Current understanding of magnetic resonance imaging biomarkers and memory in Alzheimer's disease

Abstract

Alzheimer's disease (AD) is caused by a cascade of changes to brain integrity. Neuroimaging biomarkers are important in diagnosis and monitoring the effects of interventions. As memory impairments are among the first symptoms of AD, the relationship between imaging findings and memory deficits is important in biomarker research. The most established magnetic resonance imaging (MRI) finding is hippocampal atrophy, which is related to memory decline and currently used as a diagnostic criterion for AD. While the medial temporal lobes are impacted early by the spread of neurofibrillary tangles, other networks and regional changes can be found quite early in the progression. Atrophy in several frontal and parietal regions, cortical thinning, and white matter alterations correlate with memory deficits in early AD. Changes in activation and connectivity have been detected by functional MRI (fMRI). Task-based fMRI studies have revealed medial temporal lobe hypoactivation, parietal hyperactivation, and frontal hyperactivation in AD during memory tasks, and activation patterns of these regions are also altered in preclinical and prodromal AD. Resting state fMRI has revealed alterations in default mode network activity related to memory in early AD. These studies are limited in part due to the historic inclusion of patients who had suspected AD but likely did not have the disorder. Modern biomarkers allow for more diagnostic certainty, allowing better understanding of neuroimaging markers in true AD, even in the preclinical stage. Larger patient cohorts, comparison of candidate imaging biomarkers to more established biomarkers, and inclusion of more detailed neuropsychological batteries to assess multiple aspects of memory are needed to better understand the memory deficit in AD and help develop new biomarkers. This article reviews MRI findings related to episodic memory impairments in AD and introduces a new study with multimodal imaging and comprehensive neuropsychiatric evaluation to overcome current limitations.

Quantitation of in vivo brain glutathione conformers in cingulate cortex among age‐matched control, MCI, and AD patients using MEGA‐PRESS

“…fMRI studies on the cognitive role of CC have shown increased activity in ACC during tasks involving cognitive controls, such as attention, executive functioning and working memory (Lenartowicz & McIntosh, 2005), while the damage of PCC was found to cause trouble with solving cognitive control tasks (Ries et al, 2006). Episodic memory performance related to structural changes within DMN regions also supported the reduced deactivation in task-based fMRI and its connectivity decline using resting-state fMRI (rsfMRI) (Bayram, Caldwell, & Banks, 2018). Directed functional connectivity of brain DMN regions and its alteration using rsfMRI was also reported for its role in AD early diagnosis (Yu et al, 2017).…”

Neural Correlates of Verb Fluency Performance in Cognitively Healthy Older Adults and Individuals With Dementia: A Pilot fMRI Study

“…Brain imaging is commonly utilized as a biomarker for the detection of dementing, neurodegenerative diseases as well as to monitor disease progression, and biomarkers using functional MRI have been regarded useful in the diagnosis and intervention of dementia with substantial implications in delineating neuropathological changes (Gold and Budson, 2008;McKhann et al, 2011;Li et al, 2015;Bayram et al, 2018). Currently, however, there has been limited examination of how brains with neurodegenerative disease operate in relation to language and cognitive deficits (Szatloczki et al, 2015;Li et al, 2017;Kochhann et al, 2018).…”

Value of magnetic resonance spectroscopy in geriatric patients with cognitive impairment

“…However, frontal cortex hypoactivation was reported in MCI patients with prominent cognitive decline [65, 69- 71]. Changes in frontal lobe activation in patients with MCI might be a compensatory mechanism to maintain normal cognitive ability [72].…”