gms | German Medical Science

Based on tonotopy, auditory cortex (AC) of the rat can be divided into different cortical fields. Our previous results showed that there is clear difference in electrophysiological features of neurons in different auditory fields and that the tonotopy is not the only feature which distinguishes the architecture of the AC. The extracellular recordings were carried out in 35–40 days old Wistar rats. A 16 channel multielectrode (NeuroNexus technologies) was inserted perpendicularly to the surface of the AC allowing simultaneous recording of the neuronal activity. Neuronal responses to pure tones, broad band noise of different duration and latency and click trains with changing frequency and repetition rate were recorded and processed offline with custom made MatLab routines. Only recordings form layer IV neurons were used for the further analysis. The analysis of temporal pattern of the extracellularly recorded action potentials (AP) showed two different subpopulations of neurons. The representation of these two subpopulations differed between the auditory fields. In the primary and secondary auditory fields neurons with fast AP constitute the dominant population, whereas in the belt area which surrounds the AC, neurons with slow AP are most common. Our results show clear difference in neuronal subpopulations and their representation in different fields of AC and support our previous findings of distinct subpopulations in the primary auditory field and belt area based on the patch clamp recordings. Our findings further support the theory of the serial organization of the AC in the rat.

Supported by: GACR 309/07/1336,IGA NR 8113-4, LC 554.