Evidence for the substantia nigra pars compacta as an essential component of a memory system independent of the hippocampal memory system

The aim of the present study was to test if the nigrostriatal pathway is an essential component for a water maze cued task learning and if it works independently of the hippocampal memory system. This hypothesis was tested using an animal model of Parkinson's disease in which male Wistar rats were lesioned in the substantia nigra pars compacta (SNc) by the intranigral infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), thus causing a partial depletion of striatal dopamine. SNc-lesioned and sham-operated animals were implanted bilaterally with guide cannulae above the dorsal hippocampus in order to be tested after the administration of 0.4 microl 2% lidocaine or saline into this structure. The animals were tested in a spatial or in a cued version of the water maze, memory tasks previously reported to model hippocampal-dependent spatial/relational and striatal-dependent S-R learning, respectively. Hippocampal inactivation, but not SNc lesion, impaired learning and memory in the spatial version of the water maze. An opposite situation was observed with the cued version. No significant interaction was observed between the SNc lesion and hippocampal inactivation conditions affecting scores in the spatial or in the cued version of the water maze. These results suggest that the nigrostriatal pathway is an essential part of the memory system that processes S-R learning and that it works independently of the hippocampal memory system that processes spatial/relational memories.     

Why a "word order difference" is not always a "word order" difference: a reply to Weyerts,Penke, Münte,Heinze, and Clahsen

We present evidence that the supposed processing advantage for an SV_finO word order over an SOV_fin word order in German argued for by Weyerts, Penke, Münte, Heinze, and Clahsen (2002) is supported by neither experimental nor theoretical evidence. Specifically, we show (a) that the frontocentral negativity for an SOV_fin in comparison to an SV_finO word order in Weyerts et al.'s Experiments 2 and 3 is reducible to more general differences in the electrophysiological responses elicited by nouns versus verbs in a sentence context, and (b) that the P600 difference between the two word orders in Experiment 2, as well as the reading time differences in Experiment 1, result from the fact that the two supposedly ungrammatical conditions actually differ in their degree of ill-formedness. We conclude that there is no evidence for a processing disadvantage for SOV_fin, thus reconciling Weyerts et al.'s results on German sentence processing with the grammatical regularities of German.     

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。     

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.     

Sub-threshold cuing: Saccadic responses to low-contrast,peripheral, transient visual landmark cues

Dorsal stream visual encoding was studied in three experiments, by examining effects of peripheral landmark cues on eye movements. Stimulus features and task structure were tailored to physiological and functional characterisations of the dorsal visual stream. Sub-discriminable peripheral stimuli served as landmark cue stimuli. In Experiments 1 and 2, orienting behaviour in response to cues and targets differed for participants with relatively low and relatively high peripheral contrast thresholds. In Experiment 1, low, but not high-threshold participants oriented towards landmark cues that could not be discriminated consciously. However, in Experiment 3, high-, but not low-threshold participants oriented towards near threshold cues. Hence, under appropriate conditions both groups of participants oriented in response to brief, low-contrast, peripheral information. We propose that landmark cueing may provide a useful tool for measuring individual differences in dorsal stream processing and dynamic aspects of visual functioning and awareness.