Aging and prospective memory: differences between naturalistic and laboratory tasks

The contrasting age-related trends on laboratory and naturalistic prospective memory (PM) studies were investigated with the same participants. In the first two experiments, 380 participants in three age groups (20s, 60s, and 80+) were given a naturalistic PM task of logging the time at four set times for one week. There were six between-subjects regimens that varied the complexity of the time schedule, and the opportunity to use conjunction cues and external aids. The 60s and 80+ age groups did not differ and both older adult age groups were consistently superior to the young adults on all regimens. In Experiment 3, the same participants showed a significant age-related decline on retrospective memory tasks, and on event-based and time-based laboratory PM tasks embedded within the retrospective memory tasks. The study confirmed the paradoxical age-related trends on laboratory and naturalistic PM tasks.     

Aging impairs the ability to ignore irrelevant information in frequency discrimination tasks

Age effects on the ability to ignore irrelevant auditory information were studied using frequency discrimination threshold (FDT) tasks. FDTs were determined in an unmasked condition with target tones in isolation, and in two backward-masked conditions with a nontarget masking tone presented 20 to 240 ms after the target.One masked condition included irrelevant variability in the masker frequency, but the other did not. The no-variability condition yielded more masking in older than in young adults. Masker variability induced large FDT elevations in both groups; however, the improvement in FDTs with training was large in young but only minimal in older adults.     

Aging and implicit learning of an invariant association

We investigated whether there is an age-related decline in implicit learning of an invariant association. Participants memorized letter strings in which a given letter always occurred in the second position (see Frick & Lee, 1995). Experiments 1 and 2 showed that young and older adults learned this regularity implicitly, with no significant age differences, even when a perceptual feature of the stimuli changed between encoding and test. Experiment 3 confirmed that learning had occurred during encoding, in that learning increased with the number of encoding presentations. We conclude that implicit learning of this invariant association is largely preserved in healthy aging, revealing another avenue by which older people continue to adapt efficiently to environmental regularities.     

Aging in the rhesus monkey: effects on visual discrimination learning and reversal learning.

The behavior of aged rhesus monkeys (18 years and older) was compared to that of young monkeys (3 to 6 years old) to evaluate their relative abilities to learn a series of visual discrimination and discrimination reversal problems. Using a subject-paced, automated experimental procedure designed to optimize stimulus control and facilitate execution of choice responses, no consistent age-related differences were observed in the ability to learn new color and pattern discrimination problems of varying difficulty. However, a severe and consistent deficity on reversal learning did occur. A detailed analysis of this deficit revealed that not only did the aged monkeys take longer to extinguish the old habit and return to chance performance, but they continued to display a deficit in establishing accurate performance at above-chance levels as well. Since no reliable age differences were observed on the original discrimination learning problems, these data suggest that aging impairs mechanisms involved with response rigidity and/or susceptibility to intertrial proactive interference, more severely than those involved with the simple formation of new associations.     

Aging and memory for self-performed tasks: effects of task difficulty and time pressure

An increase in task difficulty or time pressure during the performance of cognitive tasks decreased the ability of older adults to recall the tasks. In Experiments 1 and 2, adult age differences in recall of cognitive tasks were smaller for easier than for more difficult tasks, and, in Experiment 3, adult age differences were smaller for recall of cognitive tasks without time pressure than for recall of cognitive tasks with time pressure. During difficult or time-pressured cognitive tasks, older adults may become anxious about their performance, and they may have trouble inhibiting negative self-evaluative thoughts about their performance. Older adults may thus devote less attention to aspects of the cognitive tasks that would be beneficial for task recall.     

