Altered Neural Networks in the Papez Circuit: Implications for Cognitive Dysfunction after Cerebral Ischemia

Abstract

Cerebral ischemia remains a leading cause of mortality worldwide. Although the incidence of death has decreased over the years, surviving patients may suffer from long-term cognitive impairments and have an increased risk for dementia. Unfortunately, research aimed toward developing therapies that can improve cognitive outcomes following cerebral ischemia has proved difficult given the fact that little is known about the underlying processes involved. Nevertheless, mechanisms that disrupt neural network activity may provide valuable insight, since disturbances in both local and global networks in the brain have been associated with deficits in cognition. In this review, we suggest that abnormal neural dynamics within different brain networks may arise from disruptions in synaptic plasticity processes and circuitry after ischemia. This discussion primarily concerns disruptions in local network activity within the hippocampus and other extra-hippocampal components of the Papez circuit, given their role in memory processing. However, impaired synaptic plasticity processes and disruptions in structural and functional connections within the Papez circuit have important implications for alterations within the global network, as well. Although much work is required to establish this relationship, evidence thus far suggests there is a link. If pursued further, findings may lead toward a better understanding of how deficits in cognition arise, not only in cerebral ischemia, but in other neurological diseases as well.

Electroacupuncture Inhibits Neuronal Autophagy and Apoptosis via the PI3K/AKT Pathway Following Ischemic Stroke

“…As a result of ischemia, the blood supply to neurons is interrupted, which then promotes a series of pathophysiological responses. Various pathological changes are involved individually or jointly in the ischemic process, including autophagy, apoptosis, inflammation, excitatory toxicity, mitochondrial death pathways and free radical release (Khoshnam et al, 2017;Sekerdag et al, 2018), all of which lead to neuronal cell death, hindering important motor (Sun et al, 2012), sensory (Graf et al, 1986) and cognitive functions (Escobar et al, 2019;. Ischemic stroke has been considered one of the main factors that cause aging of the brain and the pathological state of neurodegenerative diseases (Sommer, 2017;Graham and Liu, 2017).…”

Assessment of cerebral low-frequency oscillations in patients with retinal vein occlusion: a preliminary functional MRI study

“…In addition, there is growing evidence that cerebrovascular disease leads to dysfunction of the Papez circuit. Escobar et al reported that cerebral ischemia patients exhibited abnormal structural and functional connections in the Papez circuit, which were closely related to cognitive function (41). Furthermore, structural and functional abnormalities in the HIP were observed in cerebrovascular disease patients (42,43).…”

Role of dietary fatty acids in microglial polarization in Alzheimer’s disease

“…Switching to alternative neuronal connection is the way to overcome this loss, which depends upon the plasticity of the brain [8]. The consistent failure of neuronal connections is responsible for daily fluctuations in behavior, and they are interconnected with the accumulation of plaques and tangles, which in turn cause neuronal loss and network dysfunction [9,10].…”