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Biomedical subjects

J Dammers

Publications and source records attributed to J Dammers.

10 recordsLinked to original sources
PubMed2003

Synchronization tomography: a method for three-dimensional localization of phase synchronized neuronal populations in the human brain using magnetoencephalography.

We present a noninvasive technique which allows the anatomical localization of phase synchronized neuronal populations in the human brain with magnetoencephalography. We study phase synchronization between the reconstructed current source density (CSD) of different brain areas as well as between the CSD and muscular activity. We asked four subjects to tap their fingers in synchrony with a rhythmic tone, and to continue tapping at the same rate after the tone was switched off. The phase synchronization behavior of brain areas relevant for movement coordination, inner voice, and time estimation changes drastically when the transition to internal pacing occurs, while their averaged amplitudes remain unchanged. Information of this kind cannot be derived with standard neuroimaging techniques like functional magnetic resonance imaging or positron emission tomography.

Brain↗
PubMed2001

Using real patients in problem-based learning: students' comments on the value of using real, as opposed to paper cases, in a problem-based learning module in general practice.

OBJECTIVES: To explore the feasibility and value of using real patients as trigger material in problem-based learning (PBL). DESIGN: A questionnaire was given to all students participating in a PBL module including a question about 'the added value of using real, as opposed to paper cases', in problem-based learning. Resources used by students and assessment of feasibility were recorded by the course tutors. SETTING: A 7-week student-selected problem-based module in general practice in the fourth-year undergraduate medical curriculum, University of Newcastle upon Tyne. SUBJECTS: 69 students participating in the module over 2 years. RESULTS: All students valued the use of real patients. A total of 10 categories were identified, all congruent with accepted educational principles for effective adult learning. Real patients stimulated the use of a very wide range of resources and imaginative presentation of what had been learned. CONCLUSION: Real patients are potent trigger stimuli in problem-based learning. The use of real patients in this general practice-based module presented no organizational or ethical difficulties. Their use should be considered more widely.

Curriculum↗
PubMed2001

Disturbed facial affect recognition in patients with schizophrenia associated with hypoactivity in distributed brain regions: a magnetoencephalographic study.

OBJECTIVE: The authors sought to identify brain mechanisms underlying the well-documented facial affect recognition deficit in patients with schizophrenia. Since this deficit is stable over the course of the illness and relatively specific for schizophrenic disorders, it was expected that knowledge about the related brain mechanisms would provide substantial information about the pathophysiology of the illness. METHOD: Fifteen partly remitted schizophrenic inpatients and 12 healthy volunteers categorized facial expressions of emotion and performed two control tasks while magnetoencephalographic recordings were done by means of a 148-channel whole head system, which revealed foci of high cerebral activity and their evolution in time. Anatomical sites were defined through coregistrated magnetic resonance images. RESULTS: The magnetoencephalography data recorded in response to facial expressions of emotion revealed that patients generated weaker activations (primary current density) in inferior prefrontal, temporal, occipital, and inferior parietal areas at circumscribed latencies. Group differences did not occur in basic visual areas during a first sensory-related activation between 60 and 120 msec. Behavioral performance was associated with strength of activation in inferior prefrontal areas, the right posterior fusiform gyrus region, right anterior temporal cortex, and the right inferior parietal cortex. CONCLUSIONS: Disturbed facial affect recognition in schizophrenic patients might be a result of hypoactivity in distributed brain regions, some of them previously related to the pathophysiology of schizophrenic disorders. These regions are probably working within a spatially and temporally defined circuitry.

Adult↗
PubMed2000

Neuromagnetic localization of CMV generators using incomplete and full-head biomagnetometer.

Contingent magnetic variation (CMV) data were recorded in three healthy male subjects using a 2 x 37 biomagnetometer system. The experiment was repeated for one of the subjects using a 151 whole-head biomagnetometer; the same auditory GO/NOGO choice reaction time paradigm as in the first experiment was used, extended to include repetitions of identical runs and additional control conditions. Magnetic field tomography was applied to the averaged data of each subject, for each run and condition (e.g., GO/NOGO). An independent estimate of the current density in the brain was obtained every few milliseconds. The slow components were emphasized by integrating the square of the current density vector, pixel by pixel, revealing in each subject activity in the auditory cortex, sensorimotor cortex, inferior prefrontal area, and posterior inferior parietal area. The intersubject variability was large, but looking across subjects the auditory and sensorimotor cortex (which were best covered by the two probes) were consistently identified in each subject as contributing to the generation of the early and late slow CMV components. These findings were confirmed by the whole-head single-subject experiment, in which slow activity was also identified in the supplementary motor area (SMA) and posterior cingulate cortex (PCC), areas very likely missed in the first experiment because of the limited view of the twin system. The PCC and particularly the SMA activations were substantially reduced when identical runs were repeated.

