EPSPs and spike discharge were recorded intracellularly from 30 fibres of the posterior canal in the isolated frog labyrinth. The resting discharge was 6.6 +/- 7 spikes/sec (Mean +/-SD). The response properties of single units were described during repeated angular acceleration steps (0.3-20 deg/sec2) of 6-12 sec duration. Only one unit exhibited a clearcut adaptation, 7 units were slightly and irregularly adapting, while 22 units did not adapt at all. The response was linearly related to acceleration, with a gain of 2.4 +/- 1.7 spikes.sec-1/deg.sec-2 (Mean +/- SD) in 17 of the units tested, while the discharge frequency of 6 units was logarithmically related to acceleration. Threshold for frequency increase ranged from 0.2 to 2 deg/sec2 and latency from 50 msec to 2 sec. The response timecourse to a single acceleration step markedly deviated from the exponential expected from the torsion pendulum model. The observed nonlinearities can be ascribed to the absence of the efferent control. However, distortions from the model may also be due both to the mechanoelectrical transduction at the receptor level and the properties of the afferent synapse; in fact, an exponential decay of the discharge is consistently observed when the cupola passively shifts to the zero position, at the end of the acceleration step.
Risposta dei neuroni del I ordine ad accelerazioni angolari controllate nel labirinto isolato di rana
ROSSI, Marialisa;MARTINI, Marta
1983
Abstract
EPSPs and spike discharge were recorded intracellularly from 30 fibres of the posterior canal in the isolated frog labyrinth. The resting discharge was 6.6 +/- 7 spikes/sec (Mean +/-SD). The response properties of single units were described during repeated angular acceleration steps (0.3-20 deg/sec2) of 6-12 sec duration. Only one unit exhibited a clearcut adaptation, 7 units were slightly and irregularly adapting, while 22 units did not adapt at all. The response was linearly related to acceleration, with a gain of 2.4 +/- 1.7 spikes.sec-1/deg.sec-2 (Mean +/- SD) in 17 of the units tested, while the discharge frequency of 6 units was logarithmically related to acceleration. Threshold for frequency increase ranged from 0.2 to 2 deg/sec2 and latency from 50 msec to 2 sec. The response timecourse to a single acceleration step markedly deviated from the exponential expected from the torsion pendulum model. The observed nonlinearities can be ascribed to the absence of the efferent control. However, distortions from the model may also be due both to the mechanoelectrical transduction at the receptor level and the properties of the afferent synapse; in fact, an exponential decay of the discharge is consistently observed when the cupola passively shifts to the zero position, at the end of the acceleration step.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
