You do not currently have permission to view the full text for this document. Please sign in to an account with an active subscription or contact support.
During the spring of 2004, Eduard Bercovici, of the University of Toronto Epilepsy Research Program, gave a presentation on “Stress, Trauma, Depression, and Limbic System Processes.” Bercovici discussed various ways that stress can be defined and viewed, based on Sapolsky's (2003) article, “Taming Stress.” Stress disturbs homeostasis, causes excitability and arousal, involves lack of control of the situation, and is generally aversive. If stress is to leave a lasting impression on the organism, it must be converted from sensory information, through short-term memory and consolidation, into long-term memory. The hippocampus subserves the formation of declarative, explicit, autobiographical memories, while other structures, including cerebellum, amygdala, and hypothalamus, subserve nondeclarative/implicit memory. The relative sizes of the structures reflect the actualities of the particular research animal's life. Much memory research has been done on the rat (as it is nonspeaking, its chief mode of communication is through activity or behavior, which can be influenced by a number of factors having nothing to do with memory), which has limited applicability to studies on declarative memory.
Papez combined a number of structures into an emotional circuit. Stress activates this circuit. The hippocampus, involving reverberating circuits, is ideally suited to memory consolidation and the formation of links. The neocortex serves as substrate for distributed storage of memory. Long-term potentiation involves the formation of synaptic connections of increased efficiency; long-term depression, the necessary reverse of the process, enables the organism to adapt to the circumstances of a changing reality. This process can be illustrated by pathways in the snow: some become well used, but eventually the entire area becomes trampled, and the whole process loses meaning and significance—and, in the brain, could result in seizures—unless the process can somehow be reversed, with the