Biomedical subjects

Steven Paul Woods

Publications and source records attributed to Steven Paul Woods.

At least 19 recordsLinked to original sources

PubMed2006

Verbal fluency impairments among middle-aged and older outpatients with schizophrenia are characterized by deficient switching.

Patients with schizophrenia demonstrate impaired verbal fluency, but no studies have examined the underlying cognitive mechanisms (e.g., clustering and switching) associated with impaired fluency among middle-aged and older, non-institutionalized patients. Using Troyer et al.'s [Troyer, A.K., Moscovitch, M., Winocur, G., 1997. Clustering and switching as two components of verbal fluency: evidence from younger and older healthy adults. Neuropsychology 11 (1), 138-146] conceptual model, we examined clustering and switching on verbal fluency tasks among 163 middle-aged and older outpatients with schizophrenia and 92 age comparable healthy comparison (HC) participants. The patients produced significantly fewer total words than HC participants on both the letter ("F", "A", "S") and Animal fluency conditions. With regard to clustering, patients were similar to HC participants on both FAS and Animal fluency tasks. However, significantly fewer switches between lexical-semantic categories were observed among patients with schizophrenia on both conditions relative to HC participants. A small, but statistically significant association was found between number of switches on the Animal fluency task and severity of negative symptoms. The absence of a difference in mean cluster size between the patient and HC groups suggests intact lexical-semantic stores among middle-aged and older outpatients with schizophrenia. Differences in switching between patients and HC participants may be driven by several cognitive impairments associated with schizophrenia. Further delineation of the cognitive mechanisms of the observed lexical-semantic switching deficits in schizophrenia should be a focus of future research.

Age Factors↗

PubMed2006

The California Verbal Learning Test--second edition: test-retest reliability, practice effects, and reliable change indices for the standard and alternate forms.

The California Verbal Learning Test - second edition (CVLT-II) is one of the most widely used neuropsychological tests in North America. The present study evaluated the 1-month test-retest reliability and practice effects associated with the standard and alternate forms of the CVLT-II in a sample of 195 healthy adults. Eighty participants underwent repeat assessment using the standard form of the CVLT-II on both occasions, whereas the remaining 115 individuals received the standard form at baseline and the alternate form at follow-up. Consistent with prior research, results revealed generally large test-retest correlation coefficients for the primary CVLT-II measures in both the standard/standard (range=0.80-0.84) and standard/alternate (range=0.61-0.73) cohorts. Despite exhibiting slightly lower test-retest reliability coefficients, participants in the alternate form group displayed notably smaller practice effects (Cohen's d range=-0.01 to 0.18) on the primary indices relative to individuals who received the standard form on both occasions (Cohen's d range=0.27-0.61). Reliable change indices were also generated and applied to primary CVLT-II variables to determine the base rates of significant improvements (range=2-10%), declines (range=0-7%), and stability (range=85-97%) in performance over time. Overall, findings from this study support the test-retest reliability of the standard and alternate forms of the CVLT-II in healthy adults and may enhance the usefulness of this test in longitudinal neuropsychological evaluations.

Adolescent↗

PubMed2006

Recency effects in HIV-associated dementia are characterized by deficient encoding.

The aim of the present study was to investigate the nature and cognitive mechanisms of serial position learning effects in HIV-associated dementia (HAD). Participants were 16 persons with HAD, 50 non-demented persons with HIV-infection, and 50 demographically comparable HIV-seronegative participants. HAD participants, relative to both comparison groups, exhibited reduced middle region (p<0.01) and elevated recency region (p<0.05) recall on the Hopkins Verbal Learning Test-Revised, but no primacy region effect (p>0.10). On recognition testing, the HAD group was impaired in discriminating targets from distractors (p<0.01) in all three serial position regions; however, they were not impaired on measures of retrieval (p>0.10) within these same regions. In sum, HAD participants relied disproportionately on recency regions of the list, indicating a passive recall style of echoing only the words within their auditory attention span. Interestingly, HAD participants did not evidence significant improvement on measures of recognition, a finding that suggests that the serial position effects are most consistent with a primary encoding deficit.

AIDS Dementia Complex↗

PubMed2006

Additive deleterious effects of methamphetamine dependence and immunosuppression on neuropsychological functioning in HIV infection.

