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Biomedical subjects

G K Shenaut

Publications and source records attributed to G K Shenaut.

11 recordsLinked to original sources
PubMed1999

Independent frontal-system deficits in schizophrenia: cognitive, clinical, and adaptive implications.

This study examined whether frontal-system impairments in schizophrenia occur independently of one another and whether they have distinct implications for information processing, symptom severity, and adaptive functioning. We assessed 26 medication-free schizophrenic outpatients and 18 normal control subjects on eight frontally mediated tasks, semantic information processing, IQ, the BPRS, and long-term psychosocial adaptation. Schizophrenic subjects showed three types of deficits, which were uncorrelated with one another: (1) Executive dysfunction (inflexible problem solving) was related to decreased use of expectancy during controlled semantic priming, lower intelligence, more severe negative symptoms and stereotyped mannerisms. (2) Disinhibition of responses (to irrelevant stimuli) was associated with increased automatic priming, a trend for more severe hallucinations, and was unrelated to intelligence. (3) Motor dyscoordination (inaccurate, dysfluent motor sequencing) was not related to semantic processing, intelligence, or symptoms. Furthermore, all three impairments were unrelated to generalized slowness, age, sex, illness length, or pre-washout neuroleptic dose. Two deficits accounted for aspects of long-term psychosocial adaptation, even after statistical correction for IQ: Executive dysfunction was associated with younger illness onset, poor purposefulness and planning, impaired social relations, and lower global functioning. Motor dyscoordination was associated with poor treatment outcome and restricted educational advancement. Furthermore, executive and motor deficits interacted significantly; subjects who had both deficits showed the least favorable treatment outcome. These findings are neither consistent with generalized impairment nor with a unitary 'frontal syndrome' in schizophrenia. They provide preliminary evidence for at least three frontal-system deficits (dorsolateral, orbital, and premotor), which are dissociable from one another, can occur without general intellectual impairment, and have distinct implications for long-term adaptive functioning.

Adaptation, Psychological↗
PubMed1999

Well-organized conceptual domains in Alzheimer's disease.

We used a novel apparatus called the flags board to elicit similarity judgments from 32 Alzheimer's disease (AD) patients and 32 elderly normal (EN) controls for two 12-member conceptual domains, ANIMALS and (musical) INSTRUMENTS. Based on Pathfinder and multidimensional scaling (MDS) analyses, performance by AD patients was nearly identical to that of EN controls for ANIMALS. Performance differed for INSTRUMENTS, but the AD group's Pathfinder network was found to agree with the intuitions of a panel of 18 raters as well as the EN group's. MDS analysis showed no deficit on abstract dimensions for the AD group, for either domain. The results are discussed in the context of degradation versus preservation of semantic memory in AD.

Aged↗
PubMed1999

Naturally occurring and experimentally induced tip-of-the-tongue experiences in three adult age groups.

Tip-of-the-tongue (TOT) experiences were examined in 30 young (ages 18-24 years), 30 young-old (ages 60-74), and 30 old-old (ages 80-92) adults. In Study 1, TOT experiences were experimentally induced with definitions of to-be-retrieved targets. If the target was not retrieved, orthographic or semantic cues were provided. Age-related increases in the occurrence of TOT experiences and in the time needed to resolve TOT experiences were found for young versus young-old and young-old versus old-old groups; all comparisons were significant except for young versus young-old TOT occurrence, which approached significance. In Study 2, the same participants recorded naturally occurring TOT experiences in structured diaries during a 4-week interval. Both the number of TOT experiences and the resolution time for TOT experiences increased with age. However, the percentage of TOT experiences resolved was equal across age groups; given enough time, even the oldest participants resolved virtually all TOT experiences.

Adult↗
PubMed1998

Slower and more variable reaction times in schizophrenia: what do they signify?

Extensive research has demonstrated that schizophrenic subjects are slower than normal comparison subjects on a range of reaction-time tasks. Some investigators have also observed that schizophrenic patients exhibit larger intraindividual variability in reaction times when performing these tasks than do normal comparison subjects. This study, using a lexical decision choice reaction time (CRT) task, explored the relation of mean CRT and it intra-individual variability (CRT-SD) to psychiatric symptoms and to performance on executive-motor tasks in 26 medication-free schizophrenic out-patients and 17 normal comparison subjects. Schizophrenic subjects had both significantly slower and more variable CRTs which were unrelated to general intellectual abilities (IQ). Among schizophrenic subjects, both CRT and CRT-SD were significantly related to severity of psychotic symptoms, failure to maintain cognitive set, and poorer motor coordination and global functioning. After controlling for mean CRT, CRT-SD showed unique covariation with clinical symptoms (positive, disorganized and tension/hostility). Conversely, mean CRT showed unique covariation with the failure to maintain cognitive set and with stereotypic mannerisms, independent of CRT-SD. These results suggest that slower CRT and increased intra-individual variability in CRT, while not fully independent of one another, may reflect separate aspects of symptomatic and cognitive dysfunction in schizophrenia.

Adult↗
PubMed1997

Automatic versus controlled semantic priming in schizophrenia.

