Prosencephalic afferents to the mediodorsal thalamic nucleus

Abstract

The afferent projections from the prosencephalon to the mediodorsal thalamic nucleus (MD) were studied in the cat by use of the method of retrograde transport of horseradish peroxidase (HRP). Cortical and subcortical prosencephalic structures project bilaterally to the MD. The cortical afferents originate mainly in the ipsilateral prefrontal cortex. The premotor, prelimbic, anterior limbic, and insular agranular cortical areas are also origins of consistent projections to the MD. The motor cortex, insular granular area, and some other cortical association areas may be the source of cortical connections to the MD. The subcortical projections originate principally in the ipsilateral rostral part of the reticular thalamic nucleus and the rostral lateral hypothalamic area. Other parts of the hypothalamus, the most caudal parts of the thalamic reticular nucleus, the basal prosencephalic structures, the zona incerta, the claustrum, and the entopeduncular and subthalamic nuclei are also sources of projections to the MD. Distinct, but somewhat overlapping areas of the prosencephalon project to the three vertical subdivisions of MD (medial, intermediate, and lateral). The medial band of the MD receives a small number of prosencephalic projections; these arise mainly in the caudal and ventral parts of the prefrontal cortex. Cortical projections also arise in the infralimbic area, while subcortical projections originate in the medial part of the rostral reticular thalamic nucleus and lateral hypothalamic area. The intermediate band of the MD receives the largest number of fibers from the prosencephalon. These arise principally in the intermediate and dorsal part of the lateral and medial surface of the prefrontal cortex, the premotor cortex, and the prelimbic and agranular insular areas. Projections also originate in basal prosencephalic formations (preoptic area, Broca's diagonal band, substantia innominata, and olfactory tubercle), rostral reticular thalamic nucleus, and lateral hypothalamic area. A large number of prosencephalic structures also project to the lateral band of the MD. These are mainly the most dorsal and caudal parts of the lateral and medial surface of the prefrontal cortex, the premotor and motor cortices, and the prelimbic, anterior limbic, and insular areas. Projections arise also in the lateral rostral and caudal parts of the reticular thalamic nucleus, the zona incerta, the lateral and dorsal hypothalamic area, the claustrum, and the entopeduncular nucleus. These and previous results demonstrate a gradation in the afferent connections to the three subdivisions of the MD.(ABSTRACT TRUNCATED AT 400 WORDS)

Cytoarchitectonic and connectional organization of the ventral lateral geniculate nucleus in the cat

“…We previously reported that D projected to the rostral part of the reticular nucleus of the thalamus and had reciprocal connections with the zona incerta (Nakamura and Kawamura, 1988). The rostral part of the reticular nucleus of the thalamus forms a network with the intralaminar nuclei, the ventral frontal cortex, and the mediodorsal nucleus (Velayos and Reinoso-Suarez, 1985). The mediodorsal nucleus also has connections with medial, orbital, and dorsolateral prefrontal areas (GoldmanRakic and Porrino, 1985;Illinsky et al, 1985;Ray and Price 1993).…”

Cortical connections of the lateral mediodorsal thalamus in cynomolgus monkeys

“…Here we emphasize that the thalamic input to the portion of area 46 surrounding the fundus of the anterior PS arises from a portion of lateral MD distinctly different from that forming connections with the portion of 46 at the outer edges of the caudal PS. These differences in the thalamic projections are likely to be associated with important functional differences, given the unique profiles of subcortical afferents associated with MDmc and MDpc (Harting et al, 1980;Porrino et al, 1981;Velayos and Reinoso-Suarez, 1982;Ilinsky et al, 1985;Velayos and Reinoso-Suarez, 1985;Russchen et al, 1987;Erickson et al, 2002).…”

Architectonics of the Thalamus in the Echidna <i>(Tachyglossus aculeatus):</i>Search for the Mediodorsal Nucleus

“…In some species, e.g., in the rhesus mon key, the cytoarchitectural heterogeneity is obvious, whereas in others, e.g., cats, rats and opossums, the cytoarchitecture is uni form throughout the nucleus [Akert, 1964;Benjamin and Golden, 1985;Krettek and Price, 1977;Velayos and Reinoso-Suarez, 1985].…”