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Chapter: Human Nervous System and Sensory Organs : Telencephalon

Fiber Connections in Archicortex

The fiber bundles from the entorhinal area (B13) are thought to be the most important afferent system, where the pathways from the primary olfactory centers (prepiriform area), from the amygdaloid body, and from various regions of the neocortex terminate.

Fiber Connections


Afferent Pathways (B)

The fiber bundles from the entorhinal area (B13) are thought to be the most important afferent system, where the pathways from the primary olfactory centers (prepiriform area), from the amygdaloid body, and from various regions of the neocortex terminate. Direct connections between olfactory bulb and hippocampus have not been demon-strated. The fibers from the cingulate gyrus collect in the cingulum (B14) and extend primarily to the subiculum.The fornix (B15) contains bundles from the septal nuclei (B16) but above all fibers fromthe hippocampus and the entorhinal area of the contralateral hemisphere (via the com-missure of the fornix).


Efferent Pathways (B)

Apart from a few fibers leaving the hippo-campus via the longitudinal stria (B17), the fornix contains all other efferent pathways. It is divided into a precommissural part and a postcommissural part. The fibers of the precommissural fornix (B18) terminate in theseptum, in the preoptic area (B19), and in the hypothalamus (B20). The fibers of the postcommissural fornix (B21) terminate in themamillary body (B22) (predominantly in the medial nucleus of the mamillary body), in the anterior thalamic nucleus (B23), and in the hypothalamus. Some fibers of the fornix ex-tend to the central gray matter of the mid-brain.

A large neuronal circuit can be recognized in this system of pathways. Hippocampal im-pulses are conducted via the fornix to the anterior thalamic nucleus. The latter is con-nected with the cingulate gyrus, from where there is feedback via the cingulum to the hippocampus (Papez circuit).


Fornix (C)

At the inferior surface of the corpus callo-sum, the two limbs of the fornix (C24) unite to form the commissure of the fornix (psal-terium) (C25) and the body of the fornix (C26), which then divides again into the two columns of the fornix (C27) above the fora-men of Monro.

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Human Nervous System and Sensory Organs : Telencephalon : Fiber Connections in Archicortex |


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