Biomedical subjects

S C Bowden

Publications and source records attributed to S C Bowden.

At least 19 recordsLinked to original sources

PubMed2004

MRI-negative PET-positive temporal lobe epilepsy: a distinct surgically remediable syndrome.

Most patients with non-lesional temporal lobe epilepsy (NLTLE) will have the findings of hippocampal sclerosis (HS) on a high resolution MRI. However, a significant minority of patients with NLTLE and electroclinically well-lateralized temporal lobe seizures have no evidence of HS on MRI. Many of these patients have concordant hypometabolism on fluorodeoxyglucose-PET ([18F]FDG-PET). The pathophysiological basis of this latter group remains uncertain. We aimed to determine whether NLTLE without HS on MRI represents a variant of or a different clinicopathological syndrome from that of NLTLE with HS on MRI. The clinical, EEG, [18F]FDG-PET, histopathological and surgical outcomes of 30 consecutive NLTLE patients with well-lateralized EEG but without HS on MRI (HS-ve TLE) were compared with 30 consecutive age- and sex-matched NLTLE patients with well-lateralized EEG with HS on MRI (HS+ve TLE). Both the HS+ve TLE group and the HS-ve TLE patients had a high degree of [18F]FDG-PET concordant lateralization (26 out of 30 HS-ve TLE versus 27 out of 27 HS+ve TLE). HS-ve TLE patients had more widespread hypometabolism on [18F]FDG-PET by blinded visual analysis [odds ratio (OR = + infinity (2.51, -), P = 0.001]. The HS-ve TLE group less frequently had a history of febrile convulsions [OR = 0.077 (0.002-0.512), P = 0.002], more commonly had a delta rhythm at ictal onset [OR = 3.67 (0.97-20.47), P = 0.057], and less frequently had histopathological evidence of HS [OR = 0 (0-0.85), P = 0.031]. There was no significant difference in surgical outcome despite half of those without HS having a hippocampal-sparing procedure. Based on the findings outlined, HS-ve PET-positive TLE may be a surgically remediable syndrome distinct from HS+ve TLE, with a pathophysiological basis that primarily involves lateral temporal neocortical rather than mesial temporal structures.

Adult↗

PubMed2004

Neuropsychological and information processing performance and its relationship to white matter changes following moderate and severe traumatic brain injury: a preliminary study.

Reductions in information processing speed have frequently been reported following moderate and severe traumatic brain injuries (TBIs), consistent with the effects of diffuse white matter damage. Although the corpus callosum (CC) is a common site for diffuse damage following TBI, the effects of this damage on information processing speed have not been adequately examined. This study assessed a TBI group and a matched control group on tests of attention, memory, fluency, and set shifting ability, together with reaction time (RT) tasks requiring the inter- and intrahemispheric processing of visual and tactile information. The RT tasks were designed to target the cognitive functions that are likely to be affected by diffuse white matter damage, including damage to the CC. The TBI group demonstrated deficits in verbal and visual fluency and verbal memory. They were also slower on the visual and tactile RT tasks, were more affected by task complexity, and slower on RT tasks requiring the interhemispheric transfer of information. In fact, one of the interhemispheric tactile RT tasks proved to be the most discriminating of all the cognitive and RT measures. MRIs completed on a subset of TBI participants indicated that the mean CC measurements were 5% to 19% smaller than a normative control group, with the most atrophied areas being the isthmus and anterior midbody. Although white matter atrophy was moderately related to visual and tactile RT performance, and total hippocampal volume related to memory performance, CC area was not related to many of the tasks that were designed to tap interhemispheric processing. None of the standard cognitive tests correlated with outcome in the TBI group, but 1 of the tactile RT measures was significantly related to 2 measures of outcome.

Adolescent↗

PubMed2001

Thiamin treatment and working memory function of alcohol-dependent people: preliminary findings.

BACKGROUND: Wernicke-Korsakoff syndrome (WKS) is most often seen in people who are alcohol dependent. Treatment with thiamin may rapidly resolve acute symptoms. However, much evidence suggests that identification of WKS on clinical examination is relatively insensitive when compared with diagnosis at postmortem. No study has investigated the therapeutic effect of thiamin in a sample of alcohol-dependent people without the clinical triad of acute WKS. METHODS: We conducted a randomized, double-blind, multidose study of thiamin treatment in 107 subjects who were detoxifying from alcohol. Five groups of subjects were assessed with the Mini-Mental State Examination and were examined for the presence of neurological signs. Subjects were given different doses of intramuscular thiamin for two consecutive days. The posttreatment performance of these groups then was examined on a test of working memory derived from comparative neuropsychology, namely, the delayed alternation task. This test has been established as sensitive to the neuropathology of WKS. RESULTS: Pretreatment measures of mental status and neurological signs were equivalent across groups. Groups were equated with respect to the background variables of age, education, typical daily alcohol consumption, and years of drinking. On the posttreatment measure, a superior performance was found in the group that received the highest dose of thiamin, compared with the other four treatment groups. CONCLUSIONS: A therapeutic relationship between dose and working memory performance was indicated. These results have important implications for the management and prevention of WKS, but further investigations are needed to substantiate the nature of the therapeutic relationship.

