Department of Cognitive Science, Johns Hopkins University Baltimore, MD, USA.
Front Psychol. 2013 Dec 25;4:964. doi: 10.3389/fpsyg.2013.00964. eCollection 2013.
Previous research has shown that damage to the neural substrates of orthographic processing can lead to functional reorganization during reading (Tsapkini et al., 2011); in this research we ask if the same is true for spelling. To examine the functional reorganization of spelling networks we present a novel three-stage Individual Peak Probability Comparison (IPPC) analysis approach for comparing the activation patterns obtained during fMRI of spelling in a single brain-damaged individual with dysgraphia to those obtained in a set of non-impaired control participants. The first analysis stage characterizes the convergence in activations across non-impaired control participants by applying a technique typically used for characterizing activations across studies: Activation Likelihood Estimate (ALE) (Turkeltaub et al., 2002). This method was used to identify locations that have a high likelihood of yielding activation peaks in the non-impaired participants. The second stage provides a characterization of the degree to which the brain-damaged individual's activations correspond to the group pattern identified in Stage 1. This involves performing a Mahalanobis distance statistics analysis (Tsapkini et al., 2011) that compares each of a control group's peak activation locations to the nearest peak generated by the brain-damaged individual. The third stage evaluates the extent to which the brain-damaged individual's peaks are atypical relative to the range of individual variation among the control participants. This IPPC analysis allows for a quantifiable, statistically sound method for comparing an individual's activation pattern to the patterns observed in a control group and, thus, provides a valuable tool for identifying functional reorganization in a brain-damaged individual with impaired spelling. Furthermore, this approach can be applied more generally to compare any individual's activation pattern with that of a set of other individuals.
先前的研究表明，字形处理的神经基质受损会导致阅读时的功能重组（Tsapkini 等人，2011 年）；在这项研究中，我们询问拼写是否也是如此。为了研究拼写网络的功能重组，我们提出了一种新颖的三阶段个体峰概率比较（IPPC）分析方法，用于比较单个患有失写症的脑损伤患者在 fMRI 拼写期间获得的激活模式与一组未受损的对照组参与者获得的激活模式。第一分析阶段通过应用一种通常用于描述跨研究激活的技术来描述非受损对照组参与者的激活收敛性：激活似然估计（ALE）（Turkeltaub 等人，2002 年）。该方法用于识别在未受损参与者中具有产生激活峰的高可能性的位置。第二阶段提供了一种特征化方法，用于描述脑损伤个体的激活与第一阶段中确定的组模式的对应程度。这涉及执行 Mahalanobis 距离统计分析（Tsapkini 等人，2011 年），该分析比较了对照组中每个参与者的峰值激活位置与脑损伤个体生成的最近峰值。第三阶段评估脑损伤个体的峰值相对于对照组参与者个体变异范围内的异常程度。这种 IPPC 分析允许对个体的激活模式与对照组观察到的模式进行可量化、统计上合理的比较，从而为识别拼写受损的脑损伤个体中的功能重组提供了有价值的工具。此外，这种方法可以更一般地应用于比较任何个体的激活模式与一组其他个体的激活模式。
