ISSN:
1432-0770
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Informatik
,
Physik
Notizen:
Summary The spike activity of eighth cranial nerve units tonically responsive to head position was recorded in cats anesthetized with pentobarbital sodium, and related with linear accelerations induced by gravity during maintained positions and during dynamic trajectories achieved through rolling around a rostro-caudal axis. The steady-state discharge of 80% of the cells had relatively small coefficients of variation, narrow histograms and periodic autocorrelograms. That of most remaining cells had large coefficients variation, nearly exponential histograms and flat or weakly periodic autocorrelograms. The static relation between head position and discharge showed that each cell had directional sensitivity, i.e. a characteristic change associated with each movement sense. Sixty-six percent of the cells had side-up increases in interval mean and standard deviation, with translation of the histogram to the right and reduction in the average autocorrelogram value: 34% had the opposite relations. Many cells showed multivaluedness, i.e. the interval mean (and other statistics) from different stations at any given position covered a range greater than that at each station. Multivaluedness varied from cell to cell. In the dynamic experiments the discharge was recorded during a continuous motion that involved a single sine wave or a mixture of sinusoids at frequencies up to 0.1 Hz. The spike trains exhibited a continuous mapping of the time varying tilt angle into the instantaneous rate with little or no evidence of multivaluedness. In addition to a tonic part, responses showed a phasic component with the characteristics of a unidirectional rate sensitivity that determined a phase-lead of the response with respect to the stimulus. The relative proportions of tonic and phasic components varied from cell to cell. Based upon anatomical and mechanical considerations (see Appendix) and upon the present results it is suggested that deformations of the trampoline-like membrane occur in a distributed manner. Multivaluedness may be due to forces which, like stiction, prevent complete relaxation of the membrane under static but not under dynamic conditions. The phasic response, whose origin is obscure, argues in favor of the otolithic receptors having a dynamic function, in addition to their role in detecting head positions with respect to gravity.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00289582
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