Interference and facilitation in spatial working memory: Age-associated differences in lure effects in the n-back paradigm.

Working memory (WM) declines prominently during normal aging. The mechanisms underlying this decline are not fully understood. The authors analyzed performance on 2 versions of a 2-back spatial WM task to assess younger and older adults' responses to lures (i.e., nontarget items that match an item earlier in the sequence but not at the current target lag). Results demonstrate lure interference effects that are particularly pronounced among older adults. At the same time, however, older adults showed facilitation for targets. Taken together, these findings suggest that the contribution of familiarity signals to WM performance increases during normal aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in task switching.

Age differences in 2 components of task-set switching speed were investigated in 118 adults aged 20 to 80 years using task-set homogeneous (e.g., AAAA…) and task-set heterogeneous (e.g., AABBAABB…) blocks. General switch costs were defined as latency differences between heterogeneous and homogeneous blocks, whereas specific switch costs were defined as differences between switch and nonswitch trials within heterogeneous blocks. Both types of costs generalized over verbal, figural, and numeric stimulus materials; were more highly correlated to fluid than to crystallized abilities; and were not eliminated after 6 sessions of practice, indicating that they reflect basic and domain-general aspects of cognitive control. Most important, age-associated increments in costs were significantly greater for general than for specific switch costs, suggesting that the ability to efficiently maintain and coordinate 2 alternating task sets in working memory instead of 1 is more negatively affected by advancing age than the ability to execute the task switch itself. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wideband TDOA/FDOA processing using summation of short-time CAF's

A commonly used method of calculating TDOA and FDOA is the cross ambiguity function (CAF). The narrowband model assumes that the Doppler is constant over the bandwidth of the signal. When time companding, caused by relative motion, becomes large enough, the CAF performance is degraded. One method of compensation is to resample the signal, but this can be computationally intensive, especially if there is a wide range of time companding. A second method is to reduce the time the CAF is computed over, but the processing gain is reduced. If the short-term CAFs are recombined after the time companding has been compensated, much of the processing gain can be recovered. In this paper, three novel methods of recombining short-time CAFs are developed and analyzed. The first method is to estimate the TDOA and FDOA for each short-time CAF. The second method is to compensate and noncoherently add the CAFs together. This improves the peak detection over the first method but not the TDOA and FDOA accuracy. The third method is to compensate for both time and phase and then coherently add the short-time CAFs together. This last method improves the FDOA accuracy over the first two methods. The effects of sampled data and frequency dual are analyzed. Simulation results are provided to verify analytical results     

Development and characterization of a purified diet to identify obesity-susceptible and resistant rat populations

A purified moderately high fat diet has been developed to examine diet-induced obesity in rats. Male Sprague-Dawley rats were fed this or an AIN-76A diet for 15 wk and energy metabolism indices were monitored. Food intake, body weight and water balance indices were recorded on a weekly or daily basis. Over the 15-wk period, rats fed the experimental diet diverged into two groups differing in the rate of body weight gain. Animals were labeled as "gainers" or "resisters" depending on their susceptibility to obesity. Following the dietary period, rats were decapitated and trunk blood was collected for glucose and insulin measurements. Gainers consumed slightly more energy than resisters over the experimental period (P < 0.05), but due to greater fecal energy loss, absorbed energy did not differ. Hence gainers became obese without significantly altered energy retention. Urinary creatinine, urea nitrogen and water balance were not different between the groups and consequently could not explain body weight differences. Further, gainers had significantly greater plasma glucose concentration than controls, indicating a potential for these animals to become diabetic. Results suggest metabolic differences must account for the divergence in weight gain observed in the two groups. The dietary model characterized in this study should provide a useful tool to study diet-induced obesity and to determine its underlying mechanism.     

Only time will tell: Cross-sectional studies offer no solution to the age–brain–cognition triangle: Comment on Salthouse (2011).

Salthouse (2011) critically reviewed cross-sectional and longitudinal relations among adult age, brain structure, and cognition (ABC) and identified problems in interpretation of the extant literature. His review, however, missed several important points. First, there is enough disparity among the measures of brain structure and cognitive performance to question the uniformity of B and C vertices of the ABC triangle. Second, age differences and age changes in brain and cognition are often nonlinear. Third, variances and correlations among measures of brain and cognition frequently vary with age. Fourth, cross-sectional comparisons among competing models of ABC associations cannot disambiguate competing hypotheses about the structure and the range of directed and reciprocal relations between changes in brain and behavior. We offer the following conclusions, based on these observations. First, individual differences among younger adults are not useful for understanding the aging of brain and behavior. Second, only multivariate longitudinal studies, age-comparative experimental interventions, and a combination of the two will deliver us from the predicaments of the ABC triangle described by Salthouse. Mediation models of cross-sectional data represent age-related differences in target variables but fail to approximate time-dependent relations; thus, they do not elucidate the dimensions and dynamics of cognitive aging. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Controlled microtribology of a metal oxide surface

