Institut de l’Audition
Feedforward propagation along the mouse auditory pathway
How spikes propagate along multiple layer networks has been extensively studied with computational models. Feedforward networks are a prominent model able to transmit information rapidly, but these networks have been difficult to isolate in the intact mammalian brain. Here, we focus on the auditory network which is characterized by multiple connected relays. We used sound and optogenetic stimulations to drive the auditory periphery and monitored neuronal activity at two locations along the auditory pathway simultaneously, using large-scale electrophysiological recordings. We observed fast and efficient propagation of pulse packets, in agreement with a feedforward description of the auditory network. We further determined the state-phase diagram of spike propagation and demonstrated the presence of an attractor fixpoint that enables robust and quick transfer of information. However, propagation was not limited to only synchronized events. Prolonged firing was also evoked and necessary to promote an efficient transfer of graded inputs and subsequent readout in downstream structures. Taken together, the auditory network combines both temporal and firing rate modes of propagation to reliably encode the different dimensions of sound features.