A New Division of the Human Claustrum Basis on the Anatomical Landmarks and Morphological Findings

Purpose: The subdivision of claustrum into parts in some species exists in literature. Those are mainly based on a pattern of its connections with various cortical areas, method of staining, immunoreactivity of its neurons etc. The aim of this study was the division of the human claustrum into different parts, for first time, based on morphology, density, arrangement of claustral neurons as well as shape of the structure on coronal sections studied with Kluver-Barrera. Materials and Methods: Ten human brains (5 males, 5 females), who died of non-neurological causes and had no history of long term neurological illness were selected. The samples after fixation in formaldehyde and embedding in paraffin were coronally cut into 25-micrometer thick serial sections. Every 20th section was stained with Kluver-Barrera, with a random posi40n for the first section. The human claustrum was divided using anatomical landmark and morphological findings of neurons. Neuron density and total number of neuron and volume of each part were measured using stereo logical methods. Results: We have distinguished in the human claustrum three parts cap, dorsal and ventral in dorsa-ventral direction. The circular insular and rhinal sulci are upper and lower borders of dorsal part. Cap is the smallest and ventral part largest part. Neuron density decreases from cap towards ventral part. We have also found three parts anterior, central (middle) and posterior in antero-posterior direction. The central part is alongside of globus palliduas nucleus, whereas anterior and posterior are referred to parts of claustrum that lie in front and behind this nucleus, respectively. The central and posterior parts are the largest and smallest parts, respectively. Neuron density decreases from anterior towards posterior part, antero-posterior of human claustrum was about 28.06±5.25 mm. Conclusion: This study demonstrated that human claustrum consists of three anatomical parts in both dorso-ventral and antero-posterior directions. Each part has its specific connections, development, function and neuron density and morphology.