Hi Naama,<div><br></div><div>This is a good question and please allow me to share my though with people in the MriStudio mailing list.<br><div><br></div><div>When we describe white matter, there are two ways. Let me use the analogy of geological maps. If I see a map of Baltimore, there are essentially two types of information; boundaries that define boarders of locations like city, county, and state. The other is road information like route 95 that travels from Washingon DC to NY. The former defines locations and the latter doesn't belong to any single location. </div>
<div><br></div><div>Likewise, WM map has two ways to define. Many WM names define locations, like the internal capsule, which is a WM location between the basal ganglia. There are many "roads" that penetrate the internal capsule like cortico-thalamic, thalamo-cortical, cortico-spinal, cortico-pontine, to name few, but they are all intermingled and it's not possible to completely decipher them, at least by DTI/MRI. There are also names of WM that imply something similar to the road names. For example, the corticospinal tract and IFO defines two destinations. </div>
<div><br></div><div>Our atlas obviously defines locations; all segments are defined by boarders. Some of the defined locations have names that implies roads (e.g. IFO, SFO, CST, ets), but they actually define locations. This is one source of confusion.</div>
<div><br></div><div>Now, there are some more confusing things. I believe many macroscopic anatomical nomenclature is based on classic histology observations. The SFO and IFO are assigned to large white matter bundles that sweep from front to back, which look like connecting the frontal and occipital lobes, but I don't think it was confirmed that there are actually axons connecting the frontal and occipital lobes. Therefore, the foundation of the assigned names are not as sound as the corticospinal tracts, which are confirmed in many animals and human. </div>
<div><br></div><div>Now, we assigned some locations of the brain "SFO" and "IFO". There is not doubt that there are large axonal bundles travelling front to back (or back to front) in the designated locations. However, if one asks, "do you know if these locations really contain axons connecting the frontal and occipital lobes?", well, I must say, "not sure". To me, it seems like an issue of nomenclature. </div>
<div><br></div><div>In any case, assignments of "road-type" names to the WM is a tricky effort because even for the "corticospinal tract", the designated locations may contain many other axons like cortico-pontine and cortico-bulbar axons. As long as they are mixed in a microscopic level, we can only say, "this region has high concentration of the corticospinal tract" and, to be strict, we can always argue that it is not correct to give a binary definition to a place like, "this is the corticospinal tract", because the "real" corticospinal tract refers to axons that connect the cortex and the spinal cord, not to many millimeters of anatomical locations visualized by MRI/DTI.</div>
<div><br></div><div>So, going back to your original question, there were controversy over the existence of SFO and now IFO . In these cases what is discussed is "is there really a large concentration of axons that connect the frontal and occipital lobes in the WM locations called SFO/IFO?" How does it affect our study? Well, for the IFO, maybe we should change the name of the location to "a large WM bundle running front-back (green color) at the junction of the frontal lobe and the temporal lobe". To me, the source of the problem is the adoption of road names to refer to locations. As long as we use our atlas to define locations and do quantitative measurements such as volumes and FAs, how we call each location is not really a critical issue. Of course, it could profoundly affect the interpretation. If the FA of "IFO" is low, we should not immediately conclude connectivity problems between the frontal and occipital lobes, simply based on the name of the location. In this sense, you raised an important issue. On the other hand, IFO/SFO have been widely used to refer some specific locations and we can communicate about anatomical locations through these terms. So, even if they are mis-nomenclature, we may need to keep using them unless the anatomist society comes up with a new set of anatomical languages to refer these anatomical locations.</div>
<div><br></div><div>Susumu</div><div><br><div class="gmail_quote">On Fri, Feb 18, 2011 at 5:07 PM, Naama Barnea-Goraly <span dir="ltr"><<a href="mailto:naamab@stanford.edu">naamab@stanford.edu</a>></span> wrote:<br>
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Dear Susumu,<br>
<br>
A recent analysis we are running yielded some significant results in the IFOF (according to the JHU White matter tractography atlas) which lead me to some investigation on this pathway. I was very surprised to read in " White matter of the Brain" ( a book by Schmahmann and Pandya), that in fact the IFOF does not exist (page 445). They think the IFOF is in fact the ILF /uncinate/extreme capsule mistaken by early anatomists as a separate tract. What do you think?<br>
<br>
Thanks,<br>
<br>
Naama<br>
<br>
<br>
<br>
Naama Barnea-Goraly M.D.<br>
Instructor<br>
Center for Interdisciplinary Brain Sciences Research<br>
Stanford University Division of Child and Adolescent Psychiatry<br>
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Stanford University School of Medicine<br>
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