The gain of the spike encoder at the afferent fibre terminal constitutes the last step in signal processing at the semicircular canal. To estimate the encoder properties EPSPs and spikes were intracellularly recorded, at rest and during rotation, from single fibres of the posterior nerve in the isolated labyrinth. The recordings were fed into the computer and analyzed. The spike frequency (encoder output) was determined and, after digital subtraction of the spikes, the EPSP rate (encoder input) was evaluated by means of a procedure of fluctuation analysis. In the examined units the main features of EPSP and spike responses can be summarized as follows: 1) resting spike rates were generally low (<3 spikes/s); 2) during excitation, while the EPSP rate was rising, the spike rate increased even faster; 3) the decline in the spike rate, after the excitatory peak, anticipated that of the EPSP rate; 4) fibres with low resting spike rates showed marked rectification of the response (silencing of spike rate during inhibition). It follows that the relation between spike and EPSP rates (encoder gain) is not linear, leading to amplification of the asymmetry in the response and rectification by the encoder. The dynamic behaviour of the encoder is also complex and determines a phase lead in the spike rate larger than that observed in the EPSP rate with respect to angular velocity.
The spike encoder at the frog semicircular canal
ROSSI, Marialisa;MARTINI, Marta;BONIFAZZI, Claudio;
1991
Abstract
The gain of the spike encoder at the afferent fibre terminal constitutes the last step in signal processing at the semicircular canal. To estimate the encoder properties EPSPs and spikes were intracellularly recorded, at rest and during rotation, from single fibres of the posterior nerve in the isolated labyrinth. The recordings were fed into the computer and analyzed. The spike frequency (encoder output) was determined and, after digital subtraction of the spikes, the EPSP rate (encoder input) was evaluated by means of a procedure of fluctuation analysis. In the examined units the main features of EPSP and spike responses can be summarized as follows: 1) resting spike rates were generally low (<3 spikes/s); 2) during excitation, while the EPSP rate was rising, the spike rate increased even faster; 3) the decline in the spike rate, after the excitatory peak, anticipated that of the EPSP rate; 4) fibres with low resting spike rates showed marked rectification of the response (silencing of spike rate during inhibition). It follows that the relation between spike and EPSP rates (encoder gain) is not linear, leading to amplification of the asymmetry in the response and rectification by the encoder. The dynamic behaviour of the encoder is also complex and determines a phase lead in the spike rate larger than that observed in the EPSP rate with respect to angular velocity.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
