Search PubMed⌕ Search

Biomedical subjects

L Deecke

Publications and source records attributed to L Deecke.

At least 55 records · Page 3Linked to original sources
PubMed2000

Idiothetic orientation and path integration in unilateral hippocampal atrophy and sclerosis.

We determined the effects of hippocampal lesions on idiothetic spatial orientation by exposing 14 patients with unilateral hippocampal atrophy and/or sclerosis (HAS) and 10 normal controls to random rotational displacements (+/-30 degrees -180 degrees ) in darkness and examined their ability to rotate themselves back to the initial position. In comparison to controls, the patients responses were distinctly hypometric (p<0.005). Patients with right hippocampal lesions showed a trend towards higher come back errors p = 0.08). Normal controls could maintain their accuracy over five consecutive trials. Patients, beginning with less accuracy, showed significant improvement after each trial (p<0.001). The findings suggest that unilateral HAS impair the immediate recall of idiothetic spatial information, but does not affect long-term spatial learning.

Adult↗
PubMed1999

A marker for differentiation of capabilities for processing of musical harmonies as detected by magnetoencephalography in musicians.

This investigation was designed to study the characteristics of a marker for harmonic processing and to test whether it could be used for differentiating harmonic processing capabilities. The first three chords of an ordinary musical cadenca were presented to the left ear to establish a harmonic context followed by a harmonic or non-harmonic target tone. Cadencas were presented rapidly and randomly in different keys to render the task difficult. Results showed a specific P3m (magnetic P300) effect to the non-harmonic targets which was only visible in subjects with low target recognition errors. Low resolution electro-magnetic tomography current density maps showed P3m sources in the right temporoparietal, left temporoparietal and frontocentral brain areas with right temporoparietal sources being strongest and most reliable. The results offer new possibilities to selectively study harmonic variables in music processing.

Adult↗
PubMed1999

Different forms of human odor memory: a developmental study.

Recognizing odors is an important biological function, both in the animal kingdom as well as for humans. It has been debated whether there exist different forms of human odor memory. For verbal memory, the concept of recollection and familiarity for conscious and unconscious recognition is widely accepted. Here we introduce a similar model for human odor memory. We use a combination of an odor naming and odor recognition memory task to estimate the relationship between depth of processing and retention of olfactory information. A developmental approach with children, young adults, middle aged adults and elderly subjects was chosen in order to study the influence of age. Our results indicate the existence of two separable forms of odor memory depending on whether the odors were correctly or incorrectly named during the naming task. These two forms of odor memory were differently represented across the human age range. Intact familiarity-based memory was found in all age groups, whereas memory based on recollection was impaired in the elderly and not yet fully developed in children. Our data show, for the first time, two different forms of human odor memory across the human life span.

Adolescent↗
PubMed1999

Event-related potential correlates of false recognitions of faces.

In a recognition memory experiment we recorded event-related brain potentials (ERPs) following the presentation of faces. We compared correctly classified repetitions of faces (hits) with new faces classified as repeated (false alarms). Stimulus-related averaging yielded significantly more negative ERPs to false alarms between 750 and 900 ms after onset of stimulus presentation. With response-related averaging we found significantly more negative ERPs to false alarms within the last 100 ms before movement onset. The differential activity was distributed over central and frontal regions and was still present in the period after the response. We interpret the phenomenon as an electrophysiological manifestation of false recognition as described by Schacter et al. (Schacter, D.L., Norman, K.A. and Koutstaal, W., The cognitive neuroscience of constructive memory, Annu. Rev. Psychol., 49 (1998) 289-318). False recognition could be the result of a preliminary decision based on illusionary familiarity and be associated with post-retrieval processing.

Evoked Potentials↗
PubMed1999

C677T MTHFR mutation and factor V Leiden mutation in patients with TIA/minor stroke: a case-control study.

