Inter-hemispheric Claustral Connections in Human Brain: A Constrained Spherical Deconvolution-Based Study

Purpose: Complex claustral connection network was widely demonstrated both in humans and animals. Moreover, several studies have suggested that claustral connections directly involve also the contralateral hemisphere. Detection of contralateral cortico-claustral and inter-claustral connections was reported mainly in animals and only partially in humans. The main purpose of this study was to provide more robust tractography-driven support of the existence of inter-hemispheric claustral connections in humans, by means of a dedicated optimized tractographic protocol. Methods: Fifteen healthy subjects were examined by means of an advanced magnetic resonance imaging-based probabilistic constrained spherical deconvolution tractographic protocol. Moreover, quantitative diffusion parameters were extracted by each reconstructed pathway. Results: In this study, further imaging-based support on the possible existence in humans of contralateral cortico-claustral and inter-claustral connections was provided. These connections were found to involve almost all the superior portion of each claustrum, showing a topographical organization. Moreover, the detection of inter-claustral connections passing through the anterior commissure was reported, for the first time, in humans. Conclusions: The possible existence of inter-claustral and cortico-claustral contralateral pathways might provide the morphological basis for the complex functional phenomena observed in previous studies. Furthermore, these connections might have several important clinical implications, since they might explain how the inter-hemispheric coordination governed by the claustrum, as well as the functional recovery subsequent to damages involving one claustrum, takes place.