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Biomedical subjects

O B Paulson

Publications and source records attributed to O B Paulson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Cortical cerebral metabolism correlates with MRI lesion load and cognitive dysfunction in MS.

OBJECTIVE: To study the association between the cortical cerebral metabolic rate of glucose (CMRglc), MRI T2-weighted total lesion area (TLA), cognitive dysfunction, and neurologic disability in MS. BACKGROUND: MRI lesion load is widely used in the clinical evaluation of the MS patient but little is known about the associated changes in cortical activation. METHODS: Twenty-three patients with clinically definite MS underwent measurements of CMRglc, TLA, motor evoked potentials (MEPs), and cognitive and neurologic disability. CMRglc was calculated using PET and 18-F-deoxyglucose and compared with nine normal control subjects. RESULTS: Reductions in CMRglc (p < 0.01) were found in the cortical global and regional lobar measurements. Furthermore, regional CMRglc (rCMRglc) was reduced in the dorsolateral prefrontal cortex, orbitofrontal cortex, caudate, putamen, thalamus, and hippocampus. Global cortical CMRglc correlated with TLA (Spearman rank correlation coefficient [SRCC] = -0.66, p = 0.001), and rCMRglc correlated with regional lesion load in all cerebral lobes (p < or = 0.05). Global cortical CMRglc and cognitive disability also correlated (SRCC = 0.58, p = 0.015), and stepwise regression analysis showed a significant association between rCMRglc of the right thalamus and cognitive performance as well as TLA. There was no correlation between CMRglc and neurologic disability (Expanded Disability Status Scale) or MEP. CONCLUSION: Global and regional cortical CMRglc is reduced significantly in MS patients compared with normal control subjects. Furthermore, the CMRglc reductions correlate with TLA as well as with cognitive dysfunction, which indicates that MRI white matter lesion burden has a deteriorating effect on cortical cerebral neural function.

Adult↗
PubMed2000

Effects of attention on dichotic listening: an 15O-PET study.

The present study investigated the effect of attention on brain activation in a dichotic listening situation. Dichotic listening is a technique to study laterality effects in the auditory sensory modality. Two different stimuli were presented simultaneously, one in each ear. Twelve subjects listened to lists of consonant-vowel syllables, or short musical instrument passages, with the task of detecting a "target" syllable or musical instrument by pressing a button. The target stimulus appeared an equal number of times in the left and right ear. The subjects were instructed to either concentrate on the stimuli presented in both ears, or only on the left or right ear stimulus. Brain activation was measured with 15O-PET, and significant changes in regional normalized counts (rNC) were evaluated using statistical parametric mapping (SPM96) software. Concentrating on either the right or left ear stimulus significantly decreased activity bilaterally in the temporal lobes compared to concentrating on both ear stimuli, at the expense of an increased activation in the right posterior and inferior superior parietal lobe. The CV-syllables activated areas corresponding to the classic language areas of Broca and Wernicke. The musical instrument stimuli mainly activated areas in visual association cortex, cerebellum, and the hippocampus. An interpretation of the findings is that attention has a facilitating effect for auditory processing, causing reduced activation in the primary auditory cortex when attention is explicitly recruited. The observed activations in the parietal lobe during the focused attention conditions could be part of a modality non-specific "attentional network".

Adult↗
PubMed2000

Reconstruction strategy for echo planar spectroscopy and its application to partially undersampled imaging.

The most commonly encountered form of echo planar spectroscopy involves oscillating gradients in one spatial dimension during readout. Data are consequently not sampled on a Cartesian grid. A fast gridding algorithm applicable to this particular situation is presented. The method is optimal, i.e., it performs as well as the full discrete Fourier transform for band limited signals while allowing for use of the fast Fourier transform. The method is demonstrated for reconstruction of data that are partially undersampled in the time domain. The advantages of undersampling are lower hardware requirements or fewer interleaves per acquisition. The method is of particular interest when large bandwidths are needed (e.g., for high field scanning) and for scanners with limited gradient performance. The unavoidable artifacts resulting from undersampling are demonstrated to be acceptable for spectroscopy with long echo times.

