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C Lamm

Publications and source records attributed to C Lamm.

At least 19 recordsLinked to original sources
PubMed2001

Evidence for premotor cortex activity during dynamic visuospatial imagery from single-trial functional magnetic resonance imaging and event-related slow cortical potentials.

A strong correspondence has been repeatedly observed between actually performed and mentally imagined object rotation. This suggests an overlap in the brain regions involved in these processes. Functional neuroimaging studies have consistently revealed parietal and occipital cortex activity during dynamic visuospatial imagery. However, results concerning the involvement of higher-order cortical motor areas have been less consistent. We investigated if and when premotor structures are active during processing of a three-dimensional cube comparison task that requires dynamic visuospatial imagery. In order to achieve a good temporal and spatial resolution, single-trial functional magnetic resonance imaging (fMRI) and scalp-recorded event-related slow cortical potentials (SCPs) were recorded from the same subjects in two separate measurement sessions. In order to reduce inter-subject variability in brain activity due to individual differences, only male subjects (n = 13) with high task-specific ability were investigated. Functional MRI revealed consistent bilateral activity in the occipital (Brodmann area BA18/19) and parietal cortex (BA7), in lateral and medial premotor areas (BA6), the dorsolateral prefrontal cortex (BA9), and the anterior insular cortex. The time-course of SCPs indicated that task-related activity in these areas commenced approximately 550-650 ms after stimulus presentation and persisted until task completion. These results provide strong and consistent evidence that the human premotor cortex is involved in dynamic visuospatial imagery.

Adult↗
PubMed2001

Restriction of task processing time affects cortical activity during processing of a cognitive task: an event-related slow cortical potential study.

As is known from psychometrics, restriction of task processing time by the instruction to respond as quickly and accurately as possible leads to task-unspecific cognitive processing. Since this task processing mode is used in most functional neuroimaging studies of human cognition, this may evoke cortical activity that is functionally not essential for the particular task under investigation. Using topographic recordings of event-related slow cortical potentials, two experiments have been performed to investigate whether cortical activity during processing of a visuo-spatial imagery task is substantially influenced by the time provided to process the task. Furthermore, it was investigated whether this effect is additionally modulated by a subject's task-specific ability. The instruction to respond as quickly and accurately as possible led to increased negative slow cortical potential amplitudes over parietal and frontal regions and significantly interacted with task-specific ability. While cortical activity recorded over parietal and frontal regions was different between subjects with low and high spatial ability when processing time was unrestricted, no such differences were found between ability groups when subjects were instructed to answer both quickly and accurately. These results suggest that restricting processing time has considerable effects on the amount and the pattern of brain activity during cognitive processing and should be taken into account more explicitly in the experimental design and interpretation of neuroimaging studies of cognition.

Adolescent↗
PubMed2001

Co-registration of EEG and MRI data using matching of spline interpolated and MRI-segmented reconstructions of the scalp surface.

Accurate co-registration of MRI and EEG data is indispensable for the correct interpretation of EEG maps or source localizations in relation to brain anatomy derived from MRI. In this study, a method for the co-registration of EEG and MRI data is presented. The method consists of an iterative matching of EEG-electrode based reconstructions of the scalp surface to scalp-segmented MRIs. EEG-electrode based surface reconstruction is achieved via spline interpolation of individually digitized 3D-electrode coordinates. In contrast to other approaches, neither fiducial determination nor any additional provisions (such as bite bars, other co-registration devices or head shape digitization) are required, and co-registration errors associated with inaccurate fiducial determination are avoided. The accuracy of the method was estimated by calculating the root-mean-square (RMS) deviation of spline interpolated and MRI-segmented surface reconstructions in 20 subjects. In addition, the distance between co-registered and genuine electrode coordinates was assessed via a simulation study, in which surface reconstruction was based on virtual electrodes determined on the scalp surface of a high-resolution MRI data set. The mean RMS deviation of surface reconstructions was 2.43 mm, and the maximal distance between any two matched surface points was 5.06 mm. The simulated co-registration revealed a mean deviation of genuine and co-registered electrode coordinates of 0.61 mm. It is concluded that surface matching using spline interpolated reconstructions of scalp surfaces is a precise and highly practicable method to co-register EEG and MRI data.

