Coherent Spontaneous Activity Identifies a Hippocampal-Parietal Memory Network

Mallinckrodt Institute of Radiology, and Department of Neurology, Washington University School of Medicine, 4525 Scott Avenue, St. Louis, MO 63110, USA.
Journal of Neurophysiology (Impact Factor: 2.89). 01/2007; 96(6):3517-31. DOI: 10.1152/jn.00048.2006
Source: PubMed


Despite traditional theories emphasizing parietal contributions to spatial attention and sensory-motor integration, functional MRI (fMRI) experiments in normal subjects suggest that specific regions within parietal cortex may also participate in episodic memory. Here we examined correlations in spontaneous blood-oxygenation-level-dependent (BOLD) signal fluctuations in a resting state to identify the network associated with the hippocampal formation (HF) and determine whether parietal regions were elements of that network. In the absence of task, stimuli, or explicit mnemonic demands, robust correlations were observed between activity in the HF and several parietal regions (including precuneus, posterior cingulate, retrosplenial cortex, and bilateral inferior parietal lobule). These HF-correlated regions in parietal cortex were spatially distinct from those correlated with the motion-sensitive MT+ complex. Reanalysis of event-related fMRI studies of recognition memory showed that the regions spontaneously correlated with the HF (but not MT+) were also modulated during directed recollection. These regions showed greater activity to successfully recollected items as compared with other trial types. Together, these results associate specific regions of parietal cortex that are sensitive to successful recollection with the HF.

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    • "Further, there is good reason to think that our algorithm will prove useful in these other domains. Similar to the somatomotor system, language and memory systems have been mapped using spontaneous activity recorded with fMRI (McCormick et al., 2013; Tie et al., 2014; Vincent et al., 2006). There is no reason to think that incorporation of spontaneous activity into preoperative mapping will be any less useful for these other systems. "
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    • "Connectional anatomy in nonhuman primates indicates that MTL structures have both afferent and efferent projections to specific posteriomedial, temporal, parietal, and medial frontal regions that are estimated to be components of the DN [Kobayashi and Amaral, 2003, 2007; Lavenex et al., 2004]. However, functional connectivity studies repeatedly find that coupling between the MTL and cortical DN regions is relatively weak as compared with corticocortical coupling, although regions within the DN are the most strongly coupled regions when the MTL itself is the initiating point for fcMRI analysis [Kahn et al., 2008; r Mueller et al. r r 12 r Vincent et al., 2006]. Conventional graph theoretical representations of the DN have suggested that MTL structures form a separated sub-unit with rather weak connections to certain other DN nodes, at least insofar as its relative coupling strength compared with cortical regions of the DN [Andrews-Hanna et al., 2010; Buckner et al., 2008]. "
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    • "future studies . Previous studies have already suggested an involvement of the hippocampus in learning and retrieval of action - outcome relationships ( Melcher et al . , 2008 , 2013 ) . Moreover , successful recollection of episodic memory content engages a hippocampal - parietal memory network as revealed by resting state connectivity analysis ( Vincent et al . , 2006 ) . Given that the angular gyrus is involved in the representation of stimulus - response - outcome contingencies , functional connectivity to the hippocampus might reflect the explicit retrieval of these contingencies in order to select the appropriate response to produce the desired outcome ."
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