Sigalovsky Irina S, Fischl Bruce, Melcher Jennifer R
Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, and Harvard-MIT Division of Health Sciences and Technology, Speech and Hearing Bioscience and Technology Program, Cambridge, MA 02139, USA.
Neuroimage. 2006 Oct 1;32(4):1524-37. doi: 10.1016/j.neuroimage.2006.05.023. Epub 2006 Jun 27.
Recently, magnetic resonance properties of cerebral gray matter have been spatially mapped--in vivo--over the cortical surface. In one of the first neuroscientific applications of this approach, this study explores what can be learned about auditory cortex in living humans by mapping longitudinal relaxation rate (R1), a property related to myelin content. Gray matter R1 (and thickness) showed repeatable trends, including the following: (1) Regions of high R1 were always found overlapping posteromedial Heschl's gyrus. They also sometimes occurred in planum temporale and never in other parts of the superior temporal lobe. We hypothesize that the high R1 overlapping Heschl's gyrus (which likely indicates dense gray matter myelination) reflects auditory koniocortex (i.e., primary cortex), a heavily myelinated area that shows comparable overlap with the gyrus. High R1 overlapping Heschl's gyrus was identified in every instance suggesting that R1 may ultimately provide a marker for koniocortex in individuals. Such a marker would be significant for auditory neuroimaging, which has no standard means (anatomic or physiologic) for localizing cortical areas in individual subjects. (2) Inter-hemispheric comparisons revealed greater R1 on the left on Heschl's gyrus, planum temporale, superior temporal gyrus and superior temporal sulcus. This asymmetry suggests greater gray matter myelination in left auditory cortex, which may be a substrate for the left hemisphere's specialized processing of speech, language, and rapid acoustic changes. These results indicate that in vivo R1 mapping can provide new insights into the structure of human cortical gray matter and its relation to function.
最近，大脑灰质的磁共振特性已在活体状态下在皮质表面进行了空间映射。在该方法最初的神经科学应用之一中，本研究通过绘制纵向弛豫率（R1，一种与髓磷脂含量相关的特性）来探索在活体人类中关于听觉皮层可以了解到什么。灰质R1（和厚度）呈现出可重复的趋势，包括以下几点：（1）高R1区域总是被发现与后内侧的颞横回重叠。它们有时也出现在颞平面，而从未出现在颞上叶的其他部位。我们推测，与颞横回重叠的高R1（这可能表明灰质髓鞘化密集）反映了听觉粒状皮质（即初级皮质），这是一个髓鞘化程度很高的区域，与该脑回有类似的重叠。在每个实例中都识别出了与颞横回重叠的高R1，这表明R1最终可能为个体中的粒状皮质提供一个标记。这样一个标记对于听觉神经成像将具有重要意义，因为在个体受试者中，听觉神经成像没有用于定位皮质区域的标准方法（解剖学或生理学方法）。（2）半球间比较显示，在颞横回、颞平面、颞上回和颞上沟上，左侧的R1更大。这种不对称表明左侧听觉皮层的灰质髓鞘化程度更高，这可能是左半球对语音、语言和快速声学变化进行专门处理的基础。这些结果表明，活体R1映射可以为人类皮质灰质的结构及其与功能的关系提供新的见解。