Methamphetamine (MA) dependence and HIV infection are independently associated with cerebral dysfunction, especially within frontal-basal ganglia circuits. Recent evidence indicates that MA dependence has an additive effect on neuropsychological (NP) deficits associated with HIV infection. This study extends prior findings by examining the combined effects of MA dependence (MA+) and immunosuppression (i.e., CD4 lymphocyte count <200) on NP functioning in 284 HIV+ individuals. Prevalence of NP impairment was examined in four demographically comparable groups: (1) MA+/CD4 < 200; (2) MA+/CD4 > or = 200; (3) MA-/CD4 < 200; and (4) MA-/CD4 > or = 200. Results revealed that both MA dependence and immunosuppression were significant predictors of NP impairment. More importantly, additive effects were evident whereby the MA+/CD4 < 200 group exhibited the highest rate of NP impairment. Findings indicate that MA dependence conveys an additive deleterious impact on NP status in immunosuppressed persons with HIV infection, perhaps reflecting the combined effects of neuropathophysiological mechanisms in fronto-striatal circuits.

Adult↗

PubMed2006

Cognitive sequelae of subthalamic nucleus deep brain stimulation in Parkinson's disease: a meta-analysis.

BACKGROUND: Deep brain stimulation of the subthalamic nucleus (STN DBS) is an increasingly common treatment for Parkinson's disease. Qualitative reviews have concluded that diminished verbal fluency is common after STN DBS, but that changes in global cognitive abilities, attention, executive functions, and memory are only inconsistently observed and, when present, often nominal or transient. We did a quantitative meta-analysis to improve understanding of the variability and clinical significance of cognitive dysfunction after STN DBS. METHODS: We searched MedLine, PsycLIT, and ISI Web of Science electronic databases for articles published between 1990 and 2006, and extracted information about number of patients, exclusion criteria, confirmation of target by microelectrode recording, verification of electrode placement via radiographic means, stimulation parameters, assessment time points, assessment measures, whether patients were on levodopa or dopaminomimetics, and summary statistics needed for computation of effect sizes. We used the random-effects meta-analytical model to assess continuous outcomes before and after STN DBS. FINDINGS: Of 40 neuropsychological studies identified, 28 cohort studies (including 612 patients) were eligible for inclusion in the meta-analysis. After adjusting for heterogeneity of variance in study effect sizes, the random effects meta-analysis revealed significant, albeit small, declines in executive functions and verbal learning and memory. Moderate declines were only reported in semantic (Cohen's d 0.73) and phonemic verbal fluency (0.51). Changes in verbal fluency were not related to patient age, disease duration, stimulation parameters, or change in dopaminomimetic dose after surgery. INTERPRETATION: STN DBS, in selected patients, seems relatively safe from a cognitive standpoint. However, difficulty in identification of factors underlying changes in verbal fluency draws attention to the need for uniform and detailed reporting of patient selection, demographic, disease, treatment, surgical, stimulation, and clinical outcome parameters.

Chi-Square Distribution↗

PubMed2006

Action (verb) fluency predicts dependence in instrumental activities of daily living in persons infected with HIV-1.

Inspired by the hypothesized neural dissociation between the retrieval of nouns and verbs, several studies now support the construct validity of Action (verb) Fluency as a measure of frontostriatal systems function. Relative to traditional noun- and letter-cued verbal fluency tests, Action Fluency is more sensitive to HIV-1-associated neuropsychological impairment, which may reflect inefficiencies engaging motor representations during action retrieval in this population. Accordingly, impaired Action Fluency might adversely impact instrumental activities of daily living (IADL) by disrupting the production and organization of script-based action schemas upon which successful IADL performance depends. The present study thus sought to evaluate the ecological validity of Action Fluency as a predictor of IADL among persons with HIV-1 infection. Action, Letter (FAS), and Noun (animal) fluency were compared in 21 HIV-1-infected participants with self-reported IADL dependence relative to 76 demographically comparable HIV-1-infected participants who reported no IADL declines. Results revealed significant between-group differences in Action and Letter Fluency, but not Noun Fluency. Action Fluency achieved an overall hit rate of 76% and was more sensitive than Letter Fluency in classifying IADL dependent participants. Individuals with impaired Action Fluency performance had a fivefold risk of concurrent IADL dependence as compared to those who performed within normal limits. Findings suggest that Action Fluency may possess incremental ecological validity in the identification of HIV-1-associated neurocognitive disorders.