Adult↗

PubMed2001

Working memory impairments in alcohol-dependent participants without clinical amnesia.

BACKGROUND: The delayed alternation (DA) task is highly sensitive to the deficits of nonhuman animals with alcohol-related brain damage. DA is thought to measure working memory which serves as a temporary store for processing of information. However, performance on this type of task has only been investigated in alcohol-dependent humans with severe cognitive deficits. The aim of the current study was to explore the validity of DA as a test sensitive to alcohol-related brain damage by manipulating storage and processing components in three versions of the task. It was hypothesized that alcohol-dependent people would perform worse than control participants and that their deficits would be more pronounced in DA versions with maximal working memory demands. METHODS: A sample of 12 alcohol-dependent participants without Wernicke-Korsakoff syndrome was compared with a sample of 12 nonalcohol-dependent controls on three versions of DA. These versions, in order of increasing working memory demand, were single alternation (LR), double alternation (LLRR), and asymmetric alternation (LRRR). DA was administered on a personal computer and performance measured by the number of trials taken to reach criterion. RESULTS: Alcohol-dependent participants, compared with the control participants, took more trials to reach learning criterion on DA on all versions when analyzed together (p = 0.002). Performance on DA was also found to deteriorate with increased working memory demands in both groups of participants (p < 0.001). However, the deficits of alcohol-dependent participants were most pronounced on the DA task with moderate (LLRR) as opposed to extreme (LRRR) working memory demands. CONCLUSIONS: The results indicate that both storage and processing demands are necessary for task performance and demonstrate sensitivity of DA to alcohol-related brain injury.

Adult↗

PubMed2001

Neurotoxicity and neurocognitive impairments with alcohol and drug-use disorders: potential roles in addiction and recovery.

This article represents the proceedings of a symposium at the 2000 RSA Meeting in Denver, Colorado. The organisers/chairs were Stephen C. Bowden and Fulton T. Crews. The presentations were (1) Age, genetic and other factors that increase risk of alcoholism also increase alcohol-induced neurotoxicity, by Fulton T. Crews; (2) A neurocognitive moderation model of addictions treatment response, by Marsha E. Bates; (3) The relationship of neurocognitive impairment and longitudinal treatment outcome among substance-abusing patients, by William Fals-Stewart; and (4) Treatment of cognition in detoxifying alcohol-dependent participants, by Margaret L. Ambrose.

Alcoholism↗

PubMed1998

Cognitive components in perseverative and nonperseverative errors on the object alternation task.

Knowledge of response rules in the object alternation (OA) task was experimentally manipulated in 20 alcohol-dependent men and 20 controls. The results suggest that perseverative and nonperseverative errors in OA are under the direct control of task-specific knowledge which must be induced and retained from trial to trial, and that impaired response inhibition is not solely responsible for poor performance on these tasks. The demonstration of a cognitive contribution to poor performance on the OA task suggests that rule induction must be achieved before successful response selection and inhibition can take place. We conclude by discussing implications for our understanding of other delayed response tasks and clinical tests of prefrontal function (e.g., the Wisconsin Card Sorting Test (WCST) and the Halstead Category Test).

Adult↗

PubMed1998

On-road assessment of driving competence after brain impairment: review of current practice and recommendations for a standardized examination.

OBJECTIVE: To examine the approaches to on-road assessment of driver competence in persons with brain impairment. Items examined were procedures, standardization, scoring methods, equipment requirements, and determination of fitness to drive. DATA SOURCES: All studies identified through citation or Medline search. STUDY SELECTION: The studies reviewed were those published from 1971 to the present that examined driving competence after brain impairment, as measured by a driving test. DATA EXTRACTION: A qualitative review of published studies reporting methodologies and authors' conclusions abstracted from sourced publications. DATA SYNTHESIS: Off-road driving assessments examine proficiency in operating a motor vehicle, but not ability to drive in traffic or accurate prediction of safe driving. On-road driving assessments have been used to examine the predictive validity of other driving assessment methods or the driving performance of subjects with brain impairment. Determining a subject's competence to drive is frequently a subjective evaluation. With a standardized driving test, a significant correlation between the objective driving score and the rater's global evaluation of fitness has been reported. CONCLUSION: Closed-course, off-road driving tests are recommended for examining vehicle operation skills and readiness for in-traffic evaluation only. This allows practice with any vehicle adaptations before on-road evaluation and identification of clients who are unsafe to proceed on-road. A practical driving test in traffic, with standardized route and driving maneuvers, is recommended for determining driver competence. Scoring of driving performance should be standardized, reliable, and specific, to identify deficient driving skills that may be amenable to training. Driving performance should be evaluated according to predefined criteria, and the judgment regarding competence should be closely related to this objective measure.

