Abstract
Functional neuroimaging have permitted the mapping of several visual areas of the human brain and have already provided provisional identification of most of the visual areas that were first described in nonhuman primates. However, the lack of an adequate description of the sulcal patterns of the human occipital lobe makes it difficult to establish clear relations between sulcal landmarks and identified visual areas with modern functional neuroimaging. Here, we examined the morphological variation of the sulci of the human occipital region in both the left and the right hemispheres of 40 normal individuals on magnetic resonance images. We identified the occipital sulci and marked their corresponding gray matter voxels on the magnetic resonance images, which had been transformed into the Montreal Neurological Institute standard proportional stereotaxic space in order to construct probability maps. In the medial occipital region, the calcarine sulcus was found to be the longest and most constant sulcus. In the inferior part of the medial occipital lobe, we identified the lingual sulcus and the posterior collateral sulcus, and, in the superior part, the inferior and superior sagittal sulci of the cuneus. On the lateral surface of the occipital lobe, we identified the lateral occipital, the lunate, the transverse and the inferior occipital sulci. The parieto-occipital fissure and the temporo-occipital incisure were also identified on the lateral and medial surfaces of the hemispheres. Finally, we examined the patterns of the occipital sulci and gyri in 20 post-mortem human hemispheres fixed in formalin. We constructed probability maps of the occipital sulci, which provide a quantitative description of the variability of these sulci and may be used to identify the location of voxels in other magnetic resonance images transformed into the same streotaxic space. These maps are a useful tool in the study of functional activations related to visual processing.