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PubMed2004

The relationship between impaired glucose tolerance, type 2 diabetes, and cognitive function.

The present review integrates findings of published studies that have evaluated the cognitive function of treated and untreated type 2 diabetic patients and provides a detailed overview of the neuropsychological assessments conducted. Cognitive deficits are observed in older people with glucose intolerance or untreated diabetes but these deficits appear to be attenuated by treatments that improve glycemic control. Cognitive decrements in treated type 2 diabetic patients are most consistently observed on measures of verbal memory (35% of the measures) and processing speed (45% of the measures) while preserved function is observed on measures of visuospatial, attention, semantic and language function. Some studies suggest that deficits in cognitive functions are associated with poorer glycemic control. A number of other factors, such as depression, cardiovascular and cerebrovascular disease, increase these deficits. We conclude that, in diabetic patients who achieve and maintain good glycemic control, type 2 diabetes only has a small impact on cognitive functions before the age of 70 years. However, early onset of type 2 diabetes, poor glycemic control and the presence of micro- and macrovascular disease may interact to produce early cognitive deficits. In older adults (70 years and over), diabetes likely interacts with other dementing processes such as vascular disease and Alzheimer's disease to hasten cognitive decline.

Cognition↗

PubMed2006

Mild memory impairment in healthy older adults is distinct from normal aging.

Mild memory impairment was detected in 28% of a sample of healthy community-dwelling older adults using the delayed recall trial of a word list learning task. Statistical analysis revealed that individuals with memory impairment also demonstrated relative deficits on other measures of memory, and tests of executive function, processing speed and global cognition, as measured by the CERAD and CogState batteries and CANTAB paired associate learning task. These relative deficits cannot be explained by age-related changes, education, intelligence, mood, health-related factors, or the individuals' ApoEepsilon4 status. Memory-impaired individuals (n = 30) did not recognize the extent of their memory and cognitive difficulties beyond the general complaints expressed by normal elderly (n = 77) within the study and their apparent difficulties did not appear to impact on their participation in life activities. These findings suggest it is unlikely that the memory and cognitive difficulties demonstrated by individuals with mild memory impairment reflect normal aging. Rather it is possible that such impairment may signal early neurodegenerative processes worthy of further investigation.

Aged↗

PubMed1999

Effects of aging, message repetition, and note-taking on memory for health information.

This study investigated whether repetition improves older adults' memory for health service appointment messages delivered by automated telephone systems. Whereas imposed repetition reduces age differences in memory (Morrow, Leirer, Carver, Tanke, & McNally, 1999), the present study examined the effect of optional repetition. Both older and younger participants in Experiment 1 chose to repeat messages. More repetition, higher cognitive ability (working memory and processing speed), and younger age were associated with better memory for appointment information. The effect of age was eliminated when cognitive ability, but not repetition, was controlled. Thus, older adults used optional repetition in automated systems, but this strategy did not eliminate age differences in memory. In Experiment 2, older as well as younger adults took accurate notes and also repeated messages. Both note-taking and message repetition improved memory for the messages but did not reduce age differences. These findings suggest that older as well as younger adults use presentation strategies in automated messaging systems. Older adults may not take full advantage of these strategies, perhaps because of age-related declines in self-initiated or metacognitive processes.

Adult↗

PubMed2005

Using the axis of rotation of polar navigator echoes to rapidly measure 3D rigid-body motion.

An improved technique to prospectively correct three-dimensional rigid-body motion using polar spherical navigator (pNAV) echoes is presented. The technique is based on acquiring pNAVs of an object in a baseline and rotated position and determining the axis of rotation (AOR) between data sets, thereby reducing 3D rotations to a 2D, planar rotation. Finding the AOR is simplified by prerotating the baseline trajectory, which forces the axis to lie within a specific polar region of a spherical shell in k-space. Orbital navigator echoes are interpolated from the pNAV data in planes orthogonal to the AOR and cross-correlated to determine the 2D rotation. The rotation about the AOR is used in conjunction with its orientation to calculate the overall 3D rotation. The pNAV-AOR technique was tested for its precision, accuracy, and processing speed in detecting compound rotations and translations of varying magnitude. In comparison to the spherical navigator echo technique, the pNAV-AOR technique is noniterative, fast, and independent of rotation magnitude and direction. At low SNR, the technique can detect compound rotations to 0.5 degrees accuracy in an estimated 100 msec, indicating that prospective 3D rigid-body motion correction may be feasible with this technique.

