Name: fiber connections of the supplementary motor area revisited: methodology of fiber dissection, dti, and three dimensional documentation
Uploaded: 2017-05-23T14:00:00.000+00:00
Duration: 16 min 23 s
Description: Watch this Scientific Journal Video about Fiber Connections of the Supplementary Motor Area Revisited: Methodology of Fiber Dissection, DTI, and Three Dimensional Documentation at JoVE.com

The data were provided in part by the Human Connectome Project, WU-Minn Consortium (Principal Investigators: David Van Essen and Kamil Ugurbil; 1U54MH091657), funded by the 16 NIH Institutes and Centers that support the NIH Blueprint for Neuroscience Research; and by the McDonnell Center for Systems Neuroscience at Washington University. Figures 2A and 2D were reproduced with permission from the Rhoton collection57 (http://rhoton.ineurodb.org/?page=21899).

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 &#34;living human beings15,16.&#34;
1. Preparation of Specimens
<ol>
	<li>Examine 5 formalin-fixed brains (10 hemispheres) and 2 whole human heads.</li>
	<li>Fix the specimens in a 10% formalin solution for at least 2 months according to Klingler&#39;s method17.</li>
	<li>Freeze all specimens at -16 &#730;C for 2 weeks in accordance with Klinger&#39;s method17.</li>
	<li>Thaw the specimens under tap water.</li>
	<li>Perform an extended frontotemporal craniotomy on the cadaveric head to expose the brain.
	<ol>
		<li>Place the cadaveric head in a three-pin skull clamp (Material Table).</li>
		<li>Make a frontotemporal skin incision with a scalpel.</li>
		<li>Remove the skin and muscles using a scalpel, forceps, and scissors.</li>
		<li>Make one or more burr holes in the skull until the dura mater is reached; use a drill with a compact speed reducer and a 14 mm cranial perforator attachment at 79,000 rpm (Material Table).</li>
		<li>Cut the bone flap and open the skull using a 2 mm x 15.6 mm fluted router with a 2.1 mm pin-shaped burr attachment at a drill speed of 80,000 rpm (Material Table).</li>
	</ol>
	</li>
	<li>Remove the dura, arachnoid, and pia mater and dissect using a microdissector under a microscope at 6X to 40X magnification5,18
 (Material Table).</li>
</ol>
2. Fiber Dissection Technique
NOTE: Perform all dissections under 6X to 40X magnification on a surgical microscope.
<ol>
	<li>Perform the fiber dissections in a stepwise manner on each hemisphere, from lateral to medial and medial to lateral.
	<ol>
		<li>Decorticate the cerebral cortex using a panfield dissector (Material Table) and remove all frontal cortical tissues to expose the short association fiber tracts, which are U-fibers or intergyral fibers that interconnect neighboring gyri5,13.</li>
		<li>Remove the short association fibers with a panfield dissector and a surgical micro hook by gently trimming under the microscope (Material Table) to reach and expose the long association fibers, which interconnect distant areas in the same hemisphere.</li>
		<li>Go deep into the long association fibers to remove the superficial association fibers using a surgical micro hook and a panfield dissector; remove each fiber bundle under a microscope (Material Table) to expose the projection commissural fibers.</li>
		<li>View each of the connections of the SMA complex according to the topographical anatomy that was previously defined in the literature2,8,18,19,20,21.</li>
	</ol>
	</li>
	<li>Keep all specimens (whole heads and brains) that were used during the dissections in 10% formaldehyde solution (Material Table) between the dissection periods.</li>
</ol>
3. 3D Photography Technique
<ol>
	<li>Use a black color platform during the photography of the specimens.</li>
	<li>Follow a 3D photography technique22.
	<ol>
		<li>Place each specimen in a designed black color platform.</li>
		<li>Select a scene with a full-frontal view of the specimen and take one shot by focusing the camera on any point on the specimen close to the center point on the camera screen (instrument table). Use an 18- to 55-mm f/3.5-5.6 SLR lens or a 100 mm f/2.8L macro lens and set the aperture to F29, ISO 100.</li>
		<li>Rotate the camera slightly left until the right-most point on the camera screen is the same as the focusing point above. Slide the camera to the right until the middle point on the screen overlaps the original focusing point on the specimen. Focus the camera on this point and take another shot.</li>
		<li>Maintain the distance and axis of the camera to the specimen being photographed at constant values.</li>
	</ol>
	</li>
	<li>Create a 3D image by using a 3D image generator program (Material Table).
	<ol>
		<li>Open the 3D software program.</li>
		<li>Choose &#34;Open stereo images from File.&#34;</li>
		<li>Select the two images (left and right) and make sure the left image is in the left slot and the right image is in the right slot.</li>
		<li>Select the &#34;Half color anaglyph RL/2&#34; option and generate the anaglyph in jpeg format.</li>
	</ol>
	</li>
</ol>
4. DTI Technique
<ol>
	<li>Acquire pre-processed diffusion data utilizing the Human Connectome Project diffusion data23 by downloading it from the referenced website. 
	NOTE: The data is downloaded pre-processed and consisted of the following procedures: The diffusion data was acquired in normal volunteers using a modified 3 T MRI device (instrument table) utilizing a spin-echo echo planar imaging (EPI) sequence with multi-band image acceleration24,25,26,27,28. Relevant sequence parameters include: TR = 5,520 ms; TE = 89.5 ms; FOV = 210 x 180 mm; matrix = 168 x 144; slice thickness = 1.25 mm (voxel size 1.25 x 1.25 x 1.25 mm); multiband factor = 3; and b-values = 1,000 s/mm2(95 directions), 2,000 s/mm2(96 directions), and 3,000 s/mm2(97 directions). The data was then processed utilizing FreeSurfer29and FSL30; the process included eddy current correction, motion correction, b0 intensity normalization, susceptibility distortion correction, and gradient-nonlinearity correction28,31,32,33. Corresponding T1-weighted MP-RAGE images are also included in the download package. Procedures are documented in the Human Connectome Project procedures manual23.</li>
