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Implicit versus explicit memory in schizophrenia
389 time) from the onset of target to response is measured. Unlike Posner et al. we alert (cue without orienting to the direction of target) the subjects with a line below the cross 20% of trials, at 800, 100 or 0 ms before the appearance of the target. In the remaining trials, we alert and also orient them to the direction of the target by an arrow placed under the cross. In 70% of the orienting trials, the cue is valid, i.e., the arrow correctly points towards the box where the target will appear 0, 100, 800 ms after the orienting cue. In 30% of the orienting trials, the cue is invalid, i.e., the target appears 0, 100 or 800 ms after the cue in the direction opposite of the one suggested by the cue. Eleven schizophrenic patients (DSM III) and 11 normals have completed the testing. In addition, oculomotor measures were obtained using an infra-red tracker. Following eye movement paradigms were administered: SPEM, anti-saccade (where the instructions are to look in the opposite direction of the target jump), saccade and fixation. Preliminary analyses of the attentional shift paradigm are completed in 6 normals and 3 schizophrenic patients. Results indicate that all subjects are benefitted by the valid orienting cue. Under this condition, subjects putatively shift their covert attention to the appropriate box and as soon as the target appears, they react by pressing the key. During the invalid cue, they have to shift covert attention to the other side to register the target and then react to it. Thus, in the presence of an invalid cue, the reaction time is the longest in all subjects. Schizophrenic patients show longer reaction times under all conditions. Also, the patients take relatively longer in the invalid condition than normals. Results from the complete analyses will be presented.
Implicit versus explicit memory in schizophrenia M. Myles-Worsley Depafimenf of Psychiatry, University of Utah School of Medicine, Salt Lake City, UT S4132, U.S.A.
There are two ways in which memory for a previously experienced event can be manifested. One is an explicit, conscious recollection of that event; the other is a more implicit, unconscious type of memory expressed in terms of enhanced perceptibility of that event when it recurs. Research with amnesic patients suggests that implicit perceptual memory may be a more durable type of memory than explicit memory. The purpose of our study was to determine whether schizophrenia differentially disrupts these two types of memory. The subjects were 20 schizophrenic patients and 20 age- and education-matched normal controls. Patients were tested when they were stable on medication and ready to be discharged. A visual word processing task was used to measure both implicit and explicit memory. Subjects first studied a series of 20 words. Memory was assessed by presenting a series of 40 words, half “old” (studied) words and half “new” (unstudied) words. Each word was initially obscured by dots which gradually disappeared making the word progressively more visible. Subjects first identified the word and then classified it as old or new. Implicit perceptual memorywas measured by repetition priming (i.e., the degree to which old words were identified faster than new words). Explicit memory was measured by recognition accuracy (i.e., hit rate minus false alarm rate). Schizophrenics were less accurate than normals in distinguishing between old and new words on the recognition test. Schizophrenics also appeared to be perceptually slower than normals: patients took approximately 1000 ms longer to identify new words through dots than normal control subjects. Nevertheless, schizophrenics showed just as much repetition priming as did normals. The data therefore suggest that schizophrenia disrupts conscious explicit memory but not unconscious implicit memory. The patients ability to recognize an event as one that occurred previously seems to be impaired, but this impairment does not extend to perceptual memory. Patients show the same perceptual enhancement of repetitive information as normals do. Further research will be required to determine whether impairments in explicit memory are associated with state or trait features of the schizophrenic illness, with the neuroleptic medication used to treat the illness, or with some combination of these factors.
Investigations of abnormal selective attention as a possible vulnerability marker for schizophrenia M. Myles-Worsley*,
R.Y. Emmerson,
R. Plaetke, P.H. Wender, W.F. Byerly
Department of Psychiatry University of Utah School of Medicine, Salt Lake City, UT S4132, U.S.A.
Implicit versus explicit memory in schizophrenia M. Myles-Worsley Depafimenf of Psychiatry, University of Utah School of Medicine, Salt Lake City, UT S4132, U.S.A.
There are two ways in which memory for a previously experienced event can be manifested. One is an explicit, conscious recollection of that event; the other is a more implicit, unconscious type of memory expressed in terms of enhanced perceptibility of that event when it recurs. Research with amnesic patients suggests that implicit perceptual memory may be a more durable type of memory than explicit memory. The purpose of our study was to determine whether schizophrenia differentially disrupts these two types of memory. The subjects were 20 schizophrenic patients and 20 age- and education-matched normal controls. Patients were tested when they were stable on medication and ready to be discharged. A visual word processing task was used to measure both implicit and explicit memory. Subjects first studied a series of 20 words. Memory was assessed by presenting a series of 40 words, half “old” (studied) words and half “new” (unstudied) words. Each word was initially obscured by dots which gradually disappeared making the word progressively more visible. Subjects first identified the word and then classified it as old or new. Implicit perceptual memorywas measured by repetition priming (i.e., the degree to which old words were identified faster than new words). Explicit memory was measured by recognition accuracy (i.e., hit rate minus false alarm rate). Schizophrenics were less accurate than normals in distinguishing between old and new words on the recognition test. Schizophrenics also appeared to be perceptually slower than normals: patients took approximately 1000 ms longer to identify new words through dots than normal control subjects. Nevertheless, schizophrenics showed just as much repetition priming as did normals. The data therefore suggest that schizophrenia disrupts conscious explicit memory but not unconscious implicit memory. The patients ability to recognize an event as one that occurred previously seems to be impaired, but this impairment does not extend to perceptual memory. Patients show the same perceptual enhancement of repetitive information as normals do. Further research will be required to determine whether impairments in explicit memory are associated with state or trait features of the schizophrenic illness, with the neuroleptic medication used to treat the illness, or with some combination of these factors.
Investigations of abnormal selective attention as a possible vulnerability marker for schizophrenia M. Myles-Worsley*,
R.Y. Emmerson,
R. Plaetke, P.H. Wender, W.F. Byerly
Department of Psychiatry University of Utah School of Medicine, Salt Lake City, UT S4132, U.S.A.