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  • 1995-1999  (6)
  • Human  (3)
  • Olfaction  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Inhibitory receptor binding events among the components of complex mixtures contribute to mixture suppression in responses of olfactory receptor neurons of spiny lobsters (1998)
    Springer
    Journal of comparative physiology 183 (1998), S. 699-707 
    Details
    ISSN: 1432-1351
    Keywords: Key words Chemoreception ; Coding ; Crustacea ; Olfaction ; Panulirus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Responses of olfactory receptor neurons of spiny lobsters Panulirus argus to two-component mixtures can be shaped by inhibitory events such as odor-activated hyperpolarizations and inhibition of odor-receptor binding (Daniel et al. 1996). In the current study, we extend this analysis to complex mixtures by examining responses of spiny lobster olfactory receptor neurons to mixtures containing up to seven odorants, consisting of adenosine-5′-monophosphate, ammonium, betaine, l-cysteine, l-glutamate, dl-succinate, and taurine. The response to a mixture was often less than the response to its most excitatory component. The effect of adding an excitatory odorant to a mixture depended on olfactory receptor neuron type, composition of the mixture, and which compound was added. In some cases the added excitatory compound had no effect or even decreased the mixture's response intensity, thus demonstrating nonlinear contributions of the components. Response intensities predicted by a noncompetitive model, which is most representative of these olfactory receptor neurons, were improved when the model included a term for empirical measurements of inhibitory binding interactions, suggesting that inhibitory binding interactions are one mechanism contributing to mixture suppression. This model's predictions were accurate for binary mixtures but not for larger mixtures, suggesting that additional inhibitory mechanisms are needed to account for mixture interactions in complex mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050292
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Responses of olfactory receptor neurons in the spiny lobster to binary mixtures are predictable using a noncompetitive model that incorporates excitatory and inhibitory transduction pathways (1996)
    Springer
    Journal of comparative physiology 178 (1996), S. 523-536 
    Details
    ISSN: 1432-1351
    Keywords: Olfaction ; Across neuron patterns ; Sensory coding ; Mixture models ; Crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Coding of binary mixtures by a population of olfactory receptor neurons in the spiny lobster (Panulirus argus) was examined. Extracellular single-unit responses of 50 neurons to seven compounds and their binary mixtures were recorded. The ability of a noncompetitive model with correction for binding inhibition to predict responses to mixtures based on responses to their components was compared with the predictive abilities of other models. This model assumes that different compounds activate different transduction processes in the same neuron leading to excitation or inhibition, and it includes a term quantifying the degree to which binding of an odorant to its receptor sites is inhibited by other compounds. The model accurately predicted the absolute response magnitude of the population of neurons for 13 of 15 mixtures assessed, which is superior to the predictive power of any of the other models. The model also accurately predicted the across neuron patterns generated by the binary mixtures, as evaluated by multidimensional scaling analysis. The results suggest that there is no emergence of unique qualities for binary mixtures relative to components of these mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190182
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Inhibition of taurine and 5′AMP olfactory receptor sites of the spiny lobster Panulirus argus by odorant compounds and mixtures (1995)
    Springer
    Journal of comparative physiology 176 (1995), S. 527-540 
    Details
    ISSN: 1432-1351
    Keywords: Olfaction ; Transduction ; Receptor ; Binding ; Chemoreception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 1. The effects of the odorant compounds adenosine-5′-monophosphate (5′AMP), ammonium, betaine, L-cysteine, L-glutamate, DL-succinate, and taurine and of mixtures of these comounds on binding of taurine and 5′AMP to dendritic membrane from the olfactory organ of spiny lobsters (Panulirus argus) were quantified to evaluate the contribution of inhibition of odorant-receptor binding to the generation of physiological responses to mixtures. 2. Taurine binding sites belong to two affinity classes, while 5′AMP binding sites belong to a single affinity class. Binding of either taurine or 5′AMP was partially inhibited in an apparently noncompetitive, concentration dependent fashion by most odorant compounds, with 25–40 % inhibition by 1 mM of odorant. Mixtures of two or more odorant compounds also inhibited binding of taurine or 5′AMP to its sites. However, the inhibition by mixtures was often significantly less than expected from the inhibition produced by a mixture's components assuming either a noncompetitive or competitive mechanism. 3. By including this binding inhibition between compounds into models for predicting physiological responses to mixtures from the responses to the components, the predictive power of the models is significantly improved. This result strongly suggests that binding inhibition can influence the physiological responsiveness of chemoreceptor cells to mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196418
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Control strategies for finger movement during touch-typing The role of the extrinsic muscles during a keystroke (1998)
    Springer
    Experimental brain research 121 (1998), S. 1-6 
