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  • 1
    Electronic Resource
    Electronic Resource
    Facilitation of somatosensory evoked potentials by exploratory finger movements (1993)
    Springer
    Experimental brain research 95 (1993), S. 330-338 
    Details
    ISSN: 1432-1106
    Keywords: Somatosensory processing ; Somatosensory ; evoked potentials ; Microneurography ; Movement ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Modification of somatosensory processing depending on the behavioral setting was studied. Active alternating movements of the fingers, passive tactile stimuli to the hand, and active exploration of objects were performed during recording of somatosensory evoked potentials (SEPs). SEPs were elicited by compound electrical median nerve stimulation and electrical stimulation at detection threshold of cutaneous median nerve fascicles identified by microneurography. Electrical stimulation was not time-locked to the studied condition. In comparison with SEPs at rest there was attenuation of early cortical potentials up to 25 ms post-trigger in all nonresting conditions. In stimulation of the compound median nerve as well as of isolated cutaneous fascicles of a hand actively exploring an object there was an additional increased negativity, peaking at 28 ms. This facilitory effect was independent of attentional focusing and was absent during exploration using the ipsilateral, non-electrically stimulated hand. In patients with parietal lesions the facilitatory effect was diminished on the affected side. Spline interpolated brain maps at this latency based on 32channel recordings in healthy volunteers showed a shift of local contralateral positive maximum from frontal to parietal during exploration, indicating enhancement of a tangential dipole. It is suggested that in conditions involving close sensorimotor interaction such as exploratory hand movements there is preactivation of a cortical area which is located in the central sulcus and receives cutaneous somatosensory inputs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229790
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Origin of P16 median nerve SEP component identified by dipole source analysis — subthalamic or within the thalamo-cortical radiation? (1995)
    Springer
    Experimental brain research 104 (1995), S. 511-518 
    Details
    ISSN: 1432-1106
    Keywords: Early SEPs ; P16 ; Source analysis ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Following median nerve stimulation, several monophasic peaks were recorded at the scalp in the 15–18 ms time range. Source analysis, using three different methods, modelled a source near the centre of the head with an orientation towards the activated hemisphere and a peak activity at 16 ms post stimulus. Magnetic recordings detected no signal in this time range, which confirmed a subcortical location of the source. From dipole localization it was not possible to assign the exact origin of the P16 source to either the subthalamic level or the thalamo-cortical radiation, because of the limited spatial resolution at the centre of the spherical head model. An estimate of the conduction velocity of the medial lemniscus pointed towards a subthalamic origin. The P16 source was preserved in two patients with a lesion of the thalamo-cortical radiation and the ventral thalamus. Further evidence for a subthalamic location of P16 was derived from the physical mechanisms generating far-field potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231985
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Chiroptical detection. Novel possibilities of its application to enantiomers (1988)
    Springer
    Chromatographia 25 (1988), S. 182-188 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Detection, chiroptical, polarimetric, circular dichroic ; Enantiomers ; Sorbents, optically active
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polarimetric and/or circular dichroic detection of enantiomers after liquid chromatography on optically active sorberts has been used for the following purposes: determination of enantiomeric purity in spite of peak overlap, investigation of enantiomerization during chromatography, monitoring of racemizations and recording of circular dichrograms without preparative enrichment of enantiomers. Novel examples for all applications are give. The general prospects for chiroptical detection are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02316442
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    Paper (German National Licenses)
    Fulltext
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