Algorithms↗
PubMed2000

Regional differences in the CBF and BOLD responses to hypercapnia: a combined PET and fMRI study.

Previous fMRI studies of the cerebrovascular response to hypercapnia have shown signal change in cerebral gray matter, but not in white matter. Therefore, the objective of the present study was to compare (15)O PET and T *(2)-weighted MRI during a hypercapnic challenge. The measurements were performed under similar conditions of hypercapnia, which were induced by inhalation of 5 or 7% CO(2). The baseline rCBF values were 65.1 ml hg(-1) min(-1) for temporal gray matter and 28.7 ml hg(-1) min(-1) for white matter. By linear regression, the increases in rCBF during hypercapnia were 23.0 and 7. 2 ml hg(-1) min(-1) kPa(-1) for gray and white matter. The signal changes were 6.9 and 1.9% for the FLASH sequence and were 3.8 and 1. 7% for the EPI sequence at comparable echo times. The regional differences in percentage signal change were significantly reduced when normalized by regional flow values. A deconvolution analysis is introduced to model the relation between fMRI signal and end-expiratory CO(2) level. Temporal parameters, such as mean transit time, were derived from this analysis and suggested a slower response in white matter than in gray matter regions. It was concluded that the differences in the magnitude of the fMRI response can largely be attributed to differences in flow and that there is a considerable difference in the time course of the response between gray and white matter.

Adult↗
PubMed2000

Categorization and category effects in normal object recognition: a PET study.

To investigate the neural correlates of the structural and semantic stages of visual object recognition and to see whether any effects of category could be found at these stages, we compared the rCBF associated with two categorization tasks (subjects decided whether pictures represented artefacts or natural objects), and two object decision tasks (subjects decided whether pictures represented real objects or nonobjects). The categorization tasks differed from each other in that the items presented in the critical scan window were drawn primarily from the category of artefacts in the one task and from the category of natural objects in the other. The same was true for the object decision tasks. The experiment thus comprised a two-by-two factorial design. The factors were Task Type with two levels (object decision vs. categorization) and Category also with two levels (natural objects vs. artefacts). The object decision tasks were associated with activation of areas involved in structural processing (fusiform gyri, right inferior frontal gyrus). In contrast, the categorization tasks were associated with activation of the left inferior temporal gyrus, a structure believed to be involved in semantic processing. In addition, activation of the left premotor cortex was found during the categorization of artefacts compared with both the categorization of natural objects and object decision to artefacts. These findings suggest that the structural and semantic stages are dissociable and that the categorization of artefacts, as opposed to the categorization of natural objects, is based, in part, on action knowledge mediated by the left premotor cortex. However, because artefacts and natural objects often caused activation in the same regions within tasks, processing of these categories is not totally segregated. Rather, the categories differ in their weight on different forms of knowledge in particular tasks.

Adult↗
PubMed2000

Cerebral activation during micturition in normal men.

