The role of the right posterior parietal cortex in temporal order judgment

Perceived order of two consecutive stimuli may not correspond to the order of their physical onsets. Such a disagreement presumably results from a difference in the speed of stimulus processing toward central decision mechanisms. Since previous evidence suggests that the right posterior parietal cortex (PPC) plays a role in modulating the processing speed of a visual target, we applied single-pulse TMS over the region in 14 normal subjects, while they judged the temporal order of two consecutive visual stimuli. Stimulus-onset-asynchrony (SOA) randomly varied between -100 and 100 ms in 20-ms steps (with a positive SOA when a target appeared on the right hemi-field before the other on the left), and a point of subjective simultaneity was measured for individual subjects. TMS stimulation was time-locked at 50, 100, 150, and 200 ms after the onset of the first stimulus, and results in trials with TMS on right PPC were compared with those in trials without TMS. TMS over the right PPC delayed the detection of a visual target in the contralateral, i.e., left hemi-field by 24 (+/-7 SE) ms and 16 (+/-4 SE) ms, when the stimulation was given at 50 and 100 ms after the first target onset. In contrast, TMS on the left PPC was not effective. These results show that the right PPC is important in a timely detection of a target appearing on the left visual field, especially in competition with another target simultaneously appearing in the opposite field.     

The symmetry of visual fields in chromatic discrimination

Both classical and recent reports suggest a right-hemisphere superiority for color discrimination. Testing highly-trained normal subjects and taking care to eliminate asymmetries from the testing situation, we found no significant differences between left and right hemifields or between upper and lower hemifields. This was the case for both of the cardinal axes of color space. In addition, there was no difference according to whether the discriminanda were delivered to the same or to different hemispheres, and we note that the same number of synapses may lie between the retina and the site of comparison whether or not the stimuli are delivered to the same hemisphere.     

Impaired embodiment and intersubjectivity

This paper considers the importance of the body for self-esteem, communication, and emotional expression and experience, through the reflections of those who live with various neurological impairments of movement and sensation; sensory deafferentation, spinal cord injury and Möbius Syndrome (the congenital absence of facial expression). People with severe sensory loss, who require conscious attention and visual feedback for movement, describe the imperative to use the same strategies to reacquire gesture, to appear normal and have embodied expression. Those paralysed after spinal cord injury struggle to have others see them as people rather than as people in wheelchairs and have been active in the disability movement, distinguishing between their medical impairment and the social induced disability others project onto them. Lastly those with Möbius reveal the importance of the face for emotional expression and communication and indeed for emotional experience itself. All these examples explore the crucial role of the body as agent for social and personal expression and self-esteem.     

情绪变化的自动化加工：来自EMMN的启示

人脑如何自动化加工瞬息万变的情绪信息?研究者们在借鉴听觉通道的失匹配负波(mismatch negativity, MMN)研究的基础上, 进一步发展出了表情失匹配负波(expression mismatch negativity, EMMN), 以此作为视觉情绪信息前注意加工的重要指标。与以往的一般视觉线索的视觉失匹配负波(visual mismatch negativity, vMMN)有所区别, EMMN研究专注于人脑如何自动化加工瞬息万变的情绪信息。当前的研究主要探讨了不同类型的面部表情、不同性别、高低流体智力个体的EMMN差异, 以及自闭症、抑郁症、精神分裂症等异常个体EMMN的特点。此外, 从预测编码的角度阐释了EMMN的机制。今后的研究有必要聚焦EMMN在临床诊断和治疗中的应用, 考察不同情绪线索EMMN的特点, 并进一步揭示EMMN的神经机制。     

跨通路识别汉字形音的偏差相关成分研究

采用提高非注意纯度的“跨通路延迟反应”实验范式,研究汉字形音识别的跨通路注意事件相关电位（ＥＲＰ）,以偏差刺激ＥＲＰ减去标准刺激ＥＲＰ的早期偏差相关负波（ＤＲＮ１）为主要分析对象。以１５名正常青年为被试。结果发现：无论注意与否及何种刺激,听觉Ｎ１最大峰均位于额中央部,而视觉Ｎ１最大峰位于两侧枕部与颠后部,具有明显的通路差异性。在本实验条件下,听觉与视觉通路的ＤＲＮ１与失匹配负波（ＭＭＮ）在许多性质上相似,反映着对汉字形音识别的自动加工。根据波幅及其头皮分布特点,注意条件下的Ｎ３５０很可能是Ｎ２００与Ｎ４００的重叠,并主要表现出Ｎ４００的特点;而非注意条件下的Ｎ３５０则可能是Ｎ２００。Ｎ３５０的属性因条件而异,表明ＥＲＰ成分反映的大脑加工机制具有可塑性。     

