Biology subjects

Taylor, J.-P.

Publications and source records attributed to Taylor, J.-P..

3 recordsLinked to original sources

bioRxiv2018

The functional brain favours segregated modular connectivity at old age unless targeted by neurodegeneration

Brains modular connectivity gives this organ resilience and adaptability. The ageing process alters the human brain, leading to modifications to its organised modularity and these changes are further accentuated by neurodegeneration, leading to disorganisation. To understand this further, we analysed modular variability--heterogeneity of modules--and modular dissociation--detachment from segregated connectivity--in two ageing cohorts and a mixed cohort of neurodegenerative diseases. Our results revealed that the brain follows a universal pattern of modular variability that matches highly active and metacognitive brain regions: the association cortices. We also proved that in ageing the brain moves towards a modular segregated structure despite presenting with increased modular heterogeneity--modules in older adults are not only segregated but their shape and size are more variable than in young adults. In the presence of neurodegeneration, the brain maintains its segregated connectivity globally but not locally; the modular brain shows patterns of differentiated pathology.

neuroscience↗

bioRxiv2018

Dynamic functional connectivity changes in dementia with Lewy bodies and Alzheimer’s disease

We studied the dynamic functional connectivity profile of dementia with Lewy bodies (DLB) and Alzheimers disease (AD) and the relationship between dynamic connectivity and the temporally transient symptoms of cognitive fluctuations and visual hallucinations in DLB.\n\nResting state fMRI data from 31 DLB, 29 AD, and 31 healthy control participants were analysed using dual regression to determine between-network functional connectivity. We used a sliding window approach followed by k-means clustering and dynamic network analyses to study dynamic functional connectivity changes associated with AD and DLB. Network measures that showed significant group differences were tested for correlations with clinical symptom severity.\n\nAD and DLB patients spent more time than controls in sparse connectivity configurations with absence of strong positive and negative connections and a relative isolation of motor networks from other networks. Additionally, DLB patients spent less time in a more strongly connected state and the variability of global brain network efficiency was reduced in DLB compared to controls. However, there were no significant correlations between dynamic connectivity measures and clinical scores.\n\nThe loss of global efficiency variability in DLB might indicate the presence of an abnormally rigid brain network and the lack of economical dynamics, factors which could contribute to an inability to respond appropriately to situational demands. However, the absence of significant clinical correlations indicates that the severity of transient cognitive symptoms such as cognitive fluctuations and visual hallucinations might not be directly related to these dynamic connectivity changes observed during a short resting state scan.

neuroscience↗

bioRxiv2017

Evidence of compensation in the brain networks of Lewy body dementia and Alzheimer’s disease patients

Dementia with Lewy bodies (DLB) and Alzheimers disease (AD) require differential management despite presenting with symptomatic overlap. A human electrophysiological difference is a decrease of dominant frequency (DF) -the highest power frequency between 4-15Hz- in DLB; a characteristic of Parkinsonian diseases. We analysed electroencephalographic (EEG) recordings from old adults: healthy controls (HCs), AD, DLB and Parkinsons disease dementia (PDD) patients. Brain networks were assessed with the minimum spanning tree (MST) within six EEG bands: delta, theta, high-theta, alpha, beta and DF. Patients showed lower alpha band connectivity and lower DF than HCs. Lewy body dementias showed a randomised MST compared with HCs and AD in high-theta and alpha but not within the DF. The MST randomisation in DLB and PDD reflects decreased brain efficiency as well as impaired neural synchronisation. However, the lack of network topology differences at the DF indicates a compensatory response of the brain to the neuropathology.

neuroscience↗