Specific cerebral lesions have shown the crucial role of the brain in the control of micturition. The precise identification of the anatomical cerebral structures involved in micturition can contribute to a better understanding of the control of micturition and the development of therapeutic models. Various neuropathological and animal studies have referred to the medulla oblongata, pons, limbic system, superior frontal lobe and premotor cortical regions as areas implicated in micturition control. The aim of this study was to investigate whether the activity of these areas during micturition can be confirmed by PET in normal men. The distribution of the regional cerebral blood flow after bolus injection of (15)O water was used as an indirect measure of cerebral activation. PET scans were performed during the following three conditions: (i) at rest with the bladder empty; (ii) during simulated micturition after instillation of isotonic saline into the urinary bladder; and (iii) the withholding of urine (saline). Normal micturition using this model was achieved in eight out of 12 right-handed normal subjects. The changes in bladder contraction, bladder pressure and intra-abdominal pressure were monitored on-line during the whole scanning session by a cystometry device. The images were analysed using statistical parametric mapping at a significance threshold of P < 0.05 with correction for multiple independent comparisons. Micturition versus rest was associated with bilateral activation of areas close to the postcentral gyrus, inferior frontal gyrus, globus pallidus, cortex cerebelli, vermis and midbrain. On the left side, activation of the middle frontal gyrus, superior frontal gyrus, superior precentral gyrus, thalamus and the caudal part of the anterior cingulate gyrus was seen, while on the right side we found activation in the supramarginal gyrus, mesencephalon and insula. When the threshold value was lowered to P < 0.001 (Z > 3.09) without correction for multiple comparisons, we found additional activation in the medial pontine tegmentum, mesencephalon, right thalamus, right middle frontal gyrus and left insula. When urine- withholding was compared with rest, the left insula showed a tendency to activate. We conclude from this study, in which urinary bladder contraction was verified cystometrically, that the onset and maintenance of micturition in normal men is associated with a vast network of cortical and subcortical regions, confirming observations from clinical and animal studies.

Adult↗
PubMed2000

Quantitation of regional cerebral blood flow corrected for partial volume effect using O-15 water and PET: I. Theory, error analysis, and stereologic comparison.

Limited spatial resolution of positron emission tomography (PET) can cause significant underestimation in the observed regional radioactivity concentration (so-called partial volume effect or PVE) resulting in systematic errors in estimating quantitative physiologic parameters. The authors have formulated four mathematical models that describe the dynamic behavior of a freely diffusible tracer (H215O) in a region of interest (ROI) incorporating estimates of regional tissue flow that are independent of PVE. The current study was intended to evaluate the feasibility of these models and to establish a methodology to accurately quantify regional cerebral blood flow (CBF) corrected for PVE in cortical gray matter regions. Five monkeys were studied with PET after IV H2(15)O two times (n = 3) or three times (n = 2) in a row. Two ROIs were drawn on structural magnetic resonance imaging (MRI) scans and projected onto the PET images in which regional CBF values and the water perfusable tissue fraction for the cortical gray matter tissue (hence the volume of gray matter) were estimated. After the PET study, the animals were killed and stereologic analysis was performed to assess the gray matter mass in the corresponding ROIs. Reproducibility of the estimated parameters and sensitivity to various error sources were also evaluated. All models tested in the current study yielded PVE-corrected regional CBF values (approximately 0.8 mL x min(-1) x g(-1) for models with a term for gray matter tissue and 0.5 mL x min(-1) x g(-1) for models with a term for a mixture of gray matter and white matter tissues). These values were greater than those obtained from ROIs tracing the gray matter cortex using conventional H2(15)O autoradiography (approximately 0.40 mL x min(-1) x g(-1)). Among the four models, configurations that included two parallel tissue compartments demonstrated better results with regards to the agreement of tissue time-activity curve and the Akaike's Information Criteria. Error sensitivity analysis suggested the model that fits three parameters of the gray matter CBF, the gray matter fraction, and the white matter fraction with fixed white matter CBF as the most reliable and suitable for estimating the gray matter CBF. Reproducibility with this model was 11% for estimating the gray matter CBF. The volume of gray matter tissue can also be estimated using this model and was significantly correlated with the results from the stereologic analysis. However, values were significantly smaller compared with those measured by stereologic analysis by 40%, which can not be explained by the methodologic errors. In conclusion, the partial volume correction was essential in quantitation of regional CBF. The method presented in this article provided the PVE-corrected regional CBF in the cortical gray matter tissue. This study also suggests that further studies are required before using MRI derived anatomic information for PVE correction in PET.

Animals↗
PubMed2000

Quantitation of regional cerebral blood flow corrected for partial volume effect using O-15 water and PET: II. Normal values and gray matter blood flow response to visual activation.

