Fedorenko Evelina, Fillmore Paul, Smith Kimberly, Bonilha Leonardo, Fridriksson Julius
Massachusetts General Hospital, Boston, Massachusetts;
University of South Carolina, Columbia, South Carolina; and.
J Neurophysiol. 2015 Apr 1;113(7):2376-82. doi: 10.1152/jn.00214.2014. Epub 2015 Jan 28.
Broca (Broca P. Bull Soc Anat Paris 36: 330-357, 1861) influentially argued that posterior left inferior frontal gyrus supports speech articulation. According to an alternative proposal (e.g., Dronkers NF. Nature 384: 159-161, 1996; Wise RJ, Greene J, Buchel C, Scott SK. Lancet 353: 1057-1061, 1999; Baldo JV, Wilkins DP, Ogar J, Willock S, Dronkers NF. Cortex 47: 800-807, 2011), a region in the anterior insula [specifically, the superior precentral gyrus of the insula (SPGI)] is the seat of articulatory abilities. Moreover, Dronkers and colleagues have argued that the SPGI is functionally specialized for (complex) speech articulation. Here, we evaluate this claim using individual-subject functional MRI (fMRI) analyses (e.g., Fedorenko E, Hsieh PJ, Nieto-Castanon A, Whitfield-Gabrieli S, Kanwisher N. J Neurophysiol 104: 1177-1194, 2010). We find that the SPGI responds weakly, if at all, during articulation (parts of Broca's area respond 3-4 times more strongly) and does not show a stronger response to higher articulatory demands. This holds regardless of whether the SPGI is defined functionally (by selecting the most articulation-responsive voxels in the vicinity of the SPGI in each subject individually) or anatomically (by using masks drawn on each individual subject's anatomy). Critically, nonspeech oral movements activate the SPGI more strongly than articulation, especially under the anatomical definition of the SPGI. In line with Hillis et al. (Hillis AE, Work M, Barker PB, Jacobs MA, Breese EL, Maurer K. Brain 127: 1479-1487, 2004; also Trupe L, Varma DD, Gomez Y, Race D, Leigh R, Hillis AE, Gottesman RF. Stroke 44: 740-744, 2013), we argue that previous links between the SPGI, and perhaps anterior insula more generally, and articulation may be due to its high base rate of ischemic damage (and activation in fMRI; Yarkoni T, Poldrack RA, Nichols TE, Van Essen DC, Wager TD. Nat Methods 8: 665-670, 2011), combined with its proximity to regions that more directly support speech articulation, such as the precentral gyrus or the posterior aspects of the inferior frontal gyrus (Richardson JD, Fillmore P, Rorden C, Lapointe LL, Fridriksson J. Brain Lang 123: 125-130, 2012), and thus susceptibility to joint damage.
布罗卡（布罗卡·P.《巴黎解剖学会公报》36: 330 - 357, 1861）有影响力地提出，左侧额下回后部支持言语表达。根据另一种观点（例如，德龙克斯·N.F.《自然》384: 159 - 161, 1996；怀斯·R.J., 格林·J., 布歇尔·C., 斯科特·S.K.《柳叶刀》353: 1057 - 1061, 1999；巴尔多·J.V., 威尔金斯·D.P., 奥加尔·J., 威洛克·S., 德龙克斯·N.F.《大脑皮层》47: 800 - 807, 2011），岛叶前部的一个区域[具体来说，岛叶的中央前回上部（SPGI）]是言语表达能力的所在部位。此外，德龙克斯及其同事认为，SPGI在功能上专门负责（复杂的）言语表达。在此，我们使用个体受试者功能磁共振成像（fMRI）分析（例如，费多伦科·E., 谢·P.J., 涅托 - 卡斯塔农·A., 惠特菲尔德 - 加布里埃利·S., 坎维舍·N.《神经生理学杂志》104: 1177 - 1194, 2010）来评估这一观点。我们发现，在言语表达过程中，SPGI即便有反应也很微弱（布罗卡区的部分区域反应强度要高3 - 4倍），并且对更高的言语表达要求并未表现出更强的反应。无论SPGI是通过功能定义（通过在每个受试者个体的SPGI附近选择对言语表达反应最强的体素）还是解剖学定义（通过使用在每个个体受试者解剖结构上绘制的掩码）来界定，都是如此。关键在于，非言语的口腔运动比言语表达更强烈地激活SPGI，尤其是在SPGI的解剖学定义下。与希利斯等人的观点一致（希利斯·A.E., 沃克·M., 巴克·P.B., 雅各布斯·M.A., 布里斯·E.L., 毛雷尔·K.《大脑》127: 1479 - 1487, 2004；还有特鲁普·L., 瓦尔马·D.D., 戈麦斯·Y., 雷斯·D., 利·R., 希利斯·A.E., 戈特斯曼·R.F.《中风》44: 740 - 744, 2013），我们认为，先前SPGI（或许更普遍地说是岛叶前部）与言语表达之间的联系可能是由于其较高的缺血性损伤发生率（以及在fMRI中的激活；亚尔科尼·T., 波德拉克·R.A., 尼科尔斯·T.E., 范·埃森·D.C., 瓦格·T.D.《自然方法》8: 665 - 670, 2011），再加上它与更直接支持言语表达的区域相邻，如中央前回或额下回后部（理查森·J.D., 菲尔莫尔·P., 罗登·C., 拉波因特·L.L., 弗里德里克松·J.《大脑与语言》123: 125 - 130, 2012），因此容易受到联合损伤。
