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Biomedical subjects

Paul Maruff

Publications and source records attributed to Paul Maruff.

At least 55 records · Page 3Linked to original sources
PubMed2003

Spectrum of saccade system function in Alzheimer disease.

BACKGROUND: In Alzheimer disease (AD), tests of "first-order capabilities," such as reaction time or motor ability, might measure central nervous system integrity or disability more reliably than those of abstract, conceptual, or cognitive behavior. Saccade system impairments are present in AD, but their sensitivity or specificity remains unevaluated. OBJECTIVES: To determine sensitivity and specificity of saccade measures for AD, precise impairments in AD, and the relationship between dementia severity and saccade system function. DESIGN: Case-control study comparing saccade system function between patients and control subjects, including correlations between saccade system function and dementia severity in patients and standardized scores examining impairment in individual patients. SETTING: Neuropsychiatric research institute. PARTICIPANTS: Two hundred forty-five healthy volunteers from the general population, and 35 patients with AD referred by memory clinics. Age- and sex-matched controls were compared with patients on random saccade (n = 35), predictive saccade (n = 11), and antisaccade (n = 18) tasks. MAIN OUTCOME MEASURES: Saccade latencies, velocities, and accuracies and antisaccade error rates. Sensitivity, specificity, and predictive positive and negative values were calculated using all control data. RESULTS: Patients had longer and more variable latencies, more hypometric and anticipatory random saccades, and higher antisaccade error rates (P<.01 for all comparisons). The antisaccade error rate correlated with dementia severity (Spearman r = -0.59, P =.02). Antisaccade measures were the most specific (0.70-0.90) and random saccade gain the most sensitive (0.87). CONCLUSIONS: Despite AD group impairment, individual patients function within the control range, reducing the sensitivity and specificity of saccade measures for AD. Longitudinal evaluation may provide more reliable classification.

Aged↗
PubMed2003

Saccade and cognitive impairment associated with kava intoxication.

Kava is an extract from the Piper methysticum Forst. f. plant that has social and spiritual importance in Pacific islands societies. Herbal remedies that contain kava are used for the psychiatric treatment of anxiety and insomnia. Laboratory studies have found only subtle, if any, changes on cognitive or motor functions from the acute effects of consuming small clinical doses of kava products. Intoxication from recreational doses of kava has not been studied. The performance of individuals intoxicated from drinking kava (n=11) was compared with a control group (n=17) using saccade and cognitive tests. On average, intoxicated individuals had consumed 205 g of kava powder each (approximately 150 times clinical doses) in a group session that went for 14.4 h and ended 8 h prior to testing. Intoxicated kava drinkers showed ataxia, tremors, sedation, blepharospasm and elevated liver enzymes (GGT and ALP), together with saccadic dysmetria, saccadic slowing and reduced accuracy performing a visual search task that only became evident as the task complexity increased. Kava intoxication is characterized by specific abnormalities of movement coordination and visual attention but normal performance of complex cognitive functions. Saccade abnormalities suggest disruption of cerebellar and GABAergic functions.

Adult↗
PubMed2003

Procedural learning in children with developmental coordination disorder.

Despite the fact that developmental coordination disorder (DCD) is characterised by a deficit in the ability to learn or automate motor skills, few studies have examined motor learning over repeated trials. In this study we examined procedural learning in a group of 10 children with DCD (aged 8-12 years) and age-matched controls without DCD. The learning task was modelled on that of Nissen and Bullemer. Children performed a serial reaction time (SRT) task in which they were required to learn a spatial sequence that repeated itself every 10 trials. Children were not aware of the repetition. Spatial targets were four (horizontal) locations presented on a computer monitor. Children responded using four response keys with the same horizontal mapping as the stimulus. They were tested over five blocks of 100 trials each. The first four blocks presented the same repeating sequence, while the fifth block was randomised. Procedural learning was indexed by the slope of the regression of RT on blocks 1-4. Results showed that most children displayed strong procedural learning of the sequence, despite having no explicit knowledge about it. Overall, there was no group difference in the magnitude of learning over blocks of trials - most children performed within the normal range. Procedural learning for simple sequential movements appears to be intact in children with DCD. This suggests that cortico-striatal circuits that are strongly implicated in the sequencing of simple movements appear to be function normally in DCD.

Attention↗
PubMed2003

Unilateral pallidotomy for Parkinson's disease disrupts ocular fixation.