One of the most limiting factors for the accurate quantification of physiologic parameters with positron emission tomography (PET) is the partial volume effect (PVE). To assess the magnitude of this contribution to the measurement of regional cerebral blood flow (rCBF), the authors have formulated four kinetic models each including a parameter defining the perfusable tissue fraction (PTF). The four kinetic models used were 2 one-tissue compartment models with (Model A) and without (Model B) a vascular term and 2 two-tissue compartment models with fixed (Model C) or variable (Model D) white matter flow. Furthermore, rCBF based on the autoradiographic method was measured. The goals of the study were to determine the following in normal humans: (1) the optimal model, (2) the optimal length of fit, (3) the model parameters and their reproducibility, and (4) the effects of data acquisition (2D or 3D). Furthermore, the authors wanted to measure the activation response in the occipital gray matter compartment, and in doing so test the stability of the PTF, during perturbations of rCBF induced by visual stimulation. Eight dynamic PET scans were acquired per subject (n = 8), each for a duration of 6 minutes after IV bolus injection of H2(15)O. Four of these scans were performed using 2D and four using 3D acquisition. Visual stimulation was presented in four scans, and four scans were during rest. Model C was found optimal based on Akaike's Information Criteria (AIC) and had the smallest coefficient of variance after a 6-minute length of fit. Using this model the average PVE corrected rCBF during rest in gray matter was 1.07 mL x min(-1) x g(-1) (0.11 SD), with an average coefficient of variance of 6%. Acquisition mode did not affect the estimated parameters, with the exception of a significant increase in the white matter rCBF using the autoradiographic method (2D: 0.17 mL x min(-1) x g(-1) (0.02 SD); 3D: 0.21 mL x min(-1) x g(-1) (0.02 SD)). At a 6-minute fit the average gray matter CBF using Models C and D were increased by 100% to 150% compared with Models A and B and the autoradiographic method. There were no significant changes in the perfusable tissue fraction by the activation induced rCBF increases. The largest activation response was found using Model C (median = 39.1%). The current study clearly demonstrates the importance of PVE correction in the quantitation of rCBF in normal humans. The potential use of this method is to cost-effectively deliver PVE corrected measures of rCBF and tissue volumes without reference to imaging modalities other than PET.

Adult↗
PubMed2000

Brain activation during mental transformation of size.

Visual comparison between different-sized objects with respect to shape can be done by encoding one of the objects as a mental image, transforming the image to the size format of the other object, and then testing for a match (Bundesen, C., & Larsen, A. [1975]. Visual transformation of size. Journal of Experimental Psychology: Human Perception and Performance, 1, 214-220). To identify the brain structures implicated in mental transformation of size, we measured the distribution of regional cerebral blood flow (rCBF) by positron emission tomography (PET) in 12 normal subjects who compared random stimulus patterns with respect to shape regardless of variations in size in a one-back match-to-sample paradigm. Each subject was PET-scanned 12 times during repetitive injections of H(2)(15)O. In one condition (three scans), all stimulus patterns were small. In a second condition (three scans), all stimuli were large. In the third condition (six scans), the stimuli alternated between small and large. Mental transformation of size should occur in the alternating-size condition but not in the fixed-size conditions. As expected, behavioral measures (reaction time [RT], d', beta) were nearly the same for the two fixed-size conditions but mean RT was longer and d' smaller in the alternating-size condition. Changes in rCBF specific to mental transformation of size were estimated by contrasting the alternating-size with the fixed-size conditions by use of statistical parametric mapping (SPM96) at a threshold of p <. 05 corrected for multiple comparisons. The detected brain structures implicated in mental transformation of size were primarily located in the dorsal pathways, comprising structures in the occipital, parietal, and temporal transition zone (predominantly in the left hemisphere), posterior parietal cortex (bilaterally), area MT/V5 (left), and vermis (bilaterally). Contrasts between the two fixed-size conditions showed significant effects in only the occipital cortex.

