The association of cardiac vagal control and executive functioning--findings from the MIDUS study.

Cardiac vagal control (CVC), an index of parasympathetic contribution to cardiac regulation, has been linked to enhanced executive functioning (EF). However, findings to date have been based on small or unique samples. Additionally, previous studies assessed the CVC-EF link only during rest or recovery period from a cognitive challenge, but not during both states. In the present study, data on 817 socioeconomically diverse participants were obtained from the Midlife Development in the United States (MIDUS) study. As part of this study, participants completed cognitive tests, including EF, along with laboratory-based measures of CVC during rest and following recovery from a cognitive challenge. Regression analyses adjusting for respiratory rate revealed no effect of CVC at rest or during recovery on a global index of EF. However, exploratory post-hoc analyses of the components of the global EF index revealed a significant association between faster vagal recovery and better attention-switching and response inhibition abilities, as indexed by faster reaction time to the mixed SGST. This association remained significant after controlling for demographic, clinical (BMI, diseases and medications altering cardiac autonomic functioning, etc.), and health behavior covariates (Beta = .148, p = .010). Our findings suggest that future studies may need to investigate the links of CVC to specific EF abilities, rather than global measures of EF. Additionally, our results highlight the importance of assessing CVC during both rest and recovery from a cognitive challenge. The authors discuss the putative neurobiological underpinning of this link, as well as suggestions for future basic and clinical research.

Regaining lost time: adult aging and the effect of time restoration on recall of time-compressed speech.

Two experiments in which time was restored to artificially accelerated (time-compressed) speech are reported. Experiment 1 showed that although both young and older adults' recall of the speech benefited from the restoration of time, time restoration failed to boost the older adults to their baseline levels for unaltered speech. In Experiment 2, either 100% or 125% of lost time was restored by inserting pauses, either at linguistic boundaries or at random points within the passages. Experiment 2 showed that the beneficial effects of time restoration depended on where processing time was inserted, as well as how much time was restored. Results are interpreted in terms of age-related slowing in speech processing moderated by preserved linguistic knowledge and short-term conceptual memory.

One voice too many: adult age differences in language processing with different types of distracting sounds.

An experiment is reported that investigated factors that might contribute to age differences in the ability to process spoken language under conditions of competition from various types of background noise. Age differences in recall of spoken sentences were shown to depend on the type of background noise as well as its intensity. Increased intensity levels of just one competing speaker produced differentially greater impairment in older adults than in young adults. Analyses showed that listening performance was predicted not only by individual differences in hearing ability but also by speed of processing, which underscores the combined role of age-related auditory and cognitive changes in processing spoken language.

Fast noisy speech: age differences in processing rapid speech with background noise.

In order to investigate the effects of age on the ability to process speech under conditions of background noise, younger and older adults listened to and reported time-compressed spoken sentences presented with varying levels of background babble. Although the two age groups did not differ significantly in terms of either pure tone averages or in the ability to accurately report the sentences when they were presented in quiet, the older participants showed less tolerance for background noise than younger adults. This age difference in performance was further magnified by increased speech rates, suggesting that both age-related slowing of processing and reduced inhibition of distracting sounds may produce age deficits in speech processing.

Response latencies for false memories: gist-based processes in normal aging.

Three experiments have demonstrated that age-related increases in both probability and speed of false recognitions for word lists depended on the use of a gist-based memory strategy. When test conditions promoted a gist strategy, both younger and older participants were as likely to falsely recognize a thematically associated lure as to correctly recognize a studied item, and both groups were equally fast in making these decisions. However, when test conditions deemphasized a gist-based strategy, older adults were more likely than younger adults, and faster, to falsely recognize both strong and weakly associated lures. These findings suggest an age-related increase in reliance on gist-based processing that may underlie age differences in false memory.

Age differences in veridical and reconstructive recall of syntactically and randomly segmented speech.

Young and elderly adults listened to spoken passages that were segmented for immediate recall either at natural syntactic boundaries (such as after sentences or major clauses), or at random, nonsyntactic intervals. In addition, speech rate was manipulated using time-compression of the speech materials. Results showed that random segmentation was especially detrimental to the elderly subjects' recall, as was the effect of increasing speech rate. An analysis of subjects' recall errors offered evidence for reconstruction in short-term segment recall in a manner similar to that usually associated with long-term memory.

Passage difficulty, speech rate, and age differences in memory for spoken text: speech recall and the complexity hypothesis.