Adult↗
PubMed2001

Direct current auditory evoked potentials during wakefulness, anesthesia, and emergence from anesthesia.

Direct current auditory evoked potentials (DC-AEPs) are a sensitive indicator of depth of anesthesia in animals. However, they have never been investigated in humans. To assess the potential usefulness of DC-AEPs as an indicator of anesthesia in humans, we performed an explorative study in which DC-AEPs were recorded during propofol and methohexital anesthesia in humans. DC-AEPs were recorded via 22 scalp electrodes in 19 volunteers randomly assigned to receive either propofol or methohexital. DC-AEPs were evoked by binaurally presented 2-s, 60-dB, 800-Hz tones; measurements were taken during awake baseline, anesthesia, and emergence. Statistical analysis included analysis of variance and discriminant analysis of data acquired during these three conditions. About 500 ms after stimulus presentation, DC-AEPs could be observed. These potentials were present only during baseline and emergence-not during anesthesia. Statistically significant differences were found between baseline and anesthesia and between anesthesia and emergence. In conclusion, similar effects, as reported in animal studies of anesthetics on the DC-AEPs, could be observed in anesthetized humans. These results demonstrate that DC-AEPs are potentially useful in the assessment of cortical function during anesthesia and might qualify the method for monitoring anesthesia in humans.

Adult↗
PubMed2000

Excessive daytime sleepiness in patients suffering from different levels of obstructive sleep apnoea syndrome.

Excessive daytime sleepiness (EDS) is a frequent symptom of patients with obstructive sleep apnoea (OSA). EDS is a high-risk factor for accidents at work and on the road. Thirty untreated patients with different levels of severity of OSA were studied concerning night sleep and EDS. The criterion for severity was the respiratory disturbance index (RDI): 15 patients were classified as 'moderately' apnoeic (RDI < 40), 15 as 'severely' apnoeic (RDI > 40). Following night-time polysomnography, objective and subjective aspects of EDS were studied. To assess objective EDS the Maintenance of Wakefulness Test (MWT) and a computer-based vigilance performance test were used. Subjective EDS was determined using the Stanford Sleepiness Scale (SSS), the Epworth Sleepiness Scale (ESS) and the Visual Analogue Scales for Performance (VAS-P) and Tiredness (VAS-T). Well-being was assessed using the Scale of Well-Being by von Zerssen (Bf-S/Bf-S'). Severe apnoea patients spent more time in stage 1 and less in slow-wave sleep. MWT latencies tended to be shorter in the severe apnoea group. Vigilance testing revealed no group differences. Patients with moderate apnoea described themselves as more impaired in all subjective scales, but only SSS scores reached statistical significance. Our results suggest that there is no simple correlation between polysomnographic and respiratory sleep variables at night on the one hand, and the extent of EDS on the other hand. Furthermore, subjective and objective evaluation of EDS does not yield the same results. New approaches which allow a more detailed analysis of night sleep and daytime function are required to identify high-risked patients.

Circadian Rhythm↗
PubMed1999

Differences in the ability to process a visuo-spatial task are reflected in event-related slow cortical potentials of human subjects.

Recent positron emission tomography (PET) and electroencephalographic (EEG) studies suggest that higher ability in a cognitive task is associated with a more efficient neuronal processing of this task. However, the validity and generalizability of these studies is limited for several reasons. We investigated 20 male and 18 female human subjects with good vs. poor spatial ability performing a visuo-spatial task (cube test). Processing-related slow event-related potentials were recorded via 22 electrodes, evenly distributed over the scalp. Significant differences between good and poor performers were found in both sexes: poor subjects showed higher activity in the parietal region, and their topography was more extended into fronto-central regions. Since the amount and topography of brain activity may vary considerably depending on subjects' ability, we conclude that careful (experimental) control of task-specific ability of subjects is mandatory for cognitive neuroscience studies.

