Age differences in dichotic listening performance

Acoustics versus linguistics? Context is Part and Parcel to lateralized processing of the parts and parcels of speech

The purpose of this review is to provide an accessible exploration of key considerations of lateralization in speech and non-speech perception using clear and defined language. From these considerations, the primary arguments for each side of the linguistics versus acoustics debate are outlined and explored in context of emerging integrative theories. This theoretical approach entails a perspective that linguistic and acoustic features differentially contribute to leftward bias, depending on the given context. Such contextual factors include stimulus parameters and variables of stimulus presentation (e.g., noise/silence and monaural/binaural) and variances in individuals (sex, handedness, age, and behavioural ability). Discussion of these factors and their interaction is also aimed towards providing an outline of variables that require consideration when developing and reviewing methodology of acoustic and linguistic processing laterality studies. Thus, there are three primary aims in the present paper: (1) to provide the reader with key theoretical perspectives from the acoustics/linguistics debate and a synthesis of the two viewpoints, (2) to highlight key caveats for generalizing findings regarding predominant models of speech laterality, and (3) to provide a practical guide for methodological control using predominant behavioural measures (i.e., gap detection and dichotic listening tasks) and/or neurophysiological measures (i.e., mismatch negativity) of speech laterality.

Risk-Taking across the Life-Span as Measured by an Intrusion-Omission Ratio on a Selective Attention Task

Data from a previously reported study were re-analyzed to determine whether increased cautiousness could explain age differences in performance requiring selective attention. 175 female volunteers, ranging in age from 17 to 72 yr., were given an auditory task requiring selective attention. An intrusion-to-omission ratio, computed for each subject, showed no significant differences across the age range. Results indicate increased cautiousness on the part of elderly persons cannot adequately explain age differences in performance requiring selective attention.

Working Memory and Reading: A Life-span Perspective

The relationships among working memory, memory span, and reading skills were studied in 1266 individuals, aged 6-49. They were administered tests of word recognition, pseudoword decoding, reading comprehension, a working memory (listening span) task that required the simultaneous processing of syntax and the recall of linguistic information, and a short-term memory task that required the recall of rhyming or nonrhyming letters presented visually. The results indicated that there is a gradual growth in the development of working memory skills from ages 6 to 19 and a gradual decline after adolescence. The short-term memory task did not show a decline in performance among older individuals. On both of these memory tasks and at most of the age levels, individuals with a reading disability performed at significantly lower levels than individuals with normal reading skills. An important component of the development of reading skills appears to be memory for verbal information. Age-related declines in memory appear to be related to the processing demands of the task, which may affect the degree to which rehearsal strategies are possible within the task.

Older adults do not notice their names: a new twist to a classic attention task

Although working memory spans are, on average, lower for older adults than young adults, we demonstrate in 5 experiments a way in which older adults paradoxically resemble higher capacity young adults. Specifically, in a selective-listening task, older adults almost always failed to notice their names presented in an unattended channel. This is an exaggeration of what high-span young adults show and the opposite of what low-span young adults show. This striking finding in older adults remained significant after controlling for working memory span and for noticing their names in an attended channel. The findings were replicated when presentation rate was slowed and when the ear in which the unattended name was presented was controlled. These results point to an account of older adults' performance involving not only an inhibition factor, which allows high-span young adults to suppress the channel to be ignored, but also an attentional capacity factor, with more unallocated capacity. This capacity allows low-span young adults to notice their names much more often than older adults with comparably low working memory spans do.

Right hemisphere role in cognitive reserve

High levels of education, occupational complexity, and/or premorbid intelligence are associated with lower levels of cognitive impairment than would be expected from a given brain pathology. This has been observed across a range of conditions including Alzheimer's disease (Roe et al., 2010), stroke (Ojala-Oksala et al., 2012), traumatic brain injury (Kesler et al., 2003), and penetrating brain injury (Grafman, 1986). This cluster of factors, which seemingly protect the brain from expressing symptoms of damage, has been termed "cognitive reserve" (Stern, 2012). The current review considers one possible neural network, which may contribute to cognitive reserve. Based on the evidence that the neurotransmitter, noradrenaline mediates cognitive reserve's protective effects (Robertson, 2013) this review identifies the neurocognitive correlates of noradrenergic (NA) activity. These involve a set of inter-related cognitive processes (arousal, sustained attention, response to novelty, and awareness) with a strongly right hemisphere, fronto-parietal localization, along with working memory, which is also strongly modulated by NA. It is proposed that this set of processes is one plausible candidate for partially mediating the protective effects of cognitive reserve. In addition to its biological effects on brain structure and function, NA function may also facilitate networks for arousal, novelty, attention, awareness, and working memory, which collectively provide for a set of additional, cognitive, mechanisms that help the brain adapt to age-related changes and disease. It is hypothesized that to the extent that the lateral surface of the right prefrontal lobe and/or the right inferior parietal lobe maintain structural (white and gray matter) and functional integrity and connectivity, cognitive reserve should benefit and behavioral expression of pathologic damage should thus be mitigated.

