and Zola-Morgan, S., 1991) and navigation ( Aguirre, G. The parahippocampal gyrus is a cortical region in the medial temporal lobe that surrounds the hippocampus and plays an important role in both spatial memory ( Squire, L. Tootell, in The Senses: A Comprehensive Reference, 2008 1.30.3.3 Parahippocampal Place Area 13 For the sake of discussion of anatomic location, the hippocampal formation will be discussed with the limbic system here. Traditionally included as part of the limbic system, most anatomists now separate these hippocampal structures from the limbic system because of their involvement in encoding new memories. The hippocampal formation consists of the dentate gyrus, hippocampal gyrus, and white matter, called fimbria, that issues from this area and eventually forms the crus (or leg) of the fornix. The hippocampal gyrus is actually part of the hippocampal formation, which is a curved, rolled-in-and-under area of cortex bulging into the floor of the temporal (inferior) horn of the lateral ventricle. Folded within the parahippocampal gyrus is the hippocampus. 2-11) is a transitional architecture representing a six-layer formation laterally with a change to a three-layer formation more medially. Webb PhD, CCC-SLP, in Neurology for the Speech-Language Pathologist (Sixth Edition), 2017 Parahippocampal and Hippocampal Gyri No studies have yet investigated human/nonhuman ape comparisons in the parahippocampal gyrus. Furthermore, positron emission tomography studies in humans have demonstrated that the parahippocampal gyrus is significantly implicated in negative but not positive emotive response, suggesting that this structure is part of a highly specialized network for processing different types of emotional stimuli ( Blood et al., 1999 Lane et al., 1997). Given the close proximity and significant innervation to olfactory areas, the parahippocampal gyrus was initially thought to be involved in olfaction only, but studies in nonhuman animals and humans indicate that the structure is involved in complex emotive processes and has significant interconnectivity to other cortical limbic structures as well as the amygdala ( Van Hoesen, 1982 Blood et al., 1999 Powell et al., 2004). The parahippocampal gyrus is made up of several cortical areas, including the primary olfactory cortex at the anterior pole and the entorhinal cortex just posterior to the anterior pole ( Van Hoesen, 1982). The parahippocampal gyrus lies along the ventromedial edge of the temporal lobe adjacent to the hippocampus and was identified as a prominent structure of the limbic lobe early on in human neuroanatomical research ( Broca, 2000 Fulton, 1953). Semendeferi, in Evolution of Nervous Systems (Second Edition), 2017 4.16.3.5 Parahippocampal Gyrus