Nonolfactory afferent telencephalic projections in frogs

The degree of modal specificity of neurons of the tectum, dorsal thalamus, and primordial hippocampus relative to visual (photic) and somatic (tactile) stimulation was investigated in experiments on frogs (Rana temporaria) immobilized with tubocurarine. The specificity of sensory information arriving at the successive levels of the frog's thalamo-telencephalic afferent system diminishes in an ascending direction. Evoked potentials arising in the telencephalon in response to electrical stimulation of the sciatic nerve and to flashes are found not only in the primordial hippocampus, but also bilaterally in the septum and striatum. It is concluded on the basis of discharges recorded in the fibers of the thalamo-telencephalic tracts during somatic and visual stimulation that fibers carrying nonolfactory information into the telencephalon run in the medial and lateral forebrain bundles.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. International Brain Research Laboratory, Kotor, Yugoslavia. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 537–544, September–October, 1973.