| Abstract: | Experiments on waking curarized turtles showed that auditory representation is located in the mediodorsal zone of the tegmentum, in the torus semicircularis, which contains monomodal auditory and bimodal somatoauditory neurons. The somatosensory system is represented more widely and overlaps in the medial zones with the auditory system. Its focus is located in the lateral zones of the dorsal tegmentum (n. intercollicularis), where monomodal somatic neurons were found. Predominance of contralateral somatic projections was discovered. Frequency-threshold curves, obtained by analysis of evoked potentials, were flattened Y-shaped. The range of frequencies received was 40–6000 Hz and the range of optimal frequencies 100–400 Hz. Responses of midbrain auditory neurons could be divided into three principal types: phasic, tonic, and bursting. Neurons with a phasic type of response were characterized by tuning to one optimal frequency, whereas most neurons with responses of tonic type were equally sensitive to two or even three frequencies.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 260–269, May–June, 1982. |
