Heterogeneity of connections in the cat's midbrain tegmentum (Russian)

The responses of single neurons in the midbrain tegmentum of a mesencephalic cat were recorded extracellularly. The microelectrode used for stimulation was 500 μm rostral to the recording one. The average latencies of direct and monosynaptic responses were 0.3 ms longer than the corresponding latencies under local microstimulation. The identification of responses was based on the data on latency, duration of refractoriness, presence of summation and dependence of the firing index on the application of glutamate to the recorded neuron. The thresholds of synaptic responses in relation to different depths of the stimulating electrode were measured. The experimental data can be approximated by parabolas. The findings indicate the horizontal orienation of rostrocaudal projections in the midbrain tegmentum.