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PubMedDate not supplied

Prognostic determination in anoxic-ischemic and traumatic encephalopathies.

Clinical assessment of the unresponsive patient is limited to examination of brainstem reflexes and simple motor responses to stimulation. It is thus difficult, especially if brainstem functions are intact, to give early, accurate prognostic information on comatose patients. Neurochemical tests and imaging have not been validated and have significant limitations. Electrophysiologic investigations provide a window into cerebral function and are tested, clinically useful, safe, available, and inexpensive. Persistent abnormalities of brainstem auditory evoked potentials and short-latency somatosensory evoked potentials reliably indicate the likelihood permanent vegetative state or death. Conversely, the presence of "cognitive" event-related brain potentials (e.g., P300 and mismatch negativity) reflects the functional integrity of higher-level information processing and, therefore, the likelihood of capacity for cognition. A combined clinical and electrophysiologic approach provides optimal prediction of outcome and level of disability.

Brain Injuries↗

PubMed1992

Cognitive slowing in Alzheimer's disease and geriatric depression.

Response slowing on psychological tasks is found both in Alzheimer's disease and depression. However, the underlying cause for this slowing may be different in the two disorders. This research examined whether the behavioral slowing found in Alzheimer patients results from a reduction in their rate of cognitive processing, whereas the slowing in depressed geriatric patients reflects a purely motor retardation. This hypothesis was tested using a task in which subjects had simply to determine the number of dots present in an array (i.e., enumeration). In all four subject groups (Alzheimer patients, depressed geriatric patients, healthy old controls, and healthy young controls), response time increased linearly with array size. The slope of this linear function (reflecting rate of enumeration) was the same in the normal and depressed patients, but was significantly greater in the Alzheimer patients, suggesting the presence of a cognitive slowing in Alzheimer's disease, but not in depression.

Aged↗

PubMed2006

Performance monitoring and stop signal inhibition in abstinent patients with cocaine dependence.

Impulsivity has been associated with drug abuse and relapse. As a measure of impulsivity, response inhibition in a stop signal task is impaired in substance abusers compared to healthy control subjects. However, cognitive processes besides response inhibition can affect performance in the stop signal task. Greater response readiness to the go signal increases stop signal reaction time (SSRT) and greater performance monitoring elicited by the stop signal decreases SSRT. Prolonged SSRT, therefore, may reflect differences in these other task-related cognitive processes rather than impaired response inhibition. Using a tracking stop-signal task, we compared 18 abstinent cocaine dependent patients with 41 age- and education-matched healthy controls. We computed SSRT for each individual subject on the basis of the horse race model. We also computed the fore-period (FP) effect to measure response readiness to the go signal and the post-signal slowing (PSS) effect to measure performance monitoring to the stop signal. Cocaine subjects showed increased SSRT and decreased PSS effect, compared to healthy controls. Covariance adjustment for the PSS effect eliminated the SSRT difference from healthy controls. These results suggest that diminished performance monitoring can be a critical cognitive mechanism underlying impaired response inhibition in cocaine dependent patients.

Adult↗

PubMed2006

Distinct neural mechanisms of risk and ambiguity: a meta-analysis of decision-making.

Converging evidence from human and animal studies suggests that decision-making relies upon a distributed neural network based in the frontal lobes. In particular, models of decision-making emphasize the involvement of orbitofrontal cortices (OFC) and the medial wall. While decision-making has been studied broadly as a class of executive function, recent models have suggested the differentiation between risky and ambiguous decision-making. Given recent emphasis on the role of OFC in affectively laden "hot" executive function and dorsolateral prefrontal cortex (DLPFC) in more purely cognitive "cool" executive function, we hypothesize that the neural substrates of decision-making may differ depending on the nature of the decision required. To test this hypothesis, we used recently developed meta-analytic techniques to examine the existent functional neuroimaging literature. An initial meta-analysis of decision-making, both risky and ambiguous, found significantly elevated probabilities of activation in frontal and parietal regions, thalamus, and caudate. Ambiguous decision-making was associated with activity in DLPFC, regions of dorsal and subcallosal anterior cingulate cortex (ACC), and parietal cortex. Risky decision-making was associated with activity in OFC, rostral portions of the ACC, and parietal cortex. Direct statistical comparisons revealed significant differences between risky and ambiguous decision-making in frontal regions, including OFC, DLPFC, and ACC, that were consistent with study hypotheses. These findings provide evidence for the dissociation of neural circuits underlying risky and ambiguous decision-making, reflecting differential involvement of affective "hot" and cognitive "cool" processes.

