Comparability, Reliability, and Practice Effects on Alternate Forms of the Digit Symbol Substitution and Symbol Digit Modalities Tests.

The present study examined the comparability of 4 alternate forms of the Digit Symbol Substitution test and the Symbol Digit Modalities (written) test, including the original versions. Male contact-sport athletes (N=112) were assessed on 1 of the 4 forms of each test. Reasonable alternate form comparability was demonstrated through establishing normality of form distributions and conducting pairwise form comparisons of means, variability, and intraclass correlations. Nonetheless, alternate forms are likely an insufficient means of controlling practice in speeded measures at brief (1-2 weeks) retest intervals. Reliable change indices demonstrated that practice must be accounted for in individual retesting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Boron Carbide–Zirconium Boride In Situ Composites by the Reactive Pressureless Sintering of Boron Carbide–Zirconia Mixtures

The heating of B₄C–YTZP (where YTZP denotes yttria-stabilized zirconia polycrystals) mixtures, under an argon atmosphere, generates B₄C–ZrB₂ composites, because of a low-temperature (<1500°C) carbide–oxide reaction. Composites derived from mixtures that include ≥15% YTZP are better sintered than monolithic B₄C that has been fired under the same conditions. Firing to ∼2160°C (1 h dwell) generates specimens with a bulk density of ≥91% of the theoretical density (TD) for cases where the initial mixture includes ≥15% YTZP. Mixtures that include 30% YTZP allow a fired density of ≥97.5% TD to be attained. The behavior of the B₄C–YTZP system is similar to that of the B₄C–TiO₂ system. Dense B₄C–ZrB₂ composites attain a hardness (Vickers) of 30–33 GPa.     

The development of auditory strategies of attention.

Investigated focused and divided attention in right-handed children in 2 age groups: 6.5–7.5 and 10–11 yrs. Ss listened to lists of simultaneous word pairs that were monitored for the presence of designated target words. An analysis of correct and incorrect response rates showed that there was a general increase in the efficiency of both attention tasks with age, although selective listening performance improved to a greater extent than divided attention. In focused attention, selecting one input and ignoring another developed at different rates. In divided attention, there was a right ear advantage that remained constant across the 2 age groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microwave sintering of amorphous silica powders

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Development of three strategies of attention in dichotic monitoring.

Investigated 3 strategies of attention in 108 Ss in 3 age groups (7, 11, and 20 yrs). Ss monitored lists of monaural and dichotic words and responded manually to target words. Target detection rates in unequal division of attention (Exp I) showed that selection of the relevant input improved with age. The degree of attenuation of the irrelevant input was dependent on which ear was being ignored, but this effect interacted with age. The 7-yr-olds could not attend effectively to left-ear items. Exp II simplified the focusing strategy by eliminating response requirements to the irrelevant input. Selectivity improved with this strategy, particularly in 7-yr-olds. Equal division of attention between the 2 ears (Exp III) revealed a constant right-ear advantage in each age group. Differentiation of the 3 voluntary strategies improved between ages 7 and 11. In adults, the 3 strategies were clearly distinguished. Results are interpreted in terms of a multiprocess model of attention: Perceptual factors such as dichotic interaction and hemispheric asymmetry were strategy dependent but not age dependent. Voluntary selective attention was age dependent and affected the degree to which hemispheric asymmetry could be overcome. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Event-related potentials associated with covert orientation of visual attention in Parkinson's disease

Event-related potentials (ERPs) were measured in a group of patients with idiopathic Parkinson's disease and compared with a matched control group during a task involving covert orientation of visual attention. Central warning cues directed attention to the probable location of a lateralized signal that required a button-press response. Parkinson patients had enhanced post-cue P1 (at Oz) and P2 (at Cz) amplitudes, delayed N1 (at Oz) latencies, and diminished CNV amplitudes. Post-target amplitudes were similar to controls, except for an enhanced P1 to invalidly cued targets, and delayed N1 and P3 target latencies. These results indicate that Parkinson patients, in addition to their motor deficits, process spatial cues more effortfully and slowly, have impaired response preparation, and process imperative stimuli more slowly.     

