Relationship between the disrupted topological efficiency of the structural brain connectome and glucose hypometabolism in normal aging

The authors previously reported that excitotoxic lesions of both the perirhinal and entorhinal cortices in baboons induce remote neocortical and hippocampal hypometabolism reminiscent of that observed in Alzheimer disease (AD), suggesting that disconnection may play a role in AD. Because the cerebral metabolic rate of glucose (CMRglc) was preferentially correlated with perirhinal damage, the area first affected by neurofibrillary tangles in both AD and normal aging, the present series of experiments aimed at assessing the specific metabolic effects of perirhinal lesions. Using PET, CMRglc was measured before surgery and sequentially over the ensuing 10 months. Compared with sham-operated baboons, perirhinal lesions induced significant—albeit late and transient—CMRglc decreases in several brain regions, which significantly correlated with histologic damage for some of these regions. Among them, the temporal and hippocampal regions are metabolically affected after extensive rhinal lesions, in early AD, and aging, while the prefrontal region is affected in aging only. Furthermore, in contrast to AD and rhinal lesions, the posterior cingulate cortex was spared. Both the progressive but significant metabolic effects and specific hypometabolic pattern after perirhinal lesions were confirmed by direct comparisons with previous data obtained after combined lesions of both rhinal areas. Thus, although perirhinal damage appears in itself insufficient to induce sustained CMRglc decreases, it may contribute to the hypometabolic profile of both AD and normal aging, most likely with a stronger contribution in the latter.

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Disrupted rich club organization and structural brain connectome in unmedicated bipolar disorder

Psychological Medicine ◽

10.1017/s0033291718001150 ◽

2018 ◽

Vol 49 (3) ◽

pp. 510-518 ◽

Cited By ~ 21

Author(s):

Ying Wang ◽

Feng Deng ◽

Yanbin Jia ◽

Junjing Wang ◽

Shuming Zhong ◽

...

Keyword(s):

Bipolar Disorder ◽

Graph Theory ◽

White Matter ◽

Diffusion Tensor ◽

Whole Brain ◽

Rich Club ◽

Brain Connectome ◽

Structural Connectome ◽

Healthy Control ◽

Structural Brain

AbstractBackgroundBipolar disorder (BD) has been associated with altered brain structural and functional connectivity. However, little is known regarding alterations of the structural brain connectome in BD. The present study aimed to use diffusion-tensor imaging (DTI) and graph theory approaches to investigate the rich club organization and white matter structural connectome in BD.MethodsForty-two patients with unmedicated BD depression and 59 age-, sex- and handedness-matched healthy control participants underwent DTI. The whole-brain structural connectome was constructed by a deterministic fiber tracking approach. Graph theory analysis was used to examine the group-specific global and nodal topological properties, and rich club organizations, and then nonparametric permutation tests were used for group comparisons of network parameters.ResultsCompared with healthy control participants, the patients with BD showed abnormal global properties, including increased characteristic path length, and decreased global efficiency and local efficiency. Locally, the patients with BD showed abnormal nodal parameters (nodal strength, nodal efficiency, and nodal betweenness) predominantly in the parietal, orbitofrontal, occipital, and cerebellar regions. Moreover, the patients with BD showed decreased rich club and feeder connectivity density.ConclusionsOur results may reflect the disrupted white matter topological organization in the whole-brain, and abnormal regional connectivity supporting cognitive and affective functioning in depressed BD, which, in part, be due to impaired rich club connectivity.

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