About: Rhinal sulcus is a(n) research topic. Over the lifetime, 116 publication(s) have been published within this topic receiving 14784 citation(s).
Papers published on a yearly basis
TL;DR: The mediodorsal nucleus of the rat thalamus has been divided into medial, central and lateral segments, and these segments have been shown by experiments using the autoradiographic method of demonstrating axonal connections to project to seven distinct cortical areas covering most of the frontal pole of the hemisphere.
Abstract: The mediodorsal nucleus of the rat thalamus has been divided into medial, central and lateral segments on the basis of its structure and axonal connections, and these segments have been shown by experiments using the autoradiographic method of demonstrating axonal connections to project to seven distinct cortical areas covering most of the frontal pole of the hemisphere. The position and cytoarchitectonic characteristics of these areas are described. The medial segment of the nucleus projects to the prelimbic area (32) on the medial surface of the hemisphere, and to the dorsal agranular insular area, dorsal to the rhinal sulcus on the lateral surface. The lateral segment projects to the anterior cingulate area (area 24) and the medial precentral area on the dorsomedial shoulder of the hemisphere, while the central segment projects to the ventral agranular insular area in the dorsal bank of the rhinal sulcus, and to a lateral part of the orbital cortex further rostrally. (The term "orbital" is used to refer to the cortex on the ventral surface of the frontal pole of the hemisphere.) A ventral part of this orbital cortex also receives fibers from the mediodorsal nucleus, possibly its lateral segment, but the medial part of the orbital cortex, and the ventrolateral orbital area in the fundus of the rhinal sulcus receive projections from the paratenial nucleus and the submedial nucleus, respectively. All of these thalamocortical projections end in layer III, and in the outer part of layer I. The basal nucleus of the ventromedial complex (the thalamic taste relay) has been shown to have a similar laminar projection (layer I and layers III/IV) to the granular insular area immediately dorsal to, but not overlapping, the mediodorsal projection field. However, the principal nucleus of the ventromedial complex appears to project to layer I, and possibly layer VI, of the entire frontal pole of the hemisphere. The anteromedial nucleus does not appear to project to layer III of the projection field of the mediodorsal nucleus, although it may project to layers I and VI, especially in the anterior cingulate and medial precentral areas. A thalamoamygdaloid projection from the medial segment of the mediodorsal nucleus to the basolateral nucleus of the amygdala has also been demonstrated, which reciprocates an amygdalothalamic projection from the basolateral nucleus to the medial segment. The habenular nuclei also appear to project to the central nucleus of the amygdala. These results are discussed in relation to the delineation and subdivision of the prefrontal cortex in the rat, and to amygdalothalamic and amygdalocortical projections which are described in a subsequent paper (Krettek and Price, '77).
TL;DR: The rat's MD-projection cortex differs from that in the monkey in that it lacks a granular layer and appears to have no prominent direct associations with temporal and juxtahippocampal areas, suggesting that the striatum or thalamus receives a proportionally larger share of the MD projection in this animal than it does in themonkey.
Abstract: The cortical projection field of the mediodorsal nucleus of the thalamus (MD) was identified in the rat using the Fink-Heimer silver technique for tracing degenerating fibers. Small stereotaxic lesions confined to MD were followed by terminal degeneration in the dorsal bank of the rhinal sulcus (sulcal cortex) and the medial wall of the hemisphere anterior and dorsal to the genu of the corpus callosum (medial cortex). No degenerating fibers were traced to the convexity of the hemisphere. The cortical formation receiving a projection from MD is of a relatively undifferentiated type which had been previously classified as juxtallocortex. A study of the efferent fiber connections of the rat's MD-projection cortex demonstrated some similarities to those of monkey prefrontal cortex. A substantial projection to the pretectal area and deep layers of the superior colliculus originates in medial cortex, a connection previously reported for caudal prefrontal (area 8) cortex in the monkey. Sulcal cortex projects to basal olfactory structures and lateral hypothalamus, as does orbital frontal cortex in the monkey. The rat's MD-projection cortex differs from that in the monkey in that it lacks a granular layer and appears to have no prominent direct associations with temporal and juxtahippocampal areas. Furthermore, retrograde degeneration does not appear in the rat thalamus after damage to MD-projection areas, suggesting that the striatum or thalamus receives a proportionally larger share of the MD projection in this animal than it does in the monkey. Comparative behavioral investigations are in progress to investigate functional differences between granular prefrontal cortex in the primate and the relatively primitive MD-projection cortex in the rat.
TL;DR: Projections are described from the basolateral, lateral and anterior cortical nuclei of the amygdaloid complex, and from the prepiriform cortex, to several discrete areas of the cerebral cortex in the rat and cat and to the mediodorsasl thalamic nucleus in the rats.