Schizophrenic individuals (n = 31), including paranoid and nonparanoid diagnostic subgroups, and normal controls (n = 20) participated in a semantic priming experiment involving a single-choice lexical decision task. For the automatic priming blocks, a 260-ms stimulus onset asynchrony (SOA) was used; for the controlled priming blocks, 1,000-ms SOA was used. The paranoid subgroup showed significantly less priming than did the control group. The nonparanoid subgroup showed a decrease in priming compared with the control group that approached significance. There was an increased priming effect for the controlled compared with the automatic priming condition; this difference was not modulated by participant group. Nonsignificant semantic priming (equal to 0) occurred only for schizophrenic subgroups and only in automatic priming conditions.

Adult↗
PubMed1997

Clinical and neurocognitive aspects of source monitoring errors in schizophrenia.

OBJECTIVE: Source monitoring, an aspect of memory that involves judgments about the origin of information, has been found to be more prone to errors in schizophrenic subjects than in normal persons. To examine the precise nature of such errors and their relationship to clinical and neurocognitive variables, the authors compared schizophrenic and normal subjects. METHOD: Schizophrenic subjects who had been medication free for 1 week (N = 26) and demographically matched normal subjects (N = 21) performed a source monitoring task and were assessed on current psychiatric symptoms, IQ, and frontal lobe functioning. RESULTS: The schizophrenic subjects had normal recognition memory of target words (recognition hits) and a normal generation effect but made more errors than the comparison subjects in identifying the source of target words. Specifically, the schizophrenic subjects made more errors in remembering the source of new and self-generated items, and they tended to attribute items to an external source. In 11 retested subjects, these errors were stable and independent from medication status after a 2-year interval. Secondary analyses suggested that certain source monitoring errors may be associated with hostility and lower IQ. When the effect of IQ was controlled, correlations with frontal dysfunction were not significant. CONCLUSIONS: Schizophrenic subjects make significantly more source monitoring errors than normal subjects, but not because of problems with recognition memory hits or with the generation effect. This tendency may be trait like and may be related to hostility. Lower IQ in schizophrenia plays a partial role in these errors, but frontal dysfunction does not.

Adult↗
PubMed1996

Methodological control of semantic priming in Alzheimer's disease.

We conducted a lexical-decision, semantic priming experiment that included 250- and 1000-ms stimulus onset asynchronies (SOAs) with 32 probable Alzheimer's disease (AD) and 40 older normal persons. Attention-based, controlled processes are assumed to occur only at the longer of the 2 SOAs. The AD group showed greater than normal priming in the long-SOA but not the short-SOA condition. We conclude that greater than normal AD priming is a function of controlled processing rather than semantic network degradation.

Aged↗
PubMed1992

Semantic priming of word pronunciation and lexical decision in schizophrenia.

Experimental assessments of semantic memory structure and function in schizophrenic subjects can be a useful approach for delineating some of the information processing deficits in schizophrenia. In this study, a pronunciation and a lexical decision semantic priming experiment were conducted with 19 schizophrenic subjects and 20 normal controls. A short stimulus-onset asynchrony (250 msec) and a relatively low proportion of related prime-target pairs were used in order to examine automatic priming and in order to avoid the contribution of attentional, controlled processes. On the pronunciation task, schizophrenic subjects showed a significant priming effect, equal to the priming shown by normal controls. However, on the lexical decision task, schizophrenics, unlike normal controls, did not show a priming effect which is significantly greater than zero, even though the group difference in priming effect (interaction of priming effect by group) was nonsignificant. The lack of priming on the lexical decision task is consistent with the hypothesis that schizophrenic subjects may show abnormalities in the realm of post-lexical, controlled information processing. The equal-to-normal priming for schizophrenic subjects indicates that the basic structure of the semantic network, including associations among related concepts, is intact in schizophrenia, and that spreading activation also occurs normally.

Adult↗
PubMed1991

Automatic semantic priming with various category relations in Alzheimer's disease and normal aging.

The 6 experiments reported here tested the effects of various category relations on automatic semantic priming in 20 Alzheimer's disease (AD), 20 older control, and 22 younger control subjects. The tasks were either word pronunciation or lexical decision; the prime-target stimulus-onset asynchrony (SOA) was always 250 ms. A variety of category relationships between prime and target were examined: highly associated category comembers, subordinate-superordinate or superordinate-subordinate pairs, and pairs selected on the basis of category typically to form typical-typical, atypical-typical, typical-atypical, and atypical-atypical pairings. Both for AD versus older control subjects and for older versus younger control subjects, no significant group differences were found in the magnitude of overall semantic priming or in the effects on priming of factors pertaining to the prime-target relationship.

Adult↗
PubMed1988

Lexical decision and priming in Alzheimer's disease.

Patients with probable Alzheimer's disease (AD) were no faster at making lexical decisions to targets preceded by a semantic prime than to those preceded by an unrelated prime, in contrast to the facilitatory effect of semantic primes for controls. Fewer errors were made by both subject groups on the targets that followed related items, indicating the preservation of associative relationships in AD. The AD patients and controls showed similar effects on lexical decision of repetition priming, word frequency, and the degree to which nonwords approximated real words. The abnormal priming effect in AD may stem from increased susceptibility to lateral inhibition in the semantic network.

Alzheimer Disease↗