Brain↗

PubMed2000

Lead concentrations in elderly urban people related to blood pressure and mental performance: results from a population-based study.

BACKGROUND: The Kungsholmen project is a longitudinal study of ageing and dementia conducted in Stockholm in 1987. In a 1994-96 follow-up, 804 subjects had their blood samples analyzed for lead. METHODS: Lead concentration in blood in an elderly population aged 75+ (mean age of 88.4 years) was studied in relation to age, blood pressure (BP), body mass index (BMI), cognitive function measured with Mini-Mental State Examination (MMSE), gender, and smoking. RESULTS: The mean blood lead level (n = 762) was 3.7 microg/dL (0.18 micromol/L) whole blood with a standard deviation of 2.3, (0.11). There was a contribution of gender with men having higher blood lead levels than women (beta = -0.20; P = 0.000001) but not of smoking habits (beta = 0.07; P = 0.08) when these variables were entered into a multiple regression model with lead as the dependent variable (R = 0.22; P < 0.000001). Different multiple regression models were tested with lead as the dependent variable. No relation was found between lead concentrations and age, BMI, systolic BP, diastolic BP, or MMSE. Systolic and diastolic BP were correlated to BMI (R = 0.10; P = 0.01 and R = 0.22; P = 0.000 001, respectively). CONCLUSIONS: In this elderly population from a specified area of Stockholm it is unlikely that lead exposure affects BP or cognition. However, high lead levels in blood may reflect earlier occupational exposure or life style factors.

Age Factors↗

PubMed2003

The importance of cognitive errors in diagnosis and strategies to minimize them.

In the area of patient safety, recent attention has focused on diagnostic error. The reduction of diagnostic error is an important goal because of its associated morbidity and potential preventability. A critical subset of diagnostic errors arises through cognitive errors, especially those associated with failures in perception, failed heuristics, and biases; collectively, these have been referred to as cognitive dispositions to respond (CDRs). Historically, models of decision-making have given insufficient attention to the contribution of such biases, and there has been a prevailing pessimism against improving cognitive performance through debiasing techniques. Recent work has catalogued the major cognitive biases in medicine; the author lists these and describes a number of strategies for reducing them ("cognitive debiasing"). Principle among them is metacognition, a reflective approach to problem solving that involves stepping back from the immediate problem to examine and reflect on the thinking process. Further research effort should be directed at a full and complete description and analysis of CDRs in the context of medicine and the development of techniques for avoiding their associated adverse outcomes. Considerable potential exists for reducing cognitive diagnostic errors with this approach. The author provides an extensive list of CDRs and a list of strategies to reduce diagnostic errors.

Cognition↗

PubMed2004

P300 recordings during event-related fMRI: a feasibility study.

