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Biomedical subjects

S D Koh

Publications and source records attributed to S D Koh.

At least 19 recordsLinked to original sources
PubMed1983

Memory scanning and retrieval in affective disorders.

Previous studies have consistently demonstrated unimpaired memory scanning and retrieval in schizophrenic patients. Using the choice-reaction time paradigm, this study assessed the speed of short-term memory processing for pictorial information in both unipolar and bipolar depressives by comparing it with that of schizophrenics. It was found that the processing rate is comparable between depressives and schizophrenics, between unipolar and bipolar depressives, and between depressives on medication and those not on medication. It was concluded, therefore, that the short-term memory scanning and retrieval processes are not impaired in depressive patients. The results further suggested that the depressives' slowness often found in simple reaction time tasks may result from a dysfunction in their stimulus encoding and/or response execution rather than in the central information-identification process.

Adult↗
PubMed1981

Affective memory and schizophrenic anhedonia.

Two experiments attempted to isolate and measure schizophrenic anhedonia as it is reflected in the mnemonic processing of affectively laden stimuli. In the first experiment, subjects were required to sort a list of words repeatedly, each in terms of pleasantness, until a consistent sorting was achieved. Then, they were unexpectedly asked to recall the list. Schizophrenics' total recall was comparable to that of normals; but while normals recalled significantly more pleasant than unpleasant words (a Pollyanna tendency), such differential recall was absent in schizophrenics (anhedonia). These results were complicated, however, by the intrusion of semantic variables into the affective processing. In the second experiment, human faces were used to minimize semantic intrusions. Subjects were induced to encode photographs of faces in the context of favorable-unfavorable personality traits, and their recognition memory for these faces was subsequently tested. In spite of comparable overall performance, normals recognized significantly more favorably than unfavorably encoded faces, and such asymmetric recognition was absent in schizophrenics. Furthermore, a significant Group by Affect interaction emerged. The results were taken as evidence of schizophrenic anhedonia and normals' Pollyanna tendency. Nonschizophrenics also served as controls but their results were equivocal. Several problems which may be typical in the experimental investigation of affect were discussed.

Adolescent↗
PubMed1981

Memory processing with lithium carbonate.

The effect of lithium carbonate treatment on the memory processing of manic-depressive patients was assessed in three memory tasks. The results suggested that memory performance and the underlying organizational processes are not adversely affected by lithium treatment.

Bipolar Disorder↗
PubMed1976

Short term memory for numerousness in schizophrenic young adults.

The short term memory of schizophrenics for random dot patterns was examined by a delayed comparison procedure. In experiment 1, the 10 schizophrenics and 10 normals compared a fixed dot pattern (standard) with a variable dot pattern (compairson) appearing 2 or 8 seconds later and decided whether the comparison stimulus had "more" or "less" dots than the standard. Memory strength, indexed by the d' value of signal-detection theory, showed neither group difference nor decay over time. In experiment 2, the interstimulus interval was filled with an unjudged dot pattern (storage interference), and the standard stimulus followed the variable comparison stimulus (encoding difficulty). The memory strength of 17 schizophrenics and 17 normals was severely impaired, and their memory strength weakened over time, but again, no group differences were found. In both experiments, the two groups showed a strong bias (beta) in underestimating the first (to-be-remembered) stimulus. It was concluded that schizophrenics' short term perceptual memory for nonverbal stimuli remains good.

Adolescent↗
PubMed1976

Postpsychotic state, convalescent environment, and therapeutic relationship in schizophrenic outcome.

The authors evaluated the following variables in the 2-3-year outcomes of 30 schizophrenic patients: the acute/chronic dichotomy, the presence of a postpsychotic regressive state, the quality of the convalescent environment, and the formation of a therapeutic relationship. They found that the presence of a postpsychotic regressive state was not associated with either good or poor short-term outcome; that the diagnosis of acute schizophrenia was almost invariably followed by good outcome, but a diagnosis of chronic schizophrenia had little predictive value; and that a favorable convalescent environment and the presence of a therapeutic relationship were signigicantly associated with good outcome.

Acute Disease↗
PubMed1975

Hypohedonia in schizophrenia.

The affective disorder in schizophrenia is an important manifestation of the schizophrenic illness. Such clinical features of joylessness, interpersonal aversion, and affective blunting have been considered by Rado and Meehl to represent a neurophysiological deficit in pleasure capacity which they termed anhedonia, but is more aptly characterized by the term hypohedonia. A free-recall task employing 24 affectively laden words presented in random order over nine trials was given to a carefully selected group of nonpsychotic hospitalized schizophrenics, hospitalized nonschizophrenics, and normals. The results of the study demonstrate that normals remember pleasant words to a significantly greater extent than upleasant words. This Pollyanna tendency or the tendency to utilize pleasant words over upleasant words has been described by Osgood as a stable cross-cultural phenomenon. By contrast, the schizophrenics show a significantly lower recall of pleasant words when compared with normals, although they remember unpleasant words to a comparable degree as normals. These findings provide experimental support for the hypohedonia hypothesis in schizophrenia. The nonshcizophrenic patients recall pleasant and unpleasant words to a significantly greater degree than neutral words. They are thus affectively governed in the free-recall task and seem equally sensitized to both pleasant and unpleasant affect in their mnemonic processing.

Adolescent↗