A common C677T mutation in the gene for the enzyme 5,10-methylenetetrahydrofolate reductase (5,10-MTHFR) has been linked to elevated levels of homocysteine and was therefore suspected to be a candidate genetic risk factor for arterial occlusive disease. Another mutation, factor V Leiden, has been established as a common hereditary risk factor for venous thrombosis, but its role in arterial disease remains controversial. We investigated the prevalence of both the C677T MTHFR mutation and the factor V Leiden mutation in 81 patients with transient ischemic attack (TIA) or minor stroke (MS) and in 81 age- and sex-matched control subjects free from clinically manifest vascular disease. We further compared clinical and laboratory data as well as clinical course of patients carrying the factor V Leiden mutation alone or in combination with the C677T MTHFR mutation and mutation-free patients. The prevalence of the MTHFR mutation did not differ between patients and control subjects with 11.1% homozygous carriers in both groups (OR for homozygous carriers 1.0; 95% CI 0.38-2.66). However, there was a trend towards a higher prevalence of carriers of factor V Leiden in patients (12.3%) than in control subjects (4.9%) (OR 2.75; 95% CI 0.83-9.17;p=0.09). Furthermore, we found some evidence that the combined occurrence of the C677T MTHFR mutation and factor V Leiden might unfavorably affect the clinical course of the disease, but the number of respective patients was small. Larger studies with a greater number of carriers of both the C677T MTHFR mutation and factor V Leiden seem therefore warranted.

Adult↗
PubMed1999

Abolished tilt suppression of the vestibulo-ocular reflex caused by a selective uvulo-nodular lesion.

Within the cerebellum several structures are considered to modulate the function of the vestibulo-ocular reflex (VOR). The nodulus and uvula have been implicated with the low-frequency components of the VOR, which are mediated by the velocity storage system. We report a patient with a selective lesion of the nodulus and ventral uvula. The findings suggest that nodulus and uvula normally exert an inhibitory effect on the velocity storage mechanism.

Cerebellum↗
PubMed1999

Neuroimage of voluntary movement: topography of the Bereitschaftspotential, a 64-channel DC current source density study.

The Bereitschaftspotential (BP) was recorded at 56 scalp positions when 17 healthy subjects performed brisk extensions of the right index finger. Aim of the study was to contribute to our understanding of the physiology underlying the BP and, in particular, to specify the situation at BP onset. For this purpose, the spatial pattern of the BP was analyzed in short time intervals (35 and/or 70 ms) starting 2.51 s before movement onset. For each time segment a spherical model of the BP was calculated by using spline interpolation. Then the spatial distribution of the electric potential at the scalp surface was transformed into a spatial distribution of current source densities (CSD map). Onset times of the BP and onset times of initial CSD-activity ranged between 2.23 and 1.81 s before movement onset. We selected a time window between 1.6 and 1.5 s before movement onset in order to analyze the spatial CSD pattern in each subject. In 10 subjects there was a significant current sink in the scalp area located over medial-wall motor areas (pre-SMA, SMA proper and anterior cingulate cortex: electrode positions C1, C2, FCz, Cz) in the absence of a significant current sink over the primary motor cortex (MI: electrode positions C3, CP3, and CP5). In three subjects significant current sinks were present at both sites and in another three subjects a current sink only over the lateral motor cortex was observed. In one subject no significant current sinks were measured. It is concluded that there is a large group of subjects (13/17) in whom BP at onset is associated with a current sink over medial-wall motor areas. At a later time interval (0.6 to 0.5 s before movement onset), significant current sinks were found in 13 subjects in medial and in 10 subjects in lateral recordings. These data were considered to be consistent with the hypothesis that, at least in a majority of subjects, medial-wall motor areas are activated earlier than lateral motor areas when organizing the initiation of a simple self-paced movement. Surface-recordings of the EEG do not allow further specification of cortical areas, which contribute to the current sinks. But in context with the current literature of the electrophysiology of nonhuman primates and of brain imaging in humans it is suggested that SMA and anterior cingulate cortex contribute to the current sink, the fronto-central midline, and that the primary motor cortex (MI) contributes to the current sink in the scalp area, which is located above MI and closely posterior to it.