Incorporation of new information into prefrontal cortical activity after learning working memory tasks

The ability to learn new tasks requires that new information is integrated into neural systems that already support other behaviors. To study how new information is incorporated into neural representations, we analyzed single-unit recordings from the prefrontal cortex (PFC), a brain region important for task acquisition and working memory, before and after monkeys learned to perform two behavioral tasks. A population-decoding analysis revealed a large increase in task-relevant information, and smaller changes in stimulus-related information, after training. This new information was contained in dynamic patterns of neural activity, with many individual neurons containing the new task-relevant information for only relatively short periods of time in the midst of other large firing rate modulations. Additionally, we found that stimulus information could be decoded with high accuracy only from dorsal PFC, whereas task-relevant information was distributed throughout both dorsal and ventral PFC. These findings help resolve a controversy about whether PFC is innately specialized to process particular types of information or whether its responses are completely determined by task demands by showing there is both regional specialization within PFC that was present before training, as well as more widespread task-relevant information that is a direct result of learning. The results also show that information is incorporated into PFC through the emergence of a small population of highly selective neurons that overlay new signals on top of patterns of activity that contain information about previously encoded variables, which gives insight into how information is coded in neural activity.     

Autonomic responses to single- and dual-chamber pacing

We investigated the autonomic effects of short-term, single- and dual-chamber pacing by evaluating frequency-domain indexes of heart rate variability (HRV). The study group comprised 25 patients (mean age 62 +/- 7 years) without organic heart disease and with normal sinus node function who were implanted with a permanent dual-chamber DDD (n = 16) or VDD (n = 9) pacing system for transient high-degree atrioventricular block. Continuous overdrive pacing for 15 minutes slightly above the intrinsic rhythm was programmed to ensure complete capture in AAI, DDD, and VVI modes, and the atrioventricular delays were set to ensure permanent ventricular pacing in DDD and VDD modes. Components of frequency-domain measures of HRV (low frequency [LF], high-frequency [HF], and LF/HF ratio) were calculated in 5-minute intervals over a 30-minute period after cessation of each pacing mode. AAI pacing did not significantly affect LF and LF/HF measures, and presented the highest HF power. DDD and VDD modes led to similar responses with slightly increased fluctuations of LF and LF/HF power. VVI pacing triggered an acceleration in heart rate (p <0.05), the most significant increases in LF power and in the LF/HF ratio, and the lowest HF power. Autonomic effects of pacing did not resolve with cessation of pacing. Atrial AAI pacing appears to have lesser effect on sympathovagal balance. Synchronous VDD and DDD stimulation favor a shift in autonomic balance toward sympathetic predominance. Asynchronous VVI pacing triggers both sympathetic overactivity and vagal withdrawal.     

Electronic energy delocalization and dissipation in single- and double-stranded DNA

The mechanism that nature applies to dissipate excess energy from solar UV light absorption in DNA is fundamental, because its efficiency determines the vulnerability of all genetic material to photodamage and subsequent mutations. Using femtosecond time-resolved broadband spectroscopy, we have traced the electronic excitation in both time and space along the base stack in a series of single-stranded and double-stranded DNA oligonucleotides. The obtained results demonstrate not only the presence of delocalized electronic domains (excitons) as a result of UV light absorption, but also reveal the spatial extent of the excitons.     

Aging effects on the identification of digitally blurred text,scenes and faces: Evidence for optical compensation on everyday tasks in the senescent eye

When older observers are defocused optically to the same reduced acuity levels as their younger adult counterparts they are better able to read distant text. This study sought to determine if this ability extended to intrinsically blurred (i.e., image-processed) stimuli of different types. Such an outcome suggests an explanation based on older persons’ greater experience with blurred stimuli; otherwise, one attributable to compensatory changes in the optic media of the older eye would be favored. Twelve young and 12 old healthy community-resident adult observers with excellent acuity were compared on their ability to identify low-pass filtered real words, nonsense words, scenes, and faces arranged in a sequence of decreasingly blurred images. Young observers were able to identify the images correctly earlier in the blur sequence than older adult observers, significantly so for both real and nonsense words. This finding suggests that compensatory changes in the eye’s optical media rather than older observers’ greater experience with blur accounts for their superior legibility performance with optically defocused text. While the image-enhancing effects of the age-related decline in pupil size (senile miosis) may be involved, further research is needed to clarify the mechanism(s) underlying this ability. Paul Bartel received his B.Sc. (Honours) in Psychology (Vision and Aging Lab) and the Bachelor of Social Work degrees from the University of Calgary. He is currently the Director of Community Programs at the North Central Community Resource Centre in Calgary. Donald W. Kline is a professor of psychology and the Director of the Vision and Aging Lab (PACE Program) at the University of Calgary. His research interests include the neural and optical mechanisms of visual aging, visual human factors, and visual health, eye surgery and quality of life. This research was supported by a grant to D. Kline (No. OGP0046593) from the Natural Sciences and Engineering Research Council of Canada (NSERC).     

