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  • 1
    Electronic Resource
    Electronic Resource
    Räumliche summation und hemmungsvorgänge im receptiven feldzentrum von retina-neuronen der katze (1969)
    Springer
    Experimental brain research 8 (1969), S. 37-52 
    Details
    ISSN: 1432-1106
    Keywords: Retinal Ganglion Cells ; Spatial Summation ; Center Inhibition ; Dynamic Organisation of Receptive Fields ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung 1. An retinalen Ganglienzellen der Katze wurde die räumliche Summation im receptiven Feldzentrum (KFZ) bei Dunkeladaptation und Helladaptation durch mittelpunktzentrierte Lichtreize verschiedener Flächengrößen untersucht. Als Kriterium dienten die Entladungsraten der ersten 200 und 500 msec nach Licht-an oder Licht-aus. Das Summationsverhalten wurde sowohl für Einzelneurone als auch gruppenstatistisch für die beiden Neuronen-Systeme B (on-Zentrum) und D (off-Zentrum) untersucht. 2. Die räumliche Summation ist auf den inneren Bereich des RFZ beschränkt: bei on-Zentrum-Neuronen steigt die Entladungsrate nur bis zu Reizflächen, die etwa 1/5 der Fläche des RFZ belichten, bei off-Zentrum-Neuronen bis zu Reizflachen von ca. 1/10 des RFZ. Bei Variation der Reizfläche zwischen 20 und 100% der Fläche des RFZ bleibt das Entladungsniveau konstant (asymptotischer Verlauf der Summationskurve). 3. Die Begrenzung der räumlichen Summation auf einen kleinen Bereich des RFZ beweist eine bereits im Feldzentrum wirksame Hemmung. Diese Zentrum-Inhibition begrenzt die Erregungssummation im RFZ bei zunehmender Flächengröße des Lichtreizes. 4. On- und off-Zentrum-Neurone unterscheiden sich in beiden Adaptationszuständen in der Höhe des Entladungsniveaus. Die Entladungsraten der on-Zentrum-Neurone nach Licht-an übertreffen um ein Mehrfaches die Entladungsraten der off-Zentrum-Neurone nach Licht-aus. Die Unterschiede sind gruppenstatistisch hoch signifikant. Die interneuronale Variabilität der Entladungsraten ist bei den onZentrum Neuronen erheblich geringer als bei den off-Zentrum-Neuronen. 5. Dunkel -und Helladaptation führt zu signifikantem Unterschied der Entladungsraten: bei Helladaptation liegt die Impulsrate beider Neuronentypen höher als bei Dunkeladaptation und der Summationsbereich ist um 5–10% größer. 6. Für die mathematische Beschreibung der Summationsverläufe ist die Hyperbel besser geeignet als die logarithmische und Potenzfunktion. Logarithmus- und Potenzfunktionen beschreiben den konstanten asymptotischen Teil der Summationskurven ungenügend und eigenen sich nur für den Kurventeil im innersten Summationsbereich. Die Bedeutung der Befunde für eine dynamische Interpretation der visuellen Feldorganisation und mögliche Beziehungen zur lateralen Umfeldhemmung werden diskutiert.
    Notes: Summary 1. Spatial summation of suprathreshold light stimuli within receptive field centers (RFZ) of retinal ganglion cells was investigated during dark and light adaptation in cats. The mean discharge rates for 200 and 500 msec following light on or off were the computed response criteria. The summation effects were analyzed for single neurones and statistically for grouped neuron populations of the two neuronal subsystems B (on-center-neurones) and D (off-center-neurones). 2. Spatial summation is restricted to a small part of the RFZ. On-centerneurones increase their on-discharge rates with increasing spot sizes, only if the stimulus illuminates less than 1/5 of the RFZ. The summating area of the off-centerneurones is smaller (about 1/10 of the RFZ). 3. The limitation of spatial summation to a small part of the RFZ indicates the existance of inhibition within the RFZ. This center-inhibition sets a constant limit for excitation summation in the RFZ. 4. The mean neuronal response rates for the 2 subsystems show significant differences: The on-discharges of the on-center-neurones exceed the off-discharges of the off-center-neurones by a factor of 3–5. These highly significant differences occur at both adaptation levels and are not due to different spontaneous activity. Interneuronal response variability of the off-center-neurones was twice as large as that of the on-center-neurones. 5. Change from dark to light adaptation had only a small but significant influence on summation properties. The poststimulus discharge rates were higher during light adaptation and the summating area was slightly larger (about 5–10%). 6. A comparative curve fitting procedure for three suitable mathematical functions revealed that the hyperbola describes the neuronal summation curves better than a logarithmic or power function. The latter do not fit the constant asymptotic part of the curve. The significance of the results for a dynamic interpretation of the organisation of visual receptive fields is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234924