Adult↗
PubMed1999

Evaluation of home audiotapes as an abbreviated test for obstructive sleep apnea syndrome (OSAS) in children.

Snoring occurs commonly in children and is sometimes associated with obstructive sleep apnea syndrome (OSAS). Based on clinical history alone, it is difficult to distinguish primary snoring, characterized by noisy breathing during sleep without apnea or hypoventilation, from snoring indicative of OSAS. An overnight polysomnogram (PSG) is required to establish a definitive diagnosis of OSAS. Because sleep evaluations are costly and resources are limited, we evaluated whether a home audiotape recording could accurately identify children with OSAS. We studied 36 children referred by pediatricians and otolaryngologists for possible OSAS. Parents completed a questionnaire about their child's sleep and breathing and made a 15-min audiotape of the child's breath sounds during sleep. Overnight PSGs were performed on all patients. There were 29 patients who completed the study: 15 patients in the Primary Snoring group (apnea/hypopnea index < 5) and 14 patients in the OSAS group (apnea/hypopnea index > or = 5). No significant statistical differences existed between the two groups for physical characteristics or questionnaire responses. Seven observers analyzed the audiotapes for the presence of a struggle sound and respiratory pauses. The median sensitivity of the audiotape as a predictor of OSAS was 71% (range 43-86%), and the median specificity was 80% (range 67-80%). The presence of a struggle sound on the audiotape was the parameter most predictive of OSAS. There was a good level of agreement among the seven audiotape observers, as demonstrated by a mean and range kappa statistic of 0.70 (0.50-0.93) for the 21 pairs of observers. Using a clinical score to predict OSAS, the sensitivity was 46%, and the specificity was 83%. We conclude that findings on a home audiotape can be suggestive of OSAS, but are not sufficiently specific to reliably distinguish primary snoring from OSAS.

Child↗
PubMed1999

Graft coronary artery disease is strongly related to the aetiology of heart failure and cellular rejections.

AIMS: To identify risk factors for the development of coronary artery disease after heart transplantation. METHODS AND RESULTS: In consecutive heart transplanted patients, who underwent coronary angiography at the first year follow-up, the aetiology of heart failure in 113 was ischaemic heart disease or dilated cardiomyopathy. Development of clinically significant graft coronary artery disease was analysed vs recipient and donor pre- and post-transplantation variables. At 1, 5 and 9 years follow-up, coronary artery disease had developed in 4%, 16%, and 20% of the included patients, respectively. Among patients with ischaemic heart disease as the aetiology of heart failure, 38% developed graft coronary artery disease, while the corresponding figure for patients with dilated cardiomyopathy was 9% (P<0.001) during 9 years of follow-up. In multivariate regression analysis, the aetiology of ischaemic heart disease and the number of cellular rejections were independent predictors of developing graft coronary artery disease, with risk ratios of 5.8, (95% confidence interval of 2.2-14.8 (P=0.0003)) and 3.3, (95% confidence interval of 1.7-6.5 (P=0.0004)), respectively. Classical risk factors for coronary artery disease did not influence the development of graft coronary artery disease. CONCLUSIONS: Ischaemic heart disease as the aetiology of heart failure and the number of cellular rejections were powerful independent predictors of development of graft coronary artery disease following heart transplantation. The low incidence of graft coronary artery disease among patients with dilated cardiomyopathy implies that coronary angiography after heart transplantation can be made on a more selective basis.

Adolescent↗
PubMed1998

Sex differences in oral asymmetries during wordrepetition.

During speech production the right side of the mouth is opened to a larger degree in most people. This facial asymmetry is thought to be related to a left hemisphere dominance in language processing and/or motor programming. We investigated asymmetrical lip separations during discrete or serial word productions in right handed persons. The results revealed a right sided lip separation bias in both genders during discrete word production in which the words had to be uttered once. As soon as the words had to be produced continuously, however, a clear sex difference appeared with males having the usual right bias but females now showing no clear asymmetry, with a tendency for larger lip separations on the left side. These results suggest the existence of two separate neural systems from which one controls the discrete task and which is left hemisphere dominant in both genders. The other is probably involved in serial word productions and shows a sex difference with regard to its asymmetry pattern.