No evidence for a cue mismatch in negative priming

An experiment is reported in which the cue mismatch hypothesis of negative priming, an important novel variant of the mismatching hypothesis, was tested. A cue mismatch and a no mismatch condition were contrasted in a visual discrimination task. In the prime display of cue mismatch ignored-repetition trials, the colour of the prime distractor was different from the colour of the cue indicating the selection feature (coloured square). In probe displays, cue and repeated stimulus had the same colour. In the no mismatch condition, the visual cue was neutral in terms of colour (always black), so that there was always no cue mismatch between prime and probe displays. Contrary to the prediction of the cue mismatch hypothesis, the negative priming effect was not larger in the cue mismatch than in the no mismatch condition. The cue mismatch hypothesis must therefore be rejected. In contrast, the episodic retrieval account is consistent with the results.     

Up by upwest: Is slope like north?

Terrain slope can be used to encode the location of a goal. However, this directional information may be encoded using a conceptual north (i.e., invariantly with respect to the environment), or in an observer-relative fashion (i.e., varying depending on the direction one faces when learning the goal). This study examines which representation is used, whether the sensory modality in which slope is encoded (visual, kinaesthetic, or both) influences representations, and whether use of slope varies for men and women. In a square room, with a sloped floor explicitly pointed out as the only useful cue, participants encoded the corner in which a goal was hidden. Without direct sensory access to slope cues, participants used a dial to point to the goal. For each trial, the goal was hidden uphill or downhill, and the participants were informed whether they faced uphill or downhill when pointing. In support of observer-relative representations, participants pointed more accurately and quickly when facing concordantly with the hiding position. There was no effect of sensory modality, providing support for functional equivalence. Sex did not interact with the findings on modality or reference frame, but spatial measures correlated with success on the slope task differently for each sex.     

Timing of human cortical functions during cognition: role of MEG

Understanding of sensory and cognitive brain processes requires information about activation timing within and between different brain sites. Such data can be obtained by magnetoencephalography (MEG) that tracks cortical activation sequences with a millisecond temporal accuracy. MEG is gaining a well-established role in human neuroscience, complementing with its excellent temporal resolution the spatially more focused brain imaging methods. As examples of MEG's role in cognitive neuroscience, we discuss time windows related to cortical processing of sensory and multisensory stimuli, effects of the subject's own voice on the activity of their auditory cortex, timing of brain activation in reading, and cortical dynamics of the human mirror-neuron system activated when the subject views another person's movements.     

Reduced P50 auditory sensory gating response in professional musicians

Evoked potential studies have demonstrated that musicians have the ability to distinguish musical sounds preattentively and automatically at the temporal, spectral, and spatial levels in more detail. It is however not known whether there is a difference in the early processes of auditory data processing of musicians. The most emphasized and studied early process, especially for neuropsychiatric purposes, is sensory gating. The suppression percentage of the midlatency auditory evoked potential P50, and rarely the N100, wave is used for sensory gating studies. Our aim in this study was to investigate whether there was a difference in the auditory P50 and N100 suppression of control subjects who were professional musicians with no psychiatric problems. 34 professional musicians and 19 non-musicians (the control group) were included in this study. P50 and N100 measurements were taken, the suppression percentage of P50 and N100 was calculated and the results compared. Musicians showed significantly less P50 suppression when compared to non-musicians. There was no significant difference for N100 suppression. What the decreased P50 suppression in musicians when compared to non-musician subjects means, when we also take into account that N100 suppression is not decreased, and how it may contribute to the music perception and production processes of these persons is discussed.     

An ERP study of sensory mismatch expressions in Japanese

Combinations of different sensory words produce mismatch expressions like smooth color and red touch in contrast to normal expressions like red color and smooth touch. Concerning these sensory mismatch expressions, results of three experiments are reported. Experiment 1 revealed that (i) mismatch expressions were less comprehensible than normal expressions, and that (ii) there were two patterns among mismatch expressions: the high-comprehensible mismatch expression (HighCME, e.g., smooth color) and the low-comprehensible mismatch expression (LowCME, e.g., red touch). Experiment 2 revealed that the mismatch expressions produced a significantly greater N400 amplitude than the normal expressions. Experiment 3 implied that the difference between High/LowCME was reflected in a later latency band or in a topographical difference of N400, although the statistical significance was marginal. It is argued that the processes to integrate linguistic elements (e.g., combining adjectives and nouns) are not homogeneous.