Perani D, Cappa S F, Tettamanti M, Rosa M, Scifo P, Miozzo A, Basso A, Fazio F
Institute of Neuroscience and Bioimaging-CNR, Via Olgettina 60, 20132, Milan, Italy.
Brain Lang. 2003 Jun;85(3):357-68. doi: 10.1016/s0093-934x(02)00561-8.
The neural mechanisms underlying recovery of cognitive functions are incompletely understood. Aim of this study was to assess, using functional magnetic resonance (fMRI), the pattern of brain activity during covert word retrieval to letter and semantic cues in five aphasic patients after stroke, in order to assess the modifications of brain function which may be related to recovery. Four out of five patients had undergone language recovery, according to standard testing, after at least 6 months of rehabilitation. The cerebral activation of each patient was evaluated and compared with the activation pattern of normal controls studied with the same fMRI paradigm. In the patients, the pattern of brain activation was influenced by the site and extent of the lesion, by the degree of recovery of language, as reflected by task performance outside the scanner, and by task requirements. In the case of word retrieval to letter cues, a good performance was directly related to the activation in Broca's area, or in the right-sided homologue. On the other hand, in the case of semantic fluency, the relationship between performance level and activation was less clear-cut, because of extensive recruitment of frontal areas in patients with defective performance. These findings suggest that the performance in letter fluency is dependent on the integrity of the left inferior frontal cortex, with the participation of the homologous right hemispheric region when the left inferior frontal cortex is entirely of partially damaged. Semantic fluency, which engages the distributed network of semantic memory, is also associated with more extensive patterns of cerebral activation, which however appear to reflect retrieval effort rather than retrieval success.
认知功能恢复背后的神经机制尚未完全明了。本研究的目的是利用功能磁共振成像（fMRI）评估5名中风后失语患者在向字母和语义线索进行隐蔽性单词检索过程中的脑活动模式，以评估可能与恢复相关的脑功能改变。根据标准测试，5名患者中有4名在至少6个月的康复治疗后语言功能得到了恢复。对每名患者的脑激活情况进行评估，并与采用相同fMRI范式研究的正常对照的激活模式进行比较。在这些患者中，脑激活模式受到病变部位和范围、扫描仪外任务表现所反映的语言恢复程度以及任务要求的影响。在向字母线索进行单词检索的情况下，良好的表现直接与布洛卡区或右侧同源区域的激活相关。另一方面，在语义流畅性方面，由于表现不佳的患者额叶区域广泛参与，表现水平与激活之间的关系不太明确。这些发现表明，字母流畅性的表现取决于左下额叶皮质的完整性，当左下额叶皮质完全或部分受损时，右侧同源半球区域会参与其中。语义流畅性涉及语义记忆的分布式网络，也与更广泛的脑激活模式相关，然而这些模式似乎反映的是检索努力而非检索成功。
