Sensory information processing in the frog olfactory pathways. Experimental basis for modeling studies

In the frog, unitary electrophysiological recordings have been extensively used to investigate odor processing along the olfactory pathways. By comparing spontaneous and odor-evoked activities of neuroreceptor, mitral and cortical cells, we have collected fundamental data relating to coding abilities of the three olfactory levels, the olfactory mucosa, the bulb and the cortex. Based on a synthesis of our experimental data related to GABAergic and dopaminergic involvement in the olfactory bulb, this paper aims to match this information with computational data and to discuss some questions on bulbar processing. This paper is also devoted to further analyze original results on coding properties of two functionally evidenced neuron subpopulations in the olfactory cortex. Thus, the assumption according to which some cortical neurons may work as temporal integrators while others as coincidence detectors is presented. Moreover, the pertinence that the neural code may be carried by a single spike with varying latency was demonstrated.