Abstract
Previous studies showed that cognitive training can improve cognitive performance in various neurodegenerative diseases but little is known about the effects of cognitive training on the brain. Here, we investigated the effects of our cognitive training paradigm, COGTIPS, on regional white matter microstructure and structural network topology. We previously showed that COGTIPS has small, positive effects on processing speed. A subsample of 79 PD patients (N = 40 cognitive training group, N = 39 active control group) underwent multi-shell diffusion-weighted imaging pre- and post-intervention. Our pre-registered analysis plan (osf.io/cht6g) entailed investigating white matter microstructural integrity (e.g., fractional anisotropy) in five tracts of interest, including the anterior thalamic radiation (ATR), whole-brain tract-based spatial statistics (TBSS), and the topology of the structural network. Relative to the active control condition, cognitive training had no effect on topology of the structural network or whole-brain TBSS. Cognitive training did lead to a reduction in fractional anisotropy in the ATR (B [SE]: − 0.32 [0.12], P = 0.01). This reduction was associated with faster responses on the Tower of London task (r = 0.42, P = 0.007), but this just fell short of our statistical threshold (P < 0.006). Post hoc “fixel-based” analyses showed that this was not due to changes in fiber density and cross section. This suggests that the observed effect in the ATR is due to training-induced alterations in neighboring fibers running through the same voxels, such as intra-striatal and thalamo-striatal fibers. These results indicate that 8 weeks of cognitive training does not alter network topology, but has subtle local effects on structural connectivity.
Highlights
Cognitive training has positive effects on cognitive performance and on the brain, showing that cognitive training can increase neural efficiency and counteract aging- or disease-related neural dysfunction
We explored the effect of the training on the connectivity strength between the default mode network (DMN), frontoparietal network (FPN), ventral attention network (VAN), and dorsal attention network (DAN) and their topology using the Yeo network parcellation [33]
We observed a significant difference in mean diffusivity (MD) in the genu of the corpus callosum (B [SE]: 0.18 [0.09], 95% CI: 0.006 to 0.35, P = 0.04; Fig. 2b) but this effect was no longer significant after adjusting for covariates
Summary
Cognitive training has positive effects on cognitive performance and on the brain, showing that cognitive training can increase neural efficiency and counteract aging- or disease-related neural dysfunction (van Balkom et al 2020). Another study showed that relative to healthy participants, white matter integrity progressively deteriorates from relatively intact in cognitive preserved PD patients, to. Widespread dysfunction in PD patients with mild cognitive impairment (MCI) and dementia, including the ATR, corpus callosum, and inferior longitudinal fascicles [10]. The topology of the structural connectome of PD patients is less efficient and clustered compared with healthy controls [11,12,13,14], especially in PD patients with cognitive impairment [15]. No study has yet investigated the effect of cognitive training on the topology of the structural connectome in PD patients. We expected cognitive training to improve the white matter microstructure of the three different segments of the corpus callosum, the inferior longitudinal fascicle, and the ATR. We hypothesized that cognitive training would improve the efficiency of the structural connectome to transfer information (measured as increased global efficiency) and improve the interconnectedness of neighboring brain regions (increased clustering coefficient)
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