	<li>Post-process the diffusion data using Diffusion Spectrum Imaging (DSI) Studio34to generate an estimated voxel-wise diffusion orientation distribution function (ODF) employing a generalized q-sampling imaging (GQI) algorithm35.
	<ol>
		<li>Load the downloaded dataset into the software by selecting &#34;STEP1: Open source images&#34; and selecting the data.nii.gz file.</li>
		<li>Select the &#34;STEP2: Reconstruction&#34; button. After verifying the brain mask, proceed to &#34;Step 2&#34; and select &#34;GQI&#34; as the reconstruction method. Select &#34;r^2 weighting&#34; with a &#34;length ratio&#34; of &#34;1.0.&#34; Leave the remaining selections as the default.</li>
		<li>Select &#34;Run reconstruction.&#34;</li>
	</ol>
	</li>
	<li>Place appropriate seeds for regions-of-interest to streamline fiber-tracking.
	<ol>
		<li>In the &#34;Region Window,&#34; click the &#34;Atlas&#34; button to place seeds for the superior longitudinal fasciculus (SLF) I. Select &#34;Brodmann&#34; and add &#34;Region 6&#34; and &#34;Region 7.&#34; In the region window, set the &#34;Region 6&#34; type to &#34;seed&#34; and the &#34;Region 7&#34; type to &#34;region-of-inclusions&#34; (ROI).
		<ol>
			<li>Select &#34;New Region&#34; in the region window and manually draw an ROI in the most posterior aspect of the superior frontal gyrus in the coronal plane. Perform fiber tracking as described in step 4.4.</li>
		</ol>
		</li>
		<li>Place seeds for SLF II in similar fashion by using &#34;New Region&#34; in the region window and drawing the &#34;seed&#34; region in the posterior aspect of the middle frontal gyrus white matter in the coronal plane. Choose an ROI using &#34;Atlas&#34; (as in step 4.3.1) and Brodmann regions 9, 10, 46, 39, and 19. Perform fiber tracking as described in step 4.4.</li>
		<li>Place seeds for SLF III with a &#34;seed&#34; region, using &#34;Atlas&#34; (as in step 4.3.1) in the region window and choosing &#34;Region 40&#34; of the Brodmann atlas and the ROI from &#34;Atlas&#8230;&#34; in &#34;Region 40&#34; and &#34;Region 44.&#34; Perform fiber tracking as described in step 4.4.</li>
		<li>Place seeds for callosal fibers using &#34;New Region&#34; in the region window and drawing a &#34;seed&#34; in the sagittal plane encompassing the corpus callosum. Perform fiber tracking as described in step 4.4.</li>
		<li>Place seeds for cingulate fibers using &#34;New Region&#34; in the region window and drawing a &#34;seed&#34; region in the mid-cingulate gyrus on the coronal view. Use &#34;New Region&#34; to draw two ROIs, one in the more anterior cingulate and one in the posterior cingulate gyrus under coronal view. Perform fiber tracking as described in step 4.4.</li>
		<li>Place seeds for claustrocortical fibers using &#34;New Region&#34; in the region window and drawing a &#34;seed&#34; in the claustrum with an ROI in the corona radiata using the &#34;Atlas&#8230;&#34; function. Select the atlas as &#34;JHU-WhiteMatter-labels-1mm.&#34;
		<ol>
			<li>Select and add the &#34;Anterior_corona_radiata&#34;, &#34;Posterior_corona_radiata,&#34; and &#34;Superior_corona_radiata&#34;. Draw a region-of-avoidance for all fibers passing through a plane inferior to the level of the claustrum in the axial plane using &#34;New Region&#34; in the region window. Perform fiber tracking as described in step 4.4.</li>
		</ol>
		</li>
		<li>Place seeds for the corticospinal tract using a &#34;seed&#34; from the &#34;Atlas...&#34; function in the region window; select &#34;JHU-WhiteMatter-labels-1mm&#34; and add the &#34;Corticospinal_tract&#34; region. Perform fiber tracking as described in step 4.4.</li>
		<li>Place seeds for the frontal aslant tract (FAT) using a &#34;seed&#34; region from the &#34;Atlas...&#34; function in the region window and selecting the Brodmann atlas and &#34;Region 6&#34; ROIs in &#34;Region 44&#34; and &#34;Region 45.&#34; Perform fiber tracking as described in step 4.4.</li>
		<li>Place seeds for the frontostriatal tract (FST) with a &#34;seed&#34; in &#34;Region 6&#34; using the &#34;Atlas...&#34; function. Insert new regions in the &#34;caudate,&#34; &#34;putamen,&#34; and &#34;globus pallidus&#34; from the &#34;HarvardOxfordSub&#34; atlas and set the type in the region window to &#34;end.&#34; 
		&#8203;NOTE: Fiber tracking for FST will be performed by selecting the Region 6 seed and only one of the subcortical seeds per tracking session (i.e., region 6 and the caudate, followed by region 6 and the putamen, and lastly region 6 and the globus pallidus).
		<ol>
			<li>Perform fiber tracking as described in step 4.4 for each combination.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Perform fiber tracking for each of the above combinations.
	<ol>
		<li>In the &#34;Options&#34; window, set the tracking parameters as: termination index of qa of 0.08, angular threshold of 75, step size of 0.675, smoothing of 0.2, minimum length of 20 mm, and maximum length of 200 mm. Select the seed orientation as &#34;All,&#34; the seed position as &#34;Subvoxel,&#34; and randomize seeding as &#34;On.&#34; Use trilinear direction interpolation with a streamline (Euler) tracking algorithm. For each combination of regions above, choose &#34;Run tracking&#34; in the &#34;Fiber Tracts&#34; window. 
		NOTE: Due to the randomized nature of the tracking, clear &#34;false fibers&#34; are identified and selectively removed, with regions-of-avoidance drawn by hand as a &#34;New Region.&#34;</li>
	</ol>
	</li>
	<li>Affine register the brain-extracted T1-weighted 3D MP-RAGE scan provided in the Human Connectome Project data set to the diffusion data using the &#34;Slices -&#62; Insert T1/T2 Images&#34; function of DSI-Studio. Generate a surface rendering of the brain by selecting &#34;Slices -&#62; Add Isosurface.&#34; Use a &#34;threshold&#34; of 665.</li>
</ol>

The authors declare no competing financial interests and no sources of funding and support, including any for equipment and medications.