Adult↗
PubMed2000

Real time processing of affective and cognitive stimuli in the human brain extracted from MEG signals.

The magnetoencephalography (MEG) signal was recorded while subjects watched a video containing separate blocks of affective and cognitive advertisements and recalled slides extracted from the video a day later. An earlier behavioural study using the same video material showed that the affective advertisements were better recalled and that administration of propranolol (a beta-adrenergic blocker) abolished this effect. Magnetic field tomography (MFT) was used to extract tomographic estimates of activity millisecond by millisecond from the continuous MEG signal. Statistically significant differences between affective and cognitive blocks were identified in posterior and prefrontal areas. Cognitive blocks produced stronger activity in posterior parietal areas and superior prefrontal cortex in all three subjects. Affective blocks modulated activity in orbitofrontal and retrosplenial cortex, amygdala and brainstem. Individual contributions to the statistical maps were traced in real time from milliseconds to many seconds. Time-locked responses from the recall session were used to compare average and single trial MFT solutions and to combine activations from all subjects into a common anatomical space. The last step produced statistically significant increases in occipital and inferior ventral cortex between 100 and 200 ms compared to a prestimulus baseline.

Adult↗
PubMed1999

Neurophysiological correlates of the recognition of facial expressions of emotion as revealed by magnetoencephalography.

MEG correlates of the recognition of facial expressions of emotion were studied in four healthy volunteers. Subjects performed a facial emotion recognition task and a control task involving recognition of complex objects including faces. Facial emotion recognition activated inferior frontal cortex, amygdala and different parts of temporal cortex in a relatively consistent time sequence. The characteristics of these activations were clearly different from those recorded during the control task. Most interesting was the fact that faces evoked different MEG responses as a function of task demands, i.e., the activations recorded during facial emotion recognition were different from those recorded during simple face recognition in the control task. These findings support the assumption that MEG is able to specifically identify the activation pattern of the brain when recognition of the emotional expression of a face is performed.

Adult↗
PubMed1998

Magnetic field tomography analysis of continuous speech.

In this article we investigate MEG correlates of syntactic violations in continuous speech. An early left anterior negativity (ELAN) has been reported in previous EEG studies and has been related to syntactic processing. We used Magnetic Field Tomography (MFT) to extract a 3D estimate of the current density distribution J, from MEG data recorded while subjects listened to continuous speech. Separate estimates were obtained from the activity associated with the first word of the sentence, and the last words of the sentence which signified syntactic violation, semantic violation or correct sentences. In each case independent 3D MFT estimates of activity were obtained 2 ms apart. After converting the solutions into a PET-like format we perform a statistical analysis on a voxel-by-voxel basis. Visual inspection of the power of J at the time of the ELAN component and the statistical maps overlaid on the individual anatomical MRI suggests generators in the vicinity of the auditory cortex and in left frontal regions. Directional activation curves are computed to show the variation of activity as a function of time, from well circumscribed areas. The activation curve for the auditory cortex has a characteristic pattern consisting of three peaks, seen in the average time-locked to the onset of the first word, and the critical word of the syntactic violation. The left auditory cortex shows a delay of about 30 ms in the syntactic violation condition compared to the first word condition. No such delay is seen in the right auditory cortex.

Adult↗
PubMed1982

Parents' meetings in two neonatal units: a way of increasing support for parents.

For a combined total of three years meetings have been held regularly on two neonatal units for parents with infants requiring neonatal intensive care. These meetings give parents an opportunity to meet each other and members of staff in an informal atmosphere in the hope that mutual support will be gained. Initial assessment shows that the parents gain confidence in their ability to look after such small babies. The staff have gained a greater insight into the parents' anxieties and problems and changes have been made in the procedures on these units. If new insight is to result in changes that benefit the parents their views must be made known and taken into account when policy decisions are made.

Counseling↗