Biomedical subjects

R K Heaton

Publications and source records attributed to R K Heaton.

At least 19 recordsLinked to original sources

PubMed2005

Hepatitis C augments cognitive deficits associated with HIV infection and methamphetamine.

OBJECTIVE: To examine the contribution of hepatitis C virus (HCV) infection to neurocognitive dysfunction in individuals with comorbid HIV infection or methamphetamine (METH) dependence. METHODS: Neurocognitive functioning was examined in 430 study participants who were either normal controls or had HCV infection, HIV infection, history of METH dependence, or combinations of these factors as risks for cognitive deficits. RESULTS: Rates of global and domain-specific neuropsychological (NP) impairment increased with the number of risk factors. HCV serostatus was a significant predictor of NP performance both globally and in the areas of learning, abstraction, and motor skills, with trends in speeded information processing and delayed recall. HCV serostatus did not predict scores in attention/working memory or verbal fluency. CONCLUSION: Hepatitis C virus infection contributes to the neuropsychological deficits observed among HIV-infected and stimulant-dependent populations.

AIDS Dementia Complex↗

PubMed2004

A multimodal assessment of driving performance in HIV infection.

OBJECTIVE: To examine if HIV-seropositive (HIV+) individuals are at risk for impaired driving. METHODS: Sixty licensed drivers (40 HIV+, 20 HIV-) completed a neuropsychological (NP) test battery and driving assessments. Eleven HIV+ subjects were NP-impaired. Driving-related skills were assessed using 1) two driving simulations (examining accident avoidance and navigational abilities), 2) the Useful Field of View (UFOV) test, and 3) an on-road evaluation. RESULTS: HIV+ NP-impaired subjects had greater difficulty than cognitively intact subjects on all driving measures, whereas the HIV- and HIV+ NP-normal groups performed similarly. On the UFOV, the HIV+ NP-impaired group had worse performance on Visual Processing and Divided Attention tasks but not in overall risk classification. They also had a higher number of simulator accidents (1.3 vs 2.0; p = 0.03), were less efficient at completing the navigation task (3.2 vs 9.2 blocks; p = 0.001), and were more likely to fail the on-road evaluation (6 vs 36%; p = 0.02). Impairment in Executive Functioning was the strongest NP predictor of failing the on-road drive test. NP performance and both simulations independently contributed to a model predicting 48% of the variance in on-road performance. CONCLUSION: HIV+ NP-impaired individuals are at increased risk for on-road driving impairments, whereas HIV+ individuals with normal cognition are not at a significantly higher risk than HIV- subjects. Executive Functioning is most strongly associated with impaired on-road performance. Cognitive and simulator testing may each provide data in identifying driving-impaired individuals.

AIDS Dementia Complex↗

PubMed2002

Neurocognitive dysfunction predicts postmortem findings of HIV encephalitis.

OBJECTIVE: To investigate the value of antemortem cognitive functioning in predicting postmortem evidence of HIV encephalitis (HIVE). METHODS: Thirty-nine subjects were assessed during life with a comprehensive neuropsychological battery and went on to autopsy within 18 months of testing. Cognitive impairment was determined by blind clinical ratings, based on demographically corrected test scores. Presence of HIVE was based on postmortem immunocytochemical detection of the viral protein gp41 or by measurement of HIV RNA by PCR in multiple brain areas as well as by histopathologic evidence such as microgliosis, presence of multinucleated giant cells, and myelin pallor in several brain regions. RESULTS: The sensitivity and specificity of neurocognitive impairment in detecting the occurrence of HIVE were 67 and 92%. Eighteen of 19 subjects with antemortem neurocognitive impairment had evidence of HIV-related brain disease (positive predictive value = 95%). CONCLUSION: Neuropsychological assessment can help select HIV-positive patients for treatment of CNS disease.

AIDS Dementia Complex↗

PubMed2001

Stability and course of neuropsychological deficits in schizophrenia.