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 was determined that all behaviors in primates have been formed by unique anatomo-functional connections and regions topographically distributed through the cortical and subcortical areas of the neural system. Although the cerebral cortex has been researched in detail, there is still a lack of knowledge on the white matter pathways of the neural system that connect different areas. Areas such as the centrum semiovale and corona radiata have been studied before under a macroscopic view. During the 1800s, researchers performed the gross dissection of monkeys using myelin coloring materials and autoradiography methods that were applied with the help of amino acids to understand the white matter fiber system. Some major association fibers, such as the cingulum and uncinate fasciculus, have been identified and named with these studies. On the other hand, the identification of other white matter pathways, such as the arcuate fasciculus/superior longitudinal fasciculus and the inferior longitudinal fasciculus, is still contradictory in the literature41,42,43,44,45.
An understanding of white matter structures is very important to providing details on the anatomical processes of high-level behavior and the structure and function of the cerebrum. A deeper understanding of the white matter pathways is also critical for clinical aims. Many diseases are caused by lesions affecting the white matter pathways. Previously, there was no unique and proper technique that could be used to describe the fiber pathways, despite improvements in radiological imaging techniques. The cadaveric fiber dissection technique, which is the oldest technique, was the ideal method for the neuroanatomical education of young neurosurgeons and the best standard among the tractography techniques based upon diffusion tensor imaging, MR tractography, diffusion spectrum tractography, and autoradiography. The fiber tracts can be visualized in vivo with MRI; however, the disadvantage of this technique is the difficulty in determining the termination and the origin of the fiber pathways. The autoradiographic technique can only be used in experimental animals. A knowledge of fiber tract anatomy is critical to gaining a better understanding of cognitive, psychiatric, and motor manifestations following white matter disorders such as multiple sclerosis.
Plasticity exists in gray matter, but not in white matter; any peri-operative damage to white matter causes irreversible deficits in the patient (Schmahmann et al.). This renders the anatomy of the fiber pathways more valuable in neurosurgery46. During preoperative surgical planning for the removal of intra-axial lesions, the location and displacement of the important fiber pathways, such as the arcuate fasciculus, optic radiations, and corticospinal tract should be taken into consideration for a successful surgery. The anatomical knowledge, together with preoperative MR tractography, provide sound evaluation and surgical planning for each patient. In the meantime, performing cadaveric fiber dissection under the operating microscope helps to improve the hand skills of the surgeon and provides a deeper understanding of the complex brain anatomy in three dimensions. To achieve these gains, the surgeon should spend time in a microsurgery laboratory. He/she should only focus on the fiber tracts during the dissection, rather than what he/she would like to see. On the other hand, today, improvements in DTI imaging techniques have made it possible to identify major fiber pathways in vivo, both in the normal brain and in clinical situations where the fiber system is affected. Initially, this method did not provide any information about the start and termination regions of major fiber bundles and was only effective in the definition of extensions. However, with the development of MR tractography and diffusion spectrum imaging (DSI), major steps have been taken to understand normal brain anatomy in in vivo and clinical studies 47,48,49. In recent years, it has been suggested that mapping of white matter pathways is very critical to prevent postoperative deficits. It is also useful to perform intraoperative electrical mapping of the white matter to help protect significant subcortical structures and their functions50,51. Therefore, the anatomy of the frontal region and the white matter pathways should be understood thoroughly for frontal-glioma surgery.
Anatomic Features and the Clinical Importance of SMA Complex
The macro-anatomical border line between the pre-SMA and the SMA proper is accepted as a vertical imaginary line passing through the level of the anterior commissure18,39. Also, the pre-SMA and the SMA proper have differences in terms of their functions. Although the SMA proper has somatotopic tasks, the pre-SMA has a somatosensory organization19. Basically, the SMA proper is responsible for the activation, control, and generation of movement, while the pre-SMA is responsible for cognitive and non-motor tasks8.
Patients with lesions of the pre-SMA present with various degrees of speech impairment, ranging from a total inability to initiate speech (i.e., mutism) to mild altered fluency52. As would be predicted by neurosurgical electrical stimulation data, resection or damage to the SMA complex produces negative motor response in motor and speech functions and eventually results in SMA syndrome. SMA syndrome is a complex neurosurgical syndrome of initiation that ranges from a total loss of motor and speech production, such as akinetic mutism, to diminished spontaneous movements and speech18,53. Therefore, the subcortical fiber tract connections of the SMA complex play an important role in surgical planning.
The Fiber Tracts of the SMA Complex
In this study, we studied all connections of the SMA complex, such as the FAT, FST, short association fibers, SLF I, callosal fibers, cingulum fibers, and claustrocortical fibers using cadaveric fiber dissection and DTI techniques that were defined in the literature in recent years8,13,18. We showed and supported our fiber dissection results via DTI. However, it is difficult to separate some projection white matter pathways, such as the FST and the corticospinal tract (CST) from other corona radiate fiber bundles via anatomical dissection. Therefore, we were able to show the topographical anatomy of these two fiber bundles more effectively via DTI. Additionally, the ability to study in vitro and to display deep fiber bundles in detail are the other advantages of DTI study.
The SLF I is a long association fiber that which connects the precuneus (superior parietal lobe) to the SMA complex and cingulate cortex. SLF I has functions relating to both the limbic system, by connecting with the anterior cingulate cortex, and the motor system, by connecting with the superior parietal lobe13,18,36,54.
The posterior parts of the superior and inferior frontal gyrus interconnect with a direct system that consist of the FAT, which was newly defined using DTI techniques2 and then with fiber dissection techniques18. The projection of this pathway is in the pre-SMA and SMA proper in the superior frontal gyrus and the pars opercularis in the inferior frontal gyrus18. Ford et al. demonstrated structural connectivity between the SMA and the Broca center for the first time, supporting the functional role of the SMA as a speech-processing cortex55. In addition to the SLF I, the FAT is a direct pathway connecting the pars opercularis with the anterior cingulate and pre-SMA, as indicated by the results in this study. Catani et al. defined the FAT through DTI and reported that cortical atrophy of the FAT connection zones on the SMA complex (pre-SMA and anterior part of the SMA proper) and the anterior cingulate in patients with primary progressive aphasia may result in verbal fluency disorders46. Previous studies have indicated that FAT may also be associated with speech initiation difficulties and speech fluency dysfunctions22.
The FST is made up of projection fibers that connect the pre-SMA and striatum (i.e., caudate nucleus and putamen). In previous studies, the termination points of the FST in the basal ganglia were not very clear. However, it was also shown in recent comprehensive DTI studies that the FST originates from the pre-SMA and terminates in the internal capsule and in the lateral surface of the putamen20,21,22. In addition to this, in another DTI study, it has been shown that the FST terminates both in the lateral and the medial surfaces of the putamen18. Functionally, Duffau et al. demonstrated anartria and/or cessation of movement during intraoperative direct electrical stimulation of the putamen, the mechanism of which is most likely through the putaminal connections of the FST21.
The corticospinal tract connects the SMA proper and primary motor cortex to the spinal cord, but the pre-SMA has no fibers of the corticospinal tract24. In an electrostimulation study by Duffao et al., an arrest of movement was observed by stimulating the SMA region in the contralateral upper limb. It was thought that this may occur because of the connection of the SMA with the spinal cord by the corticospinal tract and the contralateral SMA by callosal fibers18,56.
The claustrocortical fibers connect between the claustrum in the central core and a wide region between the anterior edge of the pre-SMA and the posterior part of the parietal lobe13. Functionally, the claustrocortical fibers are believed to play a role in consciousness and in coordinating information coming from the visual cortical region, limbic system, and somatosensory and motor cortices27. Therefore, claustrocortical fiber bundles between the SMA complex and the claustrum were thought to may play a role in the execution of higher motor and speech contro18.
Although has been stated in previous studies that the connection of SMA complex with cingular gyrus is via short association fibers, in a recent anatomical study, it was found that these connections are provided directly by cingular fibers18. Functionally, it was claimed that this pathway has a role in the motor processing of negative emotional stimulation between the SMA and the limbic cortex18.
In recent years, the clinical importance of the SMA complex (e.g., SMA syndrome and negative motor response) was revealed by an increasing number of electrostimulation studies. Therefore, the importance of topographical anatomy and subcortical connections of the SMA were gradually highlighted. It is critical to gain a better understanding of topographical anatomy, particularly through 3D anatomical studies, and to use clinical features of these connections to plan surgery.

