Subiculum

The subiculum (plural: subicula) is located in the mesial temporal lobe and is a subdivision of the hippocampal formation, along with Ammon’s horn, the entorhinal cortex and the hippocampus proper. It is the predominant output source of the hippocampal formation.

Structure

The subiculum occupies a portion of the parahippocampal gyrus in the mesial temporal lobe and is a component of the medial temporal memory system. It is made up of several cortical fields and for this reason is sometimes referred to as the subicular complex. It is positioned between the CA1 region of the hippocampus proper and the entorhinal cortex ventrally. Dorsally, it is bordered by the retrosplenial cortex.

The subicular complex is broken down into several distinct but related areas by their differing cytoarchitecture, however with slight variations between human, monkey, and rodent studies. These areas include the prosubiculum (ProS), subiculum proper (Sub), presubiculum (PrS), postsubiculum (PoS), and parasubiculum (PaS).

Sub: The subiculum proper is bordered proximally by the ProS, which separates it from the CA1 region of the hippocampus. Distally, it is bordered by the PreS.

ProS: The area separating the subiculum proper from the CA1 region of the hippocampus proper.

PrS: This area borders the subiculum proper ventrally and makes up part of the parahippocampal gyrus.

PoS: The PoS is bordered by the presubiculum ventrally and laterally, with the border between the two characterized by an abrupt change in cyto- and histochemical staining. However, some sources treat this area as the dorsal part of the presubiculum.

PaS: This area forms the ventral shoulder of the parahippocampal gyrus and continues the PrS ventrally. It is bordered laterally by the entorhinal cortex.

Radiographic features

MRI

As with the hippocampus proper, the subiculum is best visualized on coronal plane MR images. A detailed description of associated landmarks is available in the hippocampus article.

Clinical significance

There is ongoing emerging evidence of the role of the subiculum in Alzheimer disease and epilepsy.

History and etymology

The name subiculum is derived from the Latin word for support. This reflects the location of the subiculum under the hippocampus proper.