BACKGROUND: Neuropsychological deficits in schizophrenia appear to predate clinical symptoms of the disease and become more pronounced at illness onset, but controversy exists about whether and when further neuropsychological progression may occur. OBJECTIVE: To identify and characterize any subset of patients who evidenced progressive neuropsychological impairment, we compared the longitudinal stability of neuropsychological functioning in schizophrenic outpatients and normal comparison subjects. METHODS: One hundred forty-two schizophrenic outpatients and 206 normal comparison subjects were given annually scheduled comprehensive neuropsychological evaluations during an average of 3 years (range, 6 months to 10 years). Clinically and demographically defined subgroups were compared, and test-retest norms were used to identify individual patients who showed unusual worsening over time. RESULTS: The schizophrenic group was neuropsychologically more impaired than the normal comparison subjects but showed comparable test-retest reliability and comparable neuropsychological stability over both short (mean, 1.6 years) and long (mean, 5 years) follow-up periods. No significant differences in neuropsychological change were found between schizophrenic subgroups defined by current age, age at onset of illness, baseline level of neuropsychological impairment, improvement or worsening of clinical symptoms, and occurrence of incident tardive dyskinesia. Norms for change also failed to show neuropsychological progression in individuals with schizophrenia. CONCLUSIONS: Neuropsychological impairment in ambulatory persons with schizophrenia appears to remain stable, regardless of baseline characteristics and changes in clinical state. Our results may not be generalizable to the minority of institutionalized poor-outcome patients.

Adult↗

PubMed2001

Bartonella henselae serostatus is not correlated with neurocognitive decline in HIV infection.

Bartonella henselae has been implicated as a significant cause of HIV-associated dementia. We attempted to confirm this association by utilizing the database of the San Diego HIV Neurobehavioral Research Center, which collects longitudinal neurocognitive and laboratory data on over 500 HIV-infected participants. Utilizing an immunofluorescent assay we found that 11% of 177 subjects, half of whom had documented neurocognitive decline, were seropositive for B. henselae. There was no correlation between B. henselae seropositivity and neurocognitive decline. The role of B. henselae in HIV-associated dementia remains ambiguous.

AIDS Dementia Complex↗

PubMed2001

Working memory in schizophrenia: transient "online" storage versus executive functioning.

Working memory has been described as the temporary "online" storage and the subsequent manipulation and retrieval of information. It has been suggested that the prefrontal cortex is a primary site of working memory. Schizophrenia patients, who are thought to have prefrontal cortical dysfunction, have demonstrated inconsistent deficits on a variety of verbal and spatial working memory tests. This has led to questions about how to define and measure working memory, whether these deficits are distinct to one cognitive domain, and what role factors such as intelligence and symptoms play in working memory performance. We compared schizophrenia patients to normal comparison subjects in four separate studies. Based upon the results we recommend that working memory tests be characterized as either transient "online" storage and retrieval tasks (where short-term storage and retrieval of information is required) or executive-functioning working memory tasks (where storage, manipulation, and retrieval of information is required). The importance of clearly identifying which distinct aspects of working memory are assessed is discussed.

Adolescent↗

PubMed2001

Association of depressive symptoms with worse functioning in schizophrenia: a study in older outpatients.

BACKGROUND: Subsyndromal depressive symptoms are highly prevalent and associated with substantial impairments of daily function in the general population. Depressive symptoms are common in schizophrenia. However, few studies have examined the relationship of functioning and well-being to the presence of depressive symptoms in schizophrenia. METHOD: 202 middle-aged or elderly outpatients with schizophrenia (DSM-III-R or DSM-IV criteria) were categorized by severity of depressive symptoms on the Hamilton Rating Scale for Depression (HAM-D) using previously validated cutoff points, i.e., HAM-D total score < or = 6 (low), from 7 to 16 (medium), and > or = 17 (high). We also assessed severity of positive and negative symptoms, movement disorders, neurocognitive performance, daily functioning, and health-related quality of well-being with standardized measures. RESULTS: A total of 11.4% of patients had HAM-D scores > or = 17, and 56.4% had HAM-D scores from 7 to 16. Even after adjusting for severity of other psychopathology, patients with more severe depressive symptoms had significantly worse everyday functioning (p < .02), except for physical functioning, and health-related quality of well-being (r = -.365, p < .001) than did those with lower HAM-D scores. These differences were unrelated to those in demographics, extrapyramidal symptoms, tardive dyskinesia, neurocognitive performance, or number of physical illnesses. CONCLUSION: The results suggest the importance of evaluating schizophrenia patients for the presence of depressive symptoms. Effectiveness of adjunct treatment of depressive symptoms with antidepressants and psychosocial management in improving functioning of schizophrenia patients deserves further study.