Analysis of combined event-related potentials (ERP) and functional magnetic resonance imaging (fMRI) can provide a high temporal and high spatial resolution to study functional cerebral processes. However, EEG data recorded inside an MR scanner is heavily distorted by artifacts. It is important in cognitive studies to ensure that recorded data reflect the same brain activity, and this is achieved through interleaved electroencephalographic (EEG) and fMRI measurements. Here, we demonstrate the feasibility of recording P300 ERPs during fMRI using a three-stimulus visual oddball task and involving a small number of trials for each stimulus. Ten EEG channels were acquired interleaved with fMRI images in five healthy subjects. The stimuli, including rare targets "X," frequent repetitive distractors "O," and rare distractors referred to as novels, were randomly presented every 2 +/- 1 s. The post hoc filter presented here was designed and applied to EEG data to remove the cardiac pulse artifact. Interleaved EEG/fMRI acquisition evidenced two P300 ERPs evoked at Fz, Cz, and Pz by targets and novels. Novel-related ERPs were of higher amplitude than their target-related counterparts. The fMRI maps acquired concurrently showed stronger BOLD response for target condition. We have shown that interleaved acquisition allows to obtain reliable P300 data and fMRI results, likely to shed light on the anatomical location of brain regions involved in cognitive ERPs relevant to many disorders affecting CNS functions. These noninvasive multimodal neuroimaging techniques can be used to explore and better understand processes underlying the functional brain organization.

Adolescent↗

PubMed2002

Executive function deficits associated with symptoms of schizotypy and obsessive-compulsive disorder.

Research suggests that executive dysfunction is seen both in disorders of the schizophrenia constellation and in obsessive-compulsive disorder (OCD), but that the patterns of executive deficits may differ. While disorders of the schizophrenia spectrum reflect impairment of functions such as integration of cognitive activities, a tendency to perseverate, and a failure to notice details (e.g. impairment associated with the dorsolateral prefrontal cortex), OCD may involve problems of impulse control and regulation of behavior, and an inability to maintain cognitive set (e.g. impairment associated with the orbitofrontal cortex). The present study examined differences between high-scorers on a measure of schizotypy, high-scorers on a measure of OCD, high-scorers on both schizotypy and OCD and a control group in performance on executive function tests. As expected, the OCD group demonstrated relative deficits on measures thought to reflect orbitofrontal functioning. However, contrary to expectations, the schizotypal group did not demonstrate deficits on neuropsychological tests thought to reflect dorsolateral prefrontal cortex functioning, and the combined group showed no executive impairment.

Adolescent↗

PubMed1976

Hyperactives as young adults: preliminary report.

Thirty-five individuals aged 17 to 24 in whom severe chronic hyperactivity had been diagnosed 10 years before were studied together with 25 matched controls. There were no significant differences in mean height or weight or in electroencephalographic findings, but the mean pulse rate was significantly higher in the hyperactive group. Cognitive style tests indicated continued difficulty in reflection (resulting in more errors) but less impulsivity (longer reaction time) in the hyperactive individuals. Compared with controls, hyperactive subjects were continuing to have more scholastic difficulty, although this difference seemed to be less pronounced than 5 years before. Their adjustment in work situations and living arrangements did not differ significantly from that of the controls. Restlessness, both reported and observed, continued to be a problem for the hyperactive individuals, and socialization skills and sense of well-being continued to be poorer than in the controls. The hyperactive individuals did not show significantly more antisocial behaviour, nonmedical use of drugs or serious psychiatric disturbances.

Adolescent↗

PubMed2004

Influence of insulin-like growth factor-1 and hepatocyte growth factor on carotid atherosclerosis and cognitive function in the elderly.

