title: Visual presentation of novel objects and new spatial arrangements of objects differentially activates the medial temporal lobe subareas in humans.
abstract: A number of studies in rodents and monkeys report a distinction between the contributions of the hippocampus and perirhinal cortex to memory, such that the hippocampus is crucial for spatial memory whereas the perirhinal cortex has a pivotal role in perception and memory for visual objects. To determine if there is such a distinction in humans, we conducted a functional magnetic resonance imaging study to compare the medial temporal lobe responses to changes in object identity and spatial configurations of objects. We found evidence for the predicted distinction between hippocampal and perirhinal cortical activations, although part of the hippocampus was also activated by identification of novel objects. Additionally, an anterior-posterior activation gradient emerged inside the hippocampus and parahippocampal cortex. The anterior hippocampus, perirhinal cortex and anterior parahippocampal cortex are involved in perception of contextually novel objects, whereas the posterior hippocampus and posterior parahippocampal cortex are involved in processing of novel arrangements of familiar objects. These results demonstrate that there is a functional dissociation between processing of novel object identities and new spatial locations of objects among the subregions of medial temporal lobe structures in humans also.
authors.affiliation: Department of Neuroscience and Neurology, University of Kuopio, PO Box 1627, 70211 Kuopio, Finland.
authors.forename: Maija
authors.initials: M
authors.lastname: Pihlajamäki
authors.forename: Heikki
authors.initials: H
authors.lastname: Tanila
authors.forename: Mervi
authors.initials: M
authors.lastname: Könönen
authors.forename: Tuomo
authors.initials: T
authors.lastname: Hänninen
authors.forename: Anne
authors.initials: A
authors.lastname: Hämäläinen
authors.forename: Hilkka
authors.initials: H
authors.lastname: Soininen
authors.forename: Hannu J
authors.initials: HJ
authors.lastname: Aronen
mesh_terms: D000328:Adult; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology; D001931:Brain Mapping; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D013028:Space Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*