Psalterium

The hippocampal commissure, also called the commissure of the fornix, is a transversely-oriented white matter tract connecting the two hippocampi via the fornices . The specific function of the hippocampal commissure is currently unknown, although damage to the fornices has been shown to lead to memory loss .

Gross anatomy

Arching superiorly and medially over posterior surface of the thalamus, the fornix contains white matter fibers traveling from the hippocampus to the ipsilateral mammillary body . In the region of the fornix immediately below the splenium and body of the corpus callosum, a portion of the fibers within the fornix decussate and travel transversely to join the contralateral fornix . This collection of decussating fibers comprise the hippocampal commissure and form the psalterium, a thin triangular lamina spanning between the body of the left and right fornices .

Related pathology

Given the proximity of the hippocampal commissure to the interventricular foramen of Monro, the hippocampal commissure and the related fornices may be damaged during the endoscopic removal of a colloid cyst .