Objective-Generalized social phobia involves fear/avoidance, specifically of social situations, whereas generalized anxiety disorder involves intrusive worry about diverse circumstances. It remains unclear the degree to which these two, often comorbid, conditions represent distinct disorders or alternative presentations of a single, core underlying pathology. Functional magnetic resonance imaging assessed the neural response to facial expressions in generalized social phobia and generalized anxiety disorder.Method-Individuals matched on age, IQ, and gender with generalized social phobia without generalized anxiety disorder (N=17), generalized anxiety disorder (N= 17), or no psychopathology (N=17) viewed neutral, fearful, and angry expressions while ostensibly making a simple gender judgment.Results-The patients with generalized social phobia without generalized anxiety disorder showed increased activation to fearful relative to neutral expressions in several regions, including the amygdala, compared to healthy individuals. This increased amygdala response related to selfreported anxiety in patients with generalized social phobia without generalized anxiety disorder. In contrast, patients with generalized anxiety disorder showed significantly less activation to fearful relative to neutral faces compared to the healthy individuals. They did show significantly increased response to angry expressions relative to healthy individuals in a lateral region of the middle frontal gyrus. This increased lateral frontal response related to self-reported anxiety in patients with generalized anxiety disorder.Conclusions-These results suggest that neural circuitry dysfunctions differ in generalized social phobia and generalized anxiety disorder.Generalized social phobia and generalized anxiety disorder are two highly prevalent, chronic, and disabling anxiety disorders (1,2) that are sometimes comorbid. Generalized social phobia involves fear/avoidance, specifically of social situations, whereas generalized anxiety disorder involves intrusive worry about a broader array of everyday life circumstances. Although both have considerable social and economic costs, disagreement exists concerning the degree to which the conditions result from a shared or unique pathophysiology. For example, high rates of comorbidity in cross-sectional and longitudinal studies suggest that the distinction between the two conditions may be relatively subtle at the descriptive level (3,4). On the other hand, data from family-based and therapeutic research suggest the two conditions can be dissociated. Specifically, such dissociation is reflected in patterns of disorder aggregation within families (5), as well as by the fact that generalized anxiety disorder, but not social phobia, responds to most tricyclic antidepressants and to buspirone (6-8). Because no brain-imaging study has directly compared the two conditions, it remains unclear whether the two disorders have dissociable neural correlates.The principal goal of the current study was to inves...

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We review the evidence for the concept of the “initial” or prototype brain. We outline four possible modes of brain evolution suggested by our new findings on the evolutionary status of the dolphin brain. The four modes involve various forms of deviation from and conformity to the hypothesized initial brain type. These include examples of conservative evolution, progressive evolution, and combinations of the two in which features of one or the other become dominant. The four types of neocortical organization in extant mammals may be the result of selective pressures on sensory/motor systems resulting in divergent patterns of brain phylogenesis. A modular “modification/multiplication” hypothesis is proposed as a mechanism of neocortical evolution in eutherians. Representative models of the initial ancestral group of mammals include not only extant basal Insectivora but also Chiroptera; we have found that dolphins and large whales have also retained many features of the archetypal or initial brain. This group evolved from the initial mammalian stock and returned to the aquatic environment some 50 million years ago. This unique experiment of nature shows the effects of radical changes in environment on brain-body adaptations and specializations. Although the dolphin brain has certain quantitative characteristics of the evolutionary changes seen in the higher terrestrial mammals, it has also retained many of the conservative structural features of the initial brain. Its neocortical organization is accordingly different, largely in a quantitative sense, from that of terrestrial models of the initial brain such as the hedgehog.

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