In this first part of a review on recent insights into the structure and function of the γ-aminobuty rie acid type A - benzodiazepine receptor system, the γ-aminobutyric acid type A (GABAA) receptor and the different types of benzodiazepine (BDZ) receptors known at this moment are dicussed. GABAA- and BDZ receptors are coupled in a supramolecular GABAA-BDZ-ionophore receptor complex, each consisting of five acidic glycoprotein molecules called subunits. These subunits can be classified into five groups: α, β, γ, σ and ρ. Present evidence indicates the existence of multiple subtypes of these subunits. Multiple GABAA-BDZ receptors exist in the brain that show differential distribution and developmental patterns. These receptors differ from their subunit composition. The final functional properties of the receptor are determined by the different subunits constituting this receptor. Heterogeneity among α- subunits may determine the diversity of BDZ pharmacology in different regions of the nervous system.

Aim: Translation of a specific instrument to measure psychomotor retardation, the “Widlöcher Retardation Rating Scale” and validation of this Dutch translation (Widlöcher remmingsschaal, WRS). Method: In three separate studies, we studied reliability (n = 26), concurrent and divergent validity (n = 25) and predictive validity (n = 28) of the WRS. In- and outpatients with a depressive disorder or schizophrenia participated, and scores on the WRS were compared with those on the Montgomery Asberg Depression Rating Scale (MADRS) and retardation items of the Comprehensive Psychopathological Rating Scale (CPRS).

Results: The internal consistency was good (Cronbach alpha = 0.86), interrater reliability was sufficient to good, the correlation between the sumscores of both raters was r = 0.84, n = 23, p <0.01 and the kappa's were between 0.23 and 0.80. Convergent and divergent validity showed in comparing the correlation between the sum scores on the WRS and the CPRS retardation items (r = 0.91, n = 25, p < 0.01 ) with the correlation between the sumscores on the WRS and the MADRS (r = 0.40, n = 25, p = 0.1). The decrease of the sum scores on the WRS after two weeks of treatment with antide-pressants predicted remission after six weeks. A subgroup of the patients who were not in remission after six weeks, showed a predominance of retardation signs over mood disturbances. The same clinical picture was seen in a group of patients with a chronic disorder.

Conclusion: De Widlöcher Retardation Rating Scale in this Dutch translation is a usefull instrument to measure psychomotor retardation. The connection between remaining retardation symptoms and longterm prognosis deserves further investigation.

A magnetoencephalogram (MEG) is the registration of the magnetic field in points near the head. Because MEG's are weak fields, they have to be measured by means of superconducting sensors. The electric active population of neurons can be computed from the distribution of the magnetic field at a certain instant of time. This is called the inverse problem. In order to solve this probem, both the generators and the head have to be modelled. Usually, a patch of active neurons is modelled as a current dipole. Commonly, the head is described by three compartments, representing the brain, the skull and the scalp. The compartments may have the shape of spheres or they may have a realistic shape. Integration of EEG and MEG with MRI leads to a technique for functional imaging of the brain with a time resolution of one millisecond and a spatial resolution of one centimetre. Clinical applications are the non-invasive localization of an epileptic focus or the presurgical mapping of the sensorimotor cortex.