Interhemispheric co-alteration of brain homotopic regions

Abstract

Asymmetries in gray matter alterations raise important issues regarding the pathological co-alteration between hemispheres. Since homotopic areas are the most functionally connected sites between hemispheres and gray matter co-alterations depend on connectivity patterns, it is likely that this relationship might be mirrored in homologous interhemispheric co-altered areas. To explore this issue, we analyzed data of patients with Alzheimer’s disease, schizophrenia, bipolar disorder and depressive disorder from the BrainMap voxel-based morphometry database. We calculated a map showing the pathological homotopic anatomical co-alteration between homologous brain areas. This map was compared with the meta-analytic homotopic connectivity map obtained from the BrainMap functional database, so as to have a meta-analytic connectivity modeling map between homologous areas. We applied an empirical Bayesian technique so as to determine a directional pathological co-alteration on the basis of the possible tendencies in the conditional probability of being co-altered of homologous brain areas. Our analysis provides evidence that: the hemispheric homologous areas appear to be anatomically co-altered; this pathological co-alteration is similar to the pattern of connectivity exhibited by the couples of homologues; the probability to find alterations in the areas of the left hemisphere seems to be greater when their right homologues are also altered than vice versa, an intriguing asymmetry that deserves to be further investigated and explained.

Sex differences in brain homotopic co-activations: a meta-analytic study

“…The 20% threshold is arbitrary, but we previously showed that different thresholds do not greatly affect the results (Mancuso et al 2019b ). Then, the probability of two homotopic areas to be found co-activated in our sample was computed by means of the Patel’s κ, a Bayesian measure of co-activation, the calculation of which is explained in detail elsewhere (Cauda et al 2020 ; Cauda et al 2021 ; Patel et al 2006 ; Manuello et al 2018 ), thresholded at p = 0.05. In short, Patel’s κ assesses the probability of a couple of areas of being more co-activated than expected given the observed activations of the two regions, and it is tested for significance with a Monte Carlo simulation.…”

“…We assessed the meta-analytical homotopic connectivity (MHC) of female and male subjects on a large database of activation studies obtained from the BrainMap database. There is a large body of evidence showing the similarity between co-activations and functional connectivity (Toro et al 2008 ; Smith et al 2009 ; Laird et al 2011 ; Laird et al 2013 ; Torta et al 2013 ; Cauda et al 2021 ); in particular, the MHC technique has previously been shown to produce similar results to the VMHC (Mancuso et al 2019b ). This would suggest that meta-analytic homotopic co-activations could be taken both as an indicator of interhemispheric integration (vs. lateralization) and of functional connectivity.…”