Characteristics of Schizophrenic Processing - Essay Example

Running Header: CHARACTERISTICS OF SCHIZOPHRENIC PROCESSING Characteristics of Schizophrenic Processing: Hindrances in Contextual Processing Historically, patients of schizophrenia have struggled with the ways in which they receive and categorize information: specifically, the way that they group parts of a stimulus into object representations (Cox & Leventhal, 1978; Place & Gilmore, 1980; Silverstein et. al., 1996). The reason for this struggle has been unclear for some time, and of particular interest has been the disagreement over the location of the impairment. There are those who believe the impairment relates to "bottom-up" or basic visual processing, while others believe the impairment relates to "top-down" processing, which relates more to "acoustic properties and contextual cues" (Silverstein, Matteson, and Knight, 1996). As a result of their 1996 study, Silverstein, Matteson and Knight have concluded that the impairment results from a top-down impairment, specifically "in the ability to utilize contextual information" that acts as a "major factor in schizophrenia patients' perceptual organization difficulties." In their experiment, schizophrenic patients experienced the same level of confusion from a human voice imitating a sheep as that from what they thought was an actual sheep's voice, whereas the control group ceased having confusion once they learned that the voice was actually an animal, instead of a human. It is this lack of ability to adjust to reduction of ambiguity in context that is the basis of their findings. Because these findings are similar in their relation to perseveration to other studies (Heaton, 1981; Lysaker & Bell, 1994), they do not represent a "leap of faith" nor require unconventional assumptions. Because these findings appear to more closely identify the source of the impairment as an "inability to utilize explicit contextual information" (Silverman et. al., 1996), however, they do add to the general understanding of impairments in top-down processing. The key measurement in identifying the source of the impairment of top-down processing was the contrast between the control group and the schizophrenic group in ability to memorize a group of numbers read aloud by a male voice, ending with the "suffix" of a sheeplike sound. The control group had a much easier time memorizing the group of numbers, once they knew that the sheep sound was not also made by a human voice, but was rather the product of an actual sheep. The schizophrenic group, however, did not improve in their ability to memorize the list of numbers, even after the authenticity of the sheep was made clear. The definitions of these groups within the testing population were made clear, as were the criteria for statistical and clinical significance. The definitions of terms, and of the handling of the experiment, are sufficiently clear to make the process easily duplicable. The Silverman claim about top-down processing generates a significant need for further research. The authors note a need for aid in "determining if an auditory perceptual organization deficit is as specific to schizophrenia as its visual counterpart appears to be" (1996), as well as an analysis as to whether the perceptual organizational deficit is connected to one or more of the specific symptoms of schizophrenia. Because of this need for further research, the Silverman claim remains at the "descriptive" level of power. It does not speak toward influence of outcomes, or anything approaching prediction or control - however, it does permit discriminations in experience and identify specific relationships in top-down processing impairment. For their claim to be rejected, a control group would have to react to the identification of the stimulus' context in a much more similar fashion to the schizophrenia group than did the two groups in their study. If their claim is upheld by further research, however, the isolation of the source of top-down processing impairment could well be the first step towards treatment. The concepts underlying Silverman's claim about top-down processing have a fairly logical progression. Other studies have used the same paradigm of studying the effects of the auditory suffix (Ayres, Jonides, Reitman, Egan & Howard, 1979; Neath, Surprenant, & Crowder, 1993). While recent studies have shown that the context of a stimulus' interpretation can significantly affect the ability of that stimulus to interfere as a suffix (Ayres et. al., 1979; Neath et. al., 1993), this was the first study to test whether the acoustic properties of the suffix were a stronger influence than any contextual ambiguities of interpretation. That their findings reflect similarities with existing work concerning processing impairments suggest that their explanations are rational and justified. However, these claims are somewhat limited in scope. Silverman et. al. admit the lack of applicability of their findings to the area of visual perceptual organization dysfunction, and they admit that the fact that a sheep's voice would not change in its familiarity to a schizophrenic patient, regardless of its context, may represent a problem - what appears as an impairment of contextual interpretation may actually be a mere difference for the schizophrenic, who may classify stimuli by familiarity (a sheep's voice is familiar, no matter the source) versus unfamiliarity (Zubin, 1975). However, the authors are forthcoming about the limitations of their research, and urge further research to reduce or eliminate those limitations. The authors' experiment appears to have been designed appropriately for the claim under review. Within the schizophrenic group, all patients were stabilized on antipsychotic medications, and all provided informed consent for the experiment to take place. The interview consisted of a standard form contained in the APA's Diagnostic and statistical manual of mental disorders. The interviewer had a highly reliable background in conducting prior interviews in similar experimental settings. The human voice and animal sounds were consistent within their various groups, and all numerical lists were presented in the same order. Based on the way the experiment was carried out, the results could have gone in several different directions. Significance was measured among all four of the varied groups of suffix sounds (animal, human, animal-sheep, human-sheep), and so context could have proven to be a much more important component of interpretation than the physical source of the sounds. The sample, both in number of testers and in number of items given in the test, was consistent with existing experimental practice. Other than the limitations mentioned by the problem of possible familiarity of sound, internal and external sources of influence are controlled as much as could be reasonably expected. The statistical results bear a degree of significance that bears out the authors' hypothesis that, for the schizophrenic, selective attention process are at work that utilize little or no top-down influence. In other words, the way a stimulus sounds is far more important to the schizophrenic than the identity of the source of the sound. In this instance, a sheep's voice interferes just as much with a schizophrenic's ability to memorize a list of numbers if it comes from an actual sheep, or from a person who is imitating a sheep. Works Cited Ayres, T.J., Jonides, J., Reitman, J.S., Egan, J.C., & Howard, D.A. 1979. "Differing suffix effects for the same physical stimuli", Journal of Experimental Psychology: Human Learning and Memory, vol. 5, 315-321. Cox, M.D. & Leventhal, D.N. 1978. "A multivariate analysis and modification of a preattentive perceptual dysfunction in schizophrenia", Journal of Nervous and Mental Disease, vol. 166, pp. 709-718. Crowder, R.G. & Morton, J. 1969. "Precategorical acoustic storage (PAS)", Perception & Psychophysics, vol. 5, pp. 365-373. Heaton, R. 1981. Wisconsin Card Scoring Test manual. Odesa, Florida: Psychological Assessment Resources, Inc. Lysaker, P., & Bell, M. 1994. "Insight and cognitive impairment ineschizophrenia: performance on repeated administrations of the Wisconsin Card Sorting Test", Journal of Nervous and Mental Disease, vol. 182, pp. 656-660. Neath, I., Surprenant, A.M., & Crowder, R.G. 1993. "The context-dependent stimulus suffix effect", Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 19, pp. 698-703. Place, E. J. S. & Gilmore, G.C. 1980. "Perceptual organization in schizophrenia", Journal of Abnormal Psychology, vol. 89, pp. 409-418. Silverstein, S.M., Knight, R.A., Schwarzkopf, S.B., West, L.L., Osborn, L.M., & Kamin, D. 1996. "Stimulus configuration and context effects in perceptual organization in schizophrenia", Journal of Abnormal Psychology, vol. 105, pp. 410-420. Silverstein, S.M., Matteson, S., & Knight, R.A. 1996. "Reduced top-down influence in auditory perceptual organization in schizophrenia", Journal of Abnormal Psychology, vol. 105, no. 4, pp. 663-667. Zubin, J. 1975. "Problem of attention in schizophrenia". In M.L. Kietzman, S. Sutton, & J. Zubin (Eds.), Experimental approaches to psychopathology (pp. 139-166). New York: Academic Press. Read More