Showing papers on "Rhinal sulcus published in 1983"

Afferent connections of the perirhinal cortex in the rat.

Abstract: Connections of the perirhinal cortex in the.rat brain were studied using anterograde (3H-proline/leucine) and retrograde (horseradish peroxidase) tracers. The perirhinal cortex receives major projections from medial precen-tral, anterior cingulate, prelimbic, ventral lateral orbital, ventral and posterior agranular insular, temporal, superior and granular parietal, lateral occipital, agranular retrosplenial, and ectorhinal cortices, and from the pre-subiculum, subiculum, and diagonal band of Broca. Rostral neocortical areas project predominantly to rostral perirhinal regions while more caudal neocortical and subicular areas project predominantly to caudal perirhinal regions. Terminal fields are further segregated within perirhinal cortex to either the dorsal or ventral banks of the rhinal sulcus. All afferents from frontal areas terminate predominantly in the deep layers of its ventral bank; afferents from temporal, parietal, and lateral occipital areas terminate predominantly in the deep and superficial layers along its dorsal bank; and afferents from ectorhinal cortex terminate in a column within its dorsal bank. Cortical cells which project to perirhinal areas are found predominantly in layer II and the superficial part of layer III. However, ventrolateral orbital, parietal, and lateral occipital cortex projections originate predominantly from layer V. Perirhinal areas also receive afferents from the nucleus reuniens of the thalamus, lateral nucleus of the amygdala, claustrum, supramammillary nuclei, and the dorsal raphe nuclei.

Cortical and thalamic afferent connections of the insular and adjacent cortex of the cat

Abstract: Thalamic and cortical afferents to the insular and perirhinal cortex of the rat were investigated. Unilateral injections of horseradish peroxidase (HRP) were made iontophoretically along the rhinal sulcus. HRP injections covered or invaded areas along the rhinal fissure from about the level of the middle cerebral artery to the posterior end of the fissure. The most anterior injection labeled a few cells in the mediodorsal nucleus. More posterior injections labeled neurons in the basal portion of the nucleus ventralis medialis, thus suggesting that this cortical region constitutes the rat's gustatory (insular) cortex. We consider the cortex situated posterior to the gustatory cortex in and above the rhinal sulcus as the core region of the rat's (associative) insular cortex, as this cortex receives afferents from the regions of and between the nuclei suprageniculatus and geniculatus medialis, pars magnocellularis. It includes parts of the cortex termed perirhinal in other studies. The cortex dorsal and posterior to the insular cortex we consider auditory cortex, as it receives afferents from the principal part of the medial geniculate nucleus, and the cortex ventral to the insular cortex (below the fundus of the rhinal sulcus) we consider to constitute the prepiriform cortex, which is athalamic. The posterior part of the perirhinal cortex (area 35) receives afferents from nonspecific thalamic nuclei (midline nuclei). Cortical afferents to the injection loci arise from a number of regions, above all from regions of the medial and sulcal prefrontal cortex. Those injections confined to the projection cortex of the suprageniculate-magnocellular medial geniculate nuclear complex also led to labeling in contralateral prefrontal regions, particularly in area 25 (infralimbic region). A comparison of our results with those on the insular cortex of cats and monkeys suggests that on the basis of thalamocortical connections, topographical relations, and involvements of neurons in information processing and overt behavior, the insular cortex has to be regarded as a heterogeneous region which may be separated into prefrontal insular, gustatory (somatosensory) insular, and associative insular portions.

An electrophysiological analysis of some afferent and efferent pathways of the rat prefrontal cortex.

Abstract: Publisher Summary In the rat, the prefrontal cortex may be defined as the mesocortical zone receiving converging projections from the mediodorsal nucleus of the thalamus (MD) and from the dopamine (DA) cell group localized in the ventromedial mesencephalic tegmentum (VMT). It is composed of two subfields: a medial region, the pregenual medial wall of the hemisphere in reciprocal connection with the lateral part of the MD; and a lateral region on the dorsal bank of the rhinal sulcus, which is reciprocally connected with the medial part of the MD. A great number of cortical and subcortical structures receive efferents from prefrontal cortex and differences have been demonstrated anatomically as regards its medial and lateral projections. These projections involve other portions of the cortex (presubiculum, retrosplenial, perirhinal and entorhinal cortex) and subcortical structures related to the limbic system (midline thalamic nuclei, hypothalamus and the paramedian mesencephalic tegmentum) or the extrapyramidal system (striatum, substantia nigra (SN) and deep layers of the superior colliculus (CS)). The medial and lateral areas of the prefrontal cortex can also be distinguished on a functional basis because, in the rat, distinct behavioral deficits have been observed to result from their lesioning. This chapter reviews results from recent studies aimed at further characterization of the afferents to medial prefrontal cortex originating from the VMT, and the efferents from medial prefrontal cortex projecting to diencephalic and mesencephalic structures.