Episodic memory in aspects of large-scale brain networks

Abstract

Understanding human episodic memory in aspects of large-scale brain networks has become one of the central themes in neuroscience over the last decade. Traditionally, episodic memory was regarded as mostly relying on medial temporal lobe (MTL) structures. However, recent studies have suggested involvement of more widely distributed cortical network and the importance of its interactive roles in the memory process. Both direct and indirect neuro-modulations of the memory network have been tried in experimental treatments of memory disorders. In this review, we focus on the functional organization of the MTL and other neocortical areas in episodic memory. Task-related neuroimaging studies together with lesion studies suggested that specific sub-regions of the MTL are responsible for specific components of memory. However, recent studies have emphasized that connectivity within MTL structures and even their network dynamics with other cortical areas are essential in the memory process. Resting-state functional network studies also have revealed that memory function is subserved by not only the MTL system but also a distributed network, particularly the default-mode network (DMN). Furthermore, researchers have begun to investigate memory networks throughout the entire brain not restricted to the specific resting-state network (RSN). Altered patterns of functional connectivity (FC) among distributed brain regions were observed in patients with memory impairments. Recently, studies have shown that brain stimulation may impact memory through modulating functional networks, carrying future implications of a novel interventional therapy for memory impairment.

IC‐P‐034: Mediation of Episodic Memory Performance by The Executive Function Network in Patients with Amnestic Mild Cognitive Impairment: A Resting‐State Functional MRI Study

“…Converging evidence from our research group and others indicates that ReHo is altered in the RSC in the EM network [3,19,41,56] and in the DLPFC in the EF network [4,6,37,57] in aMCI patients. Therefore, it was reasonable for the present study to utilize a new approach to analyze FC that employed the ReHo results as the seed ROIs.…”

“…It is well documented that the IPL is a heterogeneous area involved in multimodal functions such as sensory motor processing [92], executive control [93], salience detection [42], and EM function [19]. The present findings may be explained by the fact that the parietal cortex and the cingulate cortex play crucial roles in the processing of EF and EM functions [3,43].…”

“…Findings from our research group and other studies suggest that brain regions with altered ReHo in patients with aMCI are located in structures associated with the EM [3,19,41,56] and EF [4,6,37,57] networks and include regions such as the hippocampus, PCC/precuneus (PCu), right inferior parietal lobule (IPL), DLPFC, and ventromedial prefrontal cortex (VMPFC) [58][59][60][61]. Therefore, the present study computed ReHo values to identify regions with abnormal local connectivity in a group of aMCI patients relative to healthy controls (HC).…”

“…It is well established that the DMN is involved with EM [16][17][18]. Additionally, memory function is not only facilitated by the medial temporal lobe (MTL) system but is supported by a distributed network, Research Paper: Pathology particularly in the DMN [19].…”

“…It is well established that the DMN is involved with EM [16][17][18]. Additionally, memory function is not only facilitated by the medial temporal lobe (MTL) system but is supported by a distributed network, Research Paper: Pathology particularly in the DMN [19]. Structural and functional imaging studies have consistently established that the retrosplenial cortex (RSC) and the posterior cingulate cortex (PCC) are the main hubs connecting with the MTL and that the prefrontal cortex (PFC) plays a central role in processing EM [20][21][22].…”