Interaction of language and control processes in monolingual and bilingual cognition

神经可塑性是指大脑的结构和功能随着经验的变化而改变，为认知能力的终身适应提供了可能性。这种适应可能是一种有效的干预方法，旨在随着年龄的增长保护认知功能。一种已被证明可以改变认知功能的经验是双语能力：在一生中，双语者在各种执行控制(EC)测试中的表现都好于单语者。然而，人们对这些影响知之甚少，特别是对双语能力和更广泛的神经可塑性。这项拟议的研究将使用行为和脑电测量来研究单语或双语的年轻人和老年人，以了解这种经历是如何影响认知能力的。这项研究有两个关键的悬而未决的问题。 1：双语认知效果的条件 虽然大量的研究已经报道了在EC中的显著的双语优势，但不同研究之间存在很大的差异，一些研究发现没有组内差异。因此，一个重要的问题是确定观察双语效果的条件。一般来说，儿童和老年人比年轻人更有可能存在群体差异，复杂任务比简单任务更有可能出现群体差异，神经成像研究比行为研究更有可能发现群体差异。将对这些因素和其他因素进行调查，以确定双语导致这些有益结果的条件。 2：加工过程中的功能变化 对于双语者增强的EC，通常的解释是双语者使用EC来控制对两种共同激活的语言的注意力，这样他们就可以选择目标语言，避免来自另一种语言的干扰。双语者对两种语言的联合激活是有据可查的，因此语言选择是双语使用中的一个长期问题。其想法是，使用欧共体网络进行语言选择加强了这一网络，并使其更有效率地用于其他目的。然而，也可能是EC网络被修改以创建一个供双语者用于言语和非言语加工的网络，该网络在性质上与单语者所使用的网络不同。双语创造了一个新的综合控制网络，这一可能性将有助于解释双语者比单语者更晚出现痴呆症迹象的发现。因为痴呆症通常首先表现为记忆问题，所以很难理解双语EC的优势如何保护成绩。然而，综合控制网络可以让双语者通过依赖更完整的控制网络来弥补某些领域的失败。因此，双语者所使用的控制网络的性质的证据对于理解神经可塑性的一个重要方面具有重要意义，该方面可能对在衰老过程中保存认知功能有一定的应用。

Neuroplasticity is the idea that brain structure and function change in response to experience, offering the possibility for lifelong adaptation of cognitive ability. Such adaptation may be a powerful approach to interventions designed to protect cognitive function with aging. One experience that has been shown to modify cognitive function is bilingualism: across the lifespan, bilinguals outperform monolinguals on various tests of executive control (EC). However, much is unknown about these effects, both for bilingualism in particular and neuroplasticity more generally. The proposed studies will use behavioural and EEG measures to study younger and older adults who are monolingual or bilingual to understand how this experience affects cognitive ability. There are two crucial outstanding issues in this research. 1: Conditions for cognitive effects of bilingualism Although a large body of research has reported significant bilingual advantages in EC, there is great variability across studies with some finding no group differences. An important question, therefore, is to determine the conditions under which effects of bilingualism are observed. In general, group differences are more likely found with children and older adults than with younger adults, with complex tasks than with simpler tasks, and with neuroimaging studies than with behavioural studies. These and other factors will be investigated to determine conditions under which bilingualism leads to these beneficial outcomes. 2: Functional changes in processing The usual explanation for enhanced EC in bilinguals is that bilinguals use EC to control attention to two jointly activated languages so they can select the target language and avoid intrusions from the other language. The joint activation of both languages for bilinguals is well documented, so language selection is a constant problem of bilingual language use. The idea is that the use of the EC network for language selection fortifies that network and makes it more efficient for other purposes. However, it may also be that the EC network is modified to create a network that is used by bilinguals for both verbal and nonverbal processing, a network that is qualitatively different from that used by monolinguals. This possibility that bilingualism creates a new integrated control network would help to explain the finding that bilinguals show signs of dementia later than monolinguals. Because dementia is usually displayed first as a memory problem, it is hard to understand how bilingual EC advantages would protect performance. However, an integrated control network could allow bilinguals to compensate for failure in some domains by relying on more intact ones. Thus, evidence for the nature of the control networks used by bilinguals has implications for understanding an important aspect of neuroplasticity that may have some application to preserving cognitive function in aging.