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  • 2
    Electronic Resource
    Electronic Resource
    Räumliche summation im receptiven feldzentrum von neuronen des geniculatum laterale der katze (1969)
    Springer
    Experimental brain research 8 (1969), S. 53-65 
    Details
    ISSN: 1432-1106
    Keywords: Lateral geniculate body ; Spatial summation ; Off-center-characteristics ; Geniculate transfer ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung 1. Die räumliche Summation im receptiven Feldzentrum von Neuronen des Corpus geniculatum laterale (CG-L) wird beschrieben und mit entsprechenden Untersuchungen an retinalen Ganglienzellen verglichen. Neben größerer interneuronaler Variabilität ergeben sich ausgeprägtere Unterschiede der Summationseigenschaften der on-und off-Zentrum-Neurone. Der effektive Summationsbereich von etwa 1/5 der Fläche des RFZ ist in Retina und CGL etwa gleich. 2. Die on-Zentrum-Neurone des CGL zeigen in beiden Adaptationszuständen einen ähnlichen Summationsverlauf wie in der Retina. Das Entladungsnieau ist im CGL jedoch erheblich geringer und nicht durch Unterschiede in der Spontanaktivität zu erklären. 3. Die Mehrzahl der off-Zentrum-Neurone des CGL zeigt bei DA inverse Summationsverläufe wie in der Retina: durchgehende Verminderung der Entladungsrate der off-Antworten bei Vergrößerung der Reizfläche im RFZ. Eine kleine Gruppe zeigt einen parabelförmigen Summationsverlauf mit Entladungszunahme bis zu Reizflächen von 10–30% der Fläche des RFZ und darauffolgender Entladungsminderung. Bei Helladaptation zeigen fast alle off-Zentrum-Neurone diesen Parabelverlauf. Das durchschnittliche Entladungsniveau ist von dem retinaler offZentrum-Neurone nicht signifikant verschieden. 4. Die interneuronale Variabilität der Summationsvorgänge im RFZ von CGLNeuronen ist gegenüber den retinalen Ganglienzellen deutlich größer. Dies gilt insbesondere für die off-Zentrum-Neurone. Das Summationsverhalten von CGLNeuronen läßt sich daher nicht wie in der Retina durch einen Funktionstyp beschreiben. 5. Die Befunde sprechen für eine Transformation des retinalen Eingangs der off-Zentrum-Neurone im CGL, während die on-Zentrum-Neurone außer der bekannten Frequenzuntersetzung keine wesentliche Umformung erkennen lassen.
    Notes: Summary 1. Spatial summation in the receptive field center of neurones of the lateral geniculate body (CGL) is limited by inhibition to a small part of field center. Variations of stimulus size are only effective if the stimulus is smaller than about 1/5 of the area of receptive field center. Thus, the active summating area of the field center in the CGL corresponds to that of the retina. Geniculate neurones, however, show less homogeneous responses and the summation properties of the two neuronal subsystems (on-center-and off-center-cells), show greater differences than in the retina. 2. The form of summation curves for the on-center-neurones of the CGL is similar to those of the retina at both adaptation levels. However, the average responses rates in the CGL are considerably lower. This is not due to differences of spontaneous activity. 3. The summation characteristics of off-responses of off-center-neurones of the CGL are quite different from those in the retina. In dark adaptation the majority of CGL neurones respond with decreasing discharge rates to increasing spot-sizes within the field center. A small number show an initial increase of discharge rates up to stimulus sizes of about 1/10 of the receptive field center before a decrease occurs. This parabolic summation type is typical for most off-center-neurones in light adaptation. The mean discharge levels are the same as those of the retinal offcenter-neurones. 4. The higher interneuronal variability of summation curves especially of the off-center-neurones of the CGL indicates a more complex determination of the discharge properties of CGL neurones. This functional differentiation of single neurones is congruent with the more complex structural and synaptic organisation in CGL. 5. With respect to spatial summation, the results indicate a transformation of the retinal input of the off-center-neurones at the geniculate level, whereas the oncenter-neurones are nearly unchanged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234925
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  • 3
    Electronic Resource
    Electronic Resource
