Hockenbury Discovering Psychology 5th txtbk

570 CHAPTER 13 Psychological DisordersFOCUS ON NEUROSCIENCESchizophrenia: A Wildfire in the BrainIn a five-year prospective study, neuroscientist Paul Thompsonand his colleagues (2001) used high-resolution brain scans tomap brain structure changes in normal adolescents and adolescentswith early-onset schizophrenia. Thompson found markeddifferences in the brain development of normal teens and teenswith schizophrenia. As expected, the healthy teenagers showeda gradual, small loss of gray matter—about 1 percent—over thefive-year study. This loss is due to the normal pruning of unusedbrain connections that takes place during adolescence (seeChapter 9).But in sharp contrast to the normal teens, the teenagers withschizophrenia showed a severe loss of gray matter that developedin a specific, wavelike pattern. The loss began in the parietallobes and, over the five years of the study, progressivelyspread forward to the temporal and frontal regions. As Thompson(2001) noted, “We were stunned to see a spreading wave of tissueloss that began in a small region of the brain. It moved acrossthe brain like a forest fire, destroying more tissue as the diseaseprogressed.”The brain images show the average rate of gray matter lossover the five-year period. Gray matter loss ranged from about 1percent (blue) in the normal teens to more than 5 percent (pink)in the schizophrenic teens. One fascinating finding was that theamount of gray matter loss was directly correlated to theteenage patients’ clinical symptoms. Psychotic symptoms increasedthe most in the participants who lost the greatest quantityof gray matter.Also, the pattern of loss mirrored the progression of neurologicaland cognitive deficits associated with schizophrenia. For example,more rapid gray matter loss in the temporal lobes was associatedwith more severe positive symptoms, such ashallucinations and delusions. More rapid loss of gray matter inthe frontal lobes was strongly correlated with the severity ofnegative symptoms, including flat affect and poverty of speech.When the participants were 18 to 19 years old and the finalbrain scans were taken, the patterns of gray matter loss weresimilar to those found in the brains of adult patients with schizophrenia.Despite the wealth of information generated by Thompson’sstudy, the critical question remains unanswered: What sparks thecerebral forest fire in the schizophrenic brain?Each of the 12 adolescents was scanned repeatedly with high-resolution MRIsover a five-year period, beginning when the teenagers were about 14. The adolescentswere carefully matched with healthy teens of the same gender, age, socioeconomicbackground, and height. The findings of this important study are featured inthe Focus on Neuroscience.Although there is evidence that brain abnormalities are found in schizophrenia,such findings do not prove that brain abnormalities are the sole cause of schizophrenia.First, some people with schizophrenia do not show brain structure abnormalities.Second, the evidence is correlational. Researchers are still investigating whether differencesin brain structures and activity are the cause or the consequence of schizophrenia.Third, the kinds of brain abnormalities seen in schizophrenia are also seen in othermental disorders. Rather than specifically causing schizophrenia, it’s quite possible thatbrain abnormalities might contribute to psychological disorders in general.dopamine hypothesisThe view that schizophrenia is related to,and may be caused by, excessive activity ofthe neurotransmitter dopamine in the brain.Abnormal Brain ChemistryThe Dopamine HypothesisAccording to the dopamine hypothesis, schizophrenia is related to excessive activityof the neurotransmitter dopamine in the brain. Two pieces of indirect evidencesupport this notion. First, antipsychotic drugs, such as Haldol, Thorazine,