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At least 253 records · Page 14Linked to original sources
PubMed1998

Noise stress impairs prefrontal cortical cognitive function in monkeys: evidence for a hyperdopaminergic mechanism.

BACKGROUND: Stress can exacerbate a number of psychiatric disorders, many of which are associated with prefrontal cortical (PFC) cognitive deficits. Biochemical studies demonstrate that mild stress preferentially increases dopamine turnover in the PFC. Our study examined the effects of acute, mild stress exposure on higher cognitive function in monkeys and the role of dopaminergic mechanisms in the stress response. METHODS: The effects of loud (105-dB) noise stress were examined on a spatial working memory task (delayed response) dependent on the PFC, and on a reference memory task with similar motor and motivational demands (visual pattern discrimination) dependent on the inferior temporal cortex. The role of dopamine mechanisms was tested by challenging the stress response with agents that decrease dopamine receptor stimulation. RESULTS: Exposure to noise stress significantly impaired delayed-response performance. Stress did not impair performance on "0-second" delay control trials and did not alter visual pattern discrimination performance, which is consistent with impaired PFC cognitive function rather than nonspecific changes in performance. Stress-induced deficits in delayed-response performance were ameliorated by pretreatment with drugs that block dopamine receptors (haloperidol, SCH 23390) or reduce stress-induced PFC dopamine turnover in rodents (clonidine, naloxone hydrochloride). CONCLUSIONS: These results indicate that stress impairs PFC cognitive function through a hyperdopaminergic mechanism. Stress may take the PFC "off-line" to allow more habitual responses mediated by posterior cortical and subcortical structures to regulate behavior. This mechanism may have survival value, but may often be maladaptive in human society, contributing to the vulnerability of the PFC in many neuropsychiatric disorders.

Animals↗
PubMed1995

Ultradian rhythms in performance on tests of specialized cognitive function.

Performance on cognitive tasks cycled at ultradian frequencies for 24 males over a test period of eight hours. The verbal task of written word production cycled at 80 minutes; the spatial task of locating points in space cycled at 96 minutes. Multiple cycles were seen for a perceptual speed task that factor loads on both the verbal and spatial task. Replication of the results for the first 12 and second 12 subjects demonstrated their robustness. The verbal and spatial tasks were chosen to reflect specialized functions of the left and right cerebral hemispheres, respectively. Accordingly, the results are interpreted as evidence that specialized task performances are associated with independent neurochemical systems. In addition, blood samples were taken at task performance to assess cyclicity of hormone levels. Luteinizing hormone had a period of 120 minutes, testosterone and cortisol were inconsistent and none seemed to be related to the cognitive tasks. However when subjects were divided according to a winter or summer testing schedule, the spatial periodicity was absent for the summer group and the verbal periodicity was absent for the winter peak.

Activity Cycles↗
PubMedDate not supplied

The effects of mild diastolic hypertension on the results of tests of cognitive function in adults 22 to 59 years of age.

OBJECTIVE: To test the hypothesis that mild diastolic hypertension (90 to 104 mm Hg) may induce asymptomatic impairment of cognitive function. DESIGN: Cross-sectional. SETTING: Community participants recruited to a university-based ambulatory care center. PARTICIPANTS: Three hundred twelve men and women with untreated essential hypertension and 47 normotensive subjects, 22 to 59 years of age. MEASUREMENTS AND MAIN RESULTS: Cognitive function tests measured reaction time to and accuracy in interpreting predetermined visual stimuli, the ability to acquire, reproduce, and change a set of arbitrary stimulus-response associations, and memory and learning of verbal information. These tests were selected to detect subtle differences in performances as opposed to differentiating neurologically normal persons from brain-damaged persons. After controlling for age, gender, and education, results showed that there was no significant difference between the normotensive and hypertensive subjects in two measures of reaction time to and four measures of accuracy in interpreting predetermined visual stimuli, in the measure of arbitrary stimulus-response associations, or in seven memory and learning variables. Although confidence intervals for the differences between means were wide, clinically significant differences were not likely to be present. Younger age was associated with faster reaction times, fewer errors, and better performance on memory and learning tasks, independent of diastolic blood pressure. CONCLUSIONS: The few detectable effects of untreated mild hypertension on cognitive function reported in the literature may be due to chance and are of questionable clinical significance.

