Three-dimensional probability maps of the rhinal and the collateral sulci in the human brain.

The sulcal segments of the collateral sulcal complex on the medial part of the temporal lobe delineate the parahippocampal gyrus involved in memory processing from the laterally adjacent fusiform gyrus. The rhinal sulcus delineates the entorhinal cortex on the anterior portion of the parahippocampal gyrus. Posterior to the rhinal sulcus lies the collateral sulcus proper which delineates the parahippocampal cortex that occupies the posterior part of the parahippocampal gyrus. A small sulcus, the parahippocampal extension of the collateral sulcus, runs transversely within the parahippocampal gyrus. The rhinal sulcus, the collateral sulcus proper, and the parahippocampal extension of the collateral sulcus were identified on magnetic resonance images of 40 healthy human brains and probability maps were created to provide quantification of the location variability within standard stereotaxic space. These probability maps can act as a reference frame for the accurate identification of key components of the parahippocampal region and assist in the interpretation of structural and functional changes obtained in neuroimaging studies.