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 of the brain1,2.
The SMA complex is a significant anatomical area that is defined by its functions and its connections. The resection and damage of this region causes significant clinical deficits known as the SMA syndrome. The SMA syndrome is an important clinical condition that is particularly observed in frontal glioma cases that contain the SMA complex3. The SMA complex has connections with the limbic system, basal ganglia, cerebellum, thalamus, contralateral SMA, superior parietal lobe, and portions of the frontal lobes via fiber tracts. The clinical effect of damage to these white matter connections may be more severe than to the cortex. This is because the consequences of injury to the cortex can be ameliorated over time due to high cortical plasticity 4,5,6,7,8,9,10,11,12,. Therefore, the SMA regional anatomy and the white matter pathways should be deeply understood, in particular for glioma surgery.
A comprehensive understanding of the anatomy of white matter pathways is important for the wide-spectrum treatment of neurosurgical lesions. Recent studies of the three-dimensional documentation of the anatomical results that were obtained in microsurgery were used to gain a better understanding of the topographical anatomy and the interrelationship of brain white matter pathways13,14. Therefore, the purpose of this study was to examine the white matter connections of the SMA complex (pre-SMA and SMA proper) using a combination of fiber dissection techniques on cadaveric specimens and magnetic resonance imaging (MRI) tractography and to explain all the methods and principles of both techniques and their detailed documentation.
Planning and Strategy of Study
Prior to performing the experiments, a literature search on the basic principles of fiber dissections, the procedures that need to be applied to specimens before and during dissections, and all connections between SMA regions that have been revealed with dissection and DTI was conducted. The previous studies on the anatomical localization and separation of pre-SMA and SMA-proper regions and on the topographic anatomy of their connections were reviewed.

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

fiber connections of the supplementary motor area revisited: methodology of fiber dissection, dti, and three dimensional documentation

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.