Although some motor functions of the basal ganglia have been well studied, the oculomotor functions are not well established. We studied eye movements in patients with Parkinson's disease (PD) undergoing pallidotomy to assess the role of the globus pallidus interna (GPi) in oculomotor control. Horizontal visually guided, gap and predictive saccades as well as ocular fixation were studied in patients with advanced PD before and 1 month after unilateral pallidotomy, and in healthy controls on two occasions 1 month apart. There was no difference in saccadic latency or accuracy, the number of saccadic anticipations or the ability to generate predictive saccades between the two assessments for either patients or controls. The number and amplitude of square wave jerks during ocular fixation however increased significantly in patients after pallidotomy. The results imply altered function of frontal or prefrontal cortical regions involved in ocular fixation resulting from a disruption to inhibitory pallidal influences on thalamocortical projections. The posteroventral GPi however appears not to be involved in externally controlled or predictive saccadic function.

Aged↗
PubMed2003

The effects of practice on the cognitive test performance of neurologically normal individuals assessed at brief test-retest intervals.

Performance on many cognitive and neuropsychological tests may be improved by prior exposure to testing stimuli and procedures. These beneficial practice effects can have a significant impact on test performance when conventional neuropsychological tests are administered at test-retest intervals of weeks, months or years. Many recent investigations have sought to determine changes in cognitive function over periods of minutes or hours (e.g., before and after anesthesia) using computerized tests. However, the effects of practice at such brief test-retest intervals has not been reported. The current study sought to determine the magnitude of practice effects in a group of 113 individuals assessed with an automated cognitive test battery on 4 occasions in 1 day. Practice effects were evident both between and within assessments, and also within individual tests. However, these effects occurred mostly between the 1st and 2nd administration of the test battery, with smaller, nonsignificant improvements observed between the 2nd, 3rd, and 4th administrations. On the basis of these results, methodological and statistical strategies that may aid in the differentiation of practice effects from drug-induced cognitive changes are proposed.

Aged↗
PubMed2003

Saccade and cognitive function in chronic kava users.

Kava is an extract from the Piper methysticum Forst. f. plant that has been consumed in the Pacific islands for millennia and more recently, among indigenous populations, in northern Australia and throughout the Western world as an herbal medicine. Through alterations on neuronal excitation, kava induces muscle relaxation, anasthesia, and has anxiolytic properties. There have been several isolated reports of psychotic syndromes, severe choreoathetosis and possible seizures following kava use. However, there is no conclusive evidence that kava interferes with normal cognitive processes. We tested a group of current, ex, and nonkava users among an indigenous population in northern Australia, using saccade and cognitive tests that have proven cross-cultural validity and are sensitive to subtle disruptions of the brain arising from substance abuse or neuropsychiatric illness. Despite collecting data from among the heaviest reported kava drinkers in the world, we found no impairment in cognitive or saccade function in individuals who were currently heavy kava users (and had been for up to 18 years), nor was there any impairment in individuals who had been heavy kava users in the past but had abstained for longer than 6 months. Current and ex-kava users showed a higher rate of kava dermopathy, lower body mass index, lowered blood lymphocytes and, in addition, current kava users showed elevated liver enzymes. While there has recently been increasing concern about potentially fatal liver damage attributed to kava use, we have found no evidence of brain dysfunction in heavy and long-term kava users.

Adolescent↗
PubMed2003

Attention deficit hyperactivity disorder, combined type: better executive function performance with longer-term psychostimulant medication.

OBJECTIVE: Executive function deficits are evident in primary school-age children with attention deficit hyperactivity disorder, combined type (ADHD-CT) and are possibly improved by longer-term psychostimulant medication. In contrast, a substantial subgroup of children with ADHD-CT become symptomatic despite longer-term psychostimulant medication use. We investigated the hypothesis that better executive function performance is associated with the use of longer-term psychostimulant medication in primary school-age children with ADHD-CT who are again symptomatic of ADHD-CT, despite its use. METHOD: A cross-sectional study of 40 primary school-age psychostimulant medication-naïve children with ADHD-CT, 26 with symptomatic ADHD-CT and treated with psychostimulant medication, and 26 control children without ADHD-CT was conducted. Nonverbal tasks of executive function were compared across the three groups. RESULTS: The longer-term psychostimulant medication-treated group had a better executive function performance, despite being symptomatic for ADHD-CT, than the psychostimulant medication-naïve group. CONCLUSION: Improved executive function may be a marker of psychostimulant medication effect in children with ADHD-CT treated in the longer term. This improvement may not correlate with that of the ADHD-CT symptoms. Longitudinal studies are required.

Attention Deficit Disorder with Hyperactivity↗
PubMed2003

CogSport: reliability and correlation with conventional cognitive tests used in postconcussion medical evaluations.