Adult↗
PubMed1998

Coronary aneurysms in patients with autosomal dominant polycystic kidney disease.

Patients with autosomal dominant polycystic kidney disease (ADPKD) have an increased risk of intracranial aneurysms. Reports on arterial aneurysms in other locations have not been conclusive. The present study was initiated to investigate the prevalence of coronary aneurysms. Thirty ADPKD patients who had undergone coronary angiography on clinical indication were identified, 15 after renal transplantation. For each ADPKD patient, a control patient was identified with end-stage renal disease, investigated by coronary angiography, and matched for age, sex, and time relation to transplantation. All angiograms were retrieved and reevaluated with respect to aneurysms, defined as an increase in artery diameter by 50% or more, as well as to pathologic ectasias not fulfilling this criterion. Aneurysms were detected in four ADPKD patients and two control subjects. Five more ADPKD patients, but none of the control subjects, had minor ectasias. One ADPKD patient had a dissecting aortic aneurysm, and another died of aortic dissection during bypass surgery. This study adds to the evidence of an increased risk of extracranial aneurysms in ADPKD patients.

Cardiovascular Diseases↗
PubMed1997

Morbidity and use of medical resources in patients with chest pain and normal or near-normal coronary arteries.

To evaluate morbidity and use of medical resources in patients with chest pain and normal or near-normal coronary angiograms: 2,639 consecutive patients who underwent coronary angiograms due to chest pain were registered. Two years thereafter all patients who showed normal or near-normal coronary angiograms were approached with a questionnaire regarding hospitalization during the last 4 years (2 years before and 2 years after angiography). All medical files were also examined. Of the patients who underwent angiography, 163 (6%) had no significant stenoses, and of these, 113 showed complete normal angiograms and 50 showed mild (i.e. <50%) stenoses. During the 2 years before diagnostic angiogram, 66% of the patients were hospitalized compared with only 35% during 2 years after angiography (p <0.001). The reduction in hospitalization was due to curtailed utilization of medical resources for cardiac reasons; mean days in hospital was 6.6 days before angiography versus 2.8 days after (p <0.001). There were no significant differences in hospitalization when comparing patients with mild stenoses and completely normal angiograms. There were, furthermore, no differences between patients with positive or negative exercise tests. Thus, the need for hospitalization is significantly reduced after a diagnostic angiogram reveals normal or near-normal coronary arteries.

Adult↗
PubMed1997

Polysomnographic findings in a patient with the mitochondrial encephalomyopathy NARP.

A 23-year-old woman with the mitochondrial encephalomyopathy NARP (neurogenic muscle weakness, ataxia, and retinitis pigmentosa) presented with symptoms of obstructive sleep apnea (OSA). An overnight polysomnogram (PSG) showed apnea, EEG slowing, and a paucity of sleep spindles. The patient had a tracheostomy for OSA, and 5 months later she had normal EEG patterns and marked clinical improvement. We propose that patients with mitochondrial encephalomyopathies should have sleep evaluations if the history suggests OSA.

Adult↗
PubMed1996

Magnetic resonance imaging in the follow-up of patients after aortic root reconstruction.

Long-term survival after replacement of the aortic root with a composite graft is improving. Late deaths are in several cases due to complications related to the previous surgery or to pathologies of the remaining aorta. Regular follow-up of these patients is of paramount importance. The purpose of this study is to evaluate the reliability of magnetic resonance imaging (MRI) in such cases. Twenty-seven patients (9 dissections and 18 aneurysms) who had undergone replacement of the aortic root with a composite graft were studied 20 to 167 months after surgery using magnetic resonance imaging with a 1.5 Tesla magnet. The left-ventricular outflow tract, the mechanical valve function, the proximal part of the coronary arteries, the graft, and the remaining aorta could be examined. No aortic insufficiency, ectasy of the proximal part of the coronaries, or pseudoaneurysms were seen. A widening of the remaining ascending aorta was noted in 4 cases. A still open, dissected pipe was visualized in 7 patients. Our conclusions are that MRI provides excellent images of the thoracic and abdominal aorta following surgical repair. The examination is becoming cost-competitive. More import is its very low risk for the patient group considered here: since it is non-invasive and requires no contrast medium or X-ray exposure, examinations can be repeated as required.

