Brain mechanisms associated with background monitoring of the environment for potentially significant sensory events

Background monitoring is a necessary prerequisite to detect unexpected changes in the environment, while being involved in a primary task. Here, we used fMRI to investigate the neural mechanisms that underlie adaptive goal-directed behavior in a cued task switching paradigm during real response conflict or, more generally, when expectations on the repetitive features of the environment were violated. Unexpected changes in sensory stimulus attributes in the currently unattended stimulus dimension thereby led to activations in a bilateral network comprising inferior lateral frontal, intraparietal, and posterior medial frontal brain regions, independent of whether these attributes elicited a factual response conflict or not. This fronto-parietal network may thus play an important role in adaptive responding to potentially significant events outside the current focus of attention.     

Synergistic influences of sensory and central stimuli on non-voluntary rhythmic arm movements

In recent years, neuromodulation of the cervical spinal circuitry has become an area of interest for investigating rhythmogenesis of the human spinal cord and interaction between cervical and lumbosacral circuitries, given the involvement of rhythmic arm muscle activity in many locomotor tasks. We have previously shown that arm muscle vibrostimulation can elicit non-voluntary upper limb oscillations in unloading body conditions. Here we investigated the excitability of the cervical spinal circuitry by applying different peripheral and central stimuli in healthy humans. The rationale for applying combined stimuli is that the efficiency of only one stimulus is generally limited. We found that low-intensity electrical stimulation of the superficial arm median nerve can evoke rhythmic arm movements. Furthermore, the movements were enhanced by additional peripheral stimuli (e.g., arm muscle vibration, head turns or passive rhythmic leg movements). Finally, low-frequency transcranial magnetic stimulation of the motor cortex significantly facilitated rhythmogenesis. The findings are discussed in the general framework of a brain-spinal interface for developing adaptive central pattern generator-modulating therapies.     

Assessing the Predictive Accuracy of hMLH1 and hMSH2 Mutation Probability Models

Hereditary nonpolyposis colorectal cancer (HNPCC) is characterized by a susceptibility to colorectal and extra-colonic cancers. Several guidelines exist for the identification of families suspected of having HNPCC, however these guidelines lack adequate sensitivity and specificity. In an attempt to improve accuracy for the detection of individuals with HNPCC, the Wijnen pre-test probability model (1998) and Myriad Genetics Laboratory prevalence table (2004) were developed. Here we evaluate the Wijnen model and Myriad table at predicting the presence of a mutation in individuals undergoing genetic testing for HNPCC. Forty-nine patients who had undergone genetic testing for germline mutations in hMLH1 and/or hMSH2 were part of our analysis. Our results revealed that the revised Bethesda guidelines performed with the highest sensitivity for germline mutations (94.4%), however the specificity was low (12.9%). Using a 10.0% mutation probability threshold, the Wijnen model and Myriad table had sensitivities of 55.6 and 60.0%, respectively and specificities of 54.8 and 23.8%, respectively. The Wijnen model and Myriad table were poor predictors of mutation prevalence, which is shown by the areas underneath their corresponding receiver operator characteristic curves (0.616 and 0.400, respectively). The results of this study demonsrate that neither the Wijnen model nor the Myriad table are sensitive or specific enough to be used as the only indication when to offer genetic testing for HNPCC.     

Crossmodal object-based attention: auditory objects affect visual processing

According to the object-based view, visual attention can be deployed to "objects" or perceptual units, regardless of spatial locations. Recently, however, the notion of object has also been extended to the auditory domain, with some authors suggesting possible interactions between visual and auditory objects. Here we show that task-irrelevant auditory objects may affect the deployment of visual attention, providing evidence that crossmodal links can also occur at an object-based level. Hence, in addition to the well documented control of visual objects over what we hear, our findings demonstrate that, in some cases, auditory objects can affect visual processing.     

关于知觉干扰效应的ERP研究

利用ERP技术,采用知觉干扰效应的经典实验范式,首次从神经生理水平上探究知觉干扰效应的内部机制。结果发现,递进条件和标准条件均诱发了P2,P3,N400和晚期正成分LPC。在P2,P3和LPC成分上,标准条件的波幅均显著大于递进条件;在N400成分上,递进条件比标准条件波幅更负,潜伏期更长。此外,对递进条件下靶字各模糊水平（Level 1～Level 5）的ERPs进行比较分析表明,N400成分的波幅在各模糊水平间的差异均不显著。基本支持失匹配理论及词汇自动加工理论。     

Duration perception in crossmodally-defined intervals

How humans perform duration judgments with multisensory stimuli is an ongoing debate. Here, we investigated how sub-second duration judgments are achieved by asking participants to compare the duration of a continuous sound to the duration of an empty interval in which onset and offset were marked by signals of different modalities using all combinations of visual, auditory and tactile stimuli. The pattern of perceived durations across five stimulus durations (ranging from 100 ms to 900 ms) follows the Vierordt Law. Furthermore, intervals with a sound as onset (audio-visual, audio-tactile) are perceived longer than intervals with a sound as offset. No modality ordering effect is found for visualtactile intervals. To infer whether a single modality-independent or multiple modality-dependent time-keeping mechanisms exist we tested whether perceived duration follows a summative or a multiplicative distortion pattern by fitting a model to all modality combinations and durations. The results confirm that perceived duration depends on sensory latency (summative distortion). Instead, we did not find evidence for multiplicative distortions. The results of the model and the behavioural data support the concept of a single time-keeping mechanism that allows for judgments of durations marked by multisensory stimuli.     

Properties of the size–weight illusion as shown by lines of subjective equality

We studied the size–weight illusion through comparative judgments. The experiment had two direct aims: to verify whether the relative contribution of size to apparent heaviness can differ for different stimulus sets, and to verify whether that contribution can differ for different methods of comparing two objects (consecutive vs. simultaneous weighing). Thirty university students participated. Results show that the relative contribution of size depends on stimulus set, but is independent of the method used for comparing objects. The first finding implies that a linear model cannot describe the integration of size and weight information in the illusion; the second finding is evidence for the low-level character of the integration process.     

PROBLEMS OF INTERNALIZATION: A BUTTON IS A BUTTON IS—NOT

Analysts hope to help the patient internalize a relationship with the analyst that contrasts with the original archaic object relation. In this paper, the author describes particular difficulties in working with a patient whose defenses and anxieties were bulimic, her movement toward internalization inevitably undone. Several issues are considered: how does the nonsymbolizing patient come to internalize the analyst's understanding, and when this does not hold, what is the nature of the patient's subsequent methods of dispersal? When the patient can maintain connection to the analyst as a good object, even fleetingly, in the depressive position, the possibility of internalization and symbolic communication is increased.     

The effect of chronic low back pain on tactile suppression during back movements

The aim of the present study was to examine whether tactile suppression, the phenomenon whereby tactile perception is suppressed during movement, would occur in the context of back movements. Of particular interest, it was investigated if tactile suppression in the back would be attenuated in those suffering from chronic low back pain. Individuals with chronic low back pain (N = 30) and a matched control group (N = 24) detected tactile stimuli on three possible locations (back, arm, chest) while performing a back or arm movement, or no movement. We hypothesized that the movements would induce tactile suppression, and that this effect would be largest for low-intense stimuli on the moving body part. We further hypothesized that, during back movements, tactile suppression on the back would be less pronounced in the chronic low back pain group than in the control group. The results showed the expected general tactile suppression effects. The hypothesis of back-specific attenuation of tactile suppression in the chronic low back pain group was not supported. However, back-specific tactile suppression in the chronic low back pain group was less pronounced in those who performed the back movements more slowly.