CLINICAL HANDBOOK OF SCHIZOPHRENIA

10. Cognitive Functioning in Schizophrenia 93The attentional deficits in schizophrenia can include inability to distinguish betweenrelevant and irrelevant stimuli or information (selective attention or “gating”), inabilityto stay mentally “on track” (sustained attention), and lack of vigilance (such as waitingfor a particular stimulus or event to occur over time). Working memory is a conceptclosely related to attention as well as to executive functioning, and involves the ability tohold and manipulate information in one’s mind for short periods of time for further processing.Working memory is a resource-limited process, and requires active rehearsal andallocation of attentional resources for retention. Goldman-Rakic (1994) and others havesuggested that deficits in working memory may underlie some of the other aspects ofschizophrenia, including executive dysfunction and some aspects of thought disorder.Episodic memory is often mentioned as one of the most frequently impaired abilitiesin schizophrenia. However, it is important to distinguish between difficulties with acquisitionof new information and/or efficiency of its retrieval, and actual loss of the memorytrace. As yet another example of his astute observational skills, in his 1919 textbook,Kraepelin accurately noted, “Memory is comparatively little disordered. The patients areable, when they like, to give a correct detailed account of their past life, and often knowaccurately to a day how long they have been in the institution” (pp. 18–19). Kraepelin’sdescriptions are consistent with contemporary neuropsychological research on memoryfunctions in schizophrenia. In particular, most patients with schizophrenia have difficultieswith initial acquisition of information (such as number of words recalled over a seriesof trials on a word list learning task) but are generally able to retain the information theyactually learn. Some patients may have difficulty showing such retention under the demandsof a free recall test, but they generally benefit from cued or multiple-choice testing,indicating that the information does in fact remain stored. This pattern contrasts sharplywith that typically seen in cortical dementias, such as dementia due to Alzheimer’s disease,wherein there is not only difficulty with acquisition but also “rapid forgetting” (lossof the memory trace) of the acquired information (Heaton et al., 1994). Whether the acquisitionand retrieval deficits reflect memory processes per se, or are instead more accuratelyconceived of as secondary effects of deficits in attention and executive functioning,remains an open question. Another common misconception is that the memory deficitsassociated with schizophrenia are primarily deficits in acquisition of verbal information.Recent research suggests that both visual and verbal learning deficits are common amongindividuals with schizophrenia.Psychomotor speed, as measured with common tasks, such as the Trail Making Testor Digit Symbol from the Wechsler Adult Intelligence Scale—Third Edition (WAIS-III),can be thought of as comprising two components: (1) mental processing speed and (2) efficiencyof psychomotor integration. Both may be affected by schizophrenia and/or itstreatment. The conventional neuroleptics were noted in particular for their tendency toelicit extrapyramidal symptoms, including psychomotor slowing, which can affect performanceon tests designed to measure an array of other cognitive ability areas.The cognitive dimension most widely studied in schizophrenia may be executivefunctions. As noted in Palmer and Heaton (2000), “A simple definition of the term executiveskills remains elusive, but in general, this construct appears to involve those cognitiveprocesses which permit an adaptive balance of initiation, maintenance, and shifting ofresponses to environmental demands permitting goal-directed behavior” (pp. 62–64).Some of the specific abilities that may fall under this rubric include abstraction, planning,mental flexibility, response inhibition, self-monitoring, evaluation, and decision making.The Wisconsin Card Sorting Test (WCST), a measure sensitive to abstraction, problemsolving, and mental flexibility, has been among the most widely used neuropsychologicalmeasures in the schizophrenia literature. For instance, a recent search of the