Low episodic memory performance in cognitively normal elderly subjects is associated with increased posterior cingulate gray matter N-acetylaspartate: a 1H MRSI study at 7 Tesla

Abstract

Low episodic memory performance characterizes elderly subjects at increased risk for Alzheimer's disease (AD) and may reflect neuronal dysfunction within the posterior cingulate cortex and precuneus (PCP) region. To investigate a potential association between cerebral neurometabolism and low episodic memory in the absence of cognitive impairment, tissue-specific magnetic resonance spectroscopic imaging at ultrahigh field strength of 7 Tesla was used to investigate the PCP region in a healthy elderly study population (n = 30, age 70 ± 5.7 years, Mini-Mental State Examination 29.4 ± 4.1). The Verbal Learning and Memory Test (VLMT) was administered as part of a neuropsychological battery for assessment of episodic memory performance. Significant differences between PCP gray and white matter could be observed for glutamate-glutamine (p = 0.001), choline (p = 0.01), and myo-inositol (p = 0.02). Low Verbal Learning and Memory Test performance was associated with high N-acetylaspartate in PCP gray matter (p = 0.01) but not in PCP white matter. Our data suggest that subtle decreases in episodic memory performance in the elderly may be associated with increased levels of N-acetylaspartate as a reflection of increased mitochondrial energy capacity in PCP gray matter.

Reproducibility of brain MRS in older healthy adults at 7T

“…However, compared with a healthy young sample that reported mean ratios of 1.8 for tNAA/Cr, 1.7 for Glu/Cr, and 0.25 for tCho/Cr, tNAA/Cr (mean ratio of 1.6) and Glu/Cr (mean ratio of 1.3) were lower and tCho/Cr (mean ratio of 0.28) was higher in the ACC in this older sample. For the PCC, metabolite ratios were similar to those reported by another study as well as those in a MRSI study of healthy elderly individuals in the posterior cingulate/precuneus region.…”

“…The observed NAA/tCr and tCho/tCr gradient across the brain is similar to results from a study 51 in a young adult cohort and another study with a broader age range. 52 While there have been many studies examining the effects of aging in specific brain regions, 48,50,52,53 to our knowledge there have been no studies examining whether these regional metabolite gradients differ between younger and older populations. When comparing CRLBs between regions, it appears that, on average, CRLBs from the PCC are lower than those from the ACC.…”

Long-term multi-species Lactobacillus and Bifidobacterium dietary supplement enhances memory and changes regional brain metabolites in middle-aged rats

“…Alternatively, the increase in myo-inositol may reflect the sensitivity of glia to changes in GABA activity (see below; Mariotti et al, 2016). Interestingly, increased frontal cortex myo-inositol levels in elderly patients has been linked with poorer episodic memory performance (Schreiner et al, 2016). It is possible, therefore, that increased myo-inositol in the frontal cortex could have a negative impact on memory, especially those involving integrative, e.g., episodic, memory.…”

Functional Brain Network Connectivity Patterns Associated With Normal Cognition at Old-Age, Local β-amyloid, Tau, and APOE4

“…The posterior cingulate and precuneus (PCP) represents a central node of the DMN needed for memory processing (Sperling et al, 2009;Cieri and Esposito, 2018). β-amyloid load affects the functionality of the PCP in old aged adults with, and without cognitive impairment (Unschuld et al, 2012;Schreiner et al, 2016;Grothe et al, 2017;Quevenco et al, 2017Quevenco et al, , 2019. The Apolipoprotein E ε4 allele (APOE4) is the strongest known genetic risk factor for late-onset AD (Corder et al, 1993;Strittmatter et al, 1993;Beffert and Poirier, 1996).…”