OBJECTIVE: This study investigated the relationship between serum levels of two neurotrophic factors, insulin-like growth factor-1 (IGF-1) and hepatocyte growth factor (HGF), and carotid atherosclerosis and cognitive function in the elderly. METHODS: Serum levels of IGF-1 and HGF, carotid artery intima-media thickness (IMT), and Mini-Mental State Examination (MMSE) scores were determined in 60 subjects over 65 years old (35 patients with vascular dementia and 25 without dementia). RESULTS: In all subjects IGF-1 levels showed a significant positive correlation with the MMSE score (r = 0.262, p = 0.0427) and a negative correlation with the IMT (r = -0.284, p = 0.0277) and the HGF level (r = -0.422, p = 0.0007). HGF levels were significantly correlated with IMT (r = 0.259, p = 0.0455) and lipoprotein(a) levels (r = 0.279, p = 0.0372). Mean MMSE scores and IGF-1 levels were significantly lower in patients with vascular dementia than in the non-demented controls. Mean IMT and the frequency of atherosclerotic plaque in the carotid arteries as well as the serum levels of HGF, LDL cholesterol, lipoprotein(a) and lipid peroxides were significantly increased in the demented patients compared with the non-demented controls. CONCLUSION: A decrease of IGF-1 along with an increase of HGF may reflect an underlying biological process that influences cognitive decline as well as carotid atherosclerosis in the elderly.

Aged↗

PubMed2005

Medical students' mindset for reflective learning: a revalidation study of the reflection-in-learning scale.

The aims of this paper are to examine the measurement properties of the Reflection-in-Learning Scale (RLS) and to identify whether there are relationships between RLS scores early in the medical program and outcomes of the students' academic activity later on. The 14-item RLS was administered to second-year students (N = 275) at start and at end of the third semester, after the students had reviewed their previous learning experience with the Course Valuing Inventory. The internal consistency, temporal stability and dimensionality of the RLS scores were investigated in relation to the start-end perspectives. Furthermore, a 2-year follow-up allowed the assessment of the relationships of third-term RLS scores with sixth-term measures of both academic achievement and diagnostic reasoning as appraised by the Diagnostic Thinking Inventory (DTI). Findings indicate that RLS data have acceptable unidimensionality and consistency of measurement, notwithstanding a significant individual-context interaction. Repeated measures revealed distinct patterns of RLS scores relating to perceived self-efficacy on the ability to reflect. Third-term RLS scores were significant, albeit weak, predictors of sixth-term cognitive achievement and DTI-related diagnostic reasoning ability. In conclusion, the results do not support a major explanatory role for RLS on knowledge representation. Nevertheless, the findings appear to substantiate the construct validity of this tool as an index of the students' frame of mind as regards reflective learning. They suggest that the RLS captures a self-regulation or cognitive housekeeping dimension of the students' reflective learning. The individual pattern of such (reflective) activity is likely to vary with specific learning conditions.

Adolescent↗

PubMed2003

The differential effect of PD and normal aging on early explicit sequence learning.

BACKGROUND: Motor sequence learning is abnormal in PD. However, it is not known whether this defect is present during the earliest stages of the illness or whether it reflects specific limitations in dividing attention between cognitive and motor requirements. METHODS: Fifteen patients with early stage PD and 10 age-matched and 9 younger normal controls moved the right dominant hand on a digitizing tablet to eight targets presented on a screen in synchrony with a tone at 1-second intervals. The tasks were as follows: 1) CCW--a timed-response task where targets appeared in a predictable counterclockwise order; 2) RAN--a reaction time task where targets were random and unpredictable; 3) SEQ--a task with multiple demands emphasizing explicit learning and target anticipation in which subjects learned a sequence while reaching for targets; and 4) VSEQ--subjects learned a visual sequence without moving. RESULTS: CCW and RAN yielded similar results in all groups. In patients with PD, sequence learning was the same in SEQ and VSEQ and was slower compared to both control groups. In older controls, learning was faster in VSEQ than in SEQ, whereas younger controls learned equally fast in both tasks. CONCLUSIONS: Despite normal motor execution, the initial phases of sequence learning are impaired in early PD independent of task requirements, possibly reflecting reduced working memory. Learning was slower in older than younger controls only in tasks with multiple demands, presumably due to reduced attentional resources.

Adult↗

PubMedDate not supplied

A novel method for the topographic analysis of neural activity reveals formation and dissolution of 'Dynamic Cell Assemblies'.

