Fornix White Matter is Correlated with Resting-State Functional Connectivity of the Thalamus and Hippocampus in Healthy Aging but Not in Mild Cognitive Impairment – A Preliminary Study

Abstract

In this study, we wished to examine the relationship between the structural connectivity of the fornix, a white matter (WM) tract in the limbic system, which is affected in amnestic mild cognitive impairment (aMCI) and Alzheimer’s disease, and the resting-state functional connectivity (FC) of two key related subcortical structures, the thalamus, and hippocampus. Twenty-two older healthy controls (HC) and 18 older adults with aMCI underwent multi-modal MRI scanning. The fornix was reconstructed using constrained-spherical deconvolution-based tractography. The FC between the thalamus and hippocampus was calculated using a region-of-interest approach from which the mean time series were exacted and correlated. Diffusion tensor imaging measures of the WM microstructure of the fornix were correlated against the Fisher Z correlation values from the FC analysis. There was no difference between the groups in the fornix WM measures, nor in the resting-state FC of the thalamus and hippocampus. We did however find that the relationship between functional and structural connectivity differed significantly between the groups. In the HCs, there was a significant positive association between linear diffusion (CL) in the fornix and the FC of the thalamus and hippocampus, however, there was no relationship between these measures in the aMCI group. These preliminary findings suggest that in aMCI, the relationship between the functional and structural connectivity of regions of the limbic system may be significantly altered compared to healthy ageing. The combined use of diffusion weighted imaging and functional MRI may advance our understanding of neural network changes in aMCI, and elucidate subtle changes in the relationship between structural and functional brain networks.

Widespread higher fractional anisotropy associates to better cognitive functions in individuals at ultra‐high risk for psychosis

“…The result indicates widespread higher FA to be strongly linked to better performance on a range of cognitive functions for UHR-individuals, but not for HCs. As a main hippocampal output pathway, the involvement of fornix in especially memory functions is well supported (Hodgetts et al, 2017;Kehoe et al, 2015). We speculate, if the result may reflect a difference in the ability to adjust and compensate for local FA-alterations.…”

“…For identifying the labels of the 48 ROIs displayed by numbers WM-alterations in fornix have been demonstrated in studies of patients with schizophrenia (Knöchel, Schmied, & Oertel-Knöchel, 2016;Thomas, Koumellis, & Dineen, 2011). As a main hippocampal output pathway, the involvement of fornix in especially memory functions is well supported (Hodgetts et al, 2017;Kehoe et al, 2015).…”

Preoperative automated fibre quantification predicts postoperative seizure outcome in temporal lobe epilepsy

“…Importantly, only by mapping individual tract pathology along the length of each tract, including that of the fornix, were we able to generate predictive markers of outcome. The fimbria-fornix is the principal connector between the posterior mesial temporal lobe and thalamus (Aggleton et al , 1986) and mediates resting-state functional connectivity between the hippocampus and thalamus (Kehoe et al , 2015). It is possible that a more extensive involvement of the fimbria-fornix may reflect a more extensive epileptogenic network, and surgery may not sufficiently disrupt this network in those with persistent postoperative seizures.…”

An In vivo Multi-Modal Structural Template for Neonatal Piglets Using High Angular Resolution and Population-Based Whole-Brain Tractography

“…Specific ROI analysis shows that fiber morphology is analogous in piglets to humans in the fornix ( Chen et al, 2015 ; Kehoe et al, 2015 ), optic chiasm ( Hofer et al, 2010 ), the genu of the CC ( Verde et al, 2014 ) and middle cerebellar peduncles ( Chanraud et al, 2009 ). However, the shape of the fibers passing through the splenium of the CC is different in piglets and humans.…”