Adult↗
PubMed1981

Medical status and cognitive functioning in alcoholic women.

The prevalence of physical health disorders and measures of cognitive functioning were compared for 100 alcoholic and 100 nonalcoholic women matched on age and education. Alcoholic women were less healthy and more impaired on visual-spatial tasks than nonalcoholic women, and there were no relationships between health and cognitive functioning for either group.

Adult↗
PubMed1989

Impact of iron supplementation on cognitive functions in preschool and school-aged children: the Indian experience.

Four studies examined impacts of iron supplementation on school children of various ages and both sexes. The first study investigated impact of iron-folic acid supplements for 60 d on cognition in 94 boys and girls aged 5-8 y. Improvement in total scores of the anemics was significantly higher than the nonanemics in 7-8-y-old children only. The second study assessed impacts of supplementation on cognition in 14 pairs of 5-6-y-old anemic boys, with clear beneficial effects on cognitive function. The third study investigated effects of varying dosages of elemental iron on cognitive function in 48 boys aged 8-15 y, with different levels of improvement. The fourth study investigated impacts of iron supplementation on 163 anemic girls aged 8-15 y with treatment and evaluations at 4 and 8 mo, with significantly improved scores in cognitive function after the eighth month.

Adolescent↗
PubMed1996

Is the cognitive function of older patients affected by antihypertensive treatment? Results from 54 months of the Medical Research Council's trial of hypertension in older adults.

OBJECTIVE: To establish whether initiation of treatment with diuretic or beta blocker is associated over 54 months with change in cognitive function. DESIGN: A cognitive substudy, nested within a randomised, placebo controlled, single blind trial. SETTING: 226 general practices from the Medical Research Council's general practice research framework. SUBJECTS: A subset of 2584 subjects sequentially recruited from among the 4396 participants aged 65-74 in the trial of treatment of hypertension in older adults. The 4396 subjects were randomised to receive diuretic, beta blocker, or placebo. Subjects had mean systolic pressures of 160-209 mm Hg and mean diastolic pressures <115 mm Hg during an eight week run in. OUTCOME MEASURES: The rate of change in paired associate learning test (PALT) and trail making test part A (TMT) scores (administered at entry and at 1, 9, 21, and 54 months) over time. RESULTS: There was no difference in the mean learning test coefficients (rate of change of score over time) between the three treatments: diuretic -0.31 (95% confidence interval -0.23 to -0.39), beta blocker -0.33 (-0.25 to -0.41), placebo -0.30, (-0.24 to -0.36). There was also no difference in the mean trail making coefficients (rate of change in time taken to complete over time) between the three groups: diuretic -2.73 (95% confidence interval -3.57 to -1.88), beta blocker -2.08 (-3.29 to -0.87), placebo -3.01, (-3.69 to -2.32). A less conservative protocol analysis confirmed this negative finding. CONCLUSION: Treating moderate hypertension in older people is unlikely to influence, for better or for worse, subsequent cognitive function.

Adrenergic beta-Antagonists↗
PubMed1993

Cognitive function. Survey of elderly persons living at home in rural Newfoundland.

We tested the cognitive function of elderly, community-dwelling residents in rural Newfoundland using the Canadian Mental Status Questionnaire. The prevalence of moderate and severe cognitive impairment was 9.3%. Physicians in the community had recognized those with severe impairment, but had not recognized any of those with moderate impairment. Cognitive function testing should be part of the periodic health examination of older patients.

Aged↗
PubMed1999

Lifetime cognitive function and timing of the natural menopause.