The study of synchronous oscillations in neural systems is a very active area of research. However, cognitive function may depend more crucially upon a dynamic alternation between synchronous and desynchronous activity rather than synchronous behaviour per se. The principle aim of this study is to develop and validate a novel method of quantifying this complex process. The method permits a direct mapping of phase synchronous dynamics and desynchronizing bursts in the spatial and temporal domains. Two data sets are analyzed: Numeric data from a model of a sparsely coupled neural cell assembly and experimental data consisting of scalp-recorded EEG from 40 human subjects. In the numeric data, the approach enables the demonstration of complex relationships between cluster size and temporal duration that cannot be detected with other methods. Dynamic patterns of phase-clustering and desynchronization are also demonstrated in the experimental data. It is further shown that in a significant proportion of the recordings, the pattern of dynamics exhibits nonlinear structure. We argue that this procedure provides a 'natural partitioning' of ongoing brain dynamics into topographically distinct synchronous epochs which may be integral to the brain's adaptive function. In particular, the character of transitions between consecutive synchronous epochs may reflect important aspects of information processing and cognitive flexibility.

Adaptation, Ocular↗

PubMed2004

Paleoenvironmental basis of cognitive evolution in great apes.

A bias favoring tree-dominated habitats and ripe-fruit frugivory has persisted in great ape evolution since the early Miocene. This bias is indicated by fossil ape paleoenvironments, molar morphology, dental microwear, the geographic pattern of extinctions, and extant apes' reliance on wooded settings. The ephemeral aspect of high-quality fruit has placed a premium on cognitive and social means of finding and defending food sources, and appears related to great apes' affinity since the Miocene for wooded, fruit-rich environments. These habitats have, however, undergone a severe withdrawal toward the low latitudes of Africa and Southeast Asia since the late Miocene, corresponding to a decline in the diversity of great apes beginning 9.5 million years ago. Plio-Pleistocene records imply that wooded settings of Africa and SE Asia were prone to substantial fragmentation and coalescence. Once apes were confined to equatorial settings, therefore, habitat instability heightened the spatial/temporal uncertainty of ripe-fruit sources. Prolonged learning, the assignment of attributes to distant places, mental representation, and reliance on fallback foods were all favored in this dynamic environmental context. These abilities helped sustain forest frugivory in most lineages. Fluid social grouping afforded the animals opportunities to locate ephemeral foods in continuous and fragmented forests. Fission-fusion grouping also magnified the problems of object impermanence (of individuals) and dispersion manifested by food sources in the ecological realm. Thus the spatial and temporal dynamics of fruit and wooded habitats since the Miocene are reflected in important components of great ape cognition, foraging, and sociality. In contrast to great apes, cercopithecoid monkeys have increased their plant dietary options and diversified in seasonal environments since the late Miocene. Early hominins eventually severed the habitat bias that characterized the evolution of great apes, and later expanded into diverse environments.

Animals↗

PubMed1997

Reduced cognitive inhibition in schizotypy.

OBJECTIVES: The relationship between negative priming and the positive symptoms of schizotypy was investigated. It was hypothesized that high schizotypes would display less negative priming than low schizotypes. A further important aim of the study was to disentangle the modalities involved in negative priming performance, since a reduction in negative priming, as revealed by schizophrenics and schizotypes, might reflect a failure to actively inhibit irrelevant information (cognitive inhibition) as well as dyslexia or a general slowness in information processing. DESIGN: A paper test based on the German version of the Stroop test was used to measure negative priming. A baseline condition of the test, colour word reading, that has proven to be a valid indicator of dyslexia was used to measure the influence of reading disturbances on negative priming. Additionally, a priming condition, termed inverted priming, in which the target of a stimulus is identical with the distractor in the subsequent stimulus, was employed. METHODS: Fifty healthy adults were drawn from the general population. After neuropsychological assessment participants completed a battery of schizotypal questionnaires. Correlational analyses and mean comparisons were used to investigate the relationship between neuropsychological data and schizotypy. RESULTS: Results suggest that reduced negative priming is related to positive schizotypy. Reduced negative priming in high schizotypes was unrelated to dyslexia, and found unlikely to be affected by deficits in early processing. The inverted priming condition produced comparatively fewer errors in high schizotypes. CONCLUSIONS: Results support the hypothesis that reduced cognitive inhibition may underlie positive schizotypal symptomatology.

