Memory influences on hippocampal and striatal neural codes: effects of a shift between task rules

Interactions with neocortical memory systems may facilitate flexible information processing by hippocampus. We sought direct evidence for such memory influences by recording hippocampal neural responses to a change in cognitive strategy. Well-trained rats switched (within a single recording session) between the use of place and response strategies to solve a plus maze task. Maze and extramaze environments were constant throughout testing. Place fields demonstrated (in-field) firing rate and location-based reorganization [Leutgeb, S., Leutgeb, J. K., Barnes, C. A., Moser, E. I., McNaughton, B. L., & Moser, M. B. (2005). Independent codes for spatial and episodic memory in hippocampal neuronal ensembles. Science, 309, 619-623] after a task switch, suggesting that hippocampus encoded each phase of testing as a different context, or episode. The task switch also resulted in qualitative and quantitative changes to discharge that were correlated with an animal's velocity or acceleration of movement. Thus, the effects of a strategy switch extended beyond the spatial domain, and the movement correlates were not passive reflections of the current behavioral state. To determine whether hippocampal neural responses were unique, striatal place and movement-correlated neurons were simultaneously recorded with hippocampal neurons. Striatal place and movement cells exhibited a response profile that was similar, but not identical, to that observed for hippocampus after a strategy switch. Thus, retrieval of a different memory led both neural systems to represent a different context. However, hippocampus may play a special (though not exclusive) role in flexible spatial processing since correlated firing amongst cell pairs was highest when rats successfully switched between two spatial tasks. Correlated firing by striatal cell pairs increased following any strategy switch, supporting the view that striatum codes change in reinforcement contingencies.     

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.     

自陈量表式测验应用IRT的可行性

对采用5级评分Likert式测题的情感能力量表的分析表明,各分量表项目都有较好的模型-数据拟合性,而且显示了参数估计的不变性,及与CTT参数的关联性。这些都表明Likert量表应用IRT模型的假设条件得到了满足,即IRT应用是可行的。研究还表明IRT能对测量精度进行更精确的估计。     

Mental architectures with selectively influenced but stochastically interdependent components

The way external factors influence distribution functions for the overall time required to perform a mental task (such as responding to a stimulus, or solving a problem) may be informative as to the underlying mental architecture, the hypothetical network of interconnected processes some of which are selectively influenced by some of the external factors. Under the assumption that all processes contributing to the overall performance time are stochastically independent, several basic results have been previously established. These results relate patterns of response time distribution functions produced by manipulating external factors to such questions as whether the hypothetical constituent processes in the mental architecture enter AND gates or OR gates, and whether pairs of processes are sequential or concurrent. The present study shows that all these results are also valid for stochastically interdependent component times, provided the selective dependence of these components upon external factors is understood within the framework of a recently proposed theory of selective influence. According to this theory each component is representable as a function of three arguments: the factor set selectively influencing it, a component-specific source of randomness, and a source of randomness shared by all the components.     

Distributional analysis of semantic interference in picture naming

In picture–word interference experiments, participants name pictures (e.g., of a cat) while trying to ignore distractor words. Mean response time (RT) is typically longer with semantically related distractor words (e.g., dog) than with unrelated words (e.g., shoe), called semantic interference. Previous research has examined the RT distributional characteristics of distractor effects by performing ex-Gaussian analyses, which reveal whether effects are present in the normal part of the distribution (the μ parameter), its long right tail (the τ parameter), or both. One previous study linked the semantic interference effect selectively to the distribution tail. In the present study, we replicated the semantic interference effect in the mean picture naming RTs. Distributional analysis of the RTs and those of a previous study revealed that semantic interference was present in both μ and τ. These results provide evidence that the effect is not selectively linked to the τ parameter, and they warn against any simple one-to-one mapping between semantic interference and distributional parameters.     

