大脑前联合及后联合

1、The CommissuresWhat are they?The commissures are fibre tracts connecting the two hemispheres. There isa posterior commissure, which connects midbrain and diencephalon structures, andlies just in front ofand above the superiorcolliculi, below the pineal gland. Theposterior commissure is not always ea

2、sy to see on a high detailed structural scan, and it is very unlikely you will be able to discern it on functional images.The anteriorcommissure(AC)connectsthemiddleandinferiortemporalgyriofthetwohemispheres, and runs across the midline just in front of the fornix. It is relatively easy to see on mo

3、st structural scans.Why the commissures?Thecommissurehavebecomekeylandmarks,becauseTalairachandTournouxchose them to determine the standard alignment of the brain for their famous atlas.To align a scan toTalairach space, a brain has to be set so that the anterior andposterior commissures are on a ho

4、rizonatal line.Where are they?Below is a little schematic (from Chris Rorden'sMriCrotutorial) of a sagittal brainview. The anterior commissure is shown in red, and the posterior commissure inyellow.1 / 4The image below shows the anterior commissure on an iconic brain from the MNIseries (see the

5、MNI space page for details). The AC is at the virtual intersection of the red lines.The AC is best seen on slice 91 in X, 131 in Y and 67 in Z of the iconic brain image.Below is an image showing the PC on the same brain, again at the intersection of the red lines. The PC can best be seen at slices X

6、 91, Y 103 and Z 70. Note that this brain is not exactly oriented according to the Talairach system, as thetwo commissures are not on the same axial plane.It may be useful to scroll through the iconic brain image provided with MRIcroGL , to get used to the landmarks around the commissures.Here is th

7、e position of the anterior commissure on the MNI 152 average brain; first on the the T1 average:(truncated)MRIcro or2 / 4and next on the T2 average (which is more similar to EPI images).Specifying the commissures on low resolution images, such as functional images, requires a little guesswork, combi

8、ned with a knowledge of where the commissures are in relation to anatomy that you can see, such as the thalamus, brainstem, and corpus callosum.Matthew Brett, Chris Rorden 17/12/99ReferencesJ. TalairachandP. Tournoux,"Co-planarStereotaxicAtlasoftheHumanBrain:3-Dimensional Proportional System- an Approach to Cerebral Imaging", ThiemeMedical Publishers, New York, NY, 1988H.M. Duvernoy, "The Human Brain: Surface, Blood Supply, and Three Dimensiona