Adult↗
PubMed1999

Kynurenine metabolism in Alzheimer's disease.

L-kynurenine (L-KYN) serves as a substrate for the synthesis of neurotoxic 3-OH-kynurenine (3-OH-KYN) and neuroprotective kynurenic acid (KYNA). KYNA is able to interact with ionotropic excitatory amino acid receptors that are involved in a variety of neurodegenerative disorders. The purpose of the present study was to investigate the biosynthetic machinery of KYNA in several regions of Alzheimer's disease (AD) brain. The endogenous levels of L-KYN, 3-OH-KYN and KYNA in frontal cortex, caudate nucleus, putamen, hippocampus, and cerebellum of 11 autopsy confirmed cases of AD and 13 age-matched controls were analyzed. Subsequently, the activity of two proteins responsible for the production of KYNA, kynurenine aminotransferases I and II (KAT I and KAT II), was investigated. There was a trend for a decrease of L-KYN and 3-OH-KYN in all examined regions of AD brain, as compared to controls. However, KYNA was increased significantly in the putamen and caudate nucleus of AD, by 192 and 177%, respectively. In other areas of AD brain only a minor increase of KYNA was present. Elevated KYNA in the caudate nucleus and putamen correlated with a significant increase of KAT I activities in both nuclei-157 and 147%, respectively. A minor increase of KAT II was measured only in the caudate nucleus of AD subjects. Kinetic analysis of KAT I and II performed in the caudate nucleus of AD patients revealed a marked increase of Vmax, by 207 and 274% of controls, respectively. Km value for L-KYN using pyruvate as amino acceptor was significantly higher for KAT II (247% of controls). The present data indicate an elevated kynurenine metabolism in AD brain. A marked increase of KYNA in the caudate nucleus and putamen may compensate the hyperactivity of the striato-frontal loop in AD brains. Blockade of NMDA receptors by KYNA may be responsible for impaired memory, learning and cognition in AD patients.

Aged↗
PubMed1999

Genetic and nongenetic factors influencing plasma homocysteine levels in patients with ischemic cerebrovascular disease and in healthy control subjects.

Moderately elevated plasma homocysteine levels have been established as an independent risk factor for atherosclerosis and its complications, including cerebrovascular disease. A common mutation (C677T) in the gene encoding for the enzyme methylenetetrahydrofolate reductase (MTHFR) has been linked to increased plasma homocysteine levels in homozygous carriers, particularly in the presence of low folate levels. However, the results of most of the previous studies suggest that the C677T MTHFR mutation is not a significant risk factor for arterial disease. This discrepancy might, at least partly, be due to the fact that plasma homocysteine levels are influenced by several other factors, including age, gender, renal function, and vitamin status. We investigated the relation between plasma homocysteine levels, the C677T MTHFR mutation, and these other factors in a population of 96 patients with transient ischemic attacks or minor strokes and in 96 age- and sex-matched healthy control subjects. We further tested the value of a multivariate model for the prediction of plasma homocysteine levels under particular consideration of the MTHFR mutation status. In the patients, plasma homocysteine levels were significantly higher than in the healthy control subjects. With regard to the MTHFR mutation, the distribution of the C/C, C/T, and T/T genotypes was not significantly different between patients and healthy control subjects. Univariate (linear regression) analysis revealed significant (positive) correlations between plasma homocysteine levels on the one hand and age and creatinine on the other, the latter particularly in subjects with creatinine levels in the upper quartile. Significant (negative) correlations were found between plasma homocysteine levels, vitamin B12, and folate levels. However, these relations could much better be expressed by means of a multiplicative regression model. T/T subjects exhibited slightly higher homocysteine levels than C/C and C/T subjects; however, the differences between the 3 genotypes were not significant. Multivariate (stepwise regression) analysis revealed age, vitamin B12 levels, folate levels, and creatinine levels as significant independent variables influencing plasma homocysteine levels, whereas the MTHFR mutation status and gender were removed from the model. Considering all 192 subjects, only 28.8% of the variance of plasma homocysteine levels could be accounted for by the model. However, in homozygous carriers of the MTHFR mutation, the predictive power of the model is very high, explaining 76.1% of the variance of plasma homocysteine levels. According to our results, the C677T mutation does not constitute a major risk factor for transient ischemic attack or minor stroke, even under consideration of other possibly confounding factors that are known to affect plasma homocysteine levels. However, it is possible to predict plasma homocysteine levels in homozygous carriers of the mutation with high accuracy. The knowledge of the MTHFR mutation status may therefore help to identify subjects at high risk for hyperhomocysteinemia.

