Schon_2004

Schon_2004 - 11088 The Journal of Neuroscience December 8 2004 24(49:11088 11097 Behavioral/Systems/Cognitive Persistence of Parahippocampal

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Behavioral/Systems/Cognitive Persistence of Parahippocampal Representation in the Absence of Stimulus Input Enhances Long-Term Encoding: A Functional Magnetic Resonance Imaging Study of Subsequent Memory after a Delayed Match-to-Sample Task Karin Schon, 1,2 Michael E. Hasselmo, 1,2,3 Matthew L. LoPresti, 2,3 Marisa D. Tricarico, 2 and Chantal E. Stern 1,2,3,4 1 Department of Psychology, 2 Center for Memory and Brain, and 3 Program in Neuroscience, Boston University, Boston, Massachusetts 02215, and 4 Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129 Recent theoretical models based on cellular processes in parahippocampal structures show that persistent neuronal spiking in the absence of stimulus input is important for encoding. The goal of this study was to examine in humans how sustained activity in the parahippocampal gyrus may underlie long-term encoding as well as active maintenance of novel information. The relationship between long-term encoding and active maintenance of novel information during brief memory delays was studied using functional magnetic resonance imaging (fMRI) in humans performing a delayed matching-to-sample (DMS) task and a post-scan subsequent recognition memory task of items encountered during DMS task performance. Multiple regression analyses revealed fMRI activity in parahippocam- pal structures associated with the active maintenance of trial-unique visual information during a brief memory delay. In addition to a role in active maintenance, we found that the subsequent memory for the sample stimuli as measured by the post-scan subsequent recogni- tion memory task correlated with activity in the parahippocampal gyrus during the delay period. The results provide direct evidence that encoding mechanisms are engaged during brief memory delays when novel information is actively maintained. The relationship between active maintenance during the delay period and long-term subsequent memory is consistent with current theoretical models and exper- imental data that suggest that long-term encoding is enhanced by sustained parahippocampal activity. Key words: memory; parahippocampal; neuroimaging; medial temporal lobe; delayed match to sample; computational modeling Introduction A number of imaging studies have demonstrated that, in humans, the medial temporal lobes (MTLs), including the parahippocam- pal gyri (PHG) and the hippocampus, are involved in long-term encoding of new information (Stern et al., 1996; Gabrieli et al., 1997; Brewer et al., 1998; Ferna `ndez et al., 1998, 1999; Kelley et al., 1998; Wagner et al., 1998; Kirchhoff et al., 2000; Otten et al., 2001). Activity in these areas has been shown to be greater during encoding of subsequently remembered than forgotten stimuli (Brewer et al., 1998; Ferna `ndez et al., 1998; Wagner et al., 1998; Kirchhoff et al., 2000). Computational frameworks suggest that encoding may de-
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This note was uploaded on 04/08/2009 for the course PS 333 taught by Professor Otto during the Spring '09 term at BU.

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Schon_2004 - 11088 The Journal of Neuroscience December 8 2004 24(49:11088 11097 Behavioral/Systems/Cognitive Persistence of Parahippocampal

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