Activities of Daily Living↗

PubMed2006

Prospective memory in HIV-1 infection.

The cognitive deficits associated with HIV-1 infection are thought to primarily reflect neuropathophysiology within the fronto-striato-thalamo-cortical circuits. Prospective memory (ProM) is a cognitive function that is largely dependent on prefronto-striatal circuits, but has not previously been examined in an HIV-1 sample. A form of episodic memory, ProM involves the complex processes of forming, monitoring, and executing future intentions vis-à-vis ongoing distractions. The current study examined ProM in 42 participants with HIV-1 infection and 29 demographically similar seronegative healthy comparison (HC) subjects. The HIV-1 sample demonstrated deficits in time- and event-based ProM, as well as more frequent 24-hour delay ProM failures and task substitution errors relative to the HC group. In contrast, there were no significant differences in recognition performance, indicating that the HIV-1 group was able to accurately retain and recognize the ProM intention when retrieval demands were minimized. Secondary analyses revealed that ProM performance correlated with validated clinical measures of executive functions, episodic memory (free recall), and verbal working memory, but not with tests of semantic memory, retention, or recognition discrimination. Taken together, these findings indicate that HIV-1 infection is associated with ProM impairment that is primarily driven by a breakdown in the strategic (i.e., executive) aspects of retrieving future intentions, which is consistent with a prefronto-striatal circuit neuropathogenesis.

Adult↗

PubMed2006

Statistical power of studies examining the cognitive effects of subthalamic nucleus deep brain stimulation in Parkinson's disease.

It has been argued that neuropsychological studies generally possess adequate statistical power to detect large effect sizes. However, low statistical power is problematic in neuropsychological research involving clinical populations and novel interventions for which available sample sizes are often limited. One notable example of this problem is evident in the literature regarding the cognitive sequelae of deep brain stimulation (DBS) of the subthalamic nucleus (STN) in persons with Parkinson's disease (PD). In the current review, a post hoc estimate of the statistical power of 30 studies examining cognitive effects of STN DBS in PD revealed adequate power to detect substantial cognitive declines (i.e., very large effect sizes), but surprisingly low estimated power to detect cognitive changes associated with conventionally small, medium, and large effect sizes. Such wide spread Type II error risk in the STN DBS cognitive outcomes literature may affect the clinical decision-making process as concerns the possible risk of postsurgical cognitive morbidity, as well as conceptual inferences to be drawn regarding the role of the STN in higher-level cognitive functions. Statistical and methodological recommendations (e.g., meta-analysis) are offered to enhance the power of current and future studies examining the neuropsychological sequelae of STN DBS in PD.

Cognition Disorders↗

PubMed2006

Demographically adjusted normative standards for new indices of performance on the Paced Auditory Serial Addition Task (PASAT).

The Paced Auditory Serial Addition Task (PASAT) is a complex cognitive test sensitive to neuropsychological disorders. Its traditional Total Correct score seemingly reflects multiple cognitive abilities, including attention, working memory, and processing speed. Snyder, Aniskiewicz, and Snyder (1993) modified scoring guidelines for the PASAT to give credit only for "dyads." This method emphasizes working memory operations and has been found superior to Total Correct scores at detecting cognitive impairments in several investigations. To date, normative standards are not available for the "dyad" scoring method, thus limiting its utility in clinical and research settings. The current investigation provides demographically adjusted normative data based on a sample of 500 healthy adults of varied age, education, sex, and race (African American and Caucasian) for various indices of performance on the PASAT, including "Total Dyads" obtained across the four PASAT trials. In addition, we describe and present normative data on four other indices designed to quantify various aspects of performance on the PASAT: invalid responding, effects of varied information processing speed demands, and tendency to omit responses and to make arithmetic errors.

Abstracting and Indexing↗

PubMed2006

Association between dyads and correct responses on the Paced Auditory Serial Addition Task (PASAT).

The sensitivity of the Paced Auditory Serial Addition Task (PASAT) to working memory deficits may be enhanced by examining "dyads" (i.e., correct responses immediately preceded by a correct response) as a complement to the traditional total correct summary score. In a sample of 397 mostly African American (79%) healthy adults, total dyad and total correct scores were highly correlated (r = .96, p < .001); however, the magnitude of this association diminished in faster stimulus presentation trials, particularly among participants with impaired working memory abilities.