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 parts18 (Figure 1A and B). We the studied cortical and subcortical connections of these two parts using fiber dissection and DTI techniques and showed them in 3D images.
Association Fibers of the SMA Complex
Removing the cortex of the frontal lobe exposed the short association fibers, the so-called U-fibers, which interconnect neighboring gyri18
 (Figure 1C). The short association fibers of the SMA complex provide connections between the SMA complex and the motor cortex posteriorly and between the SMA complex and the pre-frontal cortex anteriorly18 (Figure 2B). They also provide connections between the pre-SMA and the SMA proper in the SMA complex. The most superficial long association fibers are the superior longitudinal fasciculus II (SLF II) and the frontal opercular part of the SLF III13,36 (Figure 2A). We removed the SLF II and SLF III just in front of the precentral sulcus to expose the frontal aslant tract (FAT), which interconnects the superior frontal gyrus and the inferior frontal gyrus (Figure 2B). The FAT are superficial association fibers that arise from the pre-SMA and the pars opercularis.
During FAT dissection, it is critical to anatomically distinguish the FAT from corona radiata fibers, which run parallel in the vertical plane. As the literature indicates, FAT fibers travel obliquely from the SMA region to the inferior frontal gyri and become superficial in pars opercularis2. However, other corona radiata and claustrocortical fibers run deeply to the basal ganglia without being superficial18(Figure 2C, 3C, and 3D).
Another association fiber tract of the SMA complex is SLF I, which connects the superior parietal lobe to the superior frontal lobe (SMA complex) and the anterior cingulate cortex on the medial side of the hemisphere18,36. The dissection of SLF I was performed medial to lateral after the decortication of the medial surface of the hemisphere (Figure 2A, 3A, and 3B).
Commissural Fibers of the SMA Complex
The major commissural fiber pathway is the callosal fibers, which connect the SMA complex with the contralateral SMA complex. The callosal fibers are positioned between the corona radiate, the cingulum, and SLF I fibers and cross to the midline via the corpus callosum to reach the contralateral SMA complex (Figure 2A, 4A, and 4B).
Projection Fibers of the SMA Complex
The projection fibers consist of 4 different fiber groups related to the SMA complex: the cingulum fibers, claustrocortical fibers, frontocitriatal tract, and corticospinal tract. The cingular fibers originate from the medial surface of the hemisphere to form the cingulum and run within the cingulate gyrus. The function of these fibers is to provide connections between the SMA complex and the limbic system18 (Figure 2A and 4C).
The distribution of the claustrocortical fibers borders are the anterior edge of the pre-SMA anteriorly and the posterior part of parietal lobe posteriorly (Figure 2D and 4D). Therefore, the fibers originating from the claustrum terminate in all SMA complex areas (pre-SMA and SMA proper)37.
The frontostriatal tract (FST) connects the SMA complex and the dorsal striatum (i.e., caudate nucleus and putamen) and travels between the external and internal capsules18 (Figure 3C and 3D). It is difficult to distinguish the FST from other internal capsule fibers (e.g., the thalamic peduncles, frontopontine fibers, etc.), as well as from other fibers in the vertical plane (e.g., FAT and other corona radiata fibers), when using the fiber dissection technique. Nevertheless, Grande et al. used the DTI technique to demonstrate that the FST fibers that arise from the SMA complex terminate in both the external and internal capsules18. Approximately 10% of the cortical spinal tract fibers arise from the SMA proper and terminate in the spinal cord, but these fibers do not arise from the pre-SMA38 (Figure 4E).
<img alt="Figure 1" src="/files/ftp_upload/55681/55681fig1.jpg" /> 
Figure 1: Lateral and Medial Surface of Left Frontal Lobe View. Labeled 2D illustrations accompany each 3D illustration on the left side. Left hemisphere lateral view: SMA proper (purple) and pre-SMA (green); the SMA complex is situated in the posterior part of the superior frontal gyrus, just in front of the precentral gyrus (A). Left hemisphere medial view. An imaginary vertical line at the level of the anterior commissure, perpendicular to the line that lies between the anterior and posterior commissures, is the border between the SMA proper (purple) and the pre-SMA (green) (B)39. After decortication view. The decortication exposes short association fibers, called &#34;U fibers.&#34; U fibers connect neighboring gyri to each other, such as the pre-SMA to the SMA proper and the SMA proper to the motor cortex (C). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55681/55681fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 1" src="/files/ftp_upload/55681/55681fig2.jpg" /> 
Figure 2: Lateral-to-medial Fiber Dissection. Labeled 2D illustrations accompany each 3D illustration on the left side. Lateral view; the SLF II extends between the angular gyrus and the middle frontal gyrus and terminates at the pars opercularis and pars triangularis. The SLF III connects the supramarginal gyrus and the pars triangularis in the frontoparietal operculum. Medial view; the SLF I connects the superior parietal lobe to the anterior cingulate cortex and the medial surface of the superior frontal gyrus, which includes the SMA complex (A). After removing a part of SLF II at the coronal level, the FAT was exposed (B). FAT fibers travel obliquely from the SMA region to the inferior frontal gyri and become superficial in the pars opercularis. Other corona radiata fibers run deep to the basal ganglia without being superficial (C). Another specimen showing the exposed borderline of the claustrocortical fiber distribution on the cortical area, which is between the anterior part of the pre-SMA and the posterior part of the parietal lobe (D). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55681/55681fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 1" src="/files/ftp_upload/55681/55681fig3.jpg" /> 
Figure 3: DTI Study of SMA Connections. SLF fibers seen on a sagittal slice (A) and a coronal slice (B) on DTI. SLF I (yellow); SLF II (orange); SLF III (turquoise). Relationship of FAT (green) and FST (blue) sagittal (C) and coronal (D) slices on DTI. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55681/55681fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 1" src="/files/ftp_upload/55681/55681fig4.jpg" /> 
Figure 4: DTI Study of SMA Connections. Callosal fibers seen on a coronal slice (A) and a sagittal slice (B) on DTI. The cingular fibers (red) (C), the claustrocortical fibers (orange) (D), and the corticospinal tract (purple) (E), as seen on sagittal slices on DTI. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55681/55681fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Fiber Connections of the Supplementary Motor Area Revisited: Methodology of Fiber Dissection, DTI, and Three Dimensional Documentation at JoVE.com

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

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.

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 ...

fiber-connections-supplementary-motor-area-revisited-methodology

Nanyang Technological University

Research

JoVE Journal

Neuroscience

11.2K Views.  University of Minnesota.  Het doel van deze studie is om elke stap van de vezeldissectietechniek te tonen op menselijke cadaverische hersenen, de 3D-documentatie van deze dissecties en de diffusie-tensorbeelden van de anatomisch gedissendeerde vezelwegen. 

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

Intracortical Inhibition Within the Primary Motor Cortex Can Be Modulated by Changing the Focus of Attention

It is well recognized that an external focus (EF) compared with an internal focus (IF) of attention improves motor learning and performance. Studies have indicated benefits in accuracy, balance, force production, jumping performance, movement speed, oxygen consumption, and fatiguing task. Although behavioral outcomes of using an EF strategy are well explored, the underlying neural mechanisms remain unknown. A recent TMS study compared the activity of the primary motor cortex (M1) between an EF and an IF. More precisely, this study showed that, when adopting an EF, the activity of intracortical inhibitory circuits is enhanced.
On the behavioral level, the present protocol tests the influence of attentional foci on the time to task failure (TTF) when performing submaximal contractions of the first dorsal interosseous (FDI). Additionally, the current paper describes two TMS protocols to assess the influence of attentional conditions on the activity of cortical inhibitory circuits within the M1. Thus, the present article describes how to use single-pulse TMS at intensities below the motor threshold (subTMS) and paired-pulse TMS, inducing short-interval intracortical inhibition (SICI) when applied to the M1. As these methods are assumed to reflect the responsiveness of GABAergic inhibitory neurons, without being affected by spinal reflex circuitries, they are well suited to measuring the activity of intracortical inhibitory circuits within the M1.
The results show that directing attention externally improves motor performance, as participants were able to prolong the time to task failure. Moreover, the results were accompanied by a larger subTMS-induced electromyography suppression and SICI when adopting an EF compared to an IF. As the level of cortical inhibition within the M1 was previously demonstrated to influence motor performance, the enhanced inhibition with an EF might contribute to the better movement efficiency observed in the behavioral task, indicated by a prolonged TTF with an EF.

