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Notes: Zusammenfassung Die Zunahme des „Ecstasy”-Konsums (MDMA, 3,4-Methylendioxymethamphetamin) erhöhte ebenfalls die Anzahl lebensbedrohlicher Intoxikationen. Aus einer Medline-Recherche der Jahre 1992–1996 wurden Berichte über Intoxikationen erfaßt und ausgewertet. Intoxikation mit Ecstasy: Im Vordergrund steht neben zerebralen, kardiopulmonalen, renalen und hepatischen Symptomen auch das Hyperthermie-Syndrom im Sinne einer malignen Hyperthermie, eines neuroleptischen malignen Syndroms oder eines Serotonin-Syndroms. Neben der Diskussion der Intoxikationssymptome und deren möglicher Akut- und Intensivtherapie werden psychische und physische Wirkungen von „Ecstasy” beschrieben und zur Vervollständigung des Themas eine kurze historische Betrachtung der Droge gegeben.

Notes: Zusammenfassung Bei einer 58jährigen Patientin entwickelten sich in der frühpostoperativen Phase nach vaginaler Hysterektomie die Zeichen einer disseminierten intravasalen Gerinnung mit Verbrauchskoagulopathie sowie Fieber und im weiteren Verlauf das Bild eines septischen Schocks. Sie hatte intra- und postoperativ je eine Eigenblutkonserve erhalten. In der Blutkultur der Patientin und einer Eigenblutkonserve zeigte sich Wachstum von Pseudomonas cepacia und Serratia marcescens in hoher Keimzahl. In dieser Eigenblutkonserve konnte außerdem Staphylococcus epidermidis, in der zweiten Propionibacterium acnes nachgewiesen werden. Die Kontaminationsquelle der Konserven war nicht identifizierbar. Es zeigt sich, daß auch die autologe Hämotherapie ein nicht zu unterschätzendes Infektionsrisiko in sich birgt und die Retransfusion von Eigenblut einer strengen medizinischen Indikation bedarf.

Notes: Summary The ability of cats to discriminate between two geometrical outline patterns in the presence of superimposed Gaussian visual noise was tested before and after bilateral removal of cortical area 17 and parts of area 18. The detection probability PD was measured as a function of the signal-to-noise ratio for the parameters: noise bandwidth, spatial frequency content and rate of movement of patterns. In both normal and lesioned cats a broadband noise was found to be most effective in masking the large patterns while two other types of noise, a medium frequency noise and a high frequency noise had little or no masking effect. For recognition of the smaller patterns in normal cats the medium frequency noise was found to be more effective than the broadband noise. The performance of the lesional cats was disturbed severely at low signal-to-noise ratios and was significantly inferior to that of normal cats — especially for small patterns. However, at high S/N ratios and for large patterns the performance of the lesioned cats was comparable to that of normals while for the small patterns they reached PD values inferior to those of normal cats. It is concluded that although pattern recognition can be performed successfully by cats lacking areas 17 and 18, these cortical areas probably make an essential contribuion to this function under natural conditions in two ways: a) because of the X-type input of area 17, they increase the acuity of the system by making it more sensitive to higher spatial frequencies, and b) they permit detection of patterns at much lower S/N ratios i.e. they lower the signal-to-noise ratio at which the system is able to detect the presence of a pattern in a background of statistical visual noise. The latter effect is not limited to the higher spatial frequencies but also affects the very low spatial frequencies which are normally used for pattern detection. Previous failures to demonstrate clear deficits in pattern discrimination after 17/18 lesions in cats may be attributed to the fact that the patterns presented for discrimination were not masked by visual noise. Movement of patterns led to a slight, but not significant improvement of the performance in both normal and lesioned cats, but the deficits found for stationary and moving patterns were more or less equal.