BACKGROUND: There is evidence that ovarian steroids influence both reproductive aging and neural development. OBJECTIVE: We investigated the relationship between menopause and lifetime cognitive function in a prospective birth cohort study. METHODS: Participants were 1,572 women enrolled in the Medical Research Council National Survey of Health and Development (the British 1946 birth cohort). By age 50, 245 women were postmenopausal, 724 were pre- or perimenopausal, 288 had had a hysterectomy or bilateral oophorectomy, and 291 women had started taking hormone replacement therapy (HRT) before their menopause. The remaining 24 women, for various reasons, could not be classified into any of these groups. We investigated the association between cognitive function at ages 8, 11, 15, 26, and 43 years and menopause timing using Cox proportional hazard models, censoring for hysterectomy and bilateral oophorectomy, and initially for HRT use. The effect of including HRT use before menopause as an additional outcome was investigated using a competing risks analysis. RESULTS: Higher cognitive scores were associated with later menopause. The effect was strongest in childhood. This finding could not be explained by a variety of potential confounders, including early social background, physical development, education, adult social class, parity, smoking, and alcohol consumption. CONCLUSIONS: Childhood cognitive function is related to timing of the natural menopause. Both may be influenced by ovarian steroids across the life-span.

Adolescent↗
PubMed1992

Cognitive function--victim of disease or hostage to treatment?

In persons suffering from epilepsy, cognitive functioning may be compromised for various reasons, including--first and foremost--the learning and behavioral effects of the conditions causing the epilepsy. In addition, the epilepsy itself may cause changes in the nervous system through the metabolic and excitotoxic effects of the seizures and the neurotransmitter elements involved at the membrane level. The effect of the treatment modality, be it pharmacologic or surgical, may also play havoc with cognitive function. The neurobehavioral effects of antiepileptic drugs, although probably less important with the newer agents than in the past, must be considered, especially in polypharmacy, as recent reports have indicated. With increasing data, the effects of various surgical procedures on the cognitive elements of human behavior are becoming better recognized.

Anticonvulsants↗
PubMed1998

Estrogen therapy in postmenopausal women: effects on cognitive function and dementia.

CONTEXT: Several studies have suggested that estrogen replacement therapy in postmenopausal women improves cognition, prevents development of dementia, and improves the severity of dementia, while other studies have not found a benefit of estrogen use. OBJECTIVE: To determine whether postmenopausal estrogen therapy improves cognition, prevents development of dementia, or improves dementia severity. DATA SOURCES: We performed a literature search of studies published from January 1966 through June 1997, using MEDLINE, manually searched bibliographies of articles identified, and consulted experts. STUDY SELECTION: Studies that evaluated biological mechanisms of estrogen's effect on the central nervous system and studies that addressed the effect of estrogen on cognitive function or on dementia. DATA EXTRACTION: We reviewed studies for methods, sources of bias, and outcomes and performed a meta-analysis of the 10 studies of postmenopausal estrogen use and risk of dementia using standard meta-analytic methods. DATA SYNTHESIS: Biochemical and neurophysiologic studies suggest several mechanisms by which estrogen may affect cognition: promotion of cholinergic and serotonergic activity in specific brain regions, maintenance of neural circuitry, favorable lipoprotein alterations, and prevention of cerebral ischemia. Five observational studies and 8 trials have addressed the effect of estrogen on cognitive function in nondemented postmenopausal women. Cognition seems to improve in perimenopausal women, possibly because menopausal symptoms improve, but there is no clear benefit in asymptomatic women. Ten observational studies have measured the effect of postmenopausal estrogen use on risk of developing dementia. Meta-analysis of these studies suggests a 29% decreased risk of developing dementia among estrogen users, but the findings of the studies are heterogeneous. Four trials of estrogen therapy in women with Alzheimer disease have been conducted and have had primarily positive results, but most have been small, of short duration, non-randomized, and uncontrolled. CONCLUSIONS: There are plausible biological mechanisms by which estrogen might lead to improved cognition, reduced risk for dementia, or improvement in the severity of dementia. Studies conducted in women, however, have substantial methodologic problems and have produced conflicting results. Large placebo-controlled trials are required to address estrogen's role in prevention and treatment of Alzheimer disease and other dementias. Given the known risks of estrogen therapy, we do not recommend estrogen for the prevention or treatment of Alzheimer disease or other dementias until adequate trials have been completed.

Alzheimer Disease↗
PubMed1991

Reversed lateralization of cognitive functions in right handers. Exceptions to classical aphasiology.