Sex differences in language asymmetry are age-dependent and small: a large-scale, consonant-vowel dichotic listening study with behavioral and fMRI data

Men are often believed to have a functionally more asymmetrical brain organization than women, but the empirical evidence for sex differences in lateralization is unclear to date. Over the years we have collected data from a vast number of participants using the same consonant-vowel dichotic listening task, a reliable marker for language lateralization. One dataset comprised behavioral data from 1782 participants (885 females, 125 non-right-handers), who were divided in four age groups (children <10 yrs, adolescents = 10-15 yrs, younger adults = 16-49 yrs, and older adults >50 yrs). In addition, we had behavioral and functional imaging (fMRI) data from another 104 younger adults (49 females, aged 18-45 yrs), who completed the same dichotic listening task in a 3T scanner. This database allowed us to comprehensively test whether there is a sex difference in functional language lateralization. Across all participants and in both datasets a right ear advantage (REA) emerged, reflecting left-hemispheric language lateralization. Accordingly, the fMRI data revealed a leftward asymmetry in superior temporal lobe language processing areas. In the N = 1782 dataset no main effect of sex but a significant sex by age interaction emerged: the REA increased with age in both sexes but as a result of an earlier onset in females the REA was stronger in female than male adolescents. In turn, male younger adults showed greater asymmetry than female younger adults (accounting for <1% of variance). There were no sex differences in children and older adults. The males in the fMRI dataset (N = 104) also had a greater REA than females (accounting for 4% of variance), but no sex difference emerged in the neuroimaging data. Handedness did not affect these findings. Taken together, our findings suggest that sex differences in language lateralization as assessed with dichotic listening exist, but they are (a) not necessarily reflected in fMRI data, (b) age-dependent and (c) relatively small.

Are individual differences in speech reception related to individual differences in cognitive ability? A survey of twenty experimental studies with normal and hearing-impaired adults

This paper summarizes twenty studies, published since 1989, that have measured experimentally the relationship between speech recognition in noise and some aspect of cognition, using statistical techniques such as correlation or factor analysis. The results demonstrate that there is a link, but it is secondary to the predictive effects of hearing loss, and it is somewhat mixed across study. No one cognitive test always gave a significant result, but measures of working memory (especially reading span) were mostly effective, whereas measures of general ability, such as IQ, were mostly ineffective. Some of the studies included aided listening, and two reported the benefits from aided listening: again mixed results were found, and in some circumstances cognition was a useful predictor of hearing-aid benefit.

Toward development of a computer-based methodology for evaluating and reducing medication administration errors

The number of people aged 65 years and older in the United States is increasing. This age group consumes 30% of all prescription drugs. Many elderly people require assistance from caregivers in taking their medication. Medication administration errors can result if caregivers cannot remember to give the medications or do not understand how to give them. This study aims to determine a more effective method of presenting prescription instructions and to determine if the multiple resource hypothesis holds in the context of prescription instructions by evaluating the effect a voice prescription label (which gives audio instructions) has on comprehension and memory of a drug regimen under varying training level, task condition and instruction format. In performing a multivariate ANOVA on data collected among 48 formal and 48 informal caregivers, training level, task condition, sound condition and instruction format were found to significantly affect caregivers' memory and comprehension. There is evidence that audio instructions and the matrix format reduce errors. These results could lead to the development of a medication scheduling management SYSTEM that effectively provides prescription instructions, organizes medicines according to administration time and incorporates decision rules to determine what action should be taken if a dose is missed.

