Explaining neurocognitive aging: is one factor enough?

As an introduction to the special issue on neurocognitive factors underlying age effects, we discuss a number of recent developments in the literature on aging. The classic distinction between generalized and process-specific cognitive changes with old age has reappeared in the distinctions between the frontal lobe hypothesis and more differentiated views of neurocognitive aging. We argue that neurological decay in the frontal cortex has important implications for cognitive control, but that the frontal lobe hypothesis does not capture the plethora of changes that characterize aging and incorrectly suggests a unitary effect.     

The role of inferior frontal cortex in phonological processing

Recent neuroimaging studies of language processing are examining the neural substrate of phonology because of its critical role in mapping sound information onto higher levels of language processing (e.g., words) as well as providing codes in which verbal information can be temporarily stored in working memory. However, the precise role of the inferior frontal cortex in spoken and written phonological tasks has remained elusive. Although lesion studies have indicated the presence of selective deficits in phonological processing, the location of lesions underlying these impairments has not revealed a consistent pattern. Despite efforts to refine methods and tasks, functional neuroimaging studies have also revealed variability in activation patterns. Reanalysis of evidence from these neuroimaging studies suggests that there are functional subregions within the inferior frontal gyrus that correspond to specific components of phonological processing (e.g., orthographic to phonological conversion in reading, and segmentation in speech).     

Lesions in the Central Nucleus of the Amygdala: Discriminative Avoidance Learning, Discriminative Approach Learning, and Cingulothalamic Training-Induced Neuronal Activity

The amygdala is critically involved in discriminative avoidance learning. Large lesions of the amygdala block discriminative avoidance learning and abolish cingulothalamic training-induced neuronal activity. These results indicated that amygdalar processing is critical for cingulothalamic plasticity. The larger lesions did not allow differentiation of the specific functioning of various amygdalar nuclei. Anatomical analysis showed that damage in the central (CE) nucleus of the amygdala was correlated with the severity of the behavioral deficit. The present study was carried out to determine whether smaller lesions, centered in the CE nucleus, would impair discriminative avoidance learning and block cingulothalamic plasticity. In addition, the possible role of the CE nucleus in appetitively motivated discriminative approach learning was examined for the first time. New Zealand White rabbits with CE nuclear lesions were first trained in the discriminative approach task. After attaining asymptotic performance, discriminative avoidance training sessions were alternated with continuing approach training sessions, one session each day. The rabbits with lesions were severely impaired in avoidance learning but showed no impairment of approach learning. Surprisingly, the attenuating effects of the lesions on cingulothalamic training-induced neuronal activity were more prevalent during approach learning than during avoidance learning. These results indicated that avoidance learning can be impaired by lesions centered in the CE nucleus that leave cingulothalamic plasticity largely intact and that the CE nucleus is involved in extra-cingulothalamic learning processes.     

盲人的跨感觉通道重组

失去视觉的盲人往往伴随着行为代偿,如听觉和触觉能力的提高。脑成像等认知神经科学研究发现,盲人行为代偿的神经机制之一是大脑皮层的跨感觉通道重组,即盲人的视皮层并没有因为视觉剥夺而失去作用,而是广泛地参与了其他感知觉任务。原本暂时的神经联结由于受到新的感觉信息传入方式的持续激活而固化,从而形成新的神经回路,可能是此类跨通道重组的神经基础。     

猜谜作业中顿悟的ERP效应

采用事件相关电位(ERP)探索问题解决过程中顿悟的神经机制。以猜谜作业为实验程序,对“有顿悟”和“无顿悟”答案引发的脑电分别进行叠加和平均,并将二者相减（有顿悟-无顿悟）得到差异波。在250~500 ms “有顿悟”比“无顿悟”的ERP波形有一个更加负性的偏移,在差异波中,这个负成分的潜伏期约为380 ms（N380）。地形图和电流密度图显示,N380在额中央区活动最强。偶极子源定位分析结果显示,N380可能起源于扣带前回。因此,N380可能反映顿悟问题解决过程中思维定势的突破。     

大脑前扣带回皮层与执行功能

回顾了近期有关大脑前扣带回皮层（ACC）参与执行功能的研究资料。结果显示,ACC可以对正在进行的目标定向行为实施在线监控,在出现反应冲突或错误时提供信号,以便能及时调整与分配注意资源,因此可能是一个行为规划与执行的高级调控结构。这两年来的新发现提示,ACC的执行监控作用可能是基于动机与奖赏期待做出的对“意志行动”的整合性控制,并可能具有对行动结果的情绪评价意义。     

6-12岁儿童额叶自发脑电频谱相干的特点

EEG频谱相干分析发现额叶发育在童年中期存在可能的加速期。针对这一问题,本研究通过记录75名6至12岁正常儿童静坐和闭目状态下的自发脑电,分析δ、θ、α和β基本脑电频段下31对电极相干的变化情况,系统探索了该年龄段儿童额叶自发脑电频谱相干的变化特点,结果发现:θ波活动普遍强于α和β波活动;6至12岁儿童额叶内、额叶与其他脑叶间相干在整体上表现为随年龄增长而增加的趋势;额叶内、额叶与其他脑叶间相干在各频段均表现为7岁、11岁突增,10岁、12岁表现为高峰。上述结果支持6至12岁儿童额叶发育存在加速变化的结论。     

On the emergence of modern humans

The emergence of modern humans with their extraordinary cognitive capacities is ascribed to a novel type of cognitive computational process (sustained non-routine multi-level operations) required for abstract projectuality, held to be the common denominator of the cognitive capacities specific to modern humans. A brain operation (latching) that allows this novel computational process is proposed as well as a physics-inspired mechanism that could explain its rather recent emergence without invoking unlikely genetic or structural changes.