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  • 1
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Extracellular unit recordings were derived from the cat sensorimotor cortex by means of tungsten microelectrodes. Evidence was obtained for the value of time-locking of impulses: a critical time interval was demonstrated as essential for modifications caused in putaminally-evoked cortical local field potentials by preconditioning stimuli delivered to the nucleus entopeduncularis. A correlation analysis was carried out on responses of neurones of the sensorimotor cortex to stimulation of the pyramid or of sensory area S 1. Differentiation was made between common input and sequential firing operational conditions. Logics of and-gate and of conditional or-gate were recognized. Micro-circuitry was offered in each case. Evidence was offered for the importance of collaterals in such actions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Conduction velocities of PTN's were compared in the cat and in the squirrel monkey. In the cat these were found to be mostly between 40 and 100 m/sec while in the squirrel monkey a wider range of 10 to 120 m/sec was found. An accurate definition of PTN including for slow-conducting cells achieved by the use of as many as five criteria for such definition: spike shape, constancy of response and of latency value, response to high rates of stimulation of over 50/sec, and collision. After achieving the above definition the collision technique was used in a novel way in order to assess probabilities for impulse propagation into the axons of these neurones. Two types of propagation were thus defined qualitatively: a firm and an imtermittent one. The theory was advanced that the latter type of propagation might be related to a stochastically-based process by which the pyramidal tract utilizes the large number of fibers participating in the conduction of signals through it to correct for the signal error intrinsic to single fiber action.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1619-1560
    Keywords: Localized vasculature changes ; Latcral hypothalamus ; Sympathetic nervous system ; Superior cervical ganglion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Stimulation of specific lateral hypothalamic targets in a cat model induces vascular and/or cardiac changes. Evidence is presented that these may consist of discretely localized sympathetically mediated changes taking place in just one or two organs. Morever, following stimulation of either one of two adjacent lateral hypothalamus sites, pressor effects are induced that superficially look similar, but prove to be mediated by different pathways. To investigate possible synapsing at sympathetic ganglia, e.g. in superior cervical or stellate ganglia, 50 µg atropine methyl nitrate, a ganglionic blocker, was applied directly to the ganglia. This was shown to potentiate the pressor effects, in some cases when applied to the superior cervical ganglia, in others to stellate ganglia, presumably by blockade of a ganglionic attenuating mechanism. The contributions made by different sympathetic nerves to the lateral hypothalamus-induced pressor effect were analysed. Stimulation of one of the lateral hypothalamus sites (TAR.I) in eight cats induced a pressor effect that was abolished by severing a nerve branch, from the superior cervical ganglia laterally, shown to innervate neck muscle vasculature. In another group of nine cats stimulation of TAR.II induced a pressor effect abolished by cutting a branch from the superior cervical ganglia medially, shown to be destined to the vasculature of pharyngeal muscles and possibly lower respiratory tract. The hypothesis that central control via the sympathetic nervous system is responsible for differential organ specific regulation of blood flow to individual organs is discussed.
    Type of Medium: Electronic Resource
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