Adult↗
PubMed1999

Early occipito-parietal activity in a word recognition task: an EEG and MEG study.

OBJECTIVE: We investigated early brain activity (under 200 ms after the stimulus onset) related to the encoding and the retrieval of verbal information. METHODS: First, we compared ERPs produced by words which were encoded to ERPs produced by words from following test phases (correctly identified repetitions and correctly classified new words) in two different experiments. Experiment 1 consisted of an intentional learning paradigm and experiment 2 consisted of an incidental learning paradigm. In addition, we conducted a control experiment (experiment 3), which was a continuous recognition task with two different repetition intervals. Secondly, we conducted a magnetoencephalographic (MEG) study to further investigate early brain activity (experiment 4). The same intentional learning paradigm as in experiment 1 was used. RESULTS: We found that ERPs elicited by correctly classified test words (repeated words and new words) of both experiment 1 and experiment 2 were significantly more negative going than the ERPs elicited by the study words. This effect was apparent between 100 ms and 200 ms after the stimulus onset and was distributed over occipital and parietal scalp locations. In the control task (experiment 3), these early potential differences were missing (for both repetition intervals). Early event-related fields (ERFs) were also found to depend on the situation of the study phase and the test phase. This activity difference peaked at 120 ms after the stimulus onset. The distributions of the difference magnetic fields were occipito-parietal and thus consistent with the findings of experiment 1 (EEG-experiment). CONCLUSION: Whether the effect we defined in the present study is due to an increase of activity during the test situation or due to a decrease of activity during the study situation remains unclear. However, it might reflect attentional processes within a word recognition task depending on whether a word is encoded or an effort of word retrieval has to be made.

Adult↗
PubMed1999

High resolution DC-EEG analysis of the Bereitschaftspotential and post movement onset potentials accompanying uni- or bilateral voluntary finger movements.

UNLABELLED: Movement-related potentials (MRPs, including Bereitschaftspotential, BP) were recorded using a 64 channel DC-EEG amplifier ("High Resolution DC-EEG", Nunez et al. 1994) in 18 subjects (Ss) to explore functions of the supplementary, the cingulate, and the primary motor area (SMA, CMA and MI). Spatial and temporal resolutions on single trials, single subject and grand average data were evaluated for preparation and execution of self-initiated index finger extensions (bilateral, right and left unilateral). Results showed that [1] MRPs consisted of six waves: Early component (BP1) of the MRPs, late component (BP2) of the MRPs, Motor potential (MP), Post movement positive potential (PMPP), Movement-evoked potential I (MEP I) and Movement-evoked potential II (MEP II). [2] Onset of BP1 was earliest in the mesial wall motor areas, SMA/CMA, then in the contralateral MI (conMI) and latest in the ipsilateral MI (ipsMI). [3] MRP amplitudes were maximum in the SMA/CMA in all three tasks. In the unilateral tasks, MRP amplitudes were higher in the conMI than they were in the ipsMI. [4] The early BP component (BP1) was always localized in the fronto-central midline (overlying the mesial wall motor areas SMA and CMA). BP2, MP, PMPP, MEP1 and MEP II showed clear lateralized distributions (contralaterally larger) for unilateral movement but not for bilateral movement. [5] BP2, MP, PMPP, MEPI and MEPII in bilateral movement are not just the mathematical sum of right and left unilateral movements on both hemispheres. [6] The three tasks influenced all six MRP components. [7] Current source density maps, which were relatively robust between different tasks, further demonstrated that BP1 stemmed from the fronto-central midline (mesial wall motor areas). [8] MANOVA showed that there were several statistically significant differences (p<0.001) across the multiple combinations between time points of the epoch (20), electrodes (56) and tasks (3). CONCLUSIONS: [1] SMA/CMA participates in preparation and initiation of volitional index finger extensions, while MI participates in their execution and performance. [2] BP1 stems primarily from the mesial wall motor areas, SMA and CMA. [3] SMA/CMA subserves the temporal organization of sequential movements and bimanual coordination.