Adult↗
PubMed2000

Apoliprotein E and multiple sclerosis: impact of the epsilon-4 allele on susceptibility, clinical type and progression rate.

The purpose of this study was to investigate the relation between APOE genotype and Multiple Sclerosis (MS) in a genetically homogeneous population. We examined 240 patients consulting the MS-clinic during a period of 3 years (1996 - 1999). The mean age of the patients was 41.7 years (range 19 - 80 Y, SD 10.0 Y). As a measure of the progression rate (PR) the last registered Expanded Disability Status Scale (EDSS) score was divided by the time span (years) from disease onset until the latest assessment. The APOE genotype was determined from saliva and/or blood samples using PCR-techniques. The prevalence of different APOE genotypes was compared with the allele-distribution in a population of 361 persons from a Danish cross-sectional population study. The frequency of APOE-epsilon 4/epsilon 4 homozygotes was significantly higher in the MS-group as compared to controls (P<0.05, odds ratio: 2.3), whereas the frequency distribution of other genotypes did not differ significantly. The rate of progression was significantly faster in the APOE-epsilon 4/epsilon 4 homozygotes compared to other genotypes in the MS group (P<0.05). This study suggests that the APOE-epsilon 4/epsilon 4 homozygotes have an increased risk of developing MS. MS patients with the APOE-epsilon 4/epsilon 4 allele may also have an increased rate of disease progression. Multiple Sclerosis (2000) 6 226 - 230

Adult↗
PubMed1999

A longitudinal study of cerebral glucose metabolism, MRI, and disability in patients with MS.

OBJECTIVE: To study the time-related changes in cerebral metabolic rate of glucose (CMRglc) in MS patients and to correlate these with changes in MRI lesion load and disability. BACKGROUND: Measurements of MRI lesion load and neurologic disability are used widely to monitor disease progression in longitudinal studies of MS patients, but little is known about the associated changes in cerebral neural function. METHODS: The authors studied 10 patients with clinically definite MS who underwent serial measurements of CMRglc, MRI T2-weighted total lesion area (TLA), and clinical evaluation of disability (Expanded Disability Status Scale [EDSS]) over a period of approximately 2 years (three examinations). CMRglc was calculated using PET and 18-fluorodeoxyglucose (FDG). RESULTS: The global cortical CMRglc decreased with time (p<0.001) and the most pronounced reductions of CMRglc were detected in frontal and parietal cortical areas. There was a statistically significant increase of disability (p<0.01) and TLA (p<0.05) measurements during the study, but changes in CMRglc were not correlated to changes in TLA and EDSS. CONCLUSIONS: Global cortical cerebral metabolism in MS is decreased significantly during a 2-year observation period, suggesting a deterioration of cortical activity with disease progression. The time-related changes of cortical CMRglc are statistically stronger than changes in TLA measurements and neurologic disability, and might be a useful secondary measure of treatment efficacy.

Adult↗
PubMed1999

Determination of relative CMRO2 from CBF and BOLD changes: significant increase of oxygen consumption rate during visual stimulation.