    Different cortical organization of visceral and somatic sensation in humans (1999)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 11 (1999), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Sensory stimuli from the visceral domain exhibit perceptual characteristics different from stimuli applied to the body surface. Compared with somatosensation there is not much known about the cortical projection and functional organization of visceral sensation in humans. In this study, we determined the cortical areas activated by non-painful electrical stimulation of visceral afferents in the distal oesophagus, and somatosensory afferents in the median nerve and the lip in seven healthy volunteers using whole-head magnetoencephalography. Stimulation of somatosensory afferents elicited short-latency responses (≈ 20–60 ms) in the primary somatosensory cortex (SI) contralateral (median nerve) or bilateral (lip) to the stimulated side, and long-latency responses (≈ 60–160 ms) bilaterally in the second somatosensory cortex (SII). In contrast, stimulation of visceral oesophageal afferents did not evoke discernible responses in SI but well reproducible bilateral SII responses (≈ 70–190 ms) in close vicinity to long-latency SII responses following median nerve and lip stimuli. Psychophysically, temporal discrimination of successive stimuli became worse with increasing stimulus repetition rates (0.25 Hz, 0.5 Hz, 1 Hz, 2 Hz) only for visceral oesophageal, but not for somatosensory median nerve stimuli. Correspondingly, amplitudes of the first cortical response to oesophageal stimulation emerging in the SII cortex declined with increasing stimulus repetition rates whereas the earliest cortical response elicited by median nerve stimuli (20 ms SI response) remained unaffected by the stimulus frequency. Our results indicate that visceral afferents from the oesophagus primarily project to the SII cortex and, unlike somatosensory afferents, lack a significant SI representation. We propose that this cortical projection pattern forms the neurophysiological basis of the low temporal and spatial resolution of conscious visceral sensation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.1999.00429.x
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  • 4
    Electronic Resource
    Electronic Resource
    Eine mathematische Formulierung für Reiz-Reaktionsbeziehungen retinaler Ganglienzellen (1970)
    Springer
    Biological cybernetics 7 (1970), S. 160-166 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Summary 1. In order to describe stimulus-response relationships for retinal ganglion cells a mathematical formulation is presented on the basis of experimental data and some simple assumptions. This concept involves two mechanisms — an excitatory and an inhibitory one — both extending over the whole receptive field. 2. The following formula $$S\left( I \right) = \frac{{c{\text{ }}{I \mathord{\left/ {\vphantom {I {I_S - 1}}} \right. \kern-\nulldelimiterspace} {I_S - 1}}}}{{1 + a{\text{ }}a{I \mathord{\left/ {\vphantom {I {I_S + 1}}} \right. \kern-\nulldelimiterspace} {I_S + 1}}}}$$ is used for description of the excitatory responses (on-response for on-center neurones, off-response for off-center neurones). The value ofa depends on the area of light stimulation,c is a constant;I/I S designates the ratio of stimulus brightness to threshold brightness. 3. Thresholds and suprathreshold response curves for concentric stimuli are described quantitatively by the formula. The experimental data were obtained by computer counts of spike discharges during 200 and 500 ms following the exciting light increment or decrement. 4. Ricco's, Weber-Fechner's and Stevens's laws are included in our conception as approximations of neuronal summations. These relations are limited to certain stimulus ranges; in contrast the above response function saturates at certain maximum discharge rates, as found by the S-shaped experimental curves; thus the formula is valid over the whole range of stimulation from threshold to very high intensities. 5. Thresholds as well as excitatory and inhibitory effects depend on background illumination and stimulus parameters. Therefore, center and surround size depend on these factors. 6. The formulation is set up for stationary responses and consequently does not describe time dependent characteristics. 7. Within these limits on-center and off-center neurones appear to have identical stimulus-response functions for adequate stimuli. Since in our experiments light increments and decrements were not symmetrical with respect to background illumination, a factor of 2 had to be introduced corresponding to the lower discharge rates of off-center-neurones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571696
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  • 5
    Electronic Resource
    Electronic Resource
    Diagnose und Differenzierung von Stenosen und Verschlüssen der Arteria carotis mit der Doppler-Sonographie (1976)
    Springer
    European archives of psychiatry and clinical neuroscience 222 (1976), S. 191-207 
    Details
    ISSN: 1433-8491
