’s Lamarckism, his emphasis on drive and defenses, and his treatment of emotions as epiphenomena. Since evolutionary theory is more directly informative about function, rather than dysfunction, recent evolutionary theorizing often asserts that many behaviors that are viewed as pathological, eg, mania, psychopathy, agoraphobia, etc, are actually evolved behaviors appropriate to our neolithic ancestors, but discordant with modern Inhibitors,research,lifescience,medical times. This viewpoint discounts the starkly minority status of these illnesses, their periodicity, Inhibitors,research,lifescience,medical the evidence of brain damage, their response to medication, etc. Such glib formulations obscure the real value

of an evolutionary framework for hypothesizing the existence of covert functions that may become impaired, thus producing the syndromes associated with disease. Inhibitors,research,lifescience,medical Cannon Chronologically, Kraepelin, Pavlov, and Freud should now be in focus, but the direct intellectual descendant of Darwin was in fact Walter Cannon who in 1919 highlighted the emergency adaptive functions of anger and fear in terms of facilitating fight and flight. In strikingly modern terms, he referred to the thalamus as a discrete brain module that provided the Inhibitors,research,lifescience,medical integrative connection to the cortex and the sympathoadrenal system, and was therefore the primary instigator of emotional, visceral, and autonomic responses. A narrow focus on adrenergic mechanisms, as the exclusive generator of emergency responses, reemerged recently in attempts to link pathological anxiety to an impaired brain adrenergic system. Pavlov Pavlov, who considered himself a physiologist, made the pioneering conditioning observations. Attempts to develop animal models of “neurosis” were initiated when he found that presenting his restrictively harnessed dogs with progressively more difficult discriminations between excitatory

and inhibitory Inhibitors,research,lifescience,medical conditional stimuli led to frantic agitation (or sometimes sleep). Pavlov also noted the importance of trauma, when a fortuitous kennel flood caused his carefully trained dogs to develop disruptive else “neurotic” behaviors. Many drew the conclusion from selleck kinase inhibitor Pavlov’s work that neuroses were learned, since purely experiential procedures caused them. (Pavlov’s emphasis on constitutional variation was ignored.) Learning theory Behavioral studies led to learning theory, which maintains that, anxiety is the conditionable part of fear, serving as a secondary drive. This model, as formulated by Mowrer, seems both simple and powerful. An unconditioned stimulus (US), such as shock, causes unconditioned responses (URs), eg, fear, which leads to escape behavior. Decreases in fear, produced by successful escape, reinforce escape behavior.