Dynamical coding structure in mammal auditory system revealed by optical imaging

High performance optical recording systems were applied to analyzed dynamical neural behavior in mammal, guinea pig and rat, for investigating coding structure in the auditory system. The neural coding structure in an anaesthetized guinea pig auditory cortex was investigated by comparing the spatio-temporal neural responses evoked to simple tone bursts, a complex sound such as click and natural species specific vocalizations (in vivo experiment). The cortical coding for vocalization is due to the dynamic assembly of the neurons corresponding to these formant frequencies. The results also show that any neurons specific to the species specific vocalization do not exist in the auditory cortex. Regarding the visualization of the place coding of the interaural delay for sound localization, the in vitro optical imaging of the organotypic slice culture showed the possibility to visualize the ITD topography proposed by Jefferess.