Using two different transcranial magnetic stimulation (TMS) protocols, this manuscript describes how to measure and compare cortical inhibition within the primary motor cortex when adopting different attentional foci.

It is well recognized that an external focus (EF) compared with an internal focus (IF) of attention improves motor learning and performance. Studies have ...

Behavior

Co-analysis of Brain Structure and Function using fMRI and Diffusion-weighted Imaging

The study of complex computational systems is facilitated by network maps, such as circuit diagrams. Such mapping is particularly informative when studying the brain, as the functional role that a brain area fulfills may be largely defined by its connections to other brain areas. In this report, we describe a novel, non-invasive approach for relating brain structure and function using magnetic resonance imaging (MRI). This approach, a combination of structural imaging of long-range fiber connections and functional imaging data, is illustrated in two distinct cognitive domains, visual attention and face perception. Structural imaging is performed with diffusion-weighted imaging (DWI) and fiber tractography, which track the diffusion of water molecules along white-matter fiber tracts in the brain (Figure 1). By visualizing these fiber tracts, we are able to investigate the long-range connective architecture of the brain. The results compare favorably with one of the most widely-used techniques in DWI, diffusion tensor imaging (DTI). DTI is unable to resolve complex configurations of fiber tracts, limiting its utility for constructing detailed, anatomically-informed models of brain function. In contrast, our analyses reproduce known neuroanatomy with precision and accuracy. This advantage is partly due to data acquisition procedures: while many DTI protocols measure diffusion in a small number of directions (e.g., 6 or 12), we employ a diffusion spectrum imaging (DSI)1, 2 protocol which assesses diffusion in 257 directions and at a range of magnetic gradient strengths. Moreover, DSI data allow us to use more sophisticated methods for reconstructing acquired data. In two experiments (visual attention and face perception), tractography reveals that co-active areas of the human brain are anatomically connected, supporting extant hypotheses that they form functional networks. DWI allows us to create a "circuit diagram" and reproduce it on an individual-subject basis, for the purpose of monitoring task-relevant brain activity in networks of interest.

We describe a novel approach for simultaneous analysis of brain function and structure using magnetic resonance imaging (MRI). We assess brain structure with high-resolution diffusion-weighted imaging and white-matter fiber tractography. Unlike standard structural MRI, these techniques allow us to directly relate anatomical connectivity to functional properties of brain networks.

The study of complex computational systems is facilitated by network maps, such as circuit diagrams. Such mapping is particularly informative when ...

Diffusion Tensor Magnetic Resonance Imaging in the Analysis of Neurodegenerative Diseases

Diffusion tensor imaging (DTI) techniques provide information on the microstructural processes of the cerebral white matter (WM) in vivo. The present applications are designed to investigate differences of WM involvement patterns in different brain diseases, especially neurodegenerative disorders, by use of different DTI analyses in comparison with matched controls. 	
DTI data analysis is performed in a variate fashion, i.e. voxelwise comparison of regional diffusion direction-based metrics such as fractional anisotropy (FA), together with fiber tracking (FT) accompanied by tractwise fractional anisotropy statistics (TFAS) at the group level in order to identify differences in FA along WM structures, aiming at the definition of regional patterns of WM alterations at the group level. Transformation into a stereotaxic standard space is a prerequisite for group studies and requires thorough data processing to preserve directional inter-dependencies. The present applications show optimized technical approaches for this preservation of quantitative and directional information during spatial normalization in data analyses at the group level. On this basis, FT techniques can be applied to group averaged data in order to quantify metrics information as defined by FT. Additionally, application of DTI methods, i.e. differences in FA-maps after stereotaxic alignment, in a longitudinal analysis at an individual subject basis reveal information about the progression of neurological disorders. Further quality improvement of DTI based results can be obtained during preprocessing by application of a controlled elimination of gradient directions with high noise levels.	
In summary, DTI is used to define a distinct WM pathoanatomy of different brain diseases by the combination of whole brain-based and tract-based DTI analysis.

Diffusion tensor imaging (DTI) basically serves as an MRI-based tool to identify in vivo the microstructure of the brain and pathological processes due to neurological disorders within the cerebral white matter. DTI-based analyses allow for application to brain diseases both at the group level and in single subject data.

Diffusion tensor imaging (DTI) techniques provide information on the microstructural processes of the cerebral white matter (WM) in vivo. The present ...

Medicine

DTI of the Visual Pathway - White Matter Tracts and Cerebral Lesions

DTI is a technique that identifies white matter tracts (WMT) non-invasively in healthy and non-healthy patients using diffusion measurements. Similar to visual pathways (VP), WMT are not visible with classical MRI or intra-operatively with microscope. DTI will help neurosurgeons to prevent destruction of the VP while removing lesions adjacent to this WMT. We have performed DTI on fifty patients before and after surgery between March 2012 to January 2014. To navigate we used a 3DT1-weighted sequence. Additionally, we performed a T2-weighted and DTI-sequences. The parameters used were, FOV: 200 x 200 mm, slice thickness: 2 mm, and acquisition matrix: 96 x 96 yielding nearly isotropic voxels of 2 x 2 x 2 mm. Axial MRI was carried out using a 32 gradient direction and one b0-image. We used Echo-Planar-Imaging (EPI) and ASSET parallel imaging with an acceleration factor of 2 and b-value of 800 s/mm&#178;. The scanning time was less than 9 min.
The DTI-data obtained were processed using a FDA approved surgical navigation system program which uses a straightforward fiber-tracking approach known as fiber assignment by continuous tracking (FACT). This is based on the propagation of lines between regions of interest (ROI) which is defined by a physician. A maximum angle of 50, FA start value of 0.10 and ADC stop value of 0.20 mm&#178;/s were the parameters used for tractography.
There are some limitations to this technique. The limited acquisition time frame enforces trade-offs in the image quality. Another important point not to be neglected is the brain shift during surgery. As for the latter intra-operative MRI might be helpful. Furthermore the risk of false positive or false negative tracts needs to be taken into account which might compromise the final results.