多维测验项目参数的估计：基于SEM与MIRT方法的比较

作者简要回顾了SEM框架下分类数据因素分析(CCFA)模型和MIRT框架下测验题目和潜在能力的关系模型, 对两种框架下的主要参数估计方法进行了总结。通过模拟研究, 比较了SEM框架下WLSc和WLSMV估计方法与MIRT框架下MLR和MCMC估计方法的差异。研究结果表明：(1) WLSc得到参数估计的偏差最大, 且存在参数收敛的问题; (2)随着样本量增大, 各种项目参数估计的精度均提高, WLSMV方法与MLR方法得到的参数估计精度差异很小, 大多数情况下不比MCMC方法差; (3)除WLSc方法外, 随着每个维度测验题目的增多参数估计的精度逐渐增高; (4)测验维度对区分度参数和难度参数的影响较大, 而测验维度对项目因素载荷和阈值的影响相对较小; (5)项目参数的估计精度受项目测量维度数的影响, 只测量一个维度的项目参数估计精度较高。另外文章还对两种方法在实际应用中应该注意的问题提供了一些建议。     

Human variable ratio performance

The generality of the mathematical principles of reinforcement (MPR) was tested with humans. In Experiment 1A, participants’ mouse clicks were reinforced according to a series of variable-ratio (VR) values. In one condition, a situated task was used (searching for treasure on a map presented via a PC monitor); in the other, abstract version of the task, participants clicked on a white screen. Under the “map” condition, response rates increased with increasing ratio value before decreasing with further ratio increases; under the “no-map” condition, response rates decreased linearly from a peak at the smallest ratio. In Experiment 1B, the pattern of responding was confirmed under the “map” conditions using a different set of ratio values. In Experiment 2, reinforcer magnitude was manipulated using the “map” context. Response rates did not differ significantly when large rather than small cash reinforcers were delivered according to a VR 30 but were significantly higher when large rather than small cash reinforcers were delivered according to a VR 120. Together these experiments offer qualified support for extending MPR to the behavior of human participants.     

Comparisons of women with high and low trait impulsivity using behavioral models of response-disinhibition and reward-choice

Two types of behavioral models of impulsive behavior, response-disinhibition/attentional and reward-choice response models, were used to compare women grouped by high (Impulse+, n=43) and low (Impulse−, n=43) self-reported impulsive behavior on the Eysenck I₇ Questionnaire. Two of the four different tasks tested were response-disinhibition/attentional models; these included the Immediate and Delayed Memory Task and the GoStop Task. The other two tasks were based on the reward-choice model of impulsivity and included the Single Key Impulsivity Paradigm and the Two-Choice Reward Task. Of particular interest was whether commission errors (response-disinhibition/attentional paradigms) or a preference for smaller–sooner rewards over larger–later rewards (reward-choice) would differ between the groups. Participants completed one session of each task in a single day. The most significant findings were that the Impulse+ group had: (1) elevated commission errors; (2) lower stimulus discriminability (between target and catch stimuli); and (3) poorer response inhibition to a stop signal. Responding on the response-disinhibition/attentional tasks distinguished between the impulsivity groups while the reward-choice tasks did not. These results demonstrate that women who report higher levels of trait impulsivity respond in a manner consistent with previous studies examining impulsive behavior.     

任务转换训练和执行功能可塑性

任务转换训练是提高个体执行功能的方法之一。学者们采用不同的任务范式进行任务转换训练。研究结果发现, 任务转换训练可以降低个体的转换代价、提高其他认知任务的绩效。训练效果可以维持一定的时间。但是, 也有研究未发现明显的迁移效果和维持效果。年龄、其他执行成分的参与度、认知灵活性和策略可能会影响训练效果。任务转换训练可能通过提高个体解决任务设置冲突的能力、提高与任务转换相关的额-顶脑网络的参与程度以及建立自下而上的自动控制来提高个体的转换能力。未来研究应当对现有研究方法和程序进行标准化, 从执行功能整体与分离的结构特征角度看待任务转换训练, 寻找更为灵活的训练手段, 如tDCS技术。     

双语水平与认知控制心智转换

研究考察双语水平对认知控制心智转换的影响。通过语言转换和任务转换实验,比较两组一语水平相同而二语水平不同的“不平衡”中英双语者（40人,平均年龄20.30岁）。结果发现高水平组在语言转换中优于低水平组,但在任务转换中两组无显著差异。说明双语水平对认知控制心智转换的影响不显著。回归分析结果表明心智转换与双语水平无关,但二语使用显著预测任务转换代价,双语转换频率显著预测任务混合代价。研究表明双语水平对认知控制心智转换的促进作用不显著,但二语使用和双语转换频率可能是双语者心智转换能力增强的重要因素。研究进一步推进了双语促进认知控制的理论,明确了双语优势的具体来源及认知控制受影响的具体层面。