Rhinal sulcus

About: Rhinal sulcus is a research topic. Over the lifetime, 116 publications have been published within this topic receiving 14784 citations.

Connections of the parahippocampal cortex in the cat. III. Cortical and thalamic efferents.

Abstract: To study the distribution of the cortical and thalamic efferent projections from the parahippocampal cortex in the cat, a series of injections of anterogradely transported radioactively labeled amino acids were placed in different parts of the entorhinal and perirhinal cortices. Subsequently, some of the identified cortical and thalamic target areas were injected with retrograde tracers such as wheat germagglutinin conjugated with horseradish peroxidase (WGA-HRP) or with a fluorescent tracer-fast blue or nuclear yellow-in order to disclose the laminar origin of the parahippocampal efferent projections. The results indicate that the parahippocampal cortex gives rise to widespread projections to the association cortex, and, to a lesser extent, sends fibers to the limbic cortex and the primary sensory cortex. These projections arise mainly from the deep layers of the parahippocampal cortex and terminate predominantly in superficial layers of the cortex, with a preference for layer I. Within the cortical projections a medial-to-lateral topography could be observed such that the entorhinal cortex projects predominantly to the allocortical and periallocortical limbic areas, including parts of the subicular complex, the ventral retrosplenial and the infralimbic cortices, and olfactory related areas-i.e., the olfactory bulb, the anterior olfactory nucleus, the prepiriform cortex, and the ventral tenia tecta. The more lateral parts of the parahippocampal cortex, which surround the posterior rhinal sulcus, project in addition to extensive parts of the paralimbic association cortex that include the proisocortical cingular, prelimbic, orbitofrontal, and agranular and granular insular cortices. The most lateral portion of the parahippocampal cortex, the perirhinal cortex, furthermore issues projections to widespread neocortical areas on the lateral and medial aspects of the hemisphere that constitute part of the parasensory association cortex. Weak-to-moderate projections are found to the cortex of the middle suprasylvian and anterior ectosylvian sulci, as well as the cruciate and splenial sulci, all of which have been reported to constitute sensory convergence areas. The most marked projections from the perirhinal cortex reach a zone of neocortex directly lateral to the perirhinal cortex including ventral parts of the posterior sylvian, posterior ectosylvian, posterior suprasylvian, and lateral gyri. These projections appear to be topographically organized such that rostral parts of the perirhinal cortex project more rostrally, and more caudal parts of the perirhinal cortex project to more caudal parts of this cortical zone. The posterior sylvian gyrus may represent a para-auditory area, whereas the posterior suprasylvian and lateral gyri contain the paravisual areas 20 and 21. The rostrocaudal axis in the perirhinal cortex is thus related to an auditory-to-visual shift in the temporal association cortex. A similar relation is noted in the projections from the perirhinal cortex to the caudodorsal part of the thalamus. Rostrally located neurons in the perirhinal cortex project strongly to the auditory-related medial geniculate nucleus, whereas more caudally located perirhinal neurons project preferentially to the lateral posterior nucleus, which is strongly associated with the visual system. Additional but weaker projections are observed to reach the parafascicular, subparafascicular, and reuniens nuclei. Projections from the entorhinal cortex to the thalamus could not be demonstrated. It is concluded that major projections from the parahippocampal cortex reach widespread cortical areas and parts of the thalamus that are involved in higher-order processing of sensory information. This conclusion is discussed with respect to the intricate relations that exist between the parahippocampal cortex and the hippocampal formation.

Inferior parietal lobule projections to the presubiculum and neighboring ventromedial temporal cortical areas

Abstract: The entorhinal and perirhinal cortices have long been accorded a special role in the communications between neocortical areas and the hippocampal formation. Less attention has been paid to the presubiculum, which, however, is also a component of the parahippocampal gyrus, receives dense inputs from several cortical areas, and itself is a major source of connections to the entorhinal cortex (EC). In part of a closer investigation of corticohippocampal systems, the authors applied single-axon analysis to the connections from the inferior parietal lobule (IPL) to the presubiculum. One major result from this approach was the finding that many of these axons (at least 10 of 14) branch beyond the presubiculum. For 4 axons, branches were followed to area TF and to the border between the perirhinal and entorhinal cortices, raising the suggestion that these areas, which sometimes are viewed as serial stages, are tightly interconnected. In addition, the current data identify several features of presubicular organization that may be relevant to its functional role in visuospatial or memory processes: 1) Terminations from the IPL, as previously reported for prefrontal connections (Goldman-Rakic et al. [1984] Neuroscience 12:719 ‐743), form two to four patches in the superficial layers. These align in stripes, but only for short distances (’1.5 mm). This pattern suggests a strong compartmentalization in layers I and II that is also indicated by cytochrome oxidase and other markers. 2) Connections tend to be bistratified, terminating in layers I‐II and deeper in layer III. 3) Single axons terminate in layer I alone or in different combinations of layers. This may imply some heterogeneity of subtypes. 4) Individual axons, both ipsilateral projecting (n 5 14 axons) and contralateral projecting (n 5 6 axons), tend to have large arbors (0.3‐ 0.8 mm across). Finally, the authors observe that projections from the IPL, except for its anteriormost portion, converge at the perirhinal-entorhinal border around the posterior tip of the rhinal sulcus. These projections partially overlap with projections from ventromedial areas TE and TF, and this convergence may contribute to the severe deficits in visual recognition memory resulting from ablations of rhinal cortex. J. Comp. Neurol. 425: 510 ‐530, 2000. © 2000 Wiley-Liss, Inc.

The corticopontine system in the rat. I. Mapping of corticopontine neurons

Abstract: The expanse of cerebral cortex containing corticopontine neurons was explored in rats. The retrograde tracer horseradish peroxidase (HRP) was iontophoresed into subdivisions of the pontine nuclei (PN). The densest projection was seen to originate from somatosensory and motor areas. Visual areas also provide a major contigent of corticopontine neurons, whereas auditory areas appear to have only a minor projection. Consistent labeling of cells was also seen in the granular cingulate cortex, especially in the junction region of anterior and posterior cingulate cortex. This and a sparse projection from dorsal and posterior "insular" cortex (rhinal sulcus) have not been described in detail in previous studies.

Effect of methamphetamine on glutamate-positive neurons in the adult and developing rat somatosensory cortex

Abstract: The neurotoxic effects of methamphetamine (MA) on dopaminergic and serotonergic terminals have been well-documented. Another neurotoxic effect of MA is neuronal degeneration in the somatosensory cortex, as seen by silver staining. The neurochemical characteristics of these degenerating neurons are unknown. Using glutamate and glial fibrillary acid protein (GFAP) immunohistochemistry, it was found that MA exposure in adult rats (10 mg/kg given 4 times intraperotoneally (i.p.) at 2-h intervals) causes localized depletion of glutamate-positive neurons and astrogliosis in the somatosensory cortex 3 days following treatment. The affected region covered the middle one-third portion from the longitudinal fissure to the rhinal sulcus and was predominately seen in layers II-III of the cortex. This pattern of depletion is consistent with that demonstrated previously with silver staining following MA, d-amphetamine, and 3,4-methylenedioxymethamphetmine (MDMA) exposures. Comparable efforts were not found in developing animals at ages previously shown to also be resistant to MA-induced effects on dopaminergic terminals (age 20 and 40 days). Results suggest that MA exposure induces degeneration of glutamatergic neurons in the somatosensory cortex of adult rats.