Notes: Behavioural impairments caused by brain lesions show a considerable, though often incomplete, recovery. It is hypothesized that cortical and subcortical plasticity of sensory representations contribute to this recovery. In the hindpaw representation of somatosensory cortex of adult rats we investigated the effects of focal unilateral cortical lesions on remote areas. Cortical lesions with a diameter of ≈ 2 mm were induced in the parietal cortex by photothrombosis with the photosensitive dye Rose Bengal. Subsequently, animals were kept in standard cages for 7 days. On day seven, animals were anaesthetized and cutaneous receptive fields in the cortical hindpaw representations ipsi- and contralateral to the lesion were constructed from extracellular recordings of neurons in layer IV using glass microelectrodes. Receptive fields in the lesioned animals were compared to receptive fields measured in nonlesioned animals serving as controls. Quantitative analysis of receptive fields revealed a significant increase in size in the lesioned animals. This doubling in receptive field size was observed equally in the hemispheres ipsi- and contralateral to the lesion. The results indicate that the functional consequences of restricted cortical lesions are not limited to the area surrounding the lesion, but affect the cortical maps on the contralateral, nonlesioned hemisphere.

Notes: Abstract In addition to the asymmetry of the spatial coupling and of the specific temporal combination of excitation and inhibition, the non-linearity is very pronounced in area 18. Taking the sequence of a linear operation and a stationary nonlinear characteristic as a model, the experimental findings can be systematized and a cell classification specified which departs from the customary ones. The hypercomplex cell system probably originates in recurrent inhibition and leads to differentiation of the patterns along their contour line. Problems of cell classification and of the type of parallelism in the visual cortex are discussed.

Notes: Abstract Proceeding from previous studies on cells in area 18, neurophysiological experiments were carried out using combinations of deterministic and statistical stimuli. The evaluation of the results on the space, time and amplitude characteristics of the cells show that for nearly all cells in this area, pattern distorition and shift due to motion are eliminated by spatial asymmetry of the coupling and specific combinations of on-off systems. So, the extraction of features despite pattern movement is possible in area 18. The features are extracted in the low spatial frequency range.

Notes: Abstract Topographical and functional aspects of neuronal plasticity were studied in the primary somatosensory cortex of adult rats in acute electrophysiological experiments. Under these experimental conditions, we observed short-term reversible reorganization induced by intracortical microstimulation or by an associative pairing of peripheral tactile stimulation. Both types of stimulation generate large-scale and reversible changes of the representational topography and of single cell functional properties. We present a model to simulate the spatial and functional reorganizational aspects of this type of short-term and reversible plasticity. The columnar structure of the network architecture is described and discussed from a biological point of view. The simulated architecture contains three main levels of information processing. The first one is a sensor array corresponding to the sensory surface of the hind paw. The second level, a pre-cortical relay cell array, represents the thalamo-cortical projection with different levels of excitatory and inhibitory relay cells and inhibitory nuclei. The array of cortical columns, the third level, represents stellate, double bouquet, basket and pyramidal cell interactions. The dynamics of the network are ruled by two integro-differential equations of the lateral-inhibition type. In order to implement neuronal plasticity, synaptic weight parameters in those equations are variables. The learning rules are motivated by the original concept of Hebb, but include a combination of both Hebbian and non-Hebbian rules, which modifies different intra- and inter-columnar interactions. We discuss the implications of neuronal plasticity from a behavioral point of view in terms of information processing and computational resources.