Most current and past research on the cerebral organization of cognitive functions has presupposed certain specialized hemisphere operations. At least for right handers, language and praxis are to be organized in the left hemisphere, while affective prosody, configurational spatial capacity, and global attention are lateralized in the right hemisphere. Deviations from these presuppositions, as in crossed aphasics and perhaps left handers, are generally considered to be 'exceptions' and either to disprove the rules or to be irrelevant to the rule. We report 4 very 'exceptional' cases, right handers with almost entirely reversed lateralization of functions. Analysis of the intrahemispheric relationships between functions suggests that there may be a specific neurobiology to the interrelationships between and among cognitive functions, handedness, and the intrahemisphere localization of the function.

Adult↗
PubMed1999

Cognitive functioning in people with epilepsy plus severe learning disabilities: a systematic analysis of predictors of daytime arousal and attention.

In spite of the high prevalence of epilepsy and the importance of preserving cognitive function in people with learning disabilities, this population has received relatively little research attention. This study sets out systematically to investigate possible predictive factors of inter-ictal states of arousal and attention. The daytime function of 28 people with epilepsy and severe learning disabilities was assessed by performance on a two-choice reaction time vigilance task, behavioural analysis of time-sampled video recordings taken in naturalistic settings, and carer ratings on visual analogue scales. This methodology yielded eight discrete functional measures, from which two further index measures were derived after principal components analysis. A range of clinical and psychosocial assessments was completed and subjects had 36 hour ambulatory EEG and sleep EEG monitoring. Regression models identified significant predictors of cognitive function from a range of potential explanatory variables i.e. demographic, clinical, pharmacological, background EEG rhythms and sleep parameters. Results indicated that greater severity of learning disability, longer bedtime periods, poor sleep efficiency, frequent seizures and antiepileptic drug polytherapy were significant predictor variables. Explained variance (adjusted R2) was greater than 50% for six of 10 outcome variables (range up to 85%). Furthermore, significant regression equations (P < 0.05) were obtained for all but one variable. Thus, these results appear reasonably robust. Results support an interactional model of daytime arousal and attention in people with epilepsy plus severe learning disabilities. Inter-ictal cognitive function appears to be mediated by a combination of organic, circadian (sleep wake), clinical and pharmacological factors.

Adolescent↗
PubMed1995

Stress and cognitive function.

Stress affects cognition in a number of ways, acting rapidly via catecholamines and more slowly via glucocorticoids. Catecholamine actions involve beta adrenergic receptors and also availability of glucose, whereas glucocorticoids biphasically modulate synaptic plasticity over hours and also produce longer-term changes in dendritic structure that last for weeks. Prolonged exposure to stress leads to loss of neurons, particularly in the hippocampus. Recent evidence suggests that the glucocorticoid- and stress-related cognitive impairments involving declarative memory are probably related to the changes they effect in the hippocampus, whereas the stress-induced catecholamine effects on emotionally laden memories are postulated to involve structures such as the amgydala.

Animals↗
PubMedDate not supplied

Sensory-motor and cognitive functioning in children who have undergone bone marrow transplantation.

Sensory-motor and cognitive functioning was investigated in a group of 32 children treated with bone marrow transplantation (BMT), 1-6 years after treatment. Twenty-five of the patients had suffered from leukemia. The BMT procedure had involved a regimen of cytostatic drugs and, for leukemia patients, total body irradiation at a dose of 10 Gy, administered in one session. Cytostatic drugs and irradiation are known to be potentially neurotoxic, particularly when combined. The examination involved four neuropsychological tests of sensory-motor and cognitive functioning, as well as an age-appropriate intelligence test. For control the bone marrow donors (n = 32), siblings of the patients, were also investigated. A pronounced delay in motor development was found in four children, who had been treated with BMT including total body irradiation before 3 years of age. Patients between 3 and 11 years of age at BMT were at a slight disadvantage, compared to donors, on tasks involving perceptual and fine motor speed. In older patients no deficits were observed.

Adolescent↗
PubMed1999

Effects of subcortical cerebral infarction on cortical glucose metabolism and cognitive function.