A comparison of cognitive impairments in dementia of the Alzheimer type and depression in the elderly

General cognitive function and specific language and memory processing abilities were compared in dementia of the Alzheimer type (DAT), depressed and normal control subjects. Several tests clearly differentiated between DAT and depressed subjects including a verbal fluency task, several components of a word memory test, an IQ deterioration index, and the Mini-Mental State Examination. The inability of DAT subjects to take advantage of semantic cues in both the verbal fluency and in the memory test contrasted with the performance of depressed and normal subjects, who were able to benefit from semantic cues. Depressed patients displayed deficits compared with normal controls on the more effortful verbal fluency task but not on the memory test. Tasks that are least effortful, rely on semantic associations, and require declarative memory are most likely to discriminate between DAT and depression.     

Growth, proliferation, and cell death in the ontogeny of transient DRG (Froriep''s ganglia) of chick embryos

Chaotic regimes in a mathematical model of pacemaker activity in the bursting neurons of a snail Helix pomatia, have been investigated. The model includes a slow-wave generating mechanism, a spike-generating mechanism, an inward Ca current, intracellular Ca ions, [Ca2+]in, their fast buffering and uptake by intracellular Ca stores, and a [Ca2+]in-inhibited Ca current. Chemosensitive voltage-activated conductance, gB*, responsible for termination of the spike burst, and chemosensitive sodium conductance, gNa*, responsible for the depolarization phase of the slow-wave, were used as control parameters. These conductances in intact snail bursting neuron are regulated by neuropeptides. Time courses of the membrane potential and [Ca2+]in were employed to analyse different regimes in the model. Histograms of interspike intervals, autocorrelograms, spectral characteristics, one-dimensional return maps, phase plane trajectories, positive Lyapunov exponent and especially cascades of period-doubling bifurcations demonstrate that approaches to chaos were generated. The bifurcation diagram as a function of gB* and the ([Ca2+]in-V) phase diagram of initial conditions reveal fractal features. It has been observed that a short-lasting depolarizing current of elevation of [Ca2+]in may evoke transformation of chaotic activity into a regular bursting one. These kinds of transitions do not require any changes in the parameters of the model. The results demonstrate that chaotic regimes of neuronal activity modulated by neuropeptides may play a relevant role in information processing and storage at the level of a single neuron.     

Driving after concussion: The acute effect of mild traumatic brain injury on drivers' hazard perception.

Objective: No research has examined whether individuals recovering from a recent mild traumatic brain injury (MTBI) are safe to drive, despite cognitive impairment being a common consequence soon after MTBI. This study examined the acute effect of MTBI on drivers' hazard perception, which is defined as drivers' ability to search the road ahead to rapidly identify potentially dangerous traffic situations. Poorer hazard perception has been associated with higher crash rates in a number of studies. Method: Forty-two patients with MTBI and 43 patients with minor orthopedic injuries were recruited from the emergency department of a large metropolitan hospital within 24 hours of injury. Participants completed a computerized hazard perception test, in which they watched videos of genuine traffic scenes filmed from the driver's point of view. They were required to use the computer mouse to click on potential traffic hazards as early as possible. Results: Participants with MTBI were significantly slower to respond to traffic hazards than participants with minor orthopedic injuries (p = .03, d = .48). Conclusions: This study provides the first indication that within the acute stage postinjury, MTBI is associated with impairment in a crash-related component of driving. This suggests that patients with MTBI should be advised to refrain from driving for at least the first 24 hours' postinjury. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of selective listening and hemispheric asymmetry.

In 2 experiments binaural and dichotic tasks of varying complexity were given to 64 7- and 9-yr-old children to investigate the interaction of laterality and selective attention. One of each digit pair was spoken by a male and the other by a female. Ss recalled 3 of the digits spoken in a specified voice. With the attended voice in one ear, performance improved relative to the binaural condition in both age groups. However, when location and voice cues were uncorrelated, the younger Ss' performance was more adversely affected. The right ear advantage (REA) increased as a function of task difficulty. With slow presentation rates, the REA remained constant with age but decreased with age in the faster conditions, which was opposite to the predicted increase in cerebral asymmetry of language function with age. The 7-yr-olds responded according to their perceptual asymmetry, recalling right-ear items whether the attended voice was in the left or right ear. The developmental changes in selective attention are explained by a capacity model. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)