Diffusion tensor imaging (DTI) was performed to try to depict the major parts of the visual pathway. The goal was to use an FDA approved standard commercial workstation which could be used for everyday routine in order to try to reduce postoperative damage of the visual pathway in the patients.

DTI is a technique that identifies white matter tracts (WMT) non-invasively in healthy and non-healthy patients using diffusion measurements. Similar to ...

Targeting Neuronal Fiber Tracts for Deep Brain Stimulation Therapy Using Interactive, Patient-Specific Models

Deep brain stimulation (DBS), which involves insertion of an electrode to deliver stimulation to a localized brain region, is an established therapy for movement disorders and is being applied to a growing number of disorders. Computational modeling has been successfully used to predict the clinical effects of DBS; however, there is a need for novel modeling techniques to keep pace with the growing complexity of DBS devices. These models also need to generate predictions quickly and accurately. The goal of this project is to develop an image processing pipeline to incorporate structural magnetic resonance imaging (MRI) and diffusion weighted imaging (DWI) into an interactive, patient specific model to simulate the effects of DBS. A virtual DBS lead can be placed inside of the patient model, along with active contacts and stimulation settings, where changes in lead position or orientation generate a new finite element mesh and solution of the bioelectric field problem in near real-time, a timespan of approximately 10 seconds. This system also enables the simulation of multiple leads in close proximity to allow for current steering by varying anodes and cathodes on different leads. The techniques presented in this paper reduce the burden of generating and using computational models while providing meaningful feedback about the effects of electrode position, electrode design, and stimulation configurations to researchers or clinicians who may not be modeling experts.

The goal of this project is to develop an interactive, patient-specific modeling pipeline to simulate the effects of deep brain stimulation in near real-time and provide meaningful feedback as to how these devices influence neural activity in the brain.

Deep brain stimulation (DBS), which involves insertion of an electrode to deliver stimulation to a localized brain region, is an established therapy for ...

Bioengineering

Measuring Connectivity in the Primary Visual Pathway in Human Albinism Using Diffusion Tensor Imaging and Tractography

In albinism, the number of ipsilaterally projecting retinal ganglion cells (RGCs) is significantly reduced. The retina and optic chiasm have been proposed as candidate sites for misrouting. Since a correlation between the number of lateral geniculate nucleus (LGN) relay neurons and LGN size has been shown, and based on previously reported reductions in LGN volumes in human albinism, we suggest that fiber projections from LGN to the primary visual cortex (V1) are also reduced. Studying structural differences in the visual system of albinism can improve the understanding of the mechanism of misrouting and subsequent clinical applications. Diffusion data and tractography are useful for mapping the OR (optic radiation). This manuscript describes two algorithms for OR reconstruction in order to compare brain connectivity in albinism and controls.An MRI scanner with a 32-channel head coil was used to acquire structural scans. A T1-weighted 3D-MPRAGE sequence with 1 mm3 isotropic voxel size was used to generate high-resolution images for V1 segmentation. Multiple proton density (PD) weighted images were acquired coronally for right and left LGN localization. Diffusion tensor imaging (DTI) scans were acquired with 64 diffusion directions. Both deterministic and probabilistic tracking methods were run and compared, with LGN as the seed mask and V1 as the target mask. Though DTI provides relatively poor spatial resolution, and accurate delineation of OR may be challenging due to its low fiber density, tractography has been shown to be advantageous both in research and clinically. Tract based spatial statistics (TBSS) revealed areas of significantly reduced white matter integrity within the OR in patients with albinism compared to controls. Pairwise comparisons revealed a significant reduction in LGN to V1 connectivity in albinism compared to controls. Comparing both tracking algorithms revealed common findings, strengthening the reliability of the technique.

This manuscript describes deterministic and probabilistic algorithms for white matter (WM) reconstruction, used to examine differences in optic radiation (OR) connectivity between albinism and controls. Although probabilistic tractography follows the true course of nerve fibers more closely, deterministic tractography was run to compare the reliability and reproducibility of both techniques.

In albinism, the number of ipsilaterally projecting retinal ganglion cells (RGCs) is significantly reduced. The retina and optic chiasm have been proposed ...

Translational Brain Mapping at the University of Rochester Medical Center: Preserving the Mind Through Personalized Brain Mapping

The Translational Brain Mapping Program at the University of Rochester is an interdisciplinary effort that integrates cognitive science, neurophysiology, neuroanesthesia, and neurosurgery. Patients who have tumors or epileptogenic tissue in eloquent brain areas are studied preoperatively with functional and structural MRI, and intraoperatively with direct electrical stimulation mapping. Post-operative neural and cognitive outcome measures fuel basic science studies about the factors that mediate good versus poor outcome after surgery, and how brain mapping can be further optimized to ensure the best outcome for future patients. In this article, we describe the interdisciplinary workflow that allows our team to meet the synergistic goals of optimizing patient outcome and advancing scientific understanding of the human brain.

This article provides an overview of a multi-modal brain mapping program designed to identify regions of the brain that support critical cognitive functions in individual neurosurgery patients.

The Translational Brain Mapping Program at the University of Rochester is an interdisciplinary effort that integrates cognitive science, neurophysiology, ...

