Going round in circles—The Papez circuit in Alzheimer's disease

Abstract

The hippocampus is regarded as the pivotal structure for episodic memory symptoms associated with Alzheimer's disease (AD) pathophysiology. However, what is often overlooked is that the hippocampus is 'only' one part of a network of memory critical regions, the Papez circuit. Other Papez circuit regions are often regarded as less relevant for AD as they are thought to sit 'downstream' of the hippocampus. However, this notion is oversimplistic, and

The anterior thalamic nuclei: core components of a tripartite episodic memory system

“…Chief among these sites are the anterior thalamic nuclei. Over recent years, there has been a growing awareness that these nuclei can contribute to the cognitive changes associated with aging 51 , mild cognitive impairment 52,53 , various dementias [53][54][55] , and, potentially, an array of other neurological and psychiatric disorders [56][57][58] . Meanwhile, the discovery of neurons within the rodent anterior thalamic nuclei that signal different types of spatial information (Table 1) has forced a further rethink regarding the significance of these nuclei in cognition 59 .…”

Construction of complex memories via parallel distributed cortical–subcortical iterative integration

“…The extended Papez circuits, including the MBs and/or the anterior thalamic nuclei have been implicated in several neurological disorders that are associated with memory impairments, e.g., Korsakoff syndrome, Alzheimer’s disease, Down syndrome, and hypoxic-ischaemic encephalopathy [ 115 , 116 ]. However, there is also increasing evidence for a role for the medial diencephalon in psychiatric and neurodevelopmental disorders [ 117 - 119 ], where memory impairments are present but also emotional dysregulation.…”

Connectomic neuromodulation for Alzheimer’s disease: A systematic review and meta-analysis of invasive and non-invasive techniques

“…The cingulo-opercular SN has been shown to serve as the neural switch between CEN and DMN [ 56 ]. The Papez circuit is part of the limbic system and is involved in episodic memory and spatial navigation [ 51 ]. AD is characterized by the dysfunction of these large-scale neural networks [ 57 ].…”

“…Cognitive processes depend on the integration of complex interactions among large-scale brain networks, including DMN, SN, CEN, and the limbic system, which includes Papez circuit [11,[51][52][53][54]. The medial prefrontal-medial parietal DMN is involved in memory and abstract thought [52].…”