Functional abnormalities of the cerebellum in vascular mild cognitive impairment

Structural and iron content changes in subcortical vascular mild cognitive impairment: a combined voxel-based morphometry and quantitative susceptibility mapping study

BACKGROUND

Further studies are necessary to investigate the neural mechanisms elemental of subcortical vascular mild cognitive impairment (svMCI), which is considered as precursor to vascular dementia (VaD). This objective of this research was to investigate the alterations in gray matter volume and brain iron deposition in patients with svMCI.

METHODS

This study involved 23 patients classified as health controls (HC) and 20 patients diagnosed with svMCI. All participants received cognitive assessments and magnetic resonance imaging (MRI). This research contains voxel-based morphometry (VBM), voxel-based quantitative susceptibility mapping (QSM) analysis, ROI-based QSM analysis, and correlation analysis.

RESULTS

svMCI patients showed more seriously cognitive impairment than HC patients. VBM analyses showed gray matter atrophy in the cingulate gyrus in the svMCI. Voxel-based QSM analyses showed increased susceptibilities in the right middle frontal gyrus, left paracentral lobule, as well as decreased susceptibility in the right postcentral gyrus in the svMCI. And ROI-based QSM analyses showed increased susceptibilities in left caudate nucleus and cerebellum in the svMCI. In addition, the susceptibility in left middle cingulate cortex and paracingulate gyrus was positively correlated associated with MoCA scores (r = 0.538 p < 0.001), and the susceptibility in the right middle frontal gyrus was negatively correlated with MoCA scores (r = -0.418 p < 0.007).

CONCLUSIONS

The results of our studies suggest that morphological alterations and iron burden in the brain may be related to cognitive dysfunction in svMCI patients, providing a new way to explore underlying neural mechanisms of cognitive dysfunction.

Functional and Structural Cerebellar-Behavior Relationships in Aging

Healthy aging is associated with deficits in cognitive performance and brain changes, including in the cerebellum. Yet, the precise link between cerebellar function/structure and cognition in aging remains poorly understood. We explored this relationship in 138 healthy adults (aged 35-86, 53% female) using resting-state functional connectivity MRI (fcMRI), cerebellar volume, and cognitive and motor assessments in an aging sample. We expected to find negative relationships between lobular volume for with age, and positive relationships between specific lobular volumes with motor and cognition respectively. We predicted lower cerebellar fcMRI to cortical networks and circuits with increased age. Behaviorally, we expected higher cerebello-frontal fcMRI cerebellar connectivity with association areas to correlate with better behavioral performance. Behavioral tasks broadly assessed attention, processing speed, working memory, episodic memory, and motor abilities. Correlations were conducted between cerebellar lobules I-IV, V, Crus I, Crus II, vermis VI and behavioral measures. We found lower volumes with increased age as well as bidirectional cerebellar connectivity relationships with increased age, consistent with literature on functional connectivity and network segregation in aging. Further, we revealed unique associations for both cerebellar structure and connectivity with comprehensive behavioral measures in a healthy aging population. Our findings underscore cerebellar involvement in behavior during aging.

Aging, Neurodegenerative Disorders, and Cerebellum

An important part of the central nervous system (CNS), the cerebellum is involved in motor control, learning, reflex adaptation, and cognition. Diminished cerebellar function results in the motor and cognitive impairment observed in patients with neurodegenerative disorders such as Alzheimer's disease (AD), vascular dementia (VD), Parkinson's disease (PD), Huntington's disease (HD), spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), Friedreich's ataxia (FRDA), and multiple sclerosis (MS), and even during the normal aging process. In most neurodegenerative disorders, impairment mainly occurs as a result of morphological changes over time, although during the early stages of some disorders such as AD, the cerebellum also serves a compensatory function. Biological aging is accompanied by changes in cerebellar circuits, which are predominantly involved in motor control. Despite decades of research, the functional contributions of the cerebellum and the underlying molecular mechanisms in aging and neurodegenerative disorders remain largely unknown. Therefore, this review will highlight the molecular and cellular events in the cerebellum that are disrupted during the process of aging and the development of neurodegenerative disorders. We believe that deeper insights into the pathophysiological mechanisms of the cerebellum during aging and the development of neurodegenerative disorders will be essential for the design of new effective strategies for neuroprotection and the alleviation of some neurodegenerative disorders.