Age Factors↗

PubMed2001

Sensitivity and specificity of WAIS-III/WMS-III demographically corrected factor scores in neuropsychological assessment.

This study explored the neurodiagnostic utility of 6 factor scores identified by recent exploratory and confirmatory factor analyses of the WAIS-III and WMS-III: Verbal Comprehension, Perceptual Organization, Processing Speed, Working Memory, Auditory Memory and Visual Memory. Factor scores were corrected for age. education, sex and ethnicity to minimize their influences on diagnostic accuracy. Cut-offs at 1, 1.5 and 2 standard deviations (SDs) below the standardization sample mean were applied to data from the overlapping test normative samples (N = 1073) and 6 clinical samples described in the WAIS-III/WMS-III Technical Manual (N = 126). The analyses suggest that a I SD cut-off yields the most balanced levels of sensitivity and specificity; more strict (1.5 or 2 SD) cut-offs generally result in trading modest gains in specificity for larger losses in sensitivity. Finally, using combinations of WAIS-III/WMS-III factors together as test batteries, we explored the sensitivity and specificity implications of varying diagnostic decision rules (e.g.,1 vs. 2 impaired factors = "impairment"). For most of the disorders considered here, even a small (e.g., 3 factor) WAIS-III/WMS-III battery provides quite good overall diagnostic accuracy.

Adult↗

PubMed2001

Detecting change: A comparison of three neuropsychological methods, using normal and clinical samples.

Detecting change in individual patients is an important goal of neuropsychological testing. However, limited information is available about test-retest changes, and well-validated prediction methods are lacking. Using a large nonclinical subject group (N = 384), we recently investigated test-retest reliabilities and practice effects on the Wechsler Adult Intelligence Scale and Halstead-Reitan Battery. Data from this group also were used to develop models for predicting follow-up test scores and establish confidence intervals around them. In this article we review those findings, examine their generalizability to new nonclinical and clinical groups, and explore the sensitivity of the prediction models to real change. Despite similarities across samples in reliability coefficients and practice effects, limits to the generalizability of prediction methods were found. Also, when multiple test measures were considered together, one or more "significant" changes were common in all (including stable) subject groups. By employing normative cut-offs that correct for this, sensitivity of the models to neurological recovery and deterioration was modest to good. More complex regression models were not more accurate than the simpler Reliable Change Index with correction for practice effects when confidence intervals for all methods were adjusted for variations in level of baseline test performance.

Journal Article↗

PubMed2000

Predicting hand preference with performance on motor tasks.

Handedness may be defined as preference or hand-differences in task performance. The strength and significance of the relationship between hand preference and hand performance asymmetries have been contested. To evaluate this relationship, we administered the Edinburgh Handedness Inventory and measured asymmetries in finger tapping, Purdue Pegboard, and grip strength in 30 subjects who prefer their right hand and 30 subjects who prefer their left hand. Hand asymmetries in finger tapping, Purdue Pegboard, and grip strength each predicted hand preference scores. However, a multiple regression equation best predicted hand preference by using performance of each task. Hand asymmetries in finger tapping correlated strongly with asymmetries in Purdue Pegboard performance, but neither of these asymmetries correlated strongly with asymmetries in grip strength. These findings indicate that hand preference and asymmetries in motor proficiency are strongly related, but suggest that preference and proficiency for different aspects of motor performance may be independently lateralized.

Adult↗

PubMed2000

Demographically corrected norms for the California Verbal Learning Test.