Adult↗

PubMed2005

Construct validity of Hopkins Verbal Learning Test-Revised component process measures in an HIV-1 sample.

Executive dyscontrol of episodic verbal learning and memory secondary to prefrontostriatal circuit neuropathophysiology is a common feature of HIV-1 infection. Prior research indicates that standard clinical learning and recall indexes from Hopkins Verbal Learning Test-Revised (HVLT-R) are among the most sensitive indicators of HIV-associated neurocognitive disorders. Emerging data support the validity of qualitative component process measures derived from the HVLT-R (e.g., Semantic Clustering); however, no prior studies have examined these particular indices of performance in an HIV-1-infected population. In the present study, we examined the construct validity of HVLT-R component process indices in a sample of 42 persons with HIV-1 infection and 29 demographically similar seronegative comparison participants. The HIV-1 sample performed significantly below the seronegative group on Total and Delayed Recall, Semantic Clustering, and the Retrieval Index. No between-group differences were observed on Serial Clustering, Pair Frequency, Learning, Repetitions, Semantic False Positive Recognition Errors, or the Recognition Discrimination Index. In addition, the HVLT-R component process measures demonstrated evidence of convergent and divergent validity with standard clinical tests in the HIV-1 sample. Findings support the construct validity of HVLT-R component process measures and are commensurate with prior literature indicating that HIV-1 disease is associated with deficient executive control of encoding and retrieval within verbal episodic memory.

Adult↗

PubMed2005

A battery approach for measuring neuropsychological change.

The accurate interpretation of serial neuropsychological testing is a fundamental activity of neuropsychologists in clinical and research settings. Although prior research supports the construct validity of several individual tests for the reliable measurement of cognitive change, neuropsychologists are often interested in detecting changes in cognitive functioning across a battery of tests. In the present study, we examined the specificity of a modified Reliable Change Index (RCI) methodology applied across a focused battery of commonly used neuropsychological tests. Fifty-seven healthy controls underwent neuropsychological assessment at two time points separated by approximately 1 year. Test-retest reliability coefficients and standard RCI confidence intervals for the individual tests were broadly comparable with prior research in healthy populations. Battery change scores were generated by calculating z-scores of change for each individual test, which were summed across the entire test battery. The RCI methodology was applied to the summed z-score to provide a 90% confidence interval as an indicator of overall cognitive stability. These battery RCI normative standards demonstrated adequate specificity when applied to 29 persons with HIV-1 infection who were classified as medically and neurologically stable. Findings from this study may be useful for both clinicians and researchers seeking normative standards for determining reliable changes in performance across a commonly used battery of neuropsychological tests.

Adult↗

PubMed2005

Deficient strategic control of verbal encoding and retrieval in individuals with methamphetamine dependence.

Methamphetamine (MA) dependence is associated with deficits in episodic verbal memory, but the cognitive mechanisms underlying such impairments are not known. The authors evaluated a component process model of episodic verbal memory in 87 persons with MA dependence (MA+) and 71 demographically similar non-MA-using controls (MA-). Compared with MA- controls, MA+ participants demonstrated deficient overall learning, free recall, and utilization of semantic clustering, as well as higher rates of repetitions and intrusions. No between-groups differences were evident on measures of serial clustering, retention, or recognition discrimination. Taken together, these findings indicate that MA dependence is associated with deficient strategic (i.e., executive) control of verbal encoding and retrieval, which is consistent with the sequelae of MA-related prefronto-striatal circuit neurotoxicity.

Adult↗

PubMed2005

Test-retest reliability of component process variables within the Hopkins Verbal Learning Test-Revised.

Emerging data support the construct validity of component process variables of learning and memory within the Hopkins Verbal Learning Test-Revised (HVLT-R; Brandt & Benedict, 2001); however, the test-retest reliabilities of such measures are heretofore largely unknown. This study reveals generally modest-to-low 1-year test-retest stability for several key HVLT-R component process variables (e.g., semantic clustering) in 41 healthy, younger adults. These findings are discussed in relation to issues of clinical practice and research design in neuropsychological assessment.

Adult↗

PubMed2005

Action (verb) fluency: test-retest reliability, normative standards, and construct validity.