    Details
    ISSN: 1432-1106
    Keywords: Key words EMG ; Finger ; Typing ; Force ; Neural control ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A single keystroke during touch-typing is a rapid, goal-directed motion of the fingertip which consists of two single-direction movements. The neural control and the role of the finger extrinsic musculature during typing have not yet been explained. The fingertip motion and force, and the intramuscular electromyographic (EMG) activity (fine-wire) of the index finger extrinsic musculature were measured during touch-typing by ten experienced typists. The motions and forces were repeatable qualitatively across keystrokes. A three-burst EMG pattern was observed during a single keystroke. The three bursts were: (1) a burst of extensor activity lifted the finger before the keystroke; (2) a burst of flexor activity followed while the fingertip was moving downward; and (3) a second burst of extensor activity occurred as the fingertip reached the end of key travel. The timing of the third burst suggests the role of the extensors is to remove the fingertip from the keyswitch rather than stop the downward motion of the finger. The collision with the end of key travel stops the downward finger motion. The timing of the finger flexor EMG activity, burst 2, suggests that the flexor contraction principally overcomes the activation force of the keyswitch rather than accelerates the finger downward as expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050430
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of the muscarinic antagonist scopolamine on regional cerebral blood flow during the performance of a memory task (1995)
    Springer
    Experimental brain research 104 (1995), S. 337-348 
    Details
    ISSN: 1432-1106
    Keywords: Scopolamine ; Memory ; Positron emission tomography ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Scopolamine, a muscarinic antagonist, impairs memory performance in both humans and animals. In this study, repeated measurements of regional cerebral blood flow (rCBF) were made in normal volunteers whilst performing auditory verbal memory tasks, before and after the administration of scopolamine (0.4 mg s.c.) or placebo. Compared to placebo, scopolamine increased blood flow in the lateral occipital cortex bilaterally and the left orbitofrontal region. Scopolamine decreased rCBF in the region of the right thalamus, the precuneus and the right and left lateral premotor areas. Scopolamine attenuated memory-task-induced increases of rCBF in the left and right prefrontal cortex and the right anterior cingulate region. These data suggest that acute blockade of cholinergic neurotransmission affects diverse brain areas, including components of the visual and motor systems, and, in addition, modulates memory task activations at distinct points in a distributed network for memory function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242019
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Frequency peaks of tremor, muscle vibration and electromyographic activity at 10 Hz, 20 Hz and 40 Hz during human finger muscle contraction may reflect rhythmicities of central neural firing (1997)
    Springer
    Experimental brain research 114 (1997), S. 525-541 
    Details
    ISSN: 1432-1106
    Keywords: Key words Tremor ; Electromyogram ; Muscle vibration ; Frequency analysis ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The output from the central nervous system to muscles may be rhythmic in nature. Previous recordings investigating peripheral manifestations of such rhythmic activity are conflicting. This study attempts to resolve these conflicts by employing a novel arrangement to measure and correlate rhythms in tremor, electromyographic (EMG) activity and muscle vibration sounds during steady index finger abduction. An elastic attachment of the index finger to a strain gauge allowed a strong but relatively unfixed abducting contraction of the first dorsal interosseous (1DI). An accelerometer attached to the end of the finger recorded tremor, surface electrodes over 1DI recorded EMG signals and a heart-sounds monitor placed over 1DI recorded vibration. This arrangement enabled maintenance of a constant overall muscle contraction strength while still allowing measurement of the occurrence of tremulous movements of the finger. Ten normal subjects were studied with the index finger first extended at rest and then contracting 1DI to abduct the index finger against three different steady forces up to 50% of maximal voluntary contraction (MVC). Power spectral analysis of tremor, EMG activity and muscle vibration signals each revealed three frequency peaks occurring together at around 10 Hz, 20 Hz and 40 Hz. Coherence analysis showed that the same three peaks were present in the three signals. Phase analysis indicated a fixed time lag of tremor behind EMG of around 6.5 ms. This is compared with previous measurements of electromechanical delay. Other experiments indicated that the three peaks were of central nervous origin. Introducing mechanical perturbations or extra loading to the finger and making recordings under partial anaesthesia of the hand and forearm demonstrated preservation of all the peaks, suggesting that they did not originate from mechanical resonances or peripheral feedback loop resonances. It is concluded that, at least for a small hand muscle, there exist not one but a number of separate peak frequencies of oscillation during active contraction, and that these oscillations reflect synchronization of motor units at frequencies determined within the central nervous system. It is proposed that the multiple oscillations may be a means of frequency coding of motor commands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005662
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    Paper (German National Licenses)
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