OBJECTIVE: To determine the repeatability of a computerized cognitive test designed to monitor recovery from concussion and assist team physicians make return to play decisions (CogSport). To determine the correlation between CogSport and two conventional neuropsychological tests. DESIGN: Prospective, serial investigation of cognitive function. SETTING: Professional and semi-professional Australian Football clubs and a university affiliated research institute in Melbourne, Australia. PARTICIPANTS: Three-hundred healthy young adults, including 240 elite athletes. MAIN OUTCOME MEASURES: Intra-class correlation (ICC) coefficients for CogSport performance measures administered serially. ICC between CogSport performance measures and conventional neuropsychological tests. Normative data for CogSport performance measures. RESULTS: Measures of psychomotor function, decision making, working memory and learning were highly reliable. Some measures also displayed high correlations with conventional neuropsychological tests of information processing and attention. Preliminary normative data is described. CONCLUSIONS: CogSport is a highly reliable cognitive function test when administered to healthy young adults and elite athletes. CogSport measures similar cognitive functions as conventional tests used commonly in concussion research.

Adolescent↗
PubMed2003

Qualitative similarities in cognitive impairment associated with 24 h of sustained wakefulness and a blood alcohol concentration of 0.05%.

Previous studies that have quantified fatigue-related cognitive impairment as blood alcohol concentration (BAC) equivalents have been limited by two issues: the effect of practice on tests of cognition and, more importantly, the statistic used to quantify change in cognitive performance. The current study addressed these issues by adopting an ABACA design, which allowed for the adequate control of practice effects, and by using effect size metrics, which enabled direct comparisons to be made in performance impairments as a result of fatigue (i.e. sustained wakefulness of 24 h) and alcohol (i.e. BAC of 0.05%). Cognitive performance under the fatigue and alcohol conditions required the use of the CogState battery. It was demonstrated that fatigue caused greater impairment than alcohol on the speed of continuous attention and memory and learning, and on the accuracy of complex matching. Alcohol was more detrimental than fatigue only on the accuracy of memory and learning. Performances on the remaining tasks were the same for both the fatigue and alcohol conditions. These differences and similarities in performance impairment are discussed emphasizing the deleterious cognitive effects of relatively short periods of sustained wakefulness.

Adult↗
PubMed2002

Paracingulate morphologic differences in males with established schizophrenia: a magnetic resonance imaging morphometric study.

BACKGROUND: Our previous work on sulcal-gyral brain morphology in healthy volunteers revealed that males were characterized by greater cortical folding in the left versus right anterior cingulate cortex. Given the evidence showing an absence or reversal of normal anatomical asymmetries in patients with schizophrenia, the current study examined the anterior cingulate cortex sulcal-gyral patterns in patients with schizophrenia. METHODS: Using high-resolution magnetic resonance imaging, we examined anterior cingulate cortex surface morphology in a group of 55 patients with established schizophrenia and 75 healthy controls. All subjects were male and right-handed. Depending on the presence of a paracingulate sulcus and its antero-posterior extent, three types of anterior cingulate cortex sulcal patterns were identified: "prominent," "present," and "absent." Measures of overall cerebral hemispheric folding were used as independent variables and as covariates to ascertain the specificity of the findings to the anterior cingulate cortex. RESULTS: Examination of anterior cingulate cortex morphology showed that, compared with controls, patients with schizophrenia lacked the leftward anterior cingulate cortex sulcal asymmetry, which was explained by reduced folding in the left anterior cingulate cortex. These differences were over and above differences in cortical folding across the entire left hemisphere. CONCLUSIONS: These findings suggest that, in male patients with schizophrenia, there is a disturbance in the neurodevelopment of the left anterior cingulate cortex, as well as a more general aberration of left hemisphere development.

Adult↗
PubMed2002

Selectively impaired associative learning in older people with cognitive decline.

Older people with declining cognitive function typically display deficits in declarative memory processes, often most evident on tests of associative learning (AL). The hippocampal formation (HF) is thought to be critically involved in the encoding and retrieval of such associations, consistent with neuroimaging findings that the HF is damaged in early stages of neurodegenerative disease and in older people with AL impairments. In the clinic, older people with cognitive decline commonly report difficulties associating names with faces. However, we have observed that such people are particularly impaired on tests requiring the association of novel stimuli. In Experiment 1, a series of AL tasks were administered to older people with cognitive decline to determine whether they were impaired at simply making associations, or at making associations between novel stimuli. In Experiment 2, we measured HF function in these subjects by administering an AL task designed to differentiate between HF-damaged and HF-intact individuals. Our experimental protocols were guided by a computational model of HF function in AL described by Gluck and Myers (1997). Older people with cognitive decline displayed impaired performance on tasks designed to be highly dependent upon intact HF function, including a task in which novel patterns and spatial locations were to be associated. These results suggest that the AL impairments observed in older people with cognitive decline may be due to HF dysfunction.

Aged↗
PubMed2002

Determining the extent of cognitive change after coronary surgery: a review of statistical procedures.