The California Verbal Learning Test (CVLT) is designed to quantify components of verbal learning, retention and retrieval. The present study used multiple regression analyses to correct for demographic characteristics on CVLT performance measures. There were 906 subjects, of whom 549 were Caucasians (61%) and 357 were African Americans (39%). Age, education, ethnicity, and gender were found to be significant predictors of performance on several CVLT indices, including Total Words Recalled, Trial 1, Trial 5, List B, Short Delay Free Recall (SDFR), and Long Delay Free Recall (LDFR). Demographically corrected T-scores were calculated for a base sample of 672 subjects and cross-validated on 234 separate subjects. Tables and regression equations are offered to convert raw scores into T-scores corrected for age, gender, education, and ethnicity. Demographically corrected Recognition Discriminability cutoff scores were calculated for age and education levels. In order to provide some indices of important memory processes, we also computed indices of retrieval, Short-Delay forgetting and Long-Delay forgetting and present normative information for them.

Adolescent↗

PubMed2000

Cross-sectional study of older outpatients with schizophrenia and healthy comparison subjects: no differences in age-related cognitive decline.

OBJECTIVE: Little is known about the progression of cognitive deficits in older, community-dwelling patients with schizophrenia, especially in comparison to healthy subjects. METHOD: The authors examined the relationship of age to performance on the Mattis Dementia Rating Scale in 116 outpatients with schizophrenia and 122 normal comparison subjects. Subjects ranged in age from 40 to 85 years. RESULTS: Dementia Rating Scale scores were lower in the schizophrenia group but correlated negatively with age in both groups, with no significant differences seen between the schizophrenia and normal comparison groups in slopes that depicted age-related variation. CONCLUSIONS: This cross-sectional study suggests a relatively stable long-term course of cognitive impairment in individuals with schizophrenia, with no evidence of faster cognitive decline in outpatients with schizophrenia than in normal comparison subjects.

Adult↗

PubMed1999

Relevance of glutamate levels in the CSF of patients with HIV-1-associated dementia complex.

Chronic hyperactivation of excitatory amino acid pathways in the CNS of patients infected with HIV-1 may contribute to the pathogenesis of HIV-1-associated dementia complex. However, no correlation between the concentration of glutamate in CSF (mean 3.3 micromol/L) and either HIV-1 infection or HIV-1-associated dementia complex was observed. The results clarify several important issues regarding analysis of glutamate in the CSF and the role of excitotoxins in HIV-1-associated dementia complex.

AIDS Dementia Complex↗

PubMed1999

Extrapyramidal symptoms and neuropsychological deficits in schizophrenia.

BACKGROUND: Extrapyramidal (EP) symptoms and neuropsychological (NP) deficits are both frequently present among schizophrenia patients. EP symptoms, such as motor slowing, could hinder performance on NP tests, yet little is known about the relationship between EP symptoms and NP functioning among schizophrenia patients. METHODS: Using a comprehensive NP test battery and standard ratings of EP symptoms and other psychiatric characteristics, we conducted a cross-sectional exploration of the association between EP symptoms and NP functioning among 96 middle-aged and elderly outpatients with schizophrenia. RESULTS: Severity of EP symptoms was associated with worse NP performance, particularly the areas of learning and motor skills. Regression analyses indicated that the relationship between EP symptoms and NP deficits was not accounted for by slowed motor or mental processing, demographic characteristics, severity of psychopathology, dyskinesia, or medication status. CONCLUSIONS: The pathophysiological mechanisms underlying EP symptoms and some NP deficits in schizophrenia may overlap.

Aged↗

PubMed1999

Neuropsychological functioning in cocaine abusers with and without alcohol dependence.

Thirty codependent cocaine and alcohol users were compared with age-, education-, race-, and sex-matched cocaine abusers (N = 30) and normals (N = 30) using an extended Halstead-Reitan Neuropsychological Test Battery to determine whether cocaine abusers with alcohol dependence were more cognitively impaired than singly addicted cocaine abusers. Tests were grouped and analyzed according to 8 major ability areas. Participants who abused both cocaine and alcohol did not differ from normals on the majority of test measures. An unexpected but consistent finding was the poorer performance of the cocaine sample relative to cocaine and alcohol abusers on measures of complex psychomotor and simple motor functioning (ps < .001). Pure cocaine abusers, but not abusers of both cocaine and alcohol, also performed more poorly than normals on a measure of global neuropsychological functioning (p < .01). These results are consistent with previous reports of generally mild cognitive dysfunction in cocaine abusers. The findings also suggest that cocaine and alcohol abusers of relatively young ages may be less cognitively impaired than demographically comparable cocaine abusers. Evidence from studies of vascular functioning in abusers of cocaine and alcohol alone and in combination is discussed as possible explanation for these findings.

