The structural connectivity of the human angular gyrus as revealed by microdissection and diffusion tractography

Laurent Petit, Kariem Mahdy Ali, François Rheault, Arnaud Boré, Sandrine Cremona, Francesco Corsini, Alessandro De Benedictis, Maxime Descoteaux, Silvio Sarubbo
Brain Structure and Function. 2022-08-22; 228(1): 103-120
DOI: 10.1007/s00429-022-02551-5

Petit L(1), Ali KM(2), Rheault F(3), Boré A(4), Cremona S(5), Corsini F(6), De
Benedictis A(7), Descoteaux M(4), Sarubbo S(6).

Author information:
(1)Groupe d’Imagerie Neurofonctionnelle, Centre Broca Nouvelle-Aquitaine – 3ème
étage, Université Bordeaux, Institut des Maladies Neurodégénératives CNRS UMR
5293, 146 rue Léo Saignat – CS 61292 – Case 28, 33000, Bordeaux, France.
.
(2)Department of Neurosurgery, Medical University of Graz, Graz, Austria.
(3)Electrical and Computer Engineering, Vanderbilt University, Nashville, USA.
(4)Sherbrooke Connectivity Imaging Lab (SCIL), Université de Sherbrooke,
Sherbrooke, Canada.
(5)Groupe d’Imagerie Neurofonctionnelle, Centre Broca Nouvelle-Aquitaine – 3ème
étage, Université Bordeaux, Institut des Maladies Neurodégénératives CNRS UMR
5293, 146 rue Léo Saignat – CS 61292 – Case 28, 33000, Bordeaux, France.
(6)Department of Neurosurgery, Azienda Provinciale per i Servizi Sanitari, “S.
Chiara” Hospital, Trento, Italy.
(7)Neurosurgery Unit, Department of Neurosciences, Bambino Gesù Children’s
Hospital, IRCCS, Rome, Italy.

The angular gyrus (AG) has been described in numerous studies to be consistently
activated in various functional tasks. The angular gyrus is a critical connector
epicenter linking multiple functional networks due to its location in the
posterior part of the inferior parietal cortex, namely at the junction between
the parietal, temporal, and occipital lobes. It is thus crucial to identify the
different pathways that anatomically connect this high-order association region
to the rest of the brain. Our study revisits the three-dimensional architecture
of the structural AG connectivity by combining state-of-the-art postmortem blunt
microdissection with advanced in vivo diffusion tractography to comprehensively
describe the association, projection, and commissural fibers that connect the
human angular gyrus. AG appears as a posterior “angular stone” of associative
connections belonging to mid- and long-range dorsal and ventral fibers of the
superior and inferior longitudinal systems, respectively, to short-range
parietal, occipital, and temporal fibers, including U-shaped fibers in the
posterior transverse system. Thus, AG is at a pivotal dorso-ventral position
reflecting its critical role in the different functional networks, particularly
in language elaboration and spatial attention and awareness in the left and
right hemispheres, respectively. We also reveal striatal, thalamic, and
brainstem connections and a typical inter-hemispheric homotopic callosal
connectivity supporting the suggested AG role in the integration of sensory
input for modulating motor control and planning. The present description of AG’s
highly distributed wiring diagram may drastically improve intraoperative
subcortical testing and post-operative neurologic outcomes related to surgery in
and around the angular gyrus.