Currently, cognitive decline after coronary surgery is said to be significant if the individual's postoperative test score is at least 1 standard deviation (SD) worse than their preoperative score. This "1-SD" technique fails to account for factors that may confound interpretation of serially acquired cognitive test scores, including regression to the mean, measurement error caused by poor test-retest reliability, and practice effects. We review the many alternative and potentially superior statistical techniques that have been described in the neuropsychologic and psychiatric literature for differentiating "true" changes in cognitive test score from changes caused by these factors.

Cognition Disorders↗
PubMed2002

The cognitive neuropsychiatric approach to investigating the neurobiology of schizophrenia and other disorders.

In this paper, we examine a cognitive neuropsychiatric approach to understanding neuropsychiatric disorders by examining recent data in schizophrenia. By understanding and applying this approach, we suggest that the processes underlying the neurobiology of a range of other psychiatric disorders can be understood. Further, an assessment of the brain-behaviour relationships through this emerging discipline provides testable models for further study, using a range of techniques including functional and other imaging techniques.

Cognition Disorders↗
PubMed2002

The neurobehavioural consequences of petrol (gasoline) sniffing.

This review will introduce petrol (gasoline) sniffing as a specific form of substance abuse. Petrol sniffing is associated with dysfunctions that range in severity from subtle cognitive impairment to encephalopathy and death, and these are discussed with respect to their specific neurological and cognitive bases. Morbidity and mortality rates will also be presented that suggest severe central nervous system damage occurs as a result of petrol sniffing. The neuropharmacological actions of tetraethyl lead and volatile hydrocarbons, the components within petrol, and their contributions to the effects of sniffing petrol are investigated. Reports of human occupational or recreational exposure to either lead additives or volatile hydrocarbons (i.e. inhalants) have provided evidence of the neurological and cognitive effects that may also occur with petrol sniffing. Petrol sniffing causes a progressive decline of cognitive function that eventually leads to permanent neurological changes.

Animals↗
PubMed2002

An analysis of systems of classifying mild cognitive impairment in older people.

OBJECTIVE: Over the past two decades, a number of systems have been developed for the classification of cognitive and behavioural abnormalities in older people, in order that individuals at high risk of developing neurodegenerative disease, particularly Alzheimer's disease, may be identified well before the disease manifests clinically. This article critically examines the inclusion and exclusion criteria of a number of such classification systems, to determine the effect that variations in criterion may have on clinical, behavioural and neuroimaging outcomes reported from older people with mild cognitive impairment. METHOD: Qualitative review of the literature describing systems of classifying mild cognitive impairment, and outcomes from clinical, behavioural, neuroimaging and genetic studies of older people with mild cognitive impairment. RESULTS: The exclusion and inclusion criteria for these classification systems vary markedly, as do the design of studies upon which the validity of these systems has been assessed. Minor changes to individual exclusion/inclusion criterion may result in substantial changes to estimates of the prevalence and clinical outcome of mild cognitive impairment, while inadequate experimental design may act to confound the interpretation of results. CONCLUSIONS: As a result of these factors, accurate and consistent estimates of the outcome of mild cognitive impairments in otherwise healthy older people are yet to be obtained. On the basis of this analysis of the literature, optimal criteria via which accurate classifications of mild cognitive impairment can be made in future are proposed.

Aged↗
PubMed2002

Characteristics of parent- and child-reported anxiety in psychostimulant medication naïve, clinically referred children with attention deficit hyperactivity disorder, combined type (ADHD-CT).

OBJECTIVE: Anxiety is a frequent comorbid condition in referred primary school-age children with attention deficit hyperactivity disorder, combined type (ADHD-CT), yet there has been relatively little systematic research of the nature of this comorbid anxiety. We describe the characteristics of parent-reported child anxiety disorders and child-reported anxiety disorders in primary school-age children with ADHD-CT. METHOD: A cross-sectional study of 75 clinically-referred psychostimulant medication naïve children with ADHD-CT examining separately parent and child reports of anxiety, defined categorically and dimensionally. A two-year follow up of 12 children with parent-reported child anxiety and 12 children with child-reported anxiety was also completed. RESULTS: There was no significant association between the child and parent reports of anxiety. Generalized anxiety disorder (GAD), separation anxiety disorder (SAD), specific phobia (SpPh) and social phobia (SoPh) were the most common anxiety disorder diagnoses reported by parents and children. Two-year follow-up data revealed no decrease in the parent report but a significant decrease in the child report of anxiety disorders. CONCLUSIONS: The dissonance between the parent report of child anxiety and the child report of anxiety, emphasizes the importance of careful and thorough clinical assessment of the child's perspective. The nature of parent-reported child anxiety and children's self-report of anxiety requires further systematic research.

Anxiety Disorders↗