Decreased Fronto-Parietal and Increased Default Mode Network Activation is Associated with Subtle Cognitive Deficits in Elderly Controls

Abstract

Background: Cognitive functions progressively deteriorate during aging and neurodegenerative diseases. The present study aims at investigating differences in working memory performance as well as functional brain changes during the earliest stages of cognitive decline in health elderly individuals. Methods: 62 elderly individuals (41 females), including 41 controls (35 females) and 21 middle cognitive impairment subjects (6 females), underwent neuropsychological assessment at baseline and an fMRI examination in a N-back paradigm contrasting 2-back vs. 0-back condition. Upon a 18 months follow-up, we identified stable controls (sCON) with preserved cognition and deteriorating controls (dCON) with -1SD decrease of performances in at least two neuropsychological tests. Data analyses included accuracy and reaction time (RT) for the 2-back condition and general linear model (GLM) for the fMRI sequence. Results: At the behavioral level, sCON and dCON performed better than MCI in terms of accuracy and reaction time. At the brain level, functional differences in regions of the fronto-parietal network (FPN) and of the Default Mode Network (DFM) were observed. Significantly lower neural activations in the bilateral inferior and middle frontal gyri were found in MCI versus both dCON / sCON and for dCON versus sCON. Significantly increased activations in the anterior cingulate cortex and posterior cingulate cortex and bilateral insula were found in MCI versus both dCON / sCON and in dCON versus sCON. Conclusion: The present study suggests that brain functional changes in FPN and DMN anticipate differences in cognitive performance in healthy elderly individuals with subsequent subtle cognitive decline.

Water-Based Exercise and Resistance Training Improve Cognition in Older Adults

“…These results can be interpreted in view of the evidence suggesting that the neurodegenerative process of aging has an initial impact in the white matter, affecting cortical pathways in a fronto occipital gradient, leading to impairments in executive function and processing speed. 13,24,25 Our findings are in agreement with previous studies that point out reaction time assessments as sensitive early marker of subtles changes in cognition of community-dwelling health older adults and pathological aging, [6][7][8] indicator of quality of life, 26 as well a predictor of functional decline 27 and shorter time to death 28 and is associated with functional mobility. 29 The neuroprotection of alpha motor neurons and motor endplate found in senile exercised rats 30 may also support the shorter movement latency founded in exercised groups.…”

“…5 In this context, reaction time has been recognized as a measure of changes in cognitive function in healthy normal and pathological aging subjects and patients. [6][7][8] The mechanisms underlying these findings have been associated with the speed of nerve conduction, integrity of white matter and the gradient of neurodegenerative process on aging and physical exercise can positively modulated these results. 6,[9][10][11] In this study, we investigated the possible influences of two physical exercise modalities (resistance and water-based training) on cognitive function in healthy older adults using selected tests from an automated neuropsychological test battery (CANTAB) and investigated which one(s) of the test(s) would be the more effective indicator(s) of differences in old adults' cognitive performance.…”

Is brain connectome research the future frontier for subjective cognitive decline? A systematic review

“…In particular, alterations in the precuneus (PUN), which is considered as a main component of the Default Mode Network (DMN), have been suggested to begin more than 15 years before the manifestation of dementia-related signs (Bateman et al 2012). Moreover, several regions vulnerable and disrupted due to AD pathology coincide with the key regions (hubs) of the DMN (Sanz-Arigita et al 2010;Zanchi et al 2018) and SCD (Hafkemeijer et al 2013;Verfaillie et al 2018a). Furthermore, disrupted connectivity over brain regions of the DMN demanding encoding tasks has also been exhibited in individuals who are prone to develop AD due to genetic profiles, showing widely interruptions over the medial temporal lobe (MTL), PUN and cingulate gyrus (Bookheimer et al 2000;Bondi et al 2005;Han et al 2007;Borghesani et al 2008).…”

“…There are also several studies which have demonstrated that FC disruption involves the posterior DMN (pDMN), comprising largely the posterior cingulate cortex (PCC), which is considered as a key hub region of the DMN since it is the only hub directly connected to the rest DMN nodes (Dillen et al 2017). These disruptions in the pDMN are evident in the earliest stages of AD and MCI (Wang et al 2006;Zhang et al 2009;Cai et al 2017;Zanchi et al 2018), showing decreased FC between parietal and occipital regions.…”

Quantifying the Variability in Resting-State Networks

“…These have been proven helpful in understanding the physiology and neurology that governs the brain [ 11 ] and they have been used as a tool for the early detection of diseases [ 12 , 13 , 14 ], including neurophysiological diseases like Alzheimer’s, Parkinson’s, and attention deficit hyperactivity disorder (ADHD). In particular, it has been found that Alzheimer’s can be detected in Rs-fMRI through changes in the default mode network (DMN) and the fronto-parietal network (FPN) [ 15 ], while Parkinson’s and ADHD mostly affect the FPN [ 16 ]. Typically, these studies are done by concatenating data over subjects in the same group because of the low resolution on fMRI data (sampling rate typically smaller than ≈1 Hz, however, due to the sluggish hemodynamic response to neuronal activity, the effective temporal resolution of fMRI signal is rather ≈0.1 Hz) and the difficulty of recording long resting-state sessions.…”