Functional magnetic resonance imaging provides new constraints on theories of the psychological refractory period

We used functional magnetic resonance imaging (fMRI) to investigate the psychological refractory period (PRP), the delay in the response to the second of two tasks occurring in immediate succession. Our results were consistent with prior work on the PRP in that when two visual-manual tasks were presented within 100 ms of each other, the second response was delayed on the order of 500 ms, compared with when the two tasks were separated by 1,500 ms. Surprisingly, in brain regions postulated to be important for executive functions, there was virtually no increase in brain activation in the short-interval compared with the long-interval condition. These data suggest that passive queuing, rather than active monitoring, occurs during the PRP.     

Time window from visual images to visual short-term memory: consolidation or integration?

When two dot arrays are briefly presented, separated by a short interval of time, visual short-term memory of the first array is disrupted if the interval between arrays is shorter than 1300-1500 ms (Brockmole, Wang, & Irwin, 2002). Here we investigated whether such a time window was triggered by the necessity to integrate arrays. Using a probe task we removed the need for integration but retained the requirement to represent the images. We found that a long time window was needed for performance to reach asymptote even when integration across images was not required. Furthermore, such window was lengthened if subjects had to remember the locations of the second array, but not if they only conducted a visual search among it. We suggest that a temporal window is required for consolidation of the first array, which is vulnerable to disruption by subsequent images that also need to be memorized.     

Event-related potentials in adolescents with combined ADHD and CD disorder: a single stimulus paradigm

Some studies of the event-related potentials demonstrated a reduction of the voluntary component P3 (P300 or P3b) in youngsters with the attention deficit/hyperactivity disorder (ADHD) or in conduct disorders (CD), and a reduction of the automatic processing component, mismatch negativity, in patients with both ADHD and CD (ADHD+CD). Recently, a passive auditory P3 potential has been elicited by a single stimulus. We therefore tried this potential study in 20 healthy subjects and 20 teenagers with ADHD+CD to search for further evidence of the altered automatic cerebral processing in the latter. Subjects also answered a self-report Dimensional Assessment of Personality Pathology (DAPP). The patient group scored significantly higher on most DAPP traits that reflect problems of emotion control, showed significantly prolonged P2, N2, and P3, and reduced P3. In all subjects Stimulus Seeking was positively correlated with P3 latencies at Fz, Cz, and Pz, and with P3 amplitude at Cz. This study suggests that youngsters with ADHD+CD had pronounced emotion dysregulation, and prominent deficit in passive attention, as reflected by the automatic processing of auditory stimuli.     

Hyperspecificity in visual implicit learning: learning of spatial layout is contingent on item identity

Humans conduct visual search faster when the same display is presented for a 2nd time, showing implicit learning of repeated displays. This study examines whether learning of a spatial layout transfers to other layouts that are occupied by items of new shapes or colors. The authors show that spatial context learning is sometimes contingent on item identity. For example, when the training session included some trials with black items and other trials with white items, learning of the spatial layout became specific to the trained color--no transfer was seen when items were in a new color during testing. However, when the training session included only trials in black (or white), learning transferred to displays with a new color. Similar results held when items changed shapes after training. The authors conclude that implicit visual learning is sensitive to trial context and that spatial context learning can be identity contingent.     

Studying suicide with psychological autopsy: social and cultural feasibilities of the methodology in China

As China opens its door to the world, suicide research is making rapid progress using methods and instruments developed in the West. This is a feasibility study of the psychological autopsy methodology applied in China, with its emphasis on the social and cultural environments. With samples of 66 completed suicides and 66 community normal living controls, the authors found that it is feasible to interview at least two informants for each suicide case and each control, between 2 and 6 months after the suicide. With the Chinese-cultivated contacting method of recruiting cases, the refusal rate is nearly zero. The Western-developed methodology per se proved to be valid in the Chinese culture. Ethical considerations in the context of Chinese culture are as important as in the West. Psychological autopsy technique is shown to be an equally applicable method for the study of completed suicides in Chinese culture as it is in the West. Future epidemiological research on Chinese suicide should use the psychological autopsy method to collect data from larger samples in order to increase our understanding of the risk factors for Chinese suicides.     

Asymmetric object substitution masking

Object substitution masking occurs when a lateral mask persists beyond the duration of a target, reflecting reentrant processes in vision (V. Di Lollo, J. Enns, & R. Rensink, 2000). The authors studied whether substitution masking is location specific and whether it is symmetric around the target. A brief circular display of letters was presented along with a mask that designated the target. The mask was centered on the target or 1.1 degrees to the central or to the peripheral side. Substitution masking was found even when the target and the mask were at different locations. It was asymmetric and stronger when the mask was to the peripheral side of the target than to the central side. Asymmetric substitution was observed using various masks. It could not be explained by retina acuity gradients and was not attenuated by focused attention. The authors propose that target selection triggers an asymmetric inhibitory surround that is stronger toward the central side of the target.     

Dislocations in Bi-Pb-Sr-Ca-Cu-O superconductors

Abstract

Dislocations and dislocation networks in superconducting Bi-Pb-Sr-Ca-Cu-O have been observed by means of TEM, confirming that this compound is a layer structure with low stacking fault energy. On the basal plane, dislocations and dislocation networks dissociate into partial dislocations and partial dislocation networks. However, the dissociation of [010] dislocations is hardly observed, which is related to the structural characteristics of the compound.     

Scanning electron microscopy-electron channelling contrast investigation of recrystallization during cyclic deformation of ultrafine grained copper processed by equal channel angular pressing

Cyclic deformation has been performed at ambient temperature on ultrafine-grained copper processed by equal channel angular pressing. Observations by electron channelling contrast in a scanning electron microscope revealed that pronounced recrystallization occurred and several distinct dislocation configurations such as dislocation walls and labyrinth structures were found within the recrystallized regions. A model is proposed to account for the evolution of recrystallization, emphasizing that its development results from an interaction between the cyclic deformation and the growth of recrystallized regions. The formation of recrystallized regions of different sizes is discussed.