    Keywords: Doppler-Sonography ; Carotid Occlusion ; Carotid Stenosis ; Localization of Stenosis ; Stroke ; Doppler-Sonographie ; Karotisverschluß ; Karotisstenose ; Stenoselokalisation ; Schlaganfall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 76 Patienten wurden die Ergebnisse der dopplersonographischen Untersuchungen der Karotiden am Hals mit denen der A. supratrochlearis und mit den angiographischen Kontrollen verglichen. Dabei zeigte sich, daß die direkte selektive Beschallung der Aa. carotis communis, interna und externa am Hals eine wesentliche Verbesserung gegenüber der indirekten Untersuchung nur der A. supratrochlearis erreicht. Diese läßt sich in drei Punkten zusammenfassen: 1. Die Häufigkeit falsch-positiver und falsch-negativer Befunde ist deutlich geringer als an der A. supratrochlearis. Von 76 angiographisch kontrollierten Fällen wurden bei der Untersuchung der Karotiden am Hals jeweils nur ein falsch-negativer und ein falsch-positiver Befund erhoben. Damit wird die diagnostische Zuverlässigkeit auf 97% erhöht. In diesem Kollektiv sind auch die mittelgradigen Stenosen (50% Lumeneinengung) enthalten. 2. Die Beschallung der Karotiden erlaubt die zuverlässige Differenzierung zwischen Stenose und Verschluß. Nur in einem Fall war diese nicht richtig. Durch Untersuchung der A. supratrochlearis allein ist diese Unterscheidung nicht möglich. 3. Die Lokalisation der Strömungsbehinderung gelang in allen Fällen. Diese Aussagen beziehen sich nur auf die Erfassung von Verschlüssen und mittel-bis höhergradigen Stenosen. Für die zuverlässige Diagnostik geringerer Stenosen (〈50% Lumeneinengung) ist die Methode ungeeignet.
    Notes: Summary The Doppler examination of the carotid arteries in the neck was compared with the results of the examination of the supratrochlear artery and of the angiographic controls in 76 patients. The results of this study indicate that the insonation of the carotid arteries considerably improves the diagnostic possibilities offered by the examination of the supratrochlear artery alone. 1. The reliability of the Doppler examination is improved. The insonation of the carotid arteries of the 76 angiographically controlled patients including stenoses from 50% onward gave only one false-positive and one false-negative result. The percentage of correct diagnoses thereby attained was 97%. 2. The insonation of the carotid arteries permits reliable differentiation between stenoses and occlusions. This is not possible by the insonation of the supratrochlear artery alone. There was only one case in which the distinction was wrong. 3. The localization of the pathologic process was possible in all cases. These conclusions are only valid for the detection of occlusions and stenoses of more than 50%. Low degree stenoses cannot be detected by this method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02206617
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  • 6
    Electronic Resource
    Electronic Resource
    Die Differenzierung der Halsgefäße mit der direktionellen Doppler-Sonographie (1976)
    Springer
    European archives of psychiatry and clinical neuroscience 222 (1976), S. 177-190 
    Details
    ISSN: 1433-8491
    Keywords: Doppler Sonography ; Identification of Neck Arteries ; Carotid Arteries ; Vertebral Artery ; Screening of Stenoses ; Doppler ; Sonographie ; Unterscheidung der Halsarterien ; Karotiden ; Vertebralarterien ; Verschluß und Stenose ; Unterscheidung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 300 Gesunden und Patienten ohne stenosierende Gefäßerkrankung wird gezeigt, daß durch die direktionelle Doppler-Sonographie mit geringem Zeitaufwand die Differenzierung und damit die direkte selektive Beschallung aller extrakraniellen Hirnarterien möglich ist. Im Normalfall sind die Aa. carotis communis, interna, externa und die A. vertebralis bereits durch ihre Pulskurvencharakteristika unterscheidbar. Diese Unterschiede werden auch durch die akustische Pulswiedergabe deutlich. Im pathologischen Fall wird die zuverlässige Differenzierung der Arterien insbesondere im Bereich der Karotisbifurkation, durch Kompression von Ästen der A. carotis externa notwendig. Entsprechend den haemodynamischen Gesetzen ändert sich die Strömungsgeschwindigkeit durch eine solche Änderung des peripheren Widerstandes. Die Auswirkungen dieser Widerstandsänderungen auf die Dopplerpulskurven werden zuerst am Modell der A. radialis, dann für die Halsarterien gezeigt. Grundlage der Unterscheidung der Halsarterien ist die Änderung der Pulskurven einzelner Externaäste durch selektive Kompression. Die Unterscheidung arterieller und venöser Gefäße wird besprochen. Die Unterscheidung der Halsgefäße ermöglicht die Differentialdiagnose zwischen Verschlüssen und hochgradigen Stenosen und die Lokalisation dieser Prozesse.