Adult↗

PubMed1999

Use of oral reading to estimate premorbid intellectual and neuropsychological functioning.

Judgment of neuropsychological decline is typically made by comparing a patient's current cognitive performance to data from demographically similar normal individuals. Even within narrowly defined demographic categories, however, there is variability in level of performance, approximating the normal curve. The present study explored the degree to which oral reading scores on the American National Adult Reading Test (ANART) could more accurately predict a person's test performance relative to other demographically similar individuals. In a sample of 141 neurologically healthy participants, the ANART added modestly to the precision of WAIS-R Verbal and Full Scale IQ and Learning score predictions, beyond that achieved by demographics alone; however, ANART score did not significantly improve estimation of Performance IQ, Average Impairment Rating, or Memory score. Use of the ANART tended to improve demographic predictions primarily with "outlier" participants whose oral reading skills were relatively poor. For Verbal IQ, ANART helped with participants who had both poor ANART and relatively high education. Oral reading can be useful for estimating premorbid verbal intelligence and learning in combination with demographic variables, but it does not appear to improve estimates of other neurocognitive abilities.

Adult↗

PubMed1999

Detecting significant change in neuropsychological test performance: a comparison of four models.

A major use of neuropsychological assessment is to measure changes in functioning over time; that is, to determine whether a difference in test performance indicates a real change in the individual or just chance variation. Using 7 illustrative test measures and retest data from 384 neurologically stable adults, this paper compares different methods of predicting retest scores, and of determining whether observed changes in performance are unusual. The methods include the Reliable Change Index, with and without correction for practice effect, and models based upon simple and multiple regression. For all test variables, the most powerful predictor of follow-up performance was initial performance. Adding demographic variables and overall neuropsychological competence at baseline significantly but slightly improved prediction of all follow-up scores. The simple Reliable Change Index without correction for practice performed least well, with high error rates and large prediction intervals (confidence intervals). Overall prediction accuracy was similar for the other three methods; however, different models produce large differences in predicted scores for some individuals, especially those with extremes of initial test performance, overall competency, or demographics. All 5 measures from the Halstead-Reitan Battery had residual (observed--predicted score) variability that increased with poorer initial performance. Two variables showed significant nonnormality in the distribution of residuals. For accurate prediction with smallest prediction--confidence intervals, we recommend multiple regression models with attention to differential variability and nonnormality of residuals.

Adolescent↗

PubMed1999

The impact of HIV-related neuropsychological dysfunction on driving behavior. The HNRC Group.

HIV infection often results in neuropsychological (NP) impairment. In order to assess the impact that HIV-related NP deficits may have on automobile driving, we evaluated 68 HIV-seropositive drivers using an NP battery and two PC-based driving simulations. Thirty-two participants were classified as NP impaired; most (72%) evidenced only mild impairment, and none met criteria for HIV-associated dementia. After controlling for degree of immunosuppression and disease stage, NP-impaired participants failed a previously validated driving simulation at a much higher rate than cognitively intact participants [OR = 5.3, 95% CI (1.7, 17.0), p = .006]. Similarly, on a simulation of city driving, NP impaired participants were more likely to fail based upon the number of accidents [OR = 6.1, 95% CI (1.5, 24.6), p = .01]. Simulator performance was predicted by functioning in a number of NP domains, with NP tests accounting for 13-30% of the variance on the simulations. Although it would be premature to extrapolate these findings to impairment in on-the-road driving, they do argue for greater attention to the impact that even mild HIV-related NP deficits may have on driving skills.

AIDS Dementia Complex↗