Articles

  • the Korean Society for Brain and Neural Sciences

Article

Short Communication

Exp Neurobiol 2022; 31(1): 17-28

Published online February 28, 2022

https://doi.org/10.5607/en21047

© The Korean Society for Brain and Neural Sciences

Diffusion MRI Connections in the Octopus Brain

Russell E. Jacobs*

Department of Physiology and Neuroscience, Zilkha Neurogenetics Institute, Keck School of Medicine of USC, Los Angeles, CA 90089-2821, USA

Correspondence to: *To whom correspondence should be addressed.
TEL: 1-323-865-1668, FAX: 1-626-585-1505
e-mail: jacobsr@usc.edu

Received: November 23, 2021; Revised: February 15, 2022; Accepted: February 18, 2022

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Using high angle resolution diffusion magnetic resonance imaging (HARDI) with fiber tractography analysis we map out a meso-scale connectome of the Octopus bimaculoides brain. The brain of this cephalopod has a qualitatively different organization than that of vertebrates, yet it exhibits complex behavior, an elaborate sensory system and high cognitive abilities. Over the last 60 years wide ranging and detailed studies of octopus brain anatomy have been undertaken, including classical histological sectioning/staining, electron microscopy and neuronal tract tracing with injected dyes. These studies have elucidated many neuronal connections within and among anatomical structures. Diffusion MRI based tractography utilizes a qualitatively different method of tracing connections within the brain and offers facile three-dimensional images of anatomy and connections that can be quantitatively analyzed. Twenty-five separate lobes of the brain were segmented in the 3D MR images of each of three samples, including all five sub-structures in the vertical lobe. These parcellations were used to assay fiber tracings between lobes. The connectivity matrix constructed from diffusion MRI data was largely in agreement with that assembled from earlier studies. The one major difference was that connections between the vertical lobe and more basal supra-esophageal structures present in the literature were not found by MRI. In all, 92 connections between the 25 different lobes were noted by diffusion MRI: 53 between supra-esophageal lobes and 26 between the optic lobes and other structures. These represent the beginnings of a mesoscale connectome of the octopus brain.

Graphical Abstract


Keywords: Octopus, Cephalopod, Diffusion MRI, Connectome, Neuroimaging