Biomedical subjects

F Hassainia

Publications and source records attributed to F Hassainia.

5 recordsLinked to original sources

PubMed1997

REM sleep dream mentation in right hemispherectomized patients.

Investigations of dream mentation in brain damaged patients have shed some light on the controversial issue of cerebral lateralization of dreaming. To examine further the relationships between brain function and dreaming, we studied REM sleep dream recall and content in four patients having undergone right functional or anatomical hemispherectomy and eight matched control subjects. Patients were found to have the capacity to report dreams to much the same extent as control subjects. Further, the patients' dream content was overall similar to that of the control subjects. The results provide strong evidence that dreaming is not a right-hemisphere function, and that the left hemisphere may be more critical for the generation of dreams. In addition, some characteristics of hemispherectomized patients' dream content (characters, smells) are consistent with the possibility that a history of epilepsy may influence REM sleep imagery over the long term.

Adolescent↗

PubMed1997

Quantitative EEG and statistical mapping of wakefulness and REM sleep in the evaluation of mild to moderate Alzheimer's disease.

Statistical probability mapping was used to quantify and localize EEG differences between 27 patients with Alzheimer's disease (AD) and 25 age- and gener-matched controls. Differences in mean activity in four EEG frequency bands (delta, theta, alpha, beta) for wakefulness and for REM sleep were examined, t-statistic maps clearly highlighted common pattern anomalies in AD patients in the two states. More specifically, Alzheimer patients were more affected than control subjects in parieto-temporal and frontal regions. These differences were more prominent in REM sleep and consisted primarily in an increase in absolute delta and theta activities, and a decrease in absolute alpha and beta activities. Discriminant analysis, using a ratio of slow over fast frequencies, yielded a classification rate of 90.4% (sensitivity 81.5%, specificity 100%) for REM sleep. For wakefulness, the same measure allowed correct classification of 80.8% of the subjects (sensitivity 66.7%, specificity 96%).

Aged↗

PubMed1994

Significance probability mapping: the final touch in t-statistic mapping.

Significance Probability Mapping (SPM), based on Student's t-statistic, is widely used for comparing mean brain topography maps of two groups. The map resulting from this process represents the distribution of t-values over the entire scalp. However, t-values by themselves cannot reveal whether or not group differences are significant. Significance levels associated with a few t-values are therefore commonly indicated on map legends to give the reader an idea of the significance levels of t-values. Nevertheless, a precise significance level topography cannot be achieved with these few significance values. We introduce a new kind of map which directly displays significance level topography in order to relieve the reader from converting multiple t-values to their corresponding significance probabilities, and to obtain a good quantification and a better localization of regions with significant differences between groups. As an illustration of this type of map, we present a comparison of EEG activity in Alzheimer's patients and age-matched control subjects for both wakefulness and REM sleep.

Aged↗

PubMed1994

Three dimensional representation of brain electrical activity.

Brain topography mapping is a useful technique for the representation of electrical activity recorded on the scalp. It clarifies spatial and temporal relationships between different cortical areas. In this work we propose a system which includes several enhancements over those previously proposed, such as an optimised interpolation method and a three dimensional reconstruction of maps. This system is available in a personal computer environment. Results clearly show a superiority of the 3D representation over 2D maps obtained with different projections. The performance of this system in terms of speed and precision is comparable to that of dedicated image processing and image synthesis workstations proposed for brain mapping.

Brain↗

PubMed1994

Scalp potential and current density mapping with an enhanced spherical spline interpolation.

A method for producing rapid and accurate scalp electroencephalography, evoked potential and current density mapping is described. This method is based on the spherical spline interpolation, which has been validated as the most suitable function for this application. In comparison with the basic algorithm, the proposed technique is accurate and fast: it reduces the computation time by a factor of 10, while preserving the desired precision level. Furthermore, we study the choice of an optimal configuration and number of electrodes in order to produce a good reconstruction of brain electrical activity with this method. The implementation and application of this enhanced method in a three-dimensional brain mapping system is shown.

Algorithms↗