A Study of Thalamo-Telencephalic Afferent Systems in Frogs

Abstract

In frogs (Rana temporaria) the evoked potentials and the neuronal responses to stimulation of the optic nerve have been found in the lateral geniculate, posterocentral, posterolateral and posterior thalamic nuclei of the contralateral side. Responses to stimulation of the sciatic nerve have beenfound bilaterally in the posterior thalamic, posterocentral and posterolateral nuclei. In the primordium hippocampi bilateral responses have been registered after the stimulation of the optic and sciatic nerves and a number of diencephalic structures. Bilateral destruction of lateral geniculate, posterocentral, posterolateral and posterior thalamic nuclei abolished the visual responses in the primordium hippocampi. Somatic responses in the primordium hippocampi disappeared after bilateral lesions of the posterior thalamic nucleus and of the caudal parts of posterocentral and posterolateral nuclei. These areas are considered as relay nuclei of visual and somatic telencephalic pathways.In frogs (Rana ridibunda) unilateral lesions of the caudal part of the dorsal thalamus were made. In sections stained according to Fink and Heimer and with the modified Bielshowsky-Viktorov methods, the terminal degeneration was found in the primordium hippocampi of both hemispheres.

A Pallial Visual Area in the Telencephalon of the Bony Fish <i>Polypterus</i>

“…Similarly, the SDH bands of the dorsal (P2) and lateral (P3) pallial zones are co-extensive with one or more terminal fields whose fibers arise within the diencephalon [Braford and Northcutt, 1978]. Given the suspected homology of the dorsal (P2) and lateral (P3) pallial zones in bichirs to the dorsal and medial pallial zones in other vertebrates [Northcutt and Braford, 1980], it is possible that the ascending projections to these pallial zones are visual in nature, as has been demonstrated in other anamniotes [Vesselkin et al, 1971;Vesselkin and Kovacevic, 1973;Scalia and Colman, 1975;Nikonorov and Luk'yanov, 1980;Neary, 1984;Prechtl et al, 1998;Saidel et al, 2001]. Until recently the origin of the diencephalic projections to P2 and P3 in bichirs was unknown, but it has now been established that these projections arise from nucleus medianus of the posterior tuberculum [Holmes and Northcutt, 2003].…”

Flux, Wavelength and Movement Discrimination in Frogs: Forebrain and Midbrain Contributions

“…Golgi studies have demonstrated that some thalamic cells contribute dendrites to these neuropile regions [Scalia and G reg o ry, 1970], K aramian et al [1966] recorded visually evoked potentials from both thalamus and telencephalon in the frog. Subsequently, visually driven single units were recorded from these two regions [Vesselkin et al, 1971;L iege and G aland, 1972]. The anuran posterior thalamus is involved in prey-catching behavior [Ew er t, 1970;Ingle, 1973].…”

Role of the Accessory Optic System in the Optokinetic Nystagmus of the Frog

“…When these centers were destroyed either alone or together with the pretectal or tectal areas, the lesion in the rostral part of the diencephalon did not add more to the effect which could be obtained by the individual ablation of these two latter areas. Re cent electrophysiological studies performed on frogs showed that, as in mammals, the lateral geniculate complex is a relay station in the retinothalamo-telcnciphalic pathway [Vesselkin et al, 1971]; therefore, it may have a role in visual perception rather than in visuomotor reflexes.…”