视觉的知觉-动作双系统理论中的论争

视觉的知觉-动作双系统理论认为,视觉的腹侧和背侧通路是两个独立系统,功能分别为表征世界和指导动作,相对应的视觉加工是彼此分离的。有关两条通路之间关系的其他观点可归结为两类：一类否认这种分工,另一类强调两个系统能相互影响。首先评述各种理论的核心问题、实验证据和贡献,进而分析视觉加工发生在一个特定系统的条件,得出的结论是：两个系统之间的功能划分是相对的,并因此导致了视觉加工的多变性。     

Fluctuations in brain glucose concentration during behavioral testing: dissociations between brain areas and between brain and blood

Traditional beliefs about two aspects of glucose regulation in the brain have been challenged by recent findings. First, the absolute level of glucose in the brain's extracellular fluid appears to be lower than previously thought. Second, the level of glucose in brain extracellular fluid is less stable than previously believed. In vivo brain microdialysis was used, according to the method of zero net flux, to determine the basal concentration of glucose in the extracellular fluid of the striatum in awake, freely moving rats for comparison with recent hippocampal measurements. In addition, extracellular glucose levels in both the hippocampus and the striatum were measured before, during, and after behavioral testing in a hippocampus-dependent spontaneous alternation task. In the striatum, the resting extracellular glucose level was 0.71 mM, approximately 70% of the concentration measured previously in the hippocampus. Consistent with past findings, the hippocampal extracellular glucose level decreased by up to 30 +/- 4% during testing; no decrease, and in fact a small increase (9 +/- 3%), was seen in the striatum. Blood glucose measurements obtained during the same testing procedure and following administration of systemic glucose at a dose known to enhance memory in this task revealed a dissociation in glucose level fluctuations between the blood and both striatal and hippocampal extracellular fluid. These findings suggest, first, that glucose is compartmentalized within the brain and, second, that one mechanism by which administration of glucose enhances memory performance is via provision of increased glucose supply from the blood specifically to those brain areas involved in mediating that performance.     

Multiple memory systems: the power of interactions

Two relatively simple theories of brain function will be used to demonstrate the explanatory power of multiple memory systems in your brain interacting cooperatively or competitively to directly or indirectly influence cognition and behaviour. The view put forth in this mini-review is that interactions between memory systems produce normal and abnormal manifestations of behaviour, and by logical extension, an understanding of these complex interactions holds the key to understanding debilitating brain and psychiatric disorders.     

Immediate early gene activation in hippocampus and dorsal striatum: effects of explicit place and response training

Evidence from lesion, electrophysiological, and neuroimaging studies support the hypothesis that the hippocampus and dorsal striatum process afferent inputs in such a way that each structure regulates expression of different behaviors in learning and memory. The present study sought to determine whether rats explicitly trained to perform one of two different learning strategies, spatial or response, would display disparate immediate early gene activation in hippocampus and striatum. c-Fos and Zif268 immunoreactivity (IR) was measured in both hippocampus and striatum 30 or 90 min following criterial performance on a standard plus-maze task (place learners) or a modified T-maze task (response learners). Place and response learning differentially affected c-Fos-IR in striatum but not hippocampus. Specifically, explicit response learning induced greater c-Fos-IR activation in two subregions of the dorsal striatum. This increased c-Fos-IR was dependent upon the number of trials performed prior to reaching behavioral criterion and accuracy of performance during post-testing probe trials. Quantification of Zif268-IR in both hippocampus and striatum failed to distinguish between place and response learners. The changes in c-Fos-IR occurred 30 min, but not 90 min, post-testing. The synthesis of c-Fos early in testing could reflect the recruitment of key structures in learning. Consequently, animals that were able to learn the response task efficiently displayed greater amounts of c-Fos-IR in dorsal striatum.     