Humans↗

PubMed1998

Chronic electrical stimulation of the left ventrointermediate (Vim) thalamic nucleus for the treatment of pharmacotherapy-resistant Parkinson's disease: a differential impact on access to semantic and episodic memory?

Thalamotomy for medically refractory Parkinson's disease (PD) is considered to be efficacious and relatively safe. Because a minority of patients experience decrements in language and memory (often mild and transient) after thalamotomy, chronic thalamic deep brain stimulation (DBS) might be a safer treatment given its reversibility and the modifiability of stimulation parameters. Two preliminary studies support the relative cognitive safety of unilateral DBS of the ventral intermediate (Vim) thalamic nucleus, but it is unclear whether possibly subtle changes in language and memory represent effects of "microthalamotomy" or of stimulation per se. This report provides preliminary data concerning effects of left thalamic stimulation on information processing speed, semantic memory (verbal fluency and visual confrontation naming), and verbal episodic memory in a patient with PD. In addition to being evaluated before and 3 and 6 months after surgery, the patient was tested 18 months after surgery either on or off medications and with the stimulator turned either on or off (order counterbalanced across medication conditions). Test performance differences between the stimulation conditions were attenuated "off" as compared to "on" medication. Vim stimulation consistently, albeit subtly, improved semantic verbal fluency but interfered with immediate recall of word lists. Parallels to findings from acute, intraoperative thalamic stimulation studies are explored. The hypothesis is offered that left Vim stimulation might facilitate access to semantic memory, but interfere with episodic memory processes.

Adult↗

PubMed2001

Choice stepping reaction time: a composite measure of falls risk in older people.

BACKGROUND: This study investigated the neuropsychological, sensorimotor, speed, and balance contributions to a new test of choice stepping reaction time (CSRT) and determined whether this new test is an important predictor of falls in older people. METHODS: A total of 477 retirement-village residents aged 62 to 95 years (mean +/- SD, 79.2 +/- 6.2 years) took the CSRT test, which required them to step onto one of four panels that were illuminated in a random order. The subjects also took tests that measured neuropsychological, sensorimotor, speed, and balance function. RESULTS: Multiple regression analysis revealed that poor performance in Part B of the Trail Making Test (a neuropsychological test) and impaired quadriceps strength, simple reaction time, sway with eyes open on a compliant surface, and maximal balance range were the best predictors of increased CSRTs (multiple r(2) =.45). Subjects with a history of falls had significantly increased CSRTs compared with nonfallers (1322 +/- 331 milliseconds and 1168 +/- 203 milliseconds, respectively). Impaired CSRT was a significant and independent predictor of falls, as were two complementary sensory measures (visual contrast sensitivity and lower limb proprioception). Of these measures, CSRT was the most important in predicting falls. Furthermore, the inclusion of CSRT in the model excluded measures of strength, central processing speed, and balance, because these could not provide nonredundant information for the prediction of falls. CONCLUSIONS: This study identifies a new test that provides a composite measure of falls risk in older people and elucidates the relative importance of specific physiological and neuropsychological systems in the initiation of fast and appropriate step responses.

Accidental Falls↗

PubMed2002

Comparison of neuropsychological test scores between men and women with prior exposure to organic solvents.

The purpose of this study was to determine whether men and women with a history of similar exposure to organic solvents demonstrate differences in neuropsychological performance. An equal number of men and women were compared on a battery of neuropsychological tests. Men and women were matched on age, education, and past history of exposure (i.e., length of exposure, recency of exposure, and history of peak exposure). With the exception of 1 test, there were no differences between men and women on any of the cognitive tests. There were also no differences in self-reported psychological symptoms. There was, however, a different pattern of correlations between test scores and exposure for the men and women: In women, exposure was associated with tests of attention and processing speed, whereas in men, exposure was associated with verbal memory. After controlling for age and education, the findings were diminished for men but remained significant for women. Overall, the results show no differences in neuropsychological test scores between men and women when matched on exposure variables but raise the possibility of differences in the pattern of cognitive deficits associated with solvent exposure between men and women.

Adult↗

PubMed1984

Calculating the electrostatic potential of molecular models with separate evaluations by conventional, vector, and array processors.