The rational control of the friction and wear (damage) of engineering, as opposed to model, surfaces under practical conditions such as high contact pressures has long been a technological challenge with much fundamental interest. Lubricant fluids and physisorbed surfactant monolayers (boundary lubricants) are effective friction modifiers but often fail at high loads. We show that the chemisorption of a suitably designed single-chained phosphonate surfactant onto crystalline α-alumina surfaces produces robust protective monolayers that significantly reduce the friction forces and wear even at high loads. The mechanisms are explained, which point to some general principles that offer a basis for scale-up in many different engineering systems. This revised version was published online in June 2006 with corrections to the Cover Date.     

Working memory plasticity in old age: Practice gain, transfer, and maintenance.

Adult age differences in cognitive plasticity have been studied less often in working memory than in episodic memory. The authors investigated the effects of extensive working memory practice on performance improvement, transfer, and short-term maintenance of practice gains and transfer effects. Adults age 20-30 years and 70-80 years practiced a spatial working memory task with 2 levels of processing demands across 45 days for about 15 min per day. In both age groups and relative to age-matched, no-contact control groups, we found (a) substantial performance gains on the practiced task, (b) near transfer to a more demanding spatial n-back task and to numerical n-back tasks, and (c) 3-month maintenance of practice gains and near transfer effects, with decrements relative to postpractice performance among older but not younger adults. No evidence was found for far transfer to complex span tasks. The authors discuss neuronal mechanisms underlying adult age differences and similarities in patterns of plasticity and conclude that the potential of deliberate working memory practice as a tool for improving cognition in old age merits further exploration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emergence of a powerful connection between sensory and cognitive functions across the adult life span: A new window to the study of cognitive aging?

Six hundred eighty seven individuals ages 25–103 years were studied cross-sectionally to examine the relationship between measures of sensory functioning (visual and auditory acuity) and intelligence (14 cognitive tasks representing a 5-factor space of psychometric intelligence). As predicted, the average proportion of individual differences in intellectual functioning connected to sensory functioning increased from 11% in adulthood (25–69 years) to 31% in old age (70–103 years). However, the link between fluid intellectual abilities and sensory functioning, albeit of different size, displayed a similarly high connection to age in both age groups. Several explanations are discussed, including a "common cause" hypothesis. In this vein, we argue that the increase in the age-associated link between sensory and intellectual functioning may reflect brain aging and that the search for explanations of cognitive aging phenomena would benefit from attending to factors that are shared between the 2 domains. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The place of Mitrofanoff neourethra in the repair of exstrophy-epispadias complex

BACKGROUND: Wegener's granulomatosis is an immunepathogenic disease of unknown origin. The histopathological picture shows granulomatous inflammation with epitheloid cells, granulomas, and general vasculitis. The diagnosis of Wegener's granulomatosis is made on the basis of the clinical picture, serum cANCA, and histologic examination of biopsies. PATIENT: We present the case of a 57-year-old white male patient who was admitted to our ENT Hospital with a six weeks' history of otalgia and incomplete ipsilateral facial palsy since the day before admission. The patient had clinical features of acute otitis media without signs of mastoiditis. Despite a ten days' course of intravenous antibiotic treatment, the intensity of facial palsy progressed and the general condition of the patient worsened. A mastoidectomy and decompression of the facial nerve were performed, demonstrating sclerosis of the mastoid cells. Three weeks after release from the hospital, the patient was admitted again with recurrent fever, cephalea, loss of weight, and arthritic pain. There were no signs of recurrent otitis media or mastoiditis, and sigmoid sinus thrombosis was ruled out. Even under aggressive, intravenous antibiotic treatment the general physical condition continued to worsen; septic temperatures and signs of beginning renal failure occurred. The patient was transferred to the ICU with the diagnosis of sepsis of unknown origin. There bloodtests were positive for cANCA, which is highly specific for Wegener's granulomatosis. Under therapy with cyclophosphamide and i.v. corticosteroid, the patient recovered with 14 days. CONCLUSION: The lack of symptoms in the upper respiratory tract in our patient was unusual, indicating that in patients with recurrent otitis media, facial palsy, mastoiditis, or external otitis Wegener's granulomatosis should be ruled out as differential diagnosis.