The triadic model perspective for the study of adolescent motivated behavior

The triadic neural systems model is a heuristic tool, which was developed with the goal of providing a framework for neuroscience research into motivated behaviors. Unlike dual models that highlight dynamics between approach systems centered on striatal function and control systems centered on prefrontal cortex, the triadic model also includes an avoidance system, centered on amygdala-related circuits. A first application of this model has been to account for adolescent behavior.     

Aggression is associated with greater subsequent alcohol consumption: A shared neural basis in the ventral striatum

Alcohol use and abuse (e.g., binge drinking) are among the most reliable causes of aggressive behavior. Conversely, people with aggressive dispositions (e.g., intermittent explosive disorder) are at greater risk for subsequent substance abuse. Yet it remains unknown why aggression might promote subsequent alcohol use. Both aggressive acts and alcohol use are rewarding and linked to greater activity in neural reward circuitry. Through this shared instantiation of reward, aggression may then increase subsequent alcohol consumption. Supporting this mechanistic hypothesis, participants’ aggressive behavior directed at someone who had recently rejected them, was associated with more subsequent beer consumption on an ad‐lib drinking task. Using functional MRI, both aggressive behavior and beer consumption were associated with greater activity in the bilateral ventral striatum during acts of retaliatory aggression. These results imply that aggression is linked to subsequent alcohol abuse, and that a mechanism underlying this effect is likely to be the activation of the brain's reward circuitry during aggressive acts.

     

Parallel associative processing in the dorsal striatum: segregation of stimulus-response and cognitive control subregions

Although evidence suggests that the dorsal striatum contributes to multiple learning and memory functions, there nevertheless remains considerable disagreement on the specific associative roles of different neuroanatomical subregions. We review evidence indicating that the dorsolateral striatum (DLS) is a substrate for stimulus–response habit formation – incremental strengthening of simple S–R bonds – via input from sensorimotor neocortex while the dorsomedial striatum (DMS) contributes to behavioral flexibility – the cognitive control of behavior – via prefrontal and limbic circuits engaged in relational and spatial information processing. The parallel circuits through dorsal striatum interact with incentive/affective motivational processing in the ventral striatum and portions of the prefrontal cortex leading to overt responding under specific testing conditions. Converging evidence obtained through a detailed task analysis and neurobehavioral assessment is beginning to illuminate striatal subregional interactions and relations to the rest of the mammalian brain.     

应用动态因果模型研究阅读神经网络背、腹侧通路的协作机制

在神经网络的最新取向下, 探讨阅读脑机制中背侧和腹侧通路的协作机制, 是解决语言认知神经科学多个理论问题共同面临的焦点。本项目拟通过两个脑功能成像实验, 建构汉字阅读的动态因果模型, 系统地考察汉字阅读的神经网络, 以及阅读网络中背、腹侧通路的协作机制。实验一利用快速适应实验范式的优点, 识别和考察汉字阅读涉及的认知成分所对应的功能脑区, 以及脑区联结形成的神经回路, 并建构汉字阅读的动态因果模型; 实验二进一步考察在刺激属性(语音和语义信息)和任务要求下阅读脑区的动态激活及相互作用。通过不同任务下的模型对比, 重点探讨阅读网络的脑区联结模式变化, 尤其是背、腹侧通路受刺激和任务影响时的协作机制。研究结果将为揭示阅读的神经生理模型、解决语言特异性脑区激活的争论等理论问题提供直接的证据, 还能为语言教学、阅读障碍矫治、以及临床应用提供理论基础与指导。     

Phenomenological coping skills and the striatal memory system

Most cognitive scientists are committed to some version of representationalism, the view that intelligent behavior is caused by internal processes that involve computations over representations. Phenomenologists, however, argue that certain types of intelligent behavior, engaged coping skills, are nonrepresentational. Recent neuroscientific work on multiple memory systems indicates that while many types of intelligent behavior are representational, the types of intelligent behavior cited by phenomenologists are indeed nonrepresentational. This neuroscientific research thus vindicates a key phenomenological claim about the nature of intelligent behaviour. It also provides a framework for the ongoing reconciliation of cognitive science and phenomenology.