Automobile Driver Examination↗

PubMed1997

Which tests do neuropsychologists use?

A nationwide survey of accredited neuropsychologists in Australia was conducted to examine test use. Clinicians were asked to list the tests they give most often. Results are expressed as endorsement frequencies for tests. Comparisons with international surveys of test use are provided. Suggestions for clinicians and others concerned with test use are included to demonstrate how survey results can be used to improve neuropsychological services.

Australia↗

PubMed1997

Confirmatory factor analysis of the Wechsler Memory Scale-Revised in a sample of clients with alcohol dependency.

Previous analyses of the Wechsler Memory Scale-Revised (WMS-R; Wechsler, 1987) have reported one-, two-, and three-factor solutions and raised questions about the validity of the visual memory subtests. These various findings may stem in part from different methods of analysis, and from the study of different participant samples. To address these issues, we analysed data from the WMS-R and a spatial maze test administered to 154 participants with a history of alcohol dependence. Results from confirmatory factor analysis supported the interpretation of three factors underlying the WMS-R subtests and the spatial maze score in this sample, namely, attention-concentration, immediate memory, and delayed recall. This result held despite the inclusion of the maze score which is a well-validated measure of visuo-spatial memory.

Adult↗

PubMed1997

Alzheimer's disease and driving: prediction and assessment of driving performance.

OBJECTIVES: To examine driving competence in a group of drivers diagnosed with probable Alzheimer's Disease (AD) in terms of a standardized open road evaluation and expert judgments. To examine the validity of a standardized medical examination, including administration of the Mini-Mental Status Exam (MMSE), and a standardized neuropsychological assessment as predictors of open road driving performance. DESIGN: A prospective investigation with consecutively referred subjects. SETTING: Coorabel Driver Assessment Centre, Royal Rehabilitation Centre Sydney, Australia. PARTICIPANTS: Nineteen subjects with a diagnosis of probable AD. MEASUREMENTS: A standardized clinical medical examination, a standardized neuropsychological assessment, and a standardized open road driving evaluation. The driving evaluation provided a correct driving actions score. The outcome measure was the expert judges' rating of overall driving competence, which was termed the final on-road result. RESULTS: Seven subjects passed the on-road driving evaluation, and 12 failed. MMSE was found to be a significant predictor of final on-road result. The physician's prediction, the neuropsychology test scores, and the neuropsychologist's prediction were not found to be significantly associated with the final on-road result. The on-road driving evaluation was a reliable test. CONCLUSION: Inasmuch as all subjects except one were still driving and all wished to continue to drive, it is important to note that 63.2% of subjects failed the on-road evaluation. Conversely, 36.8% were judged safe to drive, suggesting that AD diagnosis alone may be insufficient criteria for cessation of driving. A standardized road test may be the only appropriate means of determining driving competence in people diagnosed with AD.

Aged↗

PubMed1993

Spatial memory in alcohol-dependent subjects: using a push-button maze to test the principle of equiavailability.

The principle of equiavailability states that once the locations in a spatial array are learned, then all locations in the array are simultaneously available in memory (Levine, Jankovic, & Palij, 1982). To test the application of this principle, 21 nonamnesic, alcohol-dependent, male subjects and 20 demographic and ability-matched male control subjects were required to learn a series of push-button maze paths and to perform shortcut or retrace movements on the paths. The results for the control subjects conformed to the principle of equiavailability. In contrast, the alcohol-dependent subjects did not show equiavailability. This pattern of results is interpreted as evidence of a spatial memory deficit in the alcohol-dependent subjects.

Adult↗

PubMed1992

Delayed matching to sample and concurrent learning in nonamnesic humans with alcohol dependence.

Small samples of alcohol-dependent subjects who showed no clinical signs of Wernicke-Korsakoff syndrome were compared with nonalcohol-dependent controls on two animal memory tests which are performed poorly by human amnesics. Compared to the control subjects, the alcohol-dependent subjects' performance was impaired on a version of the delayed matching to sample task. On concurrent discrimination learning the overall group difference just failed to reach significance. The results are interpreted as suggesting that behavioural impairment may occur in alcohol-dependent subjects who are not clinically amnesic, and that the impairment is similar in type to that observed in cases of severe Wernicke-Korsakoff syndrome.

