Interrelation between Regulatory Functions

One of the functions of the CNS is to take in new sensory information, categorize its importance, and integrate it with previously stored knowledge. Then, the organism needs to determine what is personally relevant and filter out irrelevant information. The brain networks that monitor relations with the outside world and assess what is new, dangerous, or gratifying involve the brainstem, hypothalamus, limbic system, and neocortex operating together in interdependent but also hierarchical ways (Panksepp, 1998). Together, these structures need to "formulate" an appropriate plan of action following the meaningful categorization of an incoming signal. As the CNS does this, it needs to attend to both short-term and long-term consequences of the anticipated action, which is clearly a cortical function (Damasio, 1999). After initiating an appropriate response and the challenge is gone, the organism needs to shift its attention. Finally, people need to be able to engage in sustained activities without being distracted by irrelevant stimuli.

A century ago William James noted that the power of the intellect is determined by people's perceptual processing style. The ability to comprehend (grasp, hold together, take hold of—from the Latin cum-prendere) depends on stimulus sampling and the formation of schematic representations of reality (Pribram, 1991). The organism needs to learn from experience and entertain a range of alternatives without becoming disorganized or without having to act on them. In order to do this, it needs to learn to discriminate relevant from irrelevant stimuli and only select what is appropriate for achieving its goals. Much of the evolution of the human brain has centered on developing the capacity to form highly complex mental images and collaborative social relationships that allow complex organization of social systems. In order to participate in this large collaborative social system, the organism needs to integrate its own immediate self-interest with a capacity to appreciate and to adhere to complex social rules (Donald, 1991).

People with PTSD have serious problems in carrying out all of these functions. There are qualitatively significant differences between the ways people with PTSD sample and categorize experience and the ways in which nontraumatized people do (van der Kolk and Ducey, 1989; McFarlane et al., 1993). Failure to comprehend the traumatizing experience (i.e., to dissociate) plays a critical role in making a stressful experience traumatic (van der Kolk et al., 1996a). People with PTSD tend to overinterpret danger, have trouble experiencing pleasure engaging in ordinary tasks, have difficulty staying focused until a job is finished; they often find it difficult collaborating with others in situations that require maintaining multiple perspectives.

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