The blood oxygenation level-dependent (BOLD) effect in functional magnetic resonance imaging depends on at least partial uncoupling between cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) changes. By measuring CBF and BOLD simultaneously, the relative change in CMRO2 can be estimated during neural activity using a reference condition obtained with known CMRO2 change. In this work, nine subjects were studied at a magnetic field of 1.5 T; each subject underwent inhalation of a 5% carbon dioxide gas mixture as a reference and two visual stimulation studies. Relative CBF and BOLD signal changes were measured simultaneously using the flow-sensitive alternating inversion recovery (FAIR) technique. During hypercapnia established by an end-tidal CO2 increase of 1.46 kPa, CBF in the visual cortex increased by 47.3 +/- 17.3% (mean +/- SD; n = 9), and deltaR2* was -0.478 +/- 0.147 sec(-1), which corresponds to BOLD signal change of 2.4 +/- 0.7% with a gradient echo time of 50 msec. During black/white visual stimulation reversing at 8 Hz, regional CBF increase in the visual cortex was 43.6 +/- 9.4% (n = 18), and deltaR2* was -0.114 +/- 0.086 sec(-1), corresponding to a BOLD signal change of 0.6 +/- 0.4%. Assuming that CMRO2 does not change during hypercapnia and that hemodynamic responses during hypercapnia and neural stimulation are similar, relative CMRO2 change was determined using BOLD biophysical models. The average CMRO2 change in the visual cortex ranged from 15.6 +/- 8.1% (n = 18) with significant cerebral blood volume (CBV) contribution to 29.6 +/- 18.8% without significant CBV contribution. A weak positive correlation between CBF and CMRO2 changes was observed, suggesting the CMRO2 increase is proportional to the CBF increase.

Adult↗
PubMed1999

Generalizable patterns in neuroimaging: how many principal components?

Generalization can be defined quantitatively and can be used to assess the performance of principal component analysis (PCA). The generalizability of PCA depends on the number of principal components retained in the analysis. We provide analytic and test set estimates of generalization. We show how the generalization error can be used to select the number of principal components in two analyses of functional magnetic resonance imaging activation sets.

Algorithms↗
PubMed1999

Brain activation during dichotic presentations of consonant-vowel and musical instrument stimuli: a 15O-PET study.

Dichotic listening means that two different stimuli are presented at the same time, one in each ear. This technique is frequently used in experimental and clinical studies as a measure of hemispheric specialization. The primary aim of the present study was to record regional changes in the distribution of cerebral blood flow (CBF) with the 15O-PET technique to dichotically presented consonant-vowel (CV) and musical instrument stimuli, in order to test the basic assumption of differential hemispheric involvement when stimuli presented to one ear dominate over stimuli presented in the other ear. All stimuli were 380 ms in duration with a 1000 ms interstimulus interval, and were presented in blocks of either CV-syllable or musical instrument pairs. Twelve normal healthy subjects had to press a button whenever they detected a CV-syllable or a musical instrument target in a stream of CV- and musical instrument distractor stimuli. The targets appeared equally often in the right and left ear channel. The CV-syllable and musical instrument targets activated bilateral areas in the superior temporal gyri. However, there were significant interactions with regard to asymmetry of the magnitude of peak activation in the significant activation clusters. The CV-syllables resulted in greater neural activation in the left temporal lobe while the musical instruments resulted in greater neural activation in the right temporal lobe. Within-subjects correlations between magnitude of dichotic listening and CBF asymmetry were, however, non-significant. The changes in neural activation were closely mimicked by the performance data which showed a right ear superiority in response accuracy for the CV-syllables, and a left ear superiority for the musical instruments. In addition to the temporal lobe activations, there were activation tendencies in the left inferior frontal lobe, right dorsolateral prefrontal cortex, left occipital lobe, and cerebellum.

Adult↗
PubMed1999

The Kety-Schmidt technique for repeated measurements of global cerebral blood flow and metabolism in the conscious rat.

