Tectal connectivity in the frog <i>Rana pipiens</i>: Tectotegmental projections and a general analysis of topographic organization

Tectal afferents were studied in adult lampreys of three species (Ichthyomyzon unicuspis, Lampetra fluviatilis, and Petromyzon marinus) following unilateral BDA injections into the optic tectum (OT). In the secondary prosencephalon, neurons projecting to the OT were observed in the pallium, the subhipoccampal lobe, the striatum, the preoptic area and the hypothalamus. Following tectal injections, backfilled diencephalic cells were found bilaterally in: prethalamic eminence, ventral geniculate nucleus, periventricular prethalamic nucleus, periventricular pretectal nucleus, precommissural nucleus, magnocellular and parvocellular nuclei of the posterior commissure and pretectal nucleus; and ipsilaterally in: nucleus of Bellonci, periventricular thalamic nucleus, nucleus of the tuberculum posterior, and the subpretectal tegmentum, as well as in the pineal organ. At midbrain levels, retrogradely labeled cells were seen in the ipsilateral torus semicircularis, the contralateral OT, and bilaterally in the mesencephalic reticular formation and inside the limits of the retinopetal nuclei. In the hindbrain, tectal projecting cells were also bilaterally labeled in the dorsal and lateral isthmic nuclei, the octavolateral area, the sensory nucleus of the descending trigeminal tract, the dorsal column nucleus and the reticular formation. The rostral spinal cord also exhibited a few labeled cells. These results demonstrate a complex pattern of connections in the lamprey OT, most of which have been reported in other vertebrates. Hence, the lamprey OT receives a large number of nonvisual afferents from all major brain areas, and so is involved in information processing from different somatic sensory modalities.

Section: Afferents From the Secondary Prosencephalonmentioning

confidence: 89%

Afferent Connections of the Optic Tectum in Lampreys: An Experimental Study

Arriba

Pombal²

2006

“…Extracellular recordings made by Smeraski and Grobstein 119911 from the ventral midbrain tegmentum in frogs have shown that tegmental cells in this region exhibit distinctive spontaneous activity and can be acti vated by stimulating either of the tecta. It has been sug gested that the tectotegmental projections may be related to visually elicited orienting behaviours in amphibians [Masino andGrobstein. 1990: Smeraski andGrobstein.…”

Section: Discussionmentioning

confidence: 99%

Excitatory and InhibitoryTransmission from the Optic Tectum to Nucleus Isthmi and Its Vicinity in Amphibians

Wu¹,

Wang²

1995

Intracellular recordings were made from nucleus isthmi (NI) and its vicinity in toads (Bufo bufo gargarizans) in response to electrical stimulation of the bilateral optic tract. The results suggest that NI mainly receives its excitatory input from the ipsilateral tectum and its inhibitory input from the contralateral tectum. Tegmental cells in a region medioventral to NI were usually characterized by strong spontaneous activity and an excitatory-inhibitory sequence of postsynaptic potentials in response to stimulation of either side of the bilateral optic tract. Sixty of the recorded cells were stained with Lucifer yellow to show their morphological features and anatomical positions within NI and its vicinity.

“…I946| demonstrate that some cells in the medial part of the central nucleus possess dendrites that extend laterally for a considerable distance where they would be in a position to receive input from the lateral, somatosensory part of the torus [Feng and Lin, 1991) and possibly, the optic tectum [Scalia. 1976b;Masino andGrobstein, 1990: Montgomery andFite. 1991 ].…”

Section: Diencephalonmentioning

confidence: 99%

Afferent Projections to the Hypothalamus in Ranid Frogs

Neary¹

1995

Hypothalamic afferents were examined following applications of wheat germ agglutinin-horseradish peroxidase in the infundibulum of bullfrogs (Rana catesbeiana). Neuronal populations were generally labelled bilaterally, with an ipsiIateral predominance. In the telencephalon, most labelled cells were present in the medial pallium, ventral lateral pallium, lateral amygdala, and lateral septal nucleus. A moderate number of cells were found in the medial amygdala and fewer still in the caudal striatum, olfactory tubercle/diagonal band nucleus, medial septal nucleus, and median septum. In the diencephalon, labelled neurons were primarily found in the anterior and central thalamic nuclei, anterior preoptic area, and suprachiasmatic nucleus. Fewer cells were present in the ventral habenular nucleus, anterior division of the lateral thalamic nucleus, posterior thalamic nucleus, ventromedial thalamic nucleus, magnocellular preoptic nucleus, posterior entopeduncular nucleus, and along the medial forebrain bundle. In the midbrain, a few labelled cells were found in the nucleus of the medial longitudinal fasciculus, suprapeduncular nucleus, and posteroventral tegmental nucleus. The secondary isthmal nucleus contained a large number of labelled neurons and moderate numbers of labelled cells were present in the grey medial to nucleus isthmi and in the isthmal raphe. A few lightly labelled cells were also seen in the parabrachial nucleus. Finally, after the largest applications, a few cells were seen in the obex region ventrolateral to the solitary tract.