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.

The rat perirhinal cortex: A review of anatomy, physiology, plasticity, and function

“…Double dissociation studies confirmed these findings showing that animals with hippocampal lesions showed impairments in recognition memory but not in spatial memory and those with perirhinal lesions showed impairments in spatial memory but not in recognition memory (Ennaceur et al, 1996;Bussey et al, 2000;Winters et al, 2004). This dissociation between hippocampal and perirhinal function was conserved across rat strains (Futter et al, 2006) and species (Pihlajamä ki et al, 2004;Buckley, 2005;Kö hler et al, 2005). Furthermore, immediate early gene imaging supports these lesion studies whereby c-Fos levels are increased in the hippocampus but not the perirhinal cortex during spatial learning tasks and they are increased in the perirhinal cortex but not the hippocampus during recognition tasks (Vann et al, 2000a;Aggleton and Brown, 2005).…”

Differences in EEG power in young and mature healthy adults during an incidental/spatial learning task are related to age and execution efficiency

“…Here, the activation of the anterior hippocampus, the perirhinal cortex and the anterior parahippocampal cortex has been shown to be related to the perception of novel objects, whereas the posterior hippocampus and the posterior parahippocampal cortex seem to be activated during the processing of novel arrangements of familiar objects (Pihlajamaki et al 2004;Smith and Milner 1981).…”

Regional activation of the human medial temporal lobe during intentional encoding of objects and positions

“…For example, some have found the perirhinal cortex to be more strongly activated by novel visual items compared to novel spatial arrangements of familiar items (Pihlajamäki et al, 2004(Pihlajamäki et al, , 2005, while others have found that the perirhinal cortex was activated during both spatial and object memory encoding (Buffalo et al, 2006). Similar conflicting findings include the hippocampus and parahippocampal cortex, where Pihlajamäki et al (2004) found an anterior-posterior gradient, in which the anterior hippocampus and anterior parahippocampal cortex were more involved in the processing of contextually novel objects, whereas the posterior hippocampus and posterior parahippocampal cortex were more involved in the processing of novel spatial arrangements. Conversely, Buffalo et al (2006) found that the anterior parahippocampal cortex, but not the anterior hippocampus, was activated during spatial encoding.…”