Notes: Abstract The contribution of the lateral suprasylvian cortex to pattern recognition was studied by behavioural detection experiments in combination with bilateral lesions of different parts of the lateral suprasylvian areas (LSA) and area 7 in seven cats. In a two-alternatives forced choice task the cats had to discriminate simple outline patterns which were additively superimposed on a structured visual background made up of broadband Gaussian noise. For various stimulus conditions (moving or stationary patterns and/or background) the detection probability (P D) of the cats was measured as a function of the signal to noise ratio (S/N). Each cat was tested before and after the lesion. Four different types of lesion could be distinguished depending on their extent: (1) lesion of parts of the (LSA); (2) lesion of parts of the LSA with undercutting of areas 17, 18 and 19; (3) lesion of area 7; (4) lesion of area 7 and parts of the LSA. 1. We found that a large bilateral lesion of the LSA led to significant deficits in all test situations which were dependent on the existence of relative velocity of moving patterns against a structured background. The ability of the cats to discriminate simple outline patterns which were kept stationary was not reduced. On the contrary, when they were tested with stationary and moving patterns on unfocused (empty) backgrounds, we found, to our great surprise, that the performance of the lesioned cats was significantly improved compared with intact animals. As these lesioned cats had no deficits with moving patterns on a uniformly grey background, we conclude that the deficits with the moving patterns must have been caused by interactions between patterns and background, and not by movement of a pattern per se. 2. As soon as the lesion of the LSA was extended by a bilateral undercutting of areas 17, 18 and 19 we found very severe deficits in all test situations, regardless of whether the patterns were moving or kept stationary, or whether they were superimposed on a background or not. The most substantial deficits occurred when the patterns were moving on a stationary background. In these situations the cats were no longer able to reach the 84% correct criterion. Again, the cats were able to reach criterion with moving patterns on a uniformly grey background indicating that this deficit is probably caused by the interaction of patterns and background and not by motion of the patterns per se. 3. A large lesion of area 7 led to modest but significant deficits of more or less the same degree in all test situations with the exception of quickly moving patterns on a structured background. In contrast, a much smaller lesion of area 7 yielded significant deficits only when the background was moved and there was a low relative velocity between the patterns and the background. 4. In brief, the combination of a lesion of area 7 with that of the LSA roughly provoked a combination of the effects of the two lesions (1 and 3) alone. We found significant deficits in all test situations. We did not find evidence for any type of functional recovery in any of the lesions described. All deficits were permanent. Our results support the idea of a functional segregation between the LSA and area 7. They confirm that the LSA are involved in pattern recognition whenever it is associated with motion in combination with object-background interactions. This suggests an involvement of the LSA in the analysis of object- and self-induced motion. An interpretation of the results of lesioning area 7 is based on the conjecture that the mechanism of vergence movements or of binocular fusion of both retina images might be impaired. Under this condition it seems conceivable to expect double images or a reduced visual acuity because the images are out of focus. This would have a similar effect on the detection performance in each stimulus configuration. In addition, the results of lesion 4 provide evidence that both functional subunits (LSA and area 7) are not able to compensate for one another. Finally, we conclude from the results after lesion 2 that the LSA is part of a system which is based on the cooperation with striate cortex and requires intact primary cortex for its full function.

Notes: Summary In respiratory modulated neurons of rabbits, vagally mediated inhibition is not bound to resting membrane potential oscillations. Latency of spinally evoked antidromical spike invasion, however, is shorter and threshold voltage is lower during the shift of membrane potential towards depolarization accompanying burst discharge.

Notes: Summary The contribution of area 19 to pattern discrimination in the cat was studied by single cell recordings in this area and by behavioural experiments before and after bilateral lesions. In order to make quantitative comparisons between behavioural performance and that of cell systems, we introduced a new parameter that characterizes visual neurons by their signal-to-noise (S/N) thresholds. A structured visual background made up of Gaussian visual broadband noise which could be moved was superimposed on the signal (moving bars or outline patterns) and the S/N characteristics of the response were determined by varying the signal intensity. The detection performance of cats after bilateral lesion of area 19 showed no deficits. Only for slowly (11 deg/s) or quickly (110 deg/s) moving patterns, or when the background was moved relative to stationary patterns, did we find slight, but significant deficits in the low S/N range. However, when the S/N ratios were higher than 5, all cats achieved their full preoperative performances and no deficits remained. The S/N thresholds of neurons in area 19 were much higher than those found for neurons in areas 17 and 18. The lowest thresholds were found with a stationary background. Introduction of relative velocity between background and bar resulted in intermediate thresholds and the highest thresholds were observed for stimulus configurations lacking relative velocity. These effects correspond to the performance of the intact animal, in which introduction of relative motion increases the performance. The S/N thresholds did not correlate with levels of spike rate recorded at high S/N ratios, direction selectivity or speed preference, indicating that S/N threshold measurements provide a significant additional description of visual neurons. A limited number of area 19 cells recorded in area 17/18 lesioned animals showed very similar thresholds suggesting that this property may be independent of the intactness of areas 17 and 18. The residual performance by 17/18 lesioned cats in detecting small patterns corresponds well to the characteristics of the single cells of area 19. This suggests that area 19 might be able to make a considerable contribution to this task when areas 17/18 are eliminated, though by itself it seems not to be able to sustain the level of performance mediated by them. The contribution of area 19 is restricted to performances at high S/N ratios only. In contrast to what was found for areas 17 and 18, area 19 makes no essential contribution to lowering the S/N ratio at which the system is able to detect the presence of a pattern in a background of irrelevant detail.