    Notes: Summary The Doppler examination of the neck arteries of 300 subjects showed, that the common, internal and external carotid arteries and the vertebral artery can reliably be distinguished on the basis of their different pulse-curve characteristics. In addition, the compression of branches of the external carotid artery can identify these vessels in particular in pathologic cases. The details of the normal flow profiles and their changes by the compression tests are described. Compression of the vessels leads to a rise in flow resistance. The effect of such a rise in resistance is demonstrated using the A. radialis as a model. The identification of the neck arteries provides the basis for diagnostic examination and localization of their stenoses and occlusions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02206616
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  • 7
    Electronic Resource
    Electronic Resource
    Electrophysiological motor testing, MRI findings and clinical course in AIDS patients with dementia (1993)
    Springer
    Journal of neurology 240 (1993), S. 439-445 
    Details
    ISSN: 1432-1459
    Keywords: Dementia ; Human immunodeficiency virus ; Electrophysiology ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Thirty-three HIV-positive patients with clinical signs of dementia according to the 1991 AAN criteria underwent psychometric, electrophysiological and radiological examination and were compared with a group of normal healthy subjects and a cohort of clinically asymptomatic HIV-1-positive individuals of comparable education and social environment. Compared with the other groups, test performance was severely impaired in the demented patients. Results of motor testing and MRI revealed that subcortical structures were not exclusively affected, but most severely and early, thus characterizing the clinical feature in HIV-1-associated dementia. In demented patients a rapid deterioration was observed, leading to death within about 12 months on average, which is a markedly shorter survival time than described in the literature for non-demented HIV-1-positive individuals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00867359
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  • 8
    Electronic Resource
    Electronic Resource
    Neuromuscular, autonomic and central cholinergic hyperactivity associated with thymoma and acetylcholine receptor-binding antibody (1987)
    Springer
    Journal of neurology 234 (1987), S. 433-436 
    Details
    ISSN: 1432-1459
    Keywords: Neuromuscular hyperactivity ; Neuromyotonia ; Myasthenia gravis ; Thymoma ; Autoimmune disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two cases of a neuromuscular hyperactivity syndrome associated with a proliferative thymoma and high serum titres of acetylcholine receptor (AChR) antibody with no signs of myasthenia are reported. The clinical and electrodiagnostic findings indicated generalized cholinergic hyperactivity at the neuromuscular junction and in the autonomic and central nervous system, resulting in generalized myokymia, excessive sweating and intermittent psychotic behaviour. The association with thymoma and raised AChR antibody suggests that this syndrome represents a unique type of autoimmune disease, in which antibodies against the AChR facilitate rather than inhibit cholinergic action. This conclusion is supported by the remission of symptoms after thymectomy and with immunosuppressive therapy in one case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00314093
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  • 9
    Electronic Resource
    Electronic Resource
    Therapeutic entrainment of circadian rhythm disorder by melatonin in a non-blind patient (1998)
    Springer
    Journal of neurology 245 (1998), S. 327-328 
    Details
    ISSN: 1432-1459
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050228
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  • 10
    Electronic Resource
    Electronic Resource
    The relationship between the rate of rise of isometric tension and motor unit recruitment in a human forearm muscle (1976)
    Springer
    Pflügers Archiv 362 (1976), S. 61-67 
    Details
    ISSN: 1432-2013
    Keywords: Human motor units ; Recruitment threshold ; Rate of rise of isometric tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The recruitment properties of single motor units from the human extensor indicis muscle were investigated during voluntary isometric contractions of different rate of rise but equal amplitude. Both the electrical and the contractile events associated with recruitment were analyzed. The threshold force of recruitment (measured as the total muscle force at firing onset) decreased with increasing rate of rise of isometric tension. This was consistently found for all units. Differences between low and high threshold units indicating a preferential tonic or phasic mode of activation were not observed. The contractile events associated with recruitment were analyzed analoguously to the electrical events. For this purpose, muscle force was measured at the time of the first twitch as it was measured at the time of the first spike. This separate measurement of the electrical and mechanical recruitment of a unit is necessary, because during a change of muscle force, force is different at firing onset and during the subsequent twitch contraction. Muscle tension at the time of the peak of the first twitch contraction was calculated from measurements of the twitch contraction time of the single motor units. In contrast to firing onset, the peak of the first twitch of a motor unit occurs at approximately the same muscle tension no matter how fast the contraction is performed. This is the consequence of the result that the average decrease of the threshold force of recruitment at successively faster contraction has the same value as the corresponding increase of total muscle force during the mean contraction time of the motor units. On the basis of this precise matching between these two changes, the mechanical recruitment of motor units occurs at approximately the same force level irrespective of the rate of rise of tension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588682
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