BACKGROUND: The mechanism of dementia in subcortical cerebral infarction is incompletely understood. OBJECTIVE: To determine how cognitive function is related to cortical metabolism in patients with subcortical infarction and a continuum of cognitive impairment. METHODS: We used positron emission tomography (PET) and the glucose metabolic tracer fludeoxyglucose F 18 to study 8 patients with subcortical stroke and normal cognitive function (S-CN), 5 patients with subcortical stroke and cognitive impairment (S-CI) who did not have dementia, 8 patients with subcortical stroke and dementia (S-D), and 11 controls with no cognitive impairment or stroke. A subset of patients had absolute regional cerebral metabolic rate of glucose (CMRglc) determined, while in all subjects regional tracer uptake normalized to whole brain tracer uptake was calculated. PET data were analyzed by constructing volumes of interest using coregistered magnetic resonance imaging data and correcting the PET data for atrophy. RESULTS: Global CMRglc was significantly lower in the patients with S-D than in the control and S-CN groups, with S-CI rates intermediate to those of the S-D and S-CN groups. Absolute regional CMRs of glucose were similar in the S-D and S-CI groups and in the control and S-CN groups. The regional pattern, however, showed lower right frontal regional CMRglc ratios in all stroke groups compared with the controls. There were modest correlations between performance on the Mini-Mental State Examination and whole brain CMRglc when all 4 groups were included. CONCLUSIONS: These results demonstrate that subcortical infarction produces global cerebral hypometabolism, which is related to the clinical status of the patients. In addition, specific frontal lobe hypometabolism also appears to be a feature of subcortical infarction. Taken together, both global and regional effects on cortical function mediate the production of clinical symptoms in patients with subcortical strokes.

Aged↗
PubMed1995

Care for demented patients in different living conditions. Effects on cognitive function, ADL-capacity and behaviour.

OBJECTIVE: To assess if and how demented patients' living conditions affect their level of functioning. DESIGN: A prospective concurrent control-study. SETTING: Sundsvall, an industrial community in the middle of Sweden. PARTICIPANTS: Forty-six demented patients in group-living (GL-group) and 62 controls (C-group). MAIN OUTCOME MEASURE: Cognitive function, ADL-capacity and behaviour were measured every third month during one year. RESULTS: Both groups deteriorated, but the decline was significantly slower in the GL-group regarding some ADL-functions, e.g. dressing and motor functions, whereas some behavioural disturbances were significantly more frequent in the GL-group. No differences were observed regarding the level of cognitive function. CONCLUSION: The living condition has small effects on cognitive function and ADL-capacity. The behavioural disturbances observed in GL should be the focus of future research.

Activities of Daily Living↗
PubMed1996

The measurement of cognitive function during acute hypoglycaemia: experimental limitations and their effect on the study of hypoglycaemia unawareness.

The risk of hypoglycaemia and the resulting impairment in brain function are major factors preventing those with diabetes achieving normoglycaemia. The need to define these risks more precisely has prompted an increasing research effort to identify which aspects of cerebral function are particularly vulnerable and at which glucose level. Much of the evidence is inconsistent, reflecting not only the wide range of methods for measuring cognitive function and inducing hypoglycaemia, but also the inherent variability of the response. Nevertheless, the data suggest that those mental activities which are relatively undemanding are often unaffected at all levels of experimental hypoglycaemia while the performance of more complex tasks deteriorates at glucose concentrations of around 3 mmol l-1. The relative imprecision of cognitive testing is reflected in the debate which surrounds the pathogenesis of hypoglycaemia unawareness. There is some evidence that the glycaemic threshold for autonomic activation and symptoms can vary while the threshold for cognitive impairment is fixed. This has led to the hypothesis that hypoglycaemia unawareness arises when the autonomic response develops at a blood glucose below that for impaired cognition, thus preventing patients from recognizing or responding to their usual symptoms. However, contradictory data suggest that the threshold for cognitive impairment can alter in line with the autonomic response, a conclusion which falls to fit either the above hypothesis or the clinical description of hypoglycaemia unawareness. These differences may be methodological or relate to the relative imprecision of measurements of cognitive function. Resolution of these discrepancies may have to await the development of advanced technology such as high resolution MRI or PET scanning. In the meantime, progress could be made if all groups agreed on a limited range of cognitive function tests and used them in a standardized manner.

Attention↗