Cerebral activation will increase cerebral blood flow (CBF) and cerebral glucose uptake (CMRglc) more than it increases cerebral uptake of oxygen (CMR(O2)). To study this phenomenon, we present an application of the Kety-Schmidt technique that enables repetitive simultaneous determination of CBF, CMR(O2), CMRglc and CMRlac on awake, non-stressed animals. After constant intravenous infusion with 133Xenon, tracer infusion is terminated, and systemic arterial blood and cerebral venous blood are continuously withdrawn for 9 min. In this paper, we evaluate if the assumptions applied with the Kety-Schmidt technique are fulfilled with our application of the method. When measured twice in the same animal, the intra-individual variation for CBF, CMR(O2), and CMRglc were 10% (SD: 25%), 8% (SD: 25%), and 9% (SD: 28%), respectively. In the awake rat the values obtained for CBF, CMR(O2) and CMRglc were 106 mL [100 g](-1) min(-1), 374 micromole [100 g](-1) min(-1) and 66 micromole [100 g](-1) min(-1), respectively. The glucose taken up by the brain during wakefulness was fully accounted for by oxidation and cerebral lactate efflux. Anaesthesia with pentobarbital induced a uniform reduction of cerebral blood flow and metabolism by approximately 40%. During halothane anaesthesia CBF and CMRglc increased by approximately 50%, while CMR(O2) was unchanged.

Animals↗
PubMed1999

High dose insulin does not increase glucose transfer across the blood-brain barrier in humans: a re-evaluation.

BACKGROUND: This study re-evaluates previously published data on blood-brain barrier transfer coefficients in humans exposed to high insulin levels. DESIGN: In this study of seven volunteers, global blood-brain barrier permeability to glucose and phenylalanine was measured by means of the intracarotid double-indicator method before, during, and after an insulin-glucose clamp. Data were reanalyzed by means of a mathematical model that takes capillary heterogeneity and labelled glucose backflux from the brain into account. RESULTS: The permeability-surface area product (PS) for glucose transport from the blood into the brain, PS1, was 0.145 (0.102-0.211) (median and quartiles), 0.146 (0.113-0.259), and 0.157 (0.133-0.181) ml g-1 min-1 before, during, and after insulin challenge, respectively. In six of the subjects, PS for transport from brain to blood over the brain glucose distribution volume, PS2/Ve decreased under hyperinsulinemia, from a baseline value of 6.56 (3.0-14.9) to 3.86 (1.41-5.32), and restored to a value of 3.8 (2.8-12.1) min-1 after insulin challenge. This decrease in PS2/Ve is probably due to an increase in the brain glucose distribution volume induced by an insulin induced increased intracellular glucose uptake during the experiment. For phenylalanine (n = 5), PS1 was unchanged before, during, and after insulin challenge. In hyperinsulinemia, PS3/Ve for phenylalanine decreased in all subjects. CONCLUSION: We conclude that acutely elevated high plasma insulin levels in humans does not alter the brain uptake of glucose or phenylalanine from the blood. It seems, however, that high plasma insulin levels induce an increase in the movement of D-glucose and L-phenylalanine from the brain interstitial fluid into the intracellular compartment.

Adolescent↗
PubMed1999

A multidisciplinary memory clinic in a neurological setting: diagnostic evaluation of 400 consecutive patients.

This report describes the operation of a multidisciplinary university hospital memory clinic in a neurological setting, and the diagnostic evaluations in 400 consecutive patients referred for cognitive symptoms and possible dementia during a period of 27 months (1 September 1995-31 December 1997). The mean age of the patients was 63.6 years (range 19-97). On clinical and neuropsychological examination, 46% of the patients fulfilled DSM IV criteria for dementia, 5% had selective amnesia, and 14% had other selective cognitive deficits. The remaining patients had either no significant cognitive deficits (31%) or were not evaluable (4%). A wide range of disorders from the fields of neurology, psychiatry, neurosurgery and internal medicine were identified as the underlying etiologies for the cognitive symptoms. Potentially reversible conditions were observed in 26% of the patients, not including the 11% in whom no specific underlying disease was identified. Concomitant conditions or risk factors with a potential influence on cognitive functions were identified in 61% of the patients. Diagnostic evaluation of patients with mild to moderate cognitive symptoms and possible dementia is an integrated multidisciplinary task, which should focus on the identification of non-progressive and potentially reversible etiologies, co-morbidity, selective cognitive deficits, and rare or atypical neurological conditions, as well as on the early identification of common progressive dementia disorders.

Adult↗