The semicircular canal transfer function was derived in the isolated frog labyrinth from the dynamic properties of the EPSPs recorded at the posterior canal cytoneural junction. At rest and during sinusoidal rotation the EPSP amplitude and frequency were determined by a modified noise analysis procedure using higher moments of fluctuations in membrane potential. After corrections for nonlinear summation and amplitude distribution of the unitary synaptic events, the resting EPSP frequency ranged between 50 and 280 EPSPs/s. No relation was found between resting discharge levels and the magnitude of the response. Positive excitatory peak values were larger than the negative inhibitory ones for accelerations stronger than 40°/s2 and during prolonged rotations they exhibited adaptation. Not only linear but also logarithmic intensity functions were detected in the different units. The EPSP emission deviates from the theoretical behaviour predicted by the torsion pendulum model. This and other distortions, which were previously revealed in the spike discharge pattern, indicate that the spiking properties do not arise at the encoder but are mainly determined by the modalities of transmitter release at the afferent synapse.
POSTERIOR CANAL TRANSFER FUNCTION ANALYZED AT THE EPSP LEVEL IN THE ISOLATED FROG LABYRINTH
ROSSI, Marialisa;MARTINI, Marta;BONIFAZZI, Claudio;
1988
Abstract
The semicircular canal transfer function was derived in the isolated frog labyrinth from the dynamic properties of the EPSPs recorded at the posterior canal cytoneural junction. At rest and during sinusoidal rotation the EPSP amplitude and frequency were determined by a modified noise analysis procedure using higher moments of fluctuations in membrane potential. After corrections for nonlinear summation and amplitude distribution of the unitary synaptic events, the resting EPSP frequency ranged between 50 and 280 EPSPs/s. No relation was found between resting discharge levels and the magnitude of the response. Positive excitatory peak values were larger than the negative inhibitory ones for accelerations stronger than 40°/s2 and during prolonged rotations they exhibited adaptation. Not only linear but also logarithmic intensity functions were detected in the different units. The EPSP emission deviates from the theoretical behaviour predicted by the torsion pendulum model. This and other distortions, which were previously revealed in the spike discharge pattern, indicate that the spiking properties do not arise at the encoder but are mainly determined by the modalities of transmitter release at the afferent synapse.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
