uncus
Acronym:
uns
The term uncus refers to a superficial feature of the rostral part of the anterior parahippocampal gyrus where it "hooks around the hippocampal sulcus to form a medially protruding convolution" ( Carpenter-1983 ) on the anteromedial surface of the limbic lobe. In the human, the histologically defined structures underlying the uncal surface include the anterodorsal part of the entorhinal area where it covers the amygdala rostrally and the portion of the hippocampal complex (HPC) that bends back on itself caudally ( Mai-1997 ). In the macaque it is formed entirely by the hook portion of the HPC ( Paxinos-2009a ). Brain atlases of the rat and mouse show no equivalent feature.
Many authors use the term 'uncus' and synonyms, such as 'uncinate gyrus', in reference to the combination of the topologically defined surface feature and the underlying histologically defined, volumetric components ( Anthoney-1994 ). In that sense, it is a hook-shaped substructure of the anterior-most part of the anterior parahippocampal gyrus ( Crosby-1962 ).
Because the boundaries of the volumetric 'uncinate gyrus' do not correspond to the boundaries of its internal, histologically defined structures, and because activation of the histologically defined structures correlates significantly better with functions of the structures ( Glasser-2016 ), the term uncus (uns) and its synonyms are classified in NeuroNames as superficial features, which are useful anatomical landmarks, separately from the volumetric hippocampal complex (HPC), which is useful for analysis of neural functions ( Bowden-1997 Bowden-2012 ). Updated 25 May 2024.
Also known as: uncus hippocampi, Uncus hippocampiNeuroNames ID : 40
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