Statistical neuroanatomy of the human inferior frontal gyrus and probabilistic atlas in a standard stereotaxic space - PubMed (original) (raw)

Statistical neuroanatomy of the human inferior frontal gyrus and probabilistic atlas in a standard stereotaxic space

Alexander Hammers et al. Hum Brain Mapp. 2007 Jan.

Abstract

We manually defined the inferior frontal gyrus (IFG) on high-resolution MRIs in native space in 30 healthy subjects (15 female, median age 31 years; 15 male, median age 30 years), resulting in 30 individual atlases. Using standard software (SPM99), these were spatially transformed to a widely used stereotaxic space (MNI/ICBM 152) to create probabilistic maps. In native space, the total IFG volume was on average 5%, and the gray matter (GM) portion 12% larger in women (not significant). Expressed as a percentage of ipsilateral frontal lobe volume (i.e., correcting for brain size), the IFG was an average of 20%, and the GM portion of the IFG 27%, larger in women (P < 0.005). Correcting for total lobar volume yielded the same result. No asymmetry was found in IFG volumes. There were significant positional differences between the right and left IFGs, with the right IFG being further lateral in both native and stereotaxic space. Variability was similar on the left and right, but more pronounced anteriorly and superiorly. We show differences in IFG volume, composition, and position between sexes and between hemispheres. Applications include probabilistic determination of location in group studies, automatic labeling of new scans, and detection of anatomical abnormalities in patients.

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Figures

Figure 1

Figure 1

Example of a 3‐D rendering of one of the 30 maps of the IFG, introducing the nomenclature and landmarks used. Relevant sulci are indicated with white arrows and the subdivisions of the IFG in yellow. The IFG is rendered in red and the precentral gyrus in blue.

Figure 2

Figure 2

Probability shells in standard stereotaxic space for the IFG in coronal orientation, overlaid onto the ICBM/MNI average brain constructed from 152 healthy volunteers resampled into a 1 × 1 × 1 mm matrix. The grid spacing is 10 mm, with bolder lines indicating the origin as defined in the ICBM/MNI template (∼2.5 mm posterior and 6 mm superior of the middle of the anterior commissure; see also

http://www.mrc-cbu.cam.ac.uk/Imaging/Common/antcomm.shtml

). Left on the image is left in the brain. The _x_‐axis increases from left to right, y from posterior to anterior, and z from inferior to superior. The probability shells are sampled every 4 mm. The color code indicates probability of a given voxel pertaining to the IFG.

Figure 3

Figure 3

Probability shells in standard stereotaxic space for the IFG in sagittal orientation. For further explanations, see legend for Figure 3.

Figure 4

Figure 4

Probability shells in standard stereotaxic space for the IFG in transverse orientation. For further explanations, see legend for Figure 3.

Figure 5

Figure 5

Probability shells in standard stereotaxic space for the GM contribution to the IFG, separately thresholded at 50% probability for men and women. Red: womens' 50% probability map larger; blue: mens' 50% probability map larger; white: common areas. Top: coronal; middle: sagittal; bottom: transverse. Position in mm relative to AC as defined in MNI/ICBM152 space; left on the image is left in the brain.

Figure 6

Figure 6

Comparison of probability maps in coronal orientation. Position in mm relative to AC as defined in MNI/ICBM152 space. Left on the image is left in the brain. Left side, cytoarchitectonic probability maps of Brodmann's area 44 based on 10 postmortem brains [Amunts et al.,1999] from the Forschungszentrum Jülich that have been spatially normalized to a single subject brain (an approximation of MNI/ICBM152 space) [Holmes et al.,1998], downloaded from

http://www.bic.mni.mcgill.ca/cytoarchitectonics

. For comparison, the color scale has been changed to match Figures 3, 4, 5. Right side, probability maps for GM contribution only based on all 30 brains in the current study. For comparison, the probability maps are here superimposed on the single subject brain.

Figure 1

Figure 1

Delineation of the IFG on reoriented images in native space. Regions other than IFG are shown (nomenclature as in Hammers et al. [2003a, 2003b]; left IFG: 56; right IFG: 57; regions surrounding the IFG are: 51: precentral gyrus; 20/21: left/right insula; 28: frontal lobe prior to further subdivision). A: Sagittal marker slice; left side: marker as it appears on sagittal image (arrow) and connection of inferior frontal sulcus with precentral sulcus (*); right side: marker as it appears on the coronal image in aid of delineation (arrow). B: Anterior part of IFG. Line from the deepest point of the inferior frontal sulcus (upper arrow) to the deepest point of the frontomarginal sulcus/lateral orbital sulcus (lower arrow). At this point, the horizontal ramus of the lateral fissure is not visible. C: Inclusion of the horizontal ramus of the lateral fissure (left arrow) when this extends more medial than the connection between the deepest point of the inferior frontal sulcus to the deepest point of the frontomarginal sulcus/lateral orbital sulcus. On the right, the corresponding position on a 3‐D‐rendered scan is shown; the blue portion corresponds to the section of IFG defined starting anteriorly. D: The lateral orbital sulcus lies inferiorly to the widening horizontal ramus of the lateral fissure; therefore, tissue superior to and inferior to the fissure leading to the insula (arrow) is included. For further explanation, see “Algorithm for IFG Definition” in Materials and Methods.

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References

    1. Amunts K, Schleicher A, Burgel U, Mohlberg H, Uylings HB, Zilles K ( 1999): Broca's region revisited: cytoarchitecture and intersubject variability. J Comp Neurol 412: 319–341. - PubMed
    1. Amunts K, Malikovic A, Mohlberg H, Schormann T, Zilles K ( 2000): Brodmann's areas 17 and 18 brought into stereotaxic space — where and how variable? Neuroimage 11: 66–84. - PubMed
    1. Amunts K, Schleicher A, Zilles K, Weiss PH, Mohlberg H, Pieperhoff P, Eickhoff S, Gurd JM, Marshall JC, Shah NJ ( 2004a): Outstanding language competence and cytoarchitecture in Broca's speech region. Brain Lang 89: 346–353. - PubMed
    1. Amunts K, Weiss PH, Mohlberg H, Pieperhoff P, Eickhoff S, Gurd JM, Marshall JC, Shah NJ, Fink GR, Zilles K ( 2004b): Analysis of neural mechanisms underlying verbal fluency in cytoarchitectonically defined stereotaxic space—the roles of Brodmann areas 44 and 45. Neuroimage 22: 42–56. - PubMed
    1. Ashburner J, Friston KJ ( 1997): Multimodal image coregistration and partitioning — a unified framework. Neuroimage 6: 209–217. - PubMed

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