任务类型对上下视野优势的影响

视觉信息加工的单侧视野优势效应一直是认知心理学领域的研究热点。本研究采用变化检测范式探讨文字和几何信息在上下视野中的优势效应。结果发现：当加工文字材料时,颜色和位置检测任务均出现上部视野优势效应;加工几何图形时,则出现下部视野优势效应。上述结果表明,任务信息所需要的加工类型影响上下视野的优势效应,支持Previc提出的视野优势效应的生态假说。     

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.     

The speed of visual recognition memory

Two processes are thought to support visual recognition memory (VRM): Familiarity and recollection. The former is generally considered to be faster. However, the relationship between the precise onset of the two processes is unclear. Here, we use a novel paradigm, the SAB (Speed and Accuracy Boosting procedure) that constrains participants to use their fastest strategy and provides a continuous distribution of their reaction times. We show that fast recognition occurs as early as ~370 ms, a limit that appears incompressible whatever types of stimuli were used. In a second experiment, running the SAB in conjunction with a modified version of the remember/know paradigm, we show that responses up to ~420 ms are based solely on familiarity. These time limits of 370 ms and 420 ms provide strong constraints on the neural mechanisms underlying VRM and suggest that the fastest, familiarity-based, responses could rely on the visual ventral stream only.     

The role of the ventral and dorsal pathways in reading Chinese characters and English words

Previous literature in alphabetic languages suggests that the occipital-temporal region (the ventral pathway) is specialized for automatic parallel word recognition, whereas the parietal region (the dorsal pathway) is specialized for serial letter-by-letter reading ( [Cohen et al., 2008] and [Ho et al., 2002] ). However, few studies have directly examined the role of the ventral and dorsal pathways in Chinese reading compared to English reading. To investigate this issue, we adopted the degraded word processing paradigm used by Cohen et al. (2008) and compared brain regions involved in the processing of degraded Chinese characters and English words during lexical decision, using functional magnetic resonance imaging (fMRI). The degraded characters/words were created by inserting blank spaces between radicals of Chinese characters or syllables of English polysyllabic words. Generally, the current study replicated the effects of Cohen et al. (2008), showing that in Chinese – like in alphabetic languages – character spacing modulates both ventral (bilateral cuneus, left middle occipital gyrus) and dorsal (left superior parietal lobule and middle frontal gyrus) pathways. In addition, the current study showed greater activation in bilateral cuneus and right lingual gyrus for Chinese versus English when comparing spaced to normal stimuli, suggesting that Chinese character recognition relies more on ventral visual-spatial processing than English word recognition. Interestingly, bilateral cuneus showed monotonic patterns in response to increasing spacing, while the rest of the regions of interest showed non-monotonic patterns, indicating different profiles for these regions in visual-spatial processing.     

Opposing amygdala and ventral striatum connectivity during emotion identification

Lesion and electrophysiological studies in animals provide evidence of opposing functions for subcortical nuclei such as the amygdala and ventral striatum, but the implications of these findings for emotion identification in humans remain poorly described. Here we report a high-resolution fMRI study in a sample of 39 healthy subjects who performed a well-characterized emotion identification task. As expected, the amygdala responded to THREAT (angry or fearful) faces more than NON-THREAT (sad or happy) faces. A functional connectivity analysis of the time series from an anatomically defined amygdala seed revealed a strong anticorrelation between the amygdala and the ventral striatum/ventral pallidum, consistent with an opposing role for these regions in during emotion identification. A second functional connectivity analysis (psychophysiological interaction) investigating relative connectivity on THREAT vs. NON-THREAT trials demonstrated that the amygdala had increased connectivity with the orbitofrontal cortex during THREAT trials, whereas the ventral striatum demonstrated increased connectivity with the posterior hippocampus on NON-THREAT trials. These results indicate that activity in the amygdala and ventral striatum may be inversely related, and that both regions may provide opposing affective bias signals during emotion identification.     

视觉系统中类别信息加工区的特异性

近年来, 神经成像的研究结果显示, 在人类的腹侧视觉皮层内可能存在与特定类别刺激加工一一对应的类别信息加工区。但是, 类别信息加工区是否具有特异性仍然存在争议。文章总结了相关研究领域对这一颇具争议的问题的研究结果, 同时指出了末来研究可能深入的方向。这些方向包括：进一步探讨不同抽象水平的类别信息加工区域的特异性问题、检验类别信息加工区的拓扑分布观点、回答不同类别信息加工区之间的信息如何交流的问题、揭示类别信息加工区的学习机制。     

Graspability and object processing in infants

This review pursues the idea that a dual visual system approach is fruitful for interpreting work on infant cognition. We provide examples from the visual perception and cognition literature demonstrating that the potential graspability of stimuli typically used in infant studies influence how these stimuli are processed by the infant brain. Specifically, we argue that small, local, familiar and moving stimuli are more likely to be processed by the dorsal (how or action) stream of visual processing. In contrast, larger, stationary objects are likely to be processed by the ventral (what or perception) stream. This analysis clarifies apparently conflicting results in the literature.     

Integrating functional neuroimaging and human operant research: brain activation correlated with presentation of discriminative stimuli

Results of numerous human imaging studies and nonhuman neurophysiological studies on "reward" highlight a role for frontal, striatal, and thalamic regions in operant learning. By integrating operant and functional neuroimaging methodologies, the present investigation examined brain activation to two types of discriminative stimuli correlated with different contingencies. Prior to neuroimaging, 10 adult human subjects completed operant discrimination training in which money was delivered following button pressing (press-money contingency) in the presence of one set of discriminative stimuli, and termination of trials followed not responding (no response-next trial contingency) in the presence of a second set of discriminative stimuli. After operant training, subjects were instructed to memorize a third set of control stimuli unassociated with contingencies. Several hours after training, functional magnetic resonance imaging was performed while subjects viewed discriminative and control stimuli that were presented individually for 1,500 ms per trial, with stimulus presentations occurring, on average, every 6 s. Activation was found in frontal and striatal brain regions to both sets of discriminative stimuli relative to control stimuli. In addition, exploratory analyses highlighted activation differences between discriminative stimuli. The results demonstrate the utility of coupling operant and imaging technologies for investigating the neural substrates of operant learning in humans.