The healing of single- and double-row stapled circular anastomoses

The healing of anastomoses performed by single- or double-row circular stapling instruments is analyzed in the dog colon. Mucosal healing is better in single-row stapled anastomoses. Apposition of the outer intestinal layers is superior in double-row stapled anastomoses. Bursting pressure and circular wall tension values are identical in both anastomotic types except at 24 hours after surgery when the strength of a double-row stapled anastomosis is superior. A cost-benefit analysis is still in favor of single-row circular instruments. In our opinion, adequate preoperative bowel preparation and a thorough surgical technique, when preparing the cut edges to be anastomosed and placing purse-string sutures, are infinitely more important than making a choice between single- or double-row stapling machines.     

Appropriate and inappropriate therapy in patients with single- or multi-chamber implantable cardioverter-defibrillators

BackgroundInappropriate ICD therapy is associated with adverse outcome. Previous studies indicated that patients with a cardiac resynchronization therapy-defibrillator (CRT-D) might have a lower risk for inappropriate device activations than patients with a single (VVI) or dual chamber (DDD) ICD.MethodsAll ICD recipients from a university cardiac center between 2000 – 2015 were included in this analysis. Outcome parameters were incidence of appropriate and inappropriate therapy and overall mortality.ResultsA total of 1471 patients were analyzed: 629 (43%) patients with a VVI-ICD, 486 (33%) patients with a DDD-ICD and 356 (24%) with a CRT-D device. During an average follow-up of 4.1 ± 3.6 years, CRT-D patients had the lowest risk to receive at least one inappropriate shock therapy (p < 0.001). Rates of appropriate (RR (Rate Ratio) = 0.45, p = 0.019) and inappropriate shock therapy (RR = 0.38, p = 0.021) were significantly lower in CRT-D patients compared to VVI-patients. CRT-D recipients had a lower rate of appropriate shock therapy (RR = 0.323, p = 0.043) compared to DDD patients, but not of inappropriate shock therapy (p = 0.371). Kaplan Meier Analysis did not reveal a significant difference in overall survival (p = 0.396). However, after adjustment for relevant confounding factors, VVI-patients had a higher risk for overall-death (HR = 1.28, p = 0.030).ConclusionsCRT-D recipients have a significantly lower rate of appropriate shock therapy and a lower rate of inappropriate shock therapy. More frequent inappropriate therapies in VVI-ICD recipients may account for their higher overall mortality.     

Aging in Chile

First some detailed demographic data concerning the elderly population in Chile are presented. Then their extremely deficient social and economic life conditions and the negative image of old age are described. The informal and formal systems of social security for the aged and their severe deficiencies are also reported upon. Finally, some institutions for the elderly are presented.     

Aging in Singapore

This paper outlines the aging trends in Singapore and takes stock of socioeconomic differences between Malay and Chinese elderly persons. It draws attention to the idea that policy response to the graying of Singapore has largely been confined to dealing with the consequences of population aging for the economy on the one hand and to creating social and community support for caregiving for elderly persons on the other. These policies cover employment, healthcare, housing, and social and recreational needs. Although fairly comprehensive, it is the position of this paper that further attention on supplementary programs that will address the particularities of specific ethnic groups will be required in order that the minority ethnic groups may also age gracefully.