Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA.
Cereb Cortex. 2012 Jan;22(1):232-42. doi: 10.1093/cercor/bhr123. Epub 2011 Jun 7.
Contralateral recruitment remains a controversial phenomenon in both the clinical and normative populations. To investigate the neural correlates of this phenomenon, we explored the tendency for older adults to recruit prefrontal cortex (PFC) regions contralateral to those most active in younger adults. Participants were scanned with diffusion tensor imaging and functional magnetic rresonance imaging during a lateralized word matching task (unilateral vs. bilateral). Cross-hemispheric communication was measured behaviorally as greater accuracy for bilateral than unilateral trials (bilateral processing advantage [BPA]) and at the neural level by functional and structural connectivity between contralateral PFC. Compared with the young, older adults exhibited 1) greater BPAs in the behavioral task, 2) greater compensatory activity in contralateral PFC during the bilateral condition, 3) greater functional connectivity between contralateral PFC during bilateral trials, and 4) a positive correlation between fractional anisotropy in the corpus callosum and both the BPA and the functional connectivity between contralateral PFC, indicating that older adults' ability to distribute processing across hemispheres is constrained by white matter integrity. These results clarify how older adults' ability to recruit extra regions in response to the demands of aging is mediated by existing structural architecture, and how this architecture engenders corresponding functional changes that allow subjects to meet those task demands.
对侧募集在临床和正常人群中仍然是一个有争议的现象。为了研究这一现象的神经相关性，我们探讨了老年人倾向于募集与年轻人最活跃的大脑区域相对侧的前额叶皮层（PFC）区域的趋势。参与者在进行侧化单词匹配任务（单侧与双侧）时接受弥散张量成像和功能磁共振成像扫描。跨半球通讯通过双侧试验比单侧试验具有更高的准确性来进行行为测量（双侧处理优势[BPA]），并通过对侧 PFC 之间的功能和结构连接在神经水平进行测量。与年轻人相比，老年人表现出：1）在行为任务中具有更大的 BPA；2）在双侧条件下，对侧 PFC 中表现出更大的代偿性活动；3）在双侧试验中对侧 PFC 之间具有更大的功能连接；4）胼胝体的各向异性分数与 BPA 和对侧 PFC 之间的功能连接之间存在正相关，这表明老年人在大脑两个半球之间分配处理的能力受到白质完整性的限制。这些结果阐明了老年人在应对衰老需求时招募额外区域的能力是如何通过现有的结构架构来介导的，以及这种架构如何产生相应的功能变化，使受试者能够满足这些任务需求。