Measuring and Manipulating Functionally Specific Neural Pathways in the Human Motor System with Transcranial Magnetic Stimulation

Understanding interactions between brain areas is important for the study of goal-directed behavior. Functional neuroimaging of brain connectivity has provided important insights into fundamental processes of the brain like cognition, learning, and motor control. However, this approach cannot provide causal evidence for the involvement of brain areas of interest. Transcranial magnetic stimulation (TMS) is a powerful, noninvasive tool for studying the human brain that can overcome this limitation by transiently modifying brain activity. Here, we highlight recent advances using a paired-pulse, dual-site TMS method with two coils that causally probes cortico-cortical interactions in the human motor system during different task contexts. Additionally, we describe a dual-site TMS protocol based on cortical paired associative stimulation (cPAS) that transiently enhances synaptic efficiency in two interconnected brain areas by applying repeated pairs of cortical stimuli with two coils. These methods can provide a better understanding of the mechanisms underlying cognitive-motor function as well as a new perspective on manipulating specific neural pathways in a targeted fashion to modulate brain circuits and improve behavior. This approach may prove to be an effective tool to develop more sophisticated models of brain-behavior relations and improve diagnosis and treatment of many neurological and psychiatric disorders.

This article describes new approaches to measure and strengthen functionally specific neural pathways with transcranial magnetic stimulation. These advanced noninvasive brain stimulation methodologies can provide new opportunities for the understanding of brain-behavior relations and development of new therapies to treat brain disorders.

Understanding interactions between brain areas is important for the study of goal-directed behavior. Functional neuroimaging of brain connectivity has ...

Improving Outcomes in Anteromesial Temporal Lobe Resections - A Demonstration of Resecting the Temporal Piriform Cortex

Anteromesial temporal lobe resection (ATLR) is a useful treatment option for drug-resistant mesial temporal lobe epilepsy (DRmTLE). Growing evidence suggests the piriform cortex plays a crucial role in the generation and propagation of seizures in DRmTLE - and that the resection of the temporal portion of the piriform cortex is associated with significantly improved rates of seizure freedom. 
Here, we present the resection of the temporal portion of the piriform cortex in ATLR, using high-resolution preoperative probabilistic tractography algorithms and fused anatomical masks of the structures of interest into the intraoperative neuronavigation and microscope head-up display (HUD). 
All patients undergoing comprehensive preoperative assessment and investigations for DRmTLE provided informed, written consent to record an intraoperative video of the procedure. Patients were identified by an expert multidisciplinary team of epileptologists, epilepsy neurosurgeons, neuropsychologists, neuropsychiatrists, and electrophysiologists at a large epilepsy surgery center. The preoperative imaging pipeline included the delineation of critical structures. This included the temporal piriform cortex, and high-resolution probabilistic tractography for essential tracts at risk (e.g., optic radiation and inferior fronto-occipital fasciculus). These were co-registered to the preoperative volumetric neuronavigation scan and uploaded to the intra-operative neuronavigation system. 
Presented here is a step-by-step procedure of ATLR, including the resection of the temporal portion of the piriform cortex. The protocol combines Advanced structural and diffusion MR imaging and intraoperative visual aids to integrate anatomical masks of critical grey matter structures and white matter tracts into the surgical workflow in the operating room.

Here, we demonstrate an approach to intraoperative neurosurgical guidance in anteromesial temporal lobe resections, specifically highlighting the use of tractography and anatomical masks to aid safe resection of the temporal portion of the piriform cortex - an area increasingly regarded as a crucial surgical target in drug-resistant mesial temporal lobe epilepsy.

Anteromesial temporal lobe resection (ATLR) is a useful treatment option for drug-resistant mesial temporal lobe epilepsy (DRmTLE). Growing evidence ...

Using Diffusion Tensor Imaging in Traumatic Brain Injury

Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel&#8212;University of Southern California
Traditional brain imaging techniques using MRI are very good at visualizing the gross structures of the brain. A structural brain image made with MRI provides high contrast of the borders between gray and white matter, and information about the size and shape of brain structures. However, these images do not detail the underlying structure and integrity of white matter networks in the brain, which consist of axon bundles that interconnect local and distant brain regions.
Diffusion MRI uses pulse sequences that are sensitive to the diffusion of water molecules. By measuring the direction of diffusion, it is possible to make inferences about the structure of white matter networks in the brain. Water molecules within an axon are constrained in their movements by the cell membrane; instead of randomly moving in every direction with equal probability (isotropic movement), they are more likely to move in certain directions, in parallel with the axon (anisotropic movement; Figure 1). Therefore, measures of diffusion anisotropy are thought to reflect properties of the white matter such as fiber density, axon thickness, and degree of myelination. One common measure is fractional anisotropy (FA). FA values range from 0, which represents completely isotropic movement, to 1, reflecting maximum anisotropy.
<img alt="Figure 1" src="/files/ftp_upload/10276/10276fig1.jpg" /> 
Figure 1: Diffusion anisotropy. When the direction of diffusion is unconstrained and random, movement is measured in all directions equally. This is isotropic diffusion (A). When water molecules are contained within the axon of a neuron, diffusion is anisotropic, tending to occur more frequently along the direction of the axon (B). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/10276/10276fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
In this experiment we will use diffusion tensor imaging (DTI) to measure white matter integrity in traumatic brain injury (TBI). TBI occurs when an external force injures the brain, such as a blow to the head or a sudden movement like the kind that might occur in a car accident. This type of brain injury from mechanical forces is associated with diffuse axonal injury-damage to white matter throughout the brain. Because it is an injury affecting white matter integrity, standard neuroimaging techniques may not reveal the damage. However, measures of diffusion are especially sensitive to these anatomical changes. Following a study by Kraus et al.1, we compare a group of healthy controls to a group of people with TBI and use diffusion imaging to measure the effect of TBI on cerebral white matter. Furthermore, we will test the relationship between white matter integrity and cognitive function using an attention task.2 This study uses a region of interest (ROI) approach focusing on three white matter tracts: the splenium of the corpus callosum, the anterior corona radiata, and the superior longitudinal fasciculus (Figure 2).
<img alt="Figure 2" src="/files/ftp_upload/10276/10276fig2.jpg" /> 
Figure 2: Regions of interest. The three ROIs, defined from the ICBM DTI-81 atlas, are shown here in horizontal slices through the brain. In green is the splenium of the corpus callosum. The splenium is the most posterior part of the corpus callosum. In blue is the anterior corona radiata. The superior longitudinal fasciculus is shown in red. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/10276/10276fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Diffusion Tensor Imaging in Traumatic Brain Injury

Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel&#8212;University of Southern California
Traditional brain imaging techniques using MRI are ...

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

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