Adult↗
PubMed1999

High resolution DC-EEG of the Bereitschaftspotential preceding anatomically congruent versus spatially congruent bimanual finger movements.

The purpose of the present study was to observe how the supplementary, cingulate and primary motor areas (SCMA, MI) participate in the spatiotemporal coordination of bimanual index finger movement and what role the SCMA plays. The Bereitschaftspotential (BP) was recorded using 64 channel direct current EEG (DC-EEG) to compare the anatomically congruent movements (abduction, adduction) with spatially congruent movements (both fingers to the right or left) in 16 normal volunteers. Subjects were required to move their two index fingers simultaneously in the horizontal plane (1) away from the midline (abduction), (2) toward the midline (adduction), (3) both index fingers to the right or (4) both fingers to the left. The results showed that there were significant differences (p<0.001) among the four tasks, across the 56 electrodes, and within the 20 different time points of the 3.5 s analysis epoch. BP amplitudes of the spatially congruent movements were significantly higher (p<0.05) than the ones of the anatomically congruent movements, and they were higher over the mesial wall motor areas SCMA than they were over the MIs. However, the significant differences differed between the left and right hemisphere in their amount and onset. The values of the difference ratio statistics between the SCMA and the MI indicated that the left hemisphere was more active than the right in our right-handed subjects for all tasks, particularly in the early (BP1) as compared to the late (BP2) component. Current source density mappings revealed that BP1 had its earliest onset in SCMA (6aalpha and 6abeta) for all four tasks. The onset times of BP2 were earlier and BP densities were higher in the spatially congruent tasks 3 and 4 as compared to the anatomically congruent tasks 1 and 2. Also, preparation (early component BP1) tended to start earlier and BP amplitudes tended to be higher for the spatially congruent tasks as compared to the anatomically congruent tasks.

Adult↗
PubMed1999

Health-related quality of life (HRQOL), activity of daily living (ADL) and depressive mood disorder in temporal lobe epilepsy patients.

We determined the interrelations of chronological age, age at seizure onset, duration of seizure disorder, cognitive functioning (IQ), scales of activities of daily living, depressive mood disorder and measures of health-related quality of life (HRQOL). Furthermore, we investigated the association of the laterality of seizure onset zone and absence/presence of hippocampal atrophy and/or sclerosis (HA/HS) with measures of HRQOL, activities of daily living (ADL) and depressive mood disorder. In the setting of pre-surgical epilepsy evaluation, a sample of 56 patients with temporal lobe epilepsy (TLE) was studied using the Bonner Skalen für Epilepsie (BPSE) and the depression inventory D-S of von Zerssen. Patients reported high levels of dependency on others and poor coping capabilities. Our data also showed specific ADL-behaviour suggesting social withdrawal and isolation. Our results indicate emotional impairment as a major problem in TLE, because 45% of our patients scored in the depressive range of the D-S depression scale. Depression score was found to be a powerful predictor of self-reported quality of life after adjusting for seizure-related variables, demographic variables and cognitive functioning (IQ). The only scale showing a significant laterality effect was ADL-home. No relationship between the dependent measures of HRQOL, ADL-social, ADL-cultural, depressive mood disorder and laterality of the epileptogenic zone or absence/presence of HA/HS was found. HRQOL and depressive mood disorder are strongly interrelated indicating that patients with depressive symptoms report lower quality of life and specific patterns of ADL. HRQOL, ADL and depressive mood disorder are largely independent of biological markers such as laterality of seizure onset zone and absence/presence of HA/HS in TLE.

