In this chapter we outline a theoretical framework for self-organization in the development of a neurological and cognitive-emotional vulnerability to major depression. We begin by outlining the basis for plasticity in embryonic and early infant neural systems. Early plasticity, we argue, forms the basis for learning and, by extension, may determine the organization of the cognitive and emotional schemas that drive behavior. Disruptions in the mechanisms of plasticity may lead to disruptions in emotional, motivational, and cognitive self-organization, rendering the person vulnerable to affective psychopathology throughout life.
Disruptions at two levels of neurological control of plasticity and self-organization may lead to vulnerability to depression. First, arousal states, under the control of brain stem and thalamic centers, are necessary to support the neural plasticity underlying learning. We propose that deficits in arousal due to early neglect and/or loss experiences may impair normal developmental plasticity. Second, we propose that particularly traumatic events, such as childhood sexual abuse, may form enduring memory traces in cortical and limbic areas. These memories, and the emotional dysregulation they engender, may then sensitize (or “kindle”) individuals to such experiences in the future. In support of these two hypotheses, we review the mechanisms of arousal control and memory consolidation, and their likely roles in neural plasticity. We then theorize on how these may be related to the neurological and cognitive sequelae of early neglect and trauma both in animal models and in studies with humans.