Adolescent↗

PubMed1992

Relative usefulness of the WMS and WMS-R: a comment on D'Elia et al. (1989)

In a previous commentary, D'Elia and colleagues reflected on the relative adequacy of normative data for the original Wechsler Memory Scale (WMS) and the Wechsler Memory Scale-Revised (WMS-R). They concluded that, for some age groups, the original version of the test is preferred. We discuss further the crux of the D'Elia and colleagues criticism of the WMS-R, namely the issue of interpolation in tables of normative data. We also consider two additional criteria: the sampling techniques used to obtain the normative samples, and the respective standard errors of measurement and scaling properties of scores on the two tests. We conclude that on each of these criteria the WMS-R is preferable.

Adolescent↗

PubMed1992

Is there more than one neuropsychological disorder commonly associated with alcohol dependence?

There are two popular neuropsychological entities commonly attributed to the effects of alcohol dependence: the well-known Wernicke-Korsakoff syndrome, and the putative alcoholic encephalopathy. Wernicke-Korsakoff syndrome is a highly variable neurological and neuropsychological disorder, which is frequently missed or misdiagnosed on clinical examination. The available prevalence figures suggest that Wernicke-Korsakoff neuropathology probably occurs with a high incidence in hospitalized alcohol-dependent people. Thus, Wernicke-Korsakoff syndrome confounds clinical descriptions of the alcoholic encephalopathy and may account for most cases presumed to suffer from the latter disorder. Even if it is assumed that there is a specific alcoholic neurotoxicity, the clinical descriptions of this condition encompass features which are all attributable to Wernicke-Korsakoff syndrome. In other words, the proponents of the alcoholic encephalopathy have failed to provide a distinctive description, thus precluding positive identification.

Journal Article↗

PubMed1990

Separating cognitive impairment in neurologically asymptomatic alcoholism from Wernicke-Korsakoff syndrome: is the neuropsychological distinction justified?

Recent studies that have combined neuropathological data and clinical histories in a retrospective fashion have shown that Wernicke-Korsakoff neuropathology is often unsuspected antemortem and that, in terms of clinical presentation, it is more heterogeneous than previously assumed. Thus, many studies of neurologically normal alcoholics may have been confounded by the inclusion of patients with neurologically asymptomatic Wernicke-Korsakoff neuropathology. Postmortem and in vivo studies have shown that alcoholics, irrespective of neurological diagnosis, have widespread pathology involving many cortical and subcortical sites. In addition, clinical studies have indicated that, like neurologically asymptomatic alcoholics, alcoholic Korsakoff patients may enjoy substantial recovery in cognitive function. Furthermore, the common research strategy of identifying a subset of neurologically diagnosed Wernicke-Korsakoff syndrome as a discrete group of "pure" Korsakoff's amnesia by using a definitional IQ-Wechsler Memory Scale quotient difference may have created a neuropsychological stereotype that is not representative of the broader clinical group. In light of these considerations, the separate treatment of cognitive impairment in groups of alcoholics distinguished by the clinical signs of Wernicke-Korsakoff syndrome may not be justified.

Alcohol Amnestic Disorder↗

PubMed1990

Early HIV-related neuropsychological impairment: relationship to stage of viral infection.

Sixty male outpatients with no past neuropsychiatric history were examined for evidence of early HIV-related neuropsychological impairment. Significant cognitive deficit, as measured by the RAVLT and WAIS-R Digit Symbol Substitution tests, and moderate correlation with indices of immune function, were observed in a group of patients with AIDS-Related Complex [ARC]. Patients with asymptomatic HIV-infection demonstrated no significant differences in performance compared to a group of HIV-seronegative controls. No significant group differences in age, education, predicted-IQ or self-rated depression and anxiety were observed. These results support the hypothesis that HIV-related cognitive disturbance occurs within the context of immunosuppression.

AIDS Dementia Complex↗

PubMed1988

Learning in young alcoholics.

A group of young male alcoholics with a mean age of 26.7 years performed less well than matched controls on a test of complex maze learning. The relatively short period of time during which these alcoholics had been drinking to excess (M = 5.7 years) suggests that acquired deficits may appear earlier in the drinking history of many alcoholics than has been previously assumed. Data from the maze was analyzed by modelling each individuals' cumulative error scores with a two-parameter hyperbolic function. The model provided an excellent fit to individual data and group differences were observed in both parameters of the model. It is concluded that curve fitting provides an efficient method for representing individual performance on a multitrial learning task.

Adult↗

PubMed1988

The hangover hypothesis and the influence of moderate social drinking on mental ability.

The "hangover" hypothesis proposes that there is some residual effect of low to moderate alcohol intake on the nervous system after the blood alcohol level has returned to zero. This notion has been invoked to explain the putative effects of moderate alcohol consumption on mental ability. We evaluated the hangover hypothesis by attempting to predict cognitive performance from self-reports of alcohol consumed during the week prior to testing. We found no meaningful evidence to support the notion that moderate alcohol ingestion produces a measurable toxic effect on brain function after the period of acute intoxication.

Adult↗