Fiber Connections of the Supplementary Motor Area Revisited: Methodology of Fiber Dissection, DTI, and Three Dimensional Documentation

Summary

The purpose of this study is to show each step of the fiber dissection technique on human cadaveric brains, the 3D documentation of these dissections, and the diffusion tensor imaging of the anatomically dissected fiber pathways.

Abstract

The purpose of this study is to show the methodology for the examination of the white matter connections of the supplementary motor area (SMA) complex (pre-SMA and SMA proper) using a combination of fiber dissection techniques on cadaveric specimens and magnetic resonance (MR) tractography. The protocol will also describe the procedure for a white matter dissection of a human brain, diffusion tensor tractography imaging, and three-dimensional documentation. The fiber dissections on human brains and the 3D documentation were performed at the University of Minnesota, Microsurgery and Neuroanatomy Laboratory, Department of Neurosurgery. Five postmortem human brain specimens and two whole heads were prepared in accordance with Klingler's method. Brain hemispheres were dissected step by step from lateral to medial and medial to lateral under an operating microscope, and 3D images were captured at every stage. All dissection results were supported by diffusion tensor imaging. Investigations on the connections in line with Meynert's fiber tract classification, including association fibers (short, superior longitudinal fasciculus I and frontal aslant tracts), projection fibers (corticospinal, claustrocortical, cingulum, and frontostriatal tracts), and commissural fibers (callosal fibers) were also conducted.

Introduction

Among the 14 frontal areas delineated by Brodmann, the premotor and prefrontal area that lies in front of the precentral motor cortex has long been considered as a silent module, despite the fact that the frontal lobe plays an important role in cognition, behavior, learning, and speech processing. In addition to the supplementary motor area (SMA) complex, consisting of the pre-SMA and the SMA proper (Brodmann Area; BA 6) that extends medially, the pre-motor/frontal module includes the dorsolateral prefrontal (BA 46, 8, and 9), frontopolar (BA 10), and ventrolateral prefrontal (BA 47) cortices, as well as part of the orbitofrontal cortex (BA 11) on the lateral surface ....

Protocol

The deceased are included here as a population, although deceased persons are not technically human subjects; human subjects are defined by 45 CF 46 as "living human beings^15,16."

1. Preparation of Specimens

1. Examine 5 formalin-fixed brains (10 hemispheres) and 2 whole human heads.
2. Fix the specimens in a 10% formalin solution for at least 2 months according to Klingler's method¹⁷.
3. Freeze all specimens at -16 ˚C for 2 weeks in accordance with Klinger's method¹⁷.
4. Thaw the spec....

Results

The SMA complex is situated in the posterior part of the superior frontal gyrus. The borders of the SMA complex are the precentral sulcus posteriorly, the superior frontal sulcus inferior-laterally, and the cingulate sulcus inferior-medially¹⁸. The SMA complex consists of two parts: the pre-SMA anteriorly and the SMA proper posteriorly¹⁸. There are differences in terms of white matter connections and function between these two parts

Discussion

The Importance of and Study Techniques for the White Matter Pathways

The cerebral cortex is accepted as a principal neural structure associated with 2.5 million years of human life. Approximately 20 billion neurons have separated into various parts based upon morphological and cellular specification⁴⁰. The architecture of each of these cortical parts has been functionally sub-grouped, such as sensorimotor sense and movement, emotional experience, and complex reasoning. It .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
%4 Paraformaldehyde Solution	AFFYMETRIX, Inc.	2046C208	used to fixation
Freezer	INSIGNA	NS-CZ70WH6	used to freez
Panfield Dissector	AESCULAP	FD305	used to dissection
Surgical Micro Scissor	W. Lorenz	04-4238	used to miscrodissection
Surgical Micro Hook	V. Mueller	NL3785-009	used to miscrodissection
MICRO VESSEL STRETCHER/DILATOR	W. Lorenz	04-4324	used to miscrodissection
Emax2 SC 2000 Electric Console	Anspach Companies	SC2102	used to craniatomy
Drill Set	Anspach Companies	NS-CZ70WH6	used to craniatomy
20-1000 operating microscope	Moeller-Wedel,Germany	FS 4-20	used to miscrodissection
Canon EOS 550D 18 MP CMOS APS-C Digital SLR Camera	Canon Inc.	DS126271	used to take photos
EF 100 mm f/2.8L IS USM Macro Lens	Canon Inc.	4657A006	used to take photos
MR-14EX II Macro Ring Lite (Flash)	Canon Inc.	9389B002	used to take photos
Tripod	Lino Manfrotto	322RC2	used to take photos
MAYFIELD Infinity Skull Clamp	Integra Inc.	A0077	used to fix the head
Modified Skrya 3T "Connectome" Scanner	Siemens Company, Inc.	A911IM-MR-15773-P1-4A00	used to scan DTI
XstereO Player	Yury Golubinsky	Version 3.6(22)	used to create anaglyphs
EF-S 18-55mm f/3.5-5.6 IS II SLR Lens	Canon Inc.	2042B002	used to take photos
Scalpel	6B INVENT	7-104-L	used to make incision
Compact Speed Reducer	Anspach Companies	CSR60	used to make burr hole
14 mm Cranial Perforator	Anspach Companies	CPERF-14-11-3F	used to make burr hole
2 mm x 15.6 mm Fluted Router	Anspach Companies	A-CRN-M	used to make craniotomy
2.1 mm Pin-shaped Burrs	Anspach Companies	03.000.130S	used to make craniotomy