Adolescent↗

PubMed1982

Interpreting the Leiter IQ: performance profiles of young normal and language-disordered children.

Language-disordered children with normal range performance IQ may nevertheless evidence cognitive deficits. This suggests the need for content validity studies of performance tests of intelligence. In the current investigation, items from the Leiter International Performance Scale (LIPS) were analyzed for their conceptual versus perceptual character; these item groupings were then used to create intratest LIPS profiles for 16 language-disordered children and 16 children with normal language, aged 4:4-5:5, who were matched for CA, sex, and Leiter IQ. Interjudge (N = 4) reliability for determination of item type was 96%, and the results of the item analysis revealed that 65% of LIPS items in the 2-8 year range were perceptual in nature. A repeated-measures ANOVA indicated that subjects performed relatively better on the perceptual items regardless of group (p less than .01) and that there were no significant group differences. Analysis of individual subject profiles, however, revealed accentuated intratest profiles for two of the language-disordered subjects and reversal of the dominant perceptual greater than conceptual trend for four of the language-disordered subjects. These results indicate that LIPS scores for children under age 8 primarily represent their ability to assess the physical characteristics of visual stimuli and may not adequately reflect the transforming, interpretive aspects of nonverbal cognition.

Age Factors↗

PubMed1987

Brain impairment in social drinkers? No cause for concern.

Correlations between measures of alcohol consumption and cognitive test scores have been interpreted to reflect a chronic toxic effect of ethanol on brain function in light to moderate social drinkers. However, the data indicate that there is little support across research groups for any specific relationship and, at best, the effect of alcohol consumption accounts for only a small proportion of variance. Consideration of test validity suggests that the principal measure of ability used in this research is not capable of elucidating cerebral deficit. Further, the pattern of observed correlations is not consistent with the assumption that the putative effects of social drinking involve deficits less severe but similar in type to those seen in chronic alcoholics. Instead, an association between innate ability, demographic variables, and drinking behavior in the general population is the most parsimonious explanation of all the data.

Age Factors↗

PubMed2004

Racial differences in health-related quality of life among hemodialysis patients.

UNLABELLED: BACKGROUND; Despite technical progress in therapy, hemodialysis patients continue to report health-related quality of life (HRQOL) substantially lower than that of the general population. While African Americans with end-stage renal disease (ESRD) survive longer than members of other races, few studies have compared the HRQOL of African Americans with that of non-African Americans. METHODS: We examined differences in sociodemographic, clinical, and HRQOL variables by race. A multiple regression model assessed the extent to which race was associated with differences in HRQOL scores after adjustment for sociodemographic and clinical variables. Racial differences in the relationship between comorbid disease severity and HRQOL were explored. RESULTS; In adjusted models, African Americans had higher scores in the Index of Well-Being and burden of kidney disease, but lower scores in cognitive function (all P < 0.05). For scales reflecting symptoms and effects of kidney disease, sleep quality, and the Physical Component Summary, the fall in HRQOL with increasing comorbidity was significantly greater in non-African Americans (all P < 0.05). After adjustment, there were no racial differences in scores on the Mental Component Summary, social support, dialysis staff encouragement, or patient satisfaction. CONCLUSION: To our knowledge, ESRD is the only chronic illness for which African Americans report significantly better psychologic well being and a lower burden of disease than non-African Americans. Further research is needed to understand whether these experiences affect health care utilization, medical decision making, and patient survival. Clarification of the reasons for race differences may suggest measures to improve HRQOL for all patients with ESRD.

Adult↗