A simple computational scheme for estimating the electrostatic potential about molecular models of moderate size is given. The large amount of calculations required for the evaluation of the hypersurface lends itself to treatment by high speed, unconventional computing machines. The essence of these calculations lies in Coulombic interactions that are computed between hypothetical proton test probes positioned in a gridded region surrounding the model and the partial electrostatic charges (CNDO/2) of each atom in the model. A specific scientific application is discussed which involves the recognition of amino acids and nucleotide bases. Three different evaluations of the potential hypersurface within the context of this approach were made. The first was performed on a VAX 11/780 which is a general purpose machine widely used in the scientific community; the second was performed using a pipelined Vector Processor, the FPS AP-120B; and the third by a processor array, the ILLIAC-IV. A comparison of the architectures and processing speeds of each class of machines is made. The computing power observed is consistent with the design and purpose of each machine. Also discussed are methods for displaying the vast amount of data that result from such calculations. It is determined that computer graphics offers an effective means for extracting information from large amounts of data. Finally, the scientific value of the calculations are briefly discussed. If caution is applied to interpreting the results, then the electrostatic potential (EP) mappings can be useful in identifying sites of potential chemical interactions.

Algorithms↗

PubMed1993

Differential effects of visual-spatial attention on response latency and temporal-order judgment.

Theorists from both classical structuralism and modern attention research have claimed that attention to a sensory stimulus enhances processing speed. However, they have used different operations to measure this effect, viz., temporal-order judgment (TOJ) and reaction-time (RT) measurement. We report two experiments that compared the effect of a spatial cue on RT and TOJ. Experiment 1 demonstrated that a nonmasked, peripheral cue (the brief brightening of a box) affected both RT and TOJ. However, the former effect was significantly larger than the latter. A masked cue had a smaller, but reliable, effect on TOJ. In Experiment 2, the effects of a masked cue on RT and TOJ were compared under identical stimulus conditions. While the cue had a strong effect on RT, it left TOJ unaffected. These results suggest that a spatial cue may have dissociable effects on response processes and the processes that lead to a conscious percept. Implications for the concept of direct parameter specification and for theories of visual attention are discussed.

Adult↗

PubMed2004

Homocysteine and the brain in midadult life: evidence for an increased risk of leukoaraiosis in men.

BACKGROUND: High serum homocysteine (HCY) levels have been associated with thromboembolic cerebrovascular disease, but their relationship to microvascular disease is uncertain. Homocysteine also has a direct neurotoxic effect and has been linked to brain atrophy and an increased risk of Alzheimer disease. OBJECTIVE: To examine the relationship of HCY levels to brain and cognitive measures in a healthy community sample. DESIGN: Cross-sectional study. SETTING: Individuals residing in Canberra and Queanbeyan, Australia, who were participating in the longitudinal PATH Through Life Project. PARTICIPANTS: Individuals aged 60 to 64 years selected randomly from the community, 196 men and 189 women. MAIN OUTCOME MEASURES: Regression coefficients with HCY level as the putative determinant and various magnetic resonance imaging measures (brain atrophy index, ventricle-brain ratios, volume of periventricular and deep white matter hyperintensities) and cognitive measures (information processing speed, verbal memory, fine motor speed) as dependent measures. RESULTS: Homocysteine levels did not have a significant relationship with brain atrophy index or ventricle-brain ratios. High HCY levels were related to increased deep white matter hyperintensities but not periventricular white matter hyperintensities, after correcting for levels of folate, vitamin B(12), creatinine, and thyrotropin; hypertension; smoking; and diabetes, the relationship being significant only in men. Homocysteine levels were related to impairment in verbal memory and fine motor speed but not after the previously mentioned correction. CONCLUSIONS: Total HCY level is independently related to leukoaraiosis in middle-aged men, and this may be functionally relevant in the form of mild cognitive impairment. The remediation of hyperhomocysteinemia should begin early in life if its deleterious effects on the brain are to be prevented.

Brain↗

PubMedDate not supplied

Cognition and fatigue in multiple sclerosis: Potential effects of medications with central nervous system activity.

To evaluate the potential effects of medications with central nervous system (CNS) activity on cognitive function and fatigue in multiple sclerosis (MS), we performed a retrospective analysis of medication use among 70 subjects with MS who were participating in a clinical trial for evaluation of the effects of yoga and exercise programs on cognition and fatigue. Among these MS subjects, 74% were taking at least one potentially CNS-active medication. These 70 subjects were divided into two groups: those taking at least one CNS-active medication (n = 52) and those not on any medications with potential CNS activity (n = 18). We compared assessments of cognitive function and fatigue using an analysis of covariance. MS subjects on CNS-active medication had greater impairment on measures of processing speed, sustained attention, and fatigue than those not on these medications. While these findings do not establish a causal relationship between medication use and cognitive impairment and fatigue, the data indicate that researchers need to control for use of CNS-active medications when conducting studies of cognitive impairment and fatigue in MS subjects.