Memory for speech in young and elderly adults was studied by varying speech rate and average predictability of prose passages (measured by a "cloze" procedure). Increased speech rate and decreased predictability yielded poorer memory performance on three retention measures (free recall, cued recall, and multiple-choice recognition), confirming passage predictability as a good predictor of empirical difficulty of a speech passage. Older adults recalled less than young adults on all three measures, with increasing speech rates producing special difficulty for the elderly subjects relative to the young. Although there was a suggestion that elderly subjects were less able to take advantage of passage predictability than the young in recall of very rapid speech, neither age group showed an interaction between passage predictability and speech rate. Results are discussed in terms of a simple extension of the complexity hypothesis to speech recall.

Rapid speech processing and divided attention: processing rate versus processing resources as an explanation of age effects.

The authors conducted a dual-task study to examine age differences in speech processing under varying loads. Younger and older adults listened to and immediately recalled spoken passages presented at various speech rates (140-280 words per min). This task was performed alone as well as in a divided-attention condition in which subjects concurrently performed a picture recognition task. Consistent with the slowing hypothesis, older adults' immediate memory performance was differentially depressed when speech rates were very fast. The Age x Speech Rate interaction, however, was not exacerbated in the divided-attention condition. This suggests that aging may reduce the rate at which the processing operations underlying memory for speech are completed, but this is conceptually distinct from an age-related reduction in attentional capacity.

Speech-processing capacity in young and older adults: a dual-task study.

Adult age differences in processing speech were examined with a dual-task paradigm. Subjects listened to spoken passages for later recall while performing a concurrent reaction time task intended to index cognitive capacity usage on the speech memory task. Age differences in secondary task decision latencies were eliminated when subgroups of young and older subjects were matched on working memory span. These findings are interpreted as showing that an age-related reduction in working memory efficiency contributes to age differences in processing discourse for memory.

Cognitive and affective disorders in elderly diabetics.

In non-insulin-dependent diabetes mellitus, performance of complex cognitive tasks requiring the storage and retrieval of new information is poorer than in age-matched controls. By contrast, performance of less demanding tasks such as immediate memory and simple reaction time is essentially equivalent for NIDDM patients and controls. This pattern parallels the cognitive change observed with normal aging, in which age differences are minimal on less demanding immediate memory tasks but older adults perform more poorly than young adults on secondary or long-term memory tasks. Age-related changes in cognitive performance have been attributed to a reduction in processing resources or working memory capacity. Although the explanation for NIDDM-related deficits remains to be identified, reduced glucose control and elevated levels of triglycerides appear to play some role in cognitive impairment. Non-insulin-dependent diabetes is associated not only with elevated levels of depression, but with an increased frequency of self-reported memory problems. Moreover, elevated levels of depression are associated with various indicators of neuropathy and with significant reductions in self-regulated control of glucose at the time of medical office visits. Diabetic patients may perceive less control over their lives as a result of the many restrictions associated with the disease. When provided with the opportunity to exercise control, however, performance on many cognitive tasks can be improved in NIDDM as well as in age-matched controls. This suggests that by providing NIDDM patients with opportunities to exercise increased control over their lives it may be possible to enhance motivation and to increase the likelihood of the patient's adopting more effective self-regulatory behaviors.

Age differences in processing expository and narrative text.

A dual-task procedure was used to examine the effects of text genre on prose processing, comprehension, and recall in 20 young (18-33 years) and 20 old (65-80 years) adults. Response latencies on a secondary task provided an index of cognitive capacity used in reading narrative and expository passages. Both groups recalled more of narratives than of expository passages, although old subjects recalled less than young. Also, the narrative protocols of both age groups showed a greater difference for recall of main ideas as compared to details. Age differences in the pattern of text genre effects were found on measures of comprehension, capacity utilization, and processing efficiency. It appears that the narrative genre facilitated most measures of performance and partially compensated for some limitations in the older group.

Memory self-assessment and performance in aged diabetics and non-diabetics.

Non-insulin dependent diabetes in older adults is associated with elevated depression and a greater decline in certain aspects of cognitive functioning than is found with normal aging. This study sought to determine whether diabetics report more memory complaints in carrying out their daily activities, and if memory self-assessments are reflective of performance on laboratory tasks. Middle-aged (55-64 years) and old (65-74 years) diabetics and non-diabetic control subjects were studied. Results showed that both diabetes and increased age were associated with poorer performance on some cognitive tests as well as with more self-reported memory problems. When depression levels were statistically controlled, the diabetes variable was no longer a significant predictor of memory complaints. The usefulness of self-assessments as an adjunct to more objective cognitive test measures was discussed.