Activities of Daily Living↗
PubMed1999

Bilateral subthalamic nucleus stimulation improves frontal cortex function in Parkinson's disease. An electrophysiological study of the contingent negative variation.

Parkinson's disease involves impaired activation of frontal cortical areas, including the supplementary motor area and prefrontal cortex, resulting from impaired thalamocortical output of the basal ganglia. Electrophysiologically, such impaired cortical activation may be seen as a reduced amplitude of the contingent negative variation (CNV), a slow negative potential shift reflecting cognitive processes associated with the preparation and/or anticipation of a response. Surgical interventions aimed at increasing basal ganglia-thalamic outflow to the cortex, such as electrical stimulation of the subthalamic nucleus with chronically implanted electrodes, have been shown to be effective in improving the clinical symptoms of Parkinson's disease. This study examined changes in cortical activity, as reflected in the CNV, associated with bilateral subthalamic nucleus stimulation in Parkinson's disease. The CNV was recorded from 10 patients with Parkinson's disease when on and off bilateral subthalamic nucleus stimulation, and was compared with the CNV of 10 healthy control subjects. Without subthalamic nucleus stimulation, Parkinson's disease patients showed reduced CNV amplitudes over the frontal and frontocentral regions compared with control subjects. With bilateral subthalamic nucleus stimulation, however, CNV amplitudes over the frontal and frontocentral regions were significantly increased. Results therefore suggest that impaired cortical functioning in Parkinson's disease, particularly within the frontal and premotor areas, is improved by subthalamic nucleus stimulation.

Adult↗
PubMed1999

Postural control and lifetime alcohol consumption in alcohol-dependent patients.

OBJECTIVES: The aim of this study was to examine the relationship between alcohol consumption and postural control in alcohol-dependent patients. MATERIAL AND METHODS: Posturographic measurements were performed in 82 abstinent patients and in 54 healthy controls. The findings in the patients were compared with those in the controls as well as with the daily alcohol consumption, the consumption during 6 months before the admission for alcohol withdrawal therapy and the estimated lifetime alcohol consumption. RESULTS: Postural control was impaired in alcohol-dependent patients compared to healthy controls. This impairment was related with the lifetime alcohol consumption, but not with the alcohol consumption per day and prior to admission, respectively. Comparing healthy controls, and alcohol-dependent patients with an estimated lifetime alcohol consumption of < 1000 kg and > or = 1000 kg revealed a significant increase in 6 of 8 sway parameters. Furthermore, the lifetime alcohol consumption increased significantly from patients with normal posturographic and clinical findings to those with abnormalities in both examinations. CONCLUSION: This study suggests that postural imbalance in abstinent alcohol-dependent patients is related to the lifetime alcohol consumption.

Adult↗
PubMed1999

Neurological function during long-term therapy with recombinant interferon alpha.

In 14 patients with myeloproliferative disorders associated with thrombocytosis, neurological and neuropsychological function were monitored prior to therapy with recombinant human interferon alpha (rIFN; dose 25 mU/week; range 10-35 mU/week) and after 3, 6, 9, and 12 months of treatment. No overt neurological side effects were observed except 1 case of cerebral insult, probably not treatment-related. Attention, memory function, and tapping improved significantly. The P2-N3 amplitudes of visually evoked potentials increased during normalization of platelet counts. Muscular strength and the amplitude of the compound muscle action potential of the median and peroneal nerves increased significantly in an inversely dose-related fashion. In patients with myeloproliferative disorders, long-term therapy with low to intermediate doses of rIFN does not seem to impair neurological function, but rather is associated with enhanced muscle power and the level of mental arousal.

Aged↗