Aortic Dissection↗
PubMed1995

Assessment of coronary artery stenosis during PTCA by measurement of the trans-stenotic pressure gradient. Comparison with quantitative coronary angiography.

A fibreoptic pressure sensor mounted on an 0.018 inch guidewire (Pressure Guide, RadiMedical Systems, Uppsala, Sweden) was used to measure the trans-stenotic pressure gradient in 20 patients admitted for percutaneous transluminal coronary angioplasty (PTCA) of a single, discrete stenosis. Pressure measurements were made both at rest and during maximal vasodilatation induced by intracoronary injection of papaverine. From the ratio of distal coronary pressure divided by the proximal pressure, the relative coronary flow reserve was calculated. The aim of the study was to compare the different pressure-derived parameters by correlating them to stenosis geometry estimated by quantitative coronary angiography. There was a moderate correlation between baseline pressure gradient and percent area stenosis; r = 0.64, P < 0.001 and minimal cross-sectional area; r = 0.45, P < 0.005. A higher correlation was found between hyperaemic pressure gradient and area stenosis (r = 0.80, P < 0.001) and minimal cross-sectional areas, respectively (r = 0.55, P < 0.005). The best correlation was found between relative coronary flow reserve and area stenosis (r = 0.86, P < 0.001) and minimal cross-sectional area (r = 0.70, P < 0.001). In conclusion, pressure measurement using a pressure guidewire is useful as a complement to angiography in evaluation of coronary stenoses during PTCA. Pressures should be measured during maximal vasodilatation. Relative coronary flow reserve calculated from the pressure measurements provides additional information about the fraction of normal maximal flow possible in the presence of a stenosis.

Aged↗
PubMed1994

Sleep-disordered breathing in children.

The recent better recognition of children with sleep-disordered breathing has led to the evaluation of more patients in the sleep laboratory and thence to the definition of sleep problems among children in a variety of clinical situations. Further investigation of these abnormalities is necessary to ascertain the clinical significance of these disorders.

Child↗
PubMed1993

High-fidelity translesional pressure gradients during percutaneous transluminal coronary angioplasty: correlation with quantitative coronary angiography.

A fiberoptic pressure sensor mounted on an 0.018-inch guidewire (Pressure Guide) was used to measure the transstenotic pressure gradient in 30 patients undergoing percutaneous transluminal coronary angioplasty (PTCA) with lesions considered suitable for quantitative coronary angiographic (QCA) assessment. The aim of the study was to correlate pressure gradients with parameters obtained with QCA. After intracoronary injection of 125 micrograms of nitroglycerin, multiple angiographic views were taken of the lesion. The Pressure Guide fiberoptic sensor was then positioned distal to the stenosis and the pressure gradients were recorded before and after PTCA. There was a significant correlation between mean pressure gradients (delta P) and percent diameter stenosis (r = 0.73; p < 0.001) and absolute stenosis diameter (r = -0.67; p < 0.001) and with percent area stenosis (r = 0.69; p < 0.001) and absolute stenosis area (r = -0.63; p < 0.001). The closest relationship, though, was found with stenotic flow reserve (SFR), which is an integrated parameter calculated from QCA. This relationship can be described by the equation: delta P = 65.2 - 12.6.SFR (r = -0.79; p < 0.001). With a measured gradient of > 15 mm Hg, the sensitivity was 94% and the specificity 96% to predict an SFR < 3.5. In conclusion, a statistically significant relationship could be found between stenosis pressure gradients and angiographic parameters in this study with lesions without complicated morphology. The independent information obtained by pressure gradient measurement may be of particular value in intermediately severe lesions or in stenoses where the angiographic assessment otherwise is difficult.

Aged↗