Action (verb) fluency is a newly developed verbal fluency task that requires the examinee to rapidly generate as many verbs (i.e., "things that people do") as possible within 1 min. Existing literature indicates that action fluency may be more sensitive to frontal-basal ganglia loop pathophysiology than traditional noun fluency tasks (e.g., animal fluency), which is consistent with the hypothesized neural dissociation between noun and verb retrieval. In the current study, a series of analyses were undertaken to examine the psychometric properties of action fluency in a sample of 174 younger healthy participants. The first set of analyses describes the development of demographically adjusted normative data for action fluency. Next, a group of hypothesis-driven correlational analyses reveals significant associations between action fluency and putative tests of executive functions, verbal working memory, verbal fluency, and information processing speed, but not between action fluency and tests of learning or constructional praxis. The final set of analyses demonstrates the test-retest stability of the action fluency test and provides standards for determining statistically reliable changes in performance. In sum, this study enhances the potential clinical applicability of action fluency by providing demographically adjusted normative data and demonstrating evidence for its reliability and construct validity.

Adolescent↗

PubMed2004

Action (verb) generation in HIV-1 infection.

It has been proposed that verb generation is primarily associated with left fronto-basal ganglia circuits, whereas the generation of nouns is principally mediated by dominant left temporo-parietal networks. Consistent with this premise, action (verb) fluency - a verbal fluency task requiring the spontaneous generation of verbs - has shown greater sensitivity to frontal-basal ganglia pathophysiology (e.g., dementia in Parkinson's disease (PDD)) than noun fluency. The present study examined action and noun fluency in persons with HIV-1 infection-a disease known to be associated with a frontal-basal ganglia circuit neuropathogenesis. Action and noun ("animals") verbal fluency protocols were administered to 97 persons with HIV-1 infection and 20 demographically comparable healthy comparison (HC) subjects. A significant interaction emerged between verbal fluency task and HIV-1 serostatus such that the HIV+ group generated significantly fewer actions (verbs) relative to the HC sample. Findings indicate that persons infected with HIV-1 experience difficulty rapidly generating verbs, but not nouns from semantic memory. Considering the prominent frontal-basal ganglia circuit neuropathophysiology of HIV-1 infection, these data are consistent with the hypothesized dissociation between noun and verb generation as pertains to generative fluency.

Adult↗

PubMed2004

Qualitative aspects of verbal fluency in HIV-associated dementia: a deficit in rule-guided lexical-semantic search processes?

HIV-associated dementia (HAD) is widely considered a "subcortical" dementia that involves a disruption of frontal-basal ganglia circuits. Deficits in verbal fluency are common in HAD; however, the cognitive underpinnings of these deficits are not well understood. To elucidate the cognitive mechanisms underlying the diminished verbal fluency output in HAD, we examined several qualitative aspects of letter fluency in 21 individuals with HAD, 51 nondemented persons with HIV infection (HIV+), and 30 healthy controls (HC) who were comparable for age, education, sex, ethnicity, and estimated premorbid verbal intelligence. The verbal fluency protocols were scored to obtain the total number of correct words, average phonemic cluster size, total number of switches between phonemic clusters, and the proportion of error responses (i.e., intrusions, perseverations, and variants). Consistent with prior research, HAD participants produced significantly fewer total correct words relative to the HC and nondemented HIV+ groups. The HAD group also demonstrated fewer switches and a higher proportion of response errors (especially intrusion errors), but no differences were observed in average cluster size. Findings are interpreted as reflecting a disruption of rule-guided lexical-semantic search strategies in HAD, perhaps mediated by prefrontal-striatal circuit dysfunction, rather than depleted lexical-semantic memory stores.

AIDS Dementia Complex↗

PubMed2004

Interrater reliability of clinical ratings and neurocognitive diagnoses in HIV.

We examined the interrater (IRR) of clinical ratings of neuropsychological (NP) impairment and neurocognitive diagnoses in HIV. Thirty participants with advanced HIV-infection who were enrolled in a multicenter HIV brain banking research project underwent comprehensive NP and neuromedical evaluations. Using a standardized system of guidelines, neuropsychologists from six participating sites independently assigned clinical ratings of NP impairment, as well as multilevel diagnoses reflecting the inferred etiology of the impairments and their effects on everyday functioning. Findings indicated excellent IRR in rating the presence and severity of NP impairment, but overall modest IRR for neurocognitive diagnoses. Not surprisingly, most diagnostic disagreements concerned the etiology of impairments in persons with medical and neuropsychiatric risk factors in addition to HIV.

Adult↗