Читать книгу Abnormal Psychology - William J. Ray - Страница 106

The basic element of the brain is the neuron that is connected to other neurons. Since the human brain has been estimated to contain 86 billion neurons and more than 100,000 kilometers of interconnections, scientists have analyzed them in the context of networks. Three specific networks have been examined relating to psychopathology—the default network (also called the intrinsic network), the central executive network, and the salience network. Psychopathological disorders have been shown to have problems in turning networks on or off as well as problems in the connections within the network itself.

Scientists have been able to use the manner in which neurons work as a window into their function. A variety of techniques for observing activity in the brain have been developed. Currently, the major types of brain imaging techniques are EEG, MEG, PET, and fMRI. There are a number of trade-offs that researchers and clinicians must consider when choosing a brain imaging technique. It begins with the research or clinical question one is asking, which determines whether the appropriate measure is one of structure (spatial resolution) or how fast a process can be measured (temporal resolution). With the opening of this window into individuals’ internal processes, the new field of neuroethics has started asking questions concerning who should have access to that information.

Genes form the blueprint that determines what an organism is to become. They are found on chromosomes in every cell of the body. Within each gene, DNA—the information storage molecule—transfers information to RNA—the information transfer molecule—to produce a particular protein. The location of the genes in the body makes a difference in that cells in the brain produce different proteins from those in the muscles, or liver, or heart. A gene is turned on (produces the protein) or turned off (does not produce the protein) relative to specific events.

The basis of evolution is genetic variations that occur in response to the environment and that can be inherited and passed on to future generations. The study of genetics begins in the 1800s with the work of Gregor Mendel, who established the initial principles of genetic inheritance. Subsequent research has added complexity to that initial conceptualization. Mitochondrial inheritance, for example, involves the mtDNA that generally is inherited only from the mother. Epigenetic inheritance is based on the fact that the processes that determine which genes turn on and off can be passed on to the next generation. Thus, although DNA itself could not be influenced by the environment, it was possible for the environment to influence future generations through its changes to those processes that turn genes on and off. Given this complexity, it is no wonder the original hope of finding a few genes that were involved in particular mental disorders has not panned out. Currently, one promising focus of research has been to identify endophenotypes—patterns of processes lying between the gene (the genotype) and the manifestations of the gene in the external environment (the phenotype)—for particular psychological disorders.

One of the main themes of evolution is the manner in which organisms are in close connection with their environment. It is this close connection that allows for change to take place, including the turning on and off of genetic processes. In humans, there is another layer of complexity involved in the process. Part of this complexity comes from the fact that humans are born less fully developed at birth than many other species and thus are sensitive to changes in their environment as they continue to develop. Unlike animals that live within nature, we as humans largely live within the backdrop of our culture. Another part of our complexity as humans is our ability to reflect on ourselves and our world. In this way, a layer of thought can be injected between the person and the environment. This allows for expectation and imagination to play a role in human behavior and experience. This lack of connectedness to our environment may take place on both an external and an internal level.

From an evolutionary perspective, the study of psychopathology begins with the three instincts of survival, sexuality, and socialness. From this perspective, psychopathology becomes a disturbance of these instinctual processes. The evolutionary perspective goes beyond the traditional psychological and physiological considerations and asks some critical questions concerning psychopathology. First, is the experience of mental illness universal? Second, is there an adaptive value to the behaviors and experiences displayed in psychopathology? Third, can we see evidence of psychopathology across human history as well as in nonhuman species? Fourth, what is the nature of psychopathology—is it qualitatively different from normal functioning, or have normal processes been taken to the extreme? Fifth, is psychopathology protective in some manner? Sixth, is psychopathology a recent process—a result of a mental system designed in prehistory interacting with a thoroughly modern environment?