Adult↗

PubMed2005

Plasma cortisol levels, brain volumes and cognition in healthy elderly men.

PURPOSE: In ageing animals, exposure to chronic high levels of glucocorticoids is associated with cognitive impairment and hippocampal atrophy. However, there are few studies examining relationships among glucocorticoids, brain volumes and cognitive function in healthy older humans. This study examined the hypotheses that higher plasma cortisol levels and altered sensitivity to glucocorticoids are associated with worse cognition and more brain atrophy in elderly men. MATERIALS AND METHODS: Ninety-seven healthy men aged 65-70 had plasma cortisol measured at 09:00, 14:30 h, and post-dexamethasone (0.25mg, 09:00 h), and had dermal sensitivity to glucocorticoids measured. They also underwent cognitive testing, with scores adjusted for estimated prior mental ability, and had MRI measurements of intracranial area (a validated estimate of intracranial capacity), and hippocampus, temporal lobe and frontal lobe volumes. RESULTS: Plasma cortisol levels at 09:00 h were significantly and negatively correlated with a summary General Cognitive Factor accounting for 51% of the variance of cognitive function (rho=-0.22, p=0.035), and specific cognitive tests: delayed paragraph recall (rho=-0.28, p=0.036) and processing speed (rho=-0.23, p=0.026). Regional brain volumes adjusted for intracranial area generally did not correlate with cortisol levels. Tissue glucocorticoid sensitivity did not correlate with any measure of cognition or brain volume. CONCLUSIONS: In healthy older men, higher plasma cortisol levels are associated with worse ageing-related overall cognitive change but not ageing-related brain atrophy.

Aged↗

PubMed2004

Neuropsychological effects of pediatric obstructive sleep apnea.

Obstructive sleep apnea (OSA) is a fairly common nocturnal breathing disorder, affecting 2-4% of individuals. Although OSA is associated with medical morbidity, its most functionally disruptive effects in adults appear to be neuropsychological in nature. Research on the neuropsychological effects of pediatric OSA has been limited. This study compared the neuropsychological functioning of school-aged children with OSA to that of healthy children. The primary goal was to clarify the presence and pattern of neuropsychological morbidity associated with pediatric OSA. Sleep was assessed with parent-report questionnaires and laboratory sleep studies. Neuropsychological functioning was assessed by formal tests and parent- and teacher-report questionnaires. Data indicated OSA-related cognitive and behavioral impairment that was particularly marked on measures of behavior regulation and some aspects of attention and executive functioning. Minimal effects were observed on measures of intelligence, verbal memory, or processing speed. Exploratory analyses failed to indicate any clear relationship between neuropsychological functioning and objective indexes of hypoxia or sleep disruption, though the sample was small. These data add to a growing literature which suggests that significant neuropsychological deficits are associated with pediatric OSA. Findings suggest a pattern of neuropsychological morbidity that is similar but not identical to that seen in adult OSA.

Attention↗

PubMed1992

Automatic film processing: analysis of 9 years of observations.

A survey method known as the sensitometric technique for the evaluation of processing (STEP) has been used to monitor processing speed of over 2,000 automatic film processors in hospitals, private offices, and mammography facilities since 1981. Analysis of data obtained through this program revealed underprocessing at 33% (76 of 231) of observed hospitals in 1987, 7% (13 of 179) of mammography facilities in 1988, and 42% (101 of 241) of private practices in 1989. Underprocessing at mammography facilities decreased from 18% (25 of 139) in 1985, which was contrary to the trend in hospitals. The consequence of underprocessing is higher radiation exposure and a degradation in film contrast. Evaluation of automatic film processors is a necessary part of any comprehensive evaluation of a diagnostic radiography facility. The STEP procedure was designed only as a field survey test; to ensure optimal conditions for obtainment of diagnostic quality radiographs, facilities should perform quality assurance evaluations of their processing equipment and verify that processing recommendations of manufacturers are being followed.

Technology, Radiologic↗

PubMed2005

Neuropsychological predictors of BOLD response during a spatial working memory task in adolescents: what can performance tell us about fMRI response patterns?