Abstract: Projections are described from the basolateral, lateral and anterior cortical nuclei of the amygdaloid complex, and from the prepiriform cortex, to several discrete areas of the cerebral cortex in the rat and cat and to the mediodorsal thalamic nucleus in the rat. These projections are very well-defined in their origin, and in their area of laminar pattern of termination. The basolateral amygdaloid nucleus can be divided into anterior and posterior divisions, based on cytoarchitectonic and connectional distinctions. In both the rat and cat the posterior division projects to the prelimbic area (area 32) and the infralimbic area (area 25) on the medical surface of the hemisphere. The anterior division projects more lightly to these areas, but also sends fibers to the dorsal and posterior agranular insular areas and the perirhinal area on the lateral surface. Furthermore, in the cat the perirhinal area is divided into two areas (areas 35 and 36) and the anterior division projects to both of these and also to a ventral part of the granular insular area; this last area is adjacent to, but separate from the auditory insular area and the second cortical taste area. In most of these areas, the fibers from the basolateral nucleus terminate predominantly in two bands: one in the deep part of layer I and layer II, and a heavier band in layer V (in the rat) or layers V and VI (in the cat). The lateral amygdaloid nucleus projects heavily to the perirhinal area, and also to the posterior agranular insular area. These fibers terminate predominantly in the middle layers of the cortex, although the cellular lamination in these two areas is relatively indistinct. The anterior cortical amygdaloid nucleus and the prepiriform cortex both project to the infralimbic area and the ventral agranular insular area, and the anterior cortical nucleus also projects to the posterior agranular area and the perirhinal area. In all of these areas, the fibers from these olfactory-related structures terminate in the middle of layer I. In the rat, the two divisions of the basolateral nucleus also project to the medial segment of the mediodorsal thalamic nucleus, with the anterior division projecting mainly to the posterior part of this segment and the posterior division to the anterior part. The endopiriform nucleus, deep to the prepiriform cortex, projects to the central segment of the mediodorsal nucleus; this may constitute the major olfactory input into the mediodorsal nucleus, since little or no projection could be demonstrated from the prepiriform cortex itself. Projections to the mediodorsal nucleus have not been found in the cat.
TL;DR: It is speculated that each of these prefrontal projections may carry highly specific information into the hippocampus, whereas the reciprocal projections may allow retrieval by prefrontal cortex of memories stored in the hippocampus.
Abstract: Anterograde and retrograde tracing methods including autoradiography, horseradish peroxidase histochemistry and fluorescent dye transport were used to demonstrate that the dorsolateral prefrontal cortex is connected with the hippocampal formation and associated cortical regions by two distinct pathways. Fibers forming a lateral pathway travel in the fronto-occipital fasciculus and connect the dorsolateral prefrontal cortex with the fundus of the rhinal sulcus, posterior subdivisions of the parahippocampal gyrus, and the presubiculum. A larger medial pathway forms in the cingulum bundle and terminates in the most caudal part of the presubiculum, as well as in adjacent transitional cortices. These cortices form a caudomedial promontory that is located between the posterior cingulate and prestriate areas. In all allo- and mesocortical targets of prefrontal cortex, labeled terminals form banding patterns reminiscent of the columnar organization of afferent fiber columns in neocortex. The same cytoarchitectonic areas that receive prefrontal afferents issue reciprocal projections. The largest source is the caudomedial lobule including its presubicular portion. Neurons in the parahippocampal gyrus and adjacent presubiculum also are retrogradely labeled following implants of horseradish peroxidase or injection of fluorescent dyes into prefrontal cortex. In addition, subicular neurons project to the prefrontal cortex although the subiculum does not appear to receive prefrontal afferent input. These findings emphasize that multiple channels of communication link the dorsolateral prefrontal cortex and the hippocampus via the parahippocampal gyrus, subiculum, presubiculum and adjacent transitional cortices. We speculate that each of these prefrontal projections may carry highly specific information into the hippocampus, whereas the reciprocal projections may allow retrieval by prefrontal cortex of memories stored in the hippocampus.
TL;DR: The caudal levels of the orbitofrontal area were found to give rise to an additional projection which terminated in the entorhinal cortex and the transitional cortices bordering the rhinal sulcus, providing a much more direct means for the frontal lobe to influence the hippocampus than those involving the cingulate gyrus.
Abstract: In this investigation, the efferent cortico-cortical projections of the orbitofrontal cortex in the rhesus monkey have been investigated using silver impregnation methods. Projections from this area were observed to terminate in the rostral portions of the temporal lobe (areas TA, TE and TG) and cingulate gyrus (area 24), the insular cortex, and some dorsolateral prefrontal areas. Although these connections characterized all areas, with the exception of Walker's area 14 and Bonin and Bailey's area FL, the caudal levels of the orbitofrontal area were found to give rise to an additional projection which terminated in the entorhinal cortex and the transitional cortices bordering the rhinal sulcus. The source of this projection correlated closely with an area labeled FF by Bonin and Bailey. This connection may provide a much more direct means for the frontal lobe to influence the hippocampus than those involving the cingulate gyrus.