13, Ammon’s horn regions CA1 through CA3. c Diagram of the various cell types of the hippocampal formation and their connections. b Cytoarchitecture of the hippocampal formation. The perforant path penetrates the subiculum to link the entorhinal area with the dentate gyrus. a Major afferent and efferent projections of the hippocampal formation: the perforant path and the fornix, respectively. Usage subject to terms and conditions of license.įig. There are different types of pyramidal cells in the in-īaehr, Duus' Topical Diagnosis in Neurology © 2005 ThiemeĪll rights reserved. The principal cell type in the hippocampus is the pyramidal cell. The hippocampus proper (Ammon’s horn or cornu Ammonis) is distinct from the dentate gyrus ( fascia dentata, Fig. Because of this different structure, the hippocampus and a few other cortical areas are called allocortex (as opposed to the six-layered isocortex). The hippocampal cortex consists of archicortex, a phylogenetically old type of cerebral cortex, which possesses only three layers instead of the usual six. Microanatomy of the Hippocampal Formation Its structure and neural connections and the clinical changes observed in patients with hippocampal lesions form the subject of this section. The hippocampal formation is the central structure of the limbic system. Furthermore, impulses from the autonomic nervous system can travel through the hypothalamus and the medial dorsal nucleus of the thalamus to reach the orbitofrontal cortex. Impulses arising in the limbic system can travel by way of the anterior nucleus of the thalamus to the cingulate gyrus, but also, via association fibers, to the neocortex. 277f.) form a regulatory circuit of their own. The mamillotegmental tract and the peduncle of the mamillary body (see Figs. The mamillary body occupies a key position in the Papez circuit because it connects the limbic system with the midbrain (nuclei of Gudden and Bekhterev) and the reticular formation. From the cingulate gyrus, impulses travel by way of the cingulum back to the hippocampus, completing the circuit (Fig. The anterior nucleus projects to the cingulate gyrus by way of the thalamocingulate radiation. This nucleus, in turn, is the site of origin of the mamillothalamic tract (of Vicq d’Azyr), which conveys impulses to the anterior nucleus of the thalamus. From the hippocampus (Ammon’s horn), impulses travel through the great arch of the fornix to the mamillary body. Papez circuit, as originally described, much further information has come to light regarding additional connections and the particular neurotransmitters used at various points in the circuit. Intracerebral Hemorrhage (Nontraumatic).Impaired Venous Drainage from the Brain.Arteries of the Anterior and Middle Cranial Fossae.Cerebrospinal Fluid Circulation and Resorption.Functional Localization in the Cerebral Cortex.Histological Organization of the Cerebral Cortex.Gross Anatomy and Subdivision of the Cerebrum.Clinical Syndromes of Basal Ganglia Lesions.Function and Dysfunction of the Basal Ganglia.The Role of the Basal Ganglia in the Motor System: Phylogenetic Aspects.Microanatomy of the Hippocampal Formation.Afferent and Efferent Projections of the Hypothalamus.Location and Components of the Diencephalon.Cerebellar Function and Cerebellar Syndromes.Connections of the Cerebellum with Other Parts of the Nervous System.Vagal System (CN IX, X, and the Cranial Portion of XI).Facial Nerve (CN VII) and Nervus Intermedius.Syndromes of the Neuromuscular Junction and Muscle.Nerve Root Syndromes (Radicular Syndromes).Complex Clinical Syndromes due to Lesions of Specific Components of the Nervous System.Clinical Syndromes of Motor Unit Lesions.Peripheral Components of the Motor System and Clinical Syndromes of Lesions Affecting Them.Other Central Components of the Motor System.Central Components of the Motor System and Clinical Syndromes of Lesions Affecting Them.Somatosensory Deficits due to Lesions at Specific Sites along the Somatosensory Pathways.Central Processing of Somatosensory Information.Other Afferent Tracts of the Spinal Cord.Posterior and Anterior Spinocerebellar Tracts.Central Components of the Somatosensory System.
Peripheral Nerve, Dorsal Root Ganglion, Posterior Root.10 Coverings of the Brain and Spinal Cord Cerebrospinal Fluid and Ventricular System.6 Diencephalon and Autonomic Nervous System.