The relationship between standardized neuropsychological test performance and functional magnetic resonance imaging (fMRI) response during cognitive tasks is largely unknown. This exploratory investigation examined the relationship between neuropsychological test performance and fMRI response to a spatial working memory (SWM) task among 49 typically developing adolescents. Participants were administered a variety of neuropsychological tests in the domains of working memory, visuospatial skills, executive functioning, attention, learning and memory, visuomotor skills and processing speed, and language functioning. Neuropsychological domain scores were used to predict fMRI response during a SWM task. Results suggest that in many brain regions, neuropsychological performance negatively predicts fMRI response, suggesting that those teens with better neuropsychological abilities required fewer neural resources to adequately perform the task. This study provides further understanding of how neuropsychological abilities relate to neural activity during fMRI tasks, and provides an important link between neuropsychological and fMRI research.

Adolescent↗

PubMed2006

The Palau Early Psychosis Study: neurocognitive functioning in high-risk adolescents.

OBJECTIVE: The purpose of the present study was to evaluate both the independent and joint effects of genetic risk and clinical status on neurocognitive functioning in adolescents from a population isolate with an elevated risk for schizophrenia and strong familial aggregation of cases. METHOD: The subjects were 310 non-help seeking, drug-naïve adolescents 14-19 years of age from the Republic of Palau. The sample comprised 98 Genetically High Risk (GHR) adolescents, 54 of whom were symptomatic, and 212 Genetically Low Risk (GLR) adolescents, including 113 Clinically High Risk (CHR) subjects who were symptomatic and 99 normal controls who were non-symptomatic. Neurocognitive testing was conducted after the clinical assessment and included Wechsler Memory Scale tests of logical, visual and working memory, the perceptual organization and processing speed subtests of the WISC-III, CPT-IP measures of sustained attention, and tests of fine and gross neuromotor function. RESULTS: GHR adolescents showed impairments in immediate logical memory, verbal working memory, CPT-IP performance, and fine motor skills. The only two cognitive components influenced by the presence of early psychosis symptoms were WISC-III perceptual organization and spatial working memory. Neurocognitive deficits did not increase with increasing levels of psychopathology. We found no significant interactive effects of genetic risk and clinical status on neurocognitive functioning. CONCLUSIONS: Genetic risk and clinical status exert independent effects on neurocognitive function in HR adolescents, and genetic risk has a broader impact than clinical status. Our results suggest that many of the neurocognitive impairments associated with early psychosis are genetically mediated and can occur in genetically vulnerable individuals regardless of their clinical status. However, visuospatial processing appears to be uniquely disrupted by emerging symptomatology.

Adolescent↗

PubMed2006

Cognitive function in candidates for coronary artery bypass graft surgery.

BACKGROUND: While many studies have investigated cognitive impairments in patients after coronary artery bypass graft surgery, very few have closely evaluated presurgical cognitive functioning of bypass candidates. METHODS: A battery of neuropsychologic tests was administered to a consecutive series of patients listed for bypass surgery (n = 109). Cognitive function of bypass candidates was compared with that of a healthy control group (n = 25) and published test norms. RESULTS: Cognitive test scores in candidates for bypass were significantly lower than those of the control group on tests of attention, information processing speed, and verbal memory. Additionally, bypass candidates' cognitive test scores were significantly reduced compared with expected values derived from validated test norms, on all but one cognitive test. CONCLUSIONS: Cognitive performances of candidates for bypass were significantly lower than those of a healthy control group and published cognitive test norms.

Aged↗

PubMed2002

Fluorescence-assisted image analysis of freshwater microalgae.

We exploit a property of microalgae-that of their ability to autofluoresce when exposed to epifluorescence illumination-to tackle the problem of detecting and analysing microalgae in sediment samples containing complex scenes. We have added fluorescence excitation to the hardware portion of our microalgae image processing system. We quantitatively measured 120 characteristics of each object detected through fluorescence excitation, and used an optimized subset of these characteristics for later automated analysis and species classification. All specimens used for training and testing our system came from natural populations found in Lake Biwa, Japan. Without the use of fluorescence excitation, automated analysis of images containing algae specimens in sediment is near impossible. We also used fluorescence imaging to target microalgae in water samples containing large numbers of obtrusive nontargeted objects, which would otherwise slow processing speed and decrease species analysis and classification accuracy. Object drift problems associated with the necessity to use both a fluorescence and greyscale image of each microscope scene were solved using techniques such as template matching and a novel form of automated seeded region growing (SRG). Our system proved to be not only user-friendly, but also highly accurate in classifying two major genera of microalgae found in Lake Biwa-the cyanobacteria Anabaena spp. and Microcystis spp. Classification accuracy was measured to be over 97%.

Anabaena↗