Age-related changes in hemispheric asymmetry depend on sex

A total of 92 participants, 50 younger (mean age 26.3 years) and 42 older (mean age 63.8 years), were tested for visual-field asymmetries. On a word-matching task, a right-visual-field (RVF) advantage increased with age, consistent with the theory that right-hemispheric function shows relatively greater decline with age than left-hemispheric function. On a figural-comparison task, a left-visual-field (LVF) advantage was marginally decreased with age in the men, but significantly increased in the women, probably because age-related changes in hormonal levels are more pronounced in women. This increase in LVF advantage is contrary to both the HAROLD theory that hemispheric asymmetry declines with age, and the theory of relative right-hemispheric decline.

Hemispheric asymmetry and aging: right hemisphere decline or asymmetry reduction

We review evidence for two models of hemispheric asymmetry and aging: the right hemi-aging model, which proposes that the right hemisphere shows greater age-related decline than the left hemisphere, and the hemispheric asymmetry reduction in old adults (HAROLD) model, which proposes that frontal activity during cognitive performance tends to be less lateralized in older than in younger adults. The right hemi-aging model is supported by behavioral studies in the domains of cognitive, affective, and sensorimotor processing, but the evidence has been mixed. In contrast, available evidence is generally consistent with the HAROLD model, which is supported primarily by functional neuroimaging evidence in the domains of episodic memory encoding and retrieval, semantic memory retrieval, working memory, perception, and inhibitory control. Age-related asymmetry reductions may reflect functional compensation or dedifferentiation, and the evidence, although scarce, tends to support the compensation hypothesis. The right hemi-aging and the HAROLD models are not incompatible. For example, the latter may apply to prefrontal regions and the former to other brain regions.

Is there a divided attention deficit in patients with early Parkinson's disease?

Divided attention was studied in a group of patients with early Parkinson's disease and compared to normal controls matched for age, gender and intellectual status using a dichotic monitoring task. The Parkinson patients had more difficulty dividing their attention between two competing auditory inputs than the normal subjects. This impairment in divided attention or general attentiveness may be due to changes in the ascending monoamine projections, which have been shown to have a role in auditory attention. A right ear advantage (REA) was also observed. Not only were speech messages discriminated better by the right than the left ear, but these messages were processed more quickly by the right ear.

Effects of aging, skill modification, and demand alternation on multiple-task performance

The magnitude of age effects in single- and dual-tasks may be affected by the degree to which performance depends on well-learned skills that were previously developed. In addition, age-effects may be affected by the requirement to modify these skills and by attentional requirements emerging from the mutual relation of subtasks. Effects of skill modification and emergent attentional processes were examined in an experiment in which experienced subjects performed two perceptual-motor tasks, a vehicle steering task and car-following task in a driving simulator. Car-following was performed under two conditions of familiarity, determining whether or not a normal psychomotor routine had to be modified. In dual-task performance, the demand of subtasks was constant or alternating in counterphase. In general, the older subjects' performance did not differ from that of their younger counterparts, except when the single- or dual-task involved routine modification in car-following. Dual-task costs were basically manifested in the car-following task. Post hoc interpretations of the data indicated that the results were not completely consistent with the complexity hypothesis.

Effects of age and task similarity on dual-task performance

When a dual tracking task consisting of two incoherent (uncorrelated) subtasks is partly integrated, such that it is characterized by incompatibility of similarity, or when axis similarity of subtasks is high, it may be difficult to map subtask stimuli to the proper responses. Especially for older adults, an increase in mapping demands may be a source of confusion (cross talk). In the present experiment this issue was addressed with a dual task consisting of two unrelated one-dimensional compensatory tracking tasks with position dynamics. Task performance was measured in terms of root mean square tracking error and cross-axial correlations. Tracking error data were consistent with the hypothesis that older subjects are penalized when there is incompatibility between control and display integration. In general, negative effects of incompatibility of integrality were the greatest when partial integration involved integration of the response component. Both performance measures indicated that with increasing incoherent similarity, task performance of the old subjects was more hampered than was that of their young counterparts.

Dichotic asymmetries in aging and alcoholic subjects

It has been suggested that certain cognitive changes found both with aging and with chronic alcoholism are accompanied by alterations in hemispheric functional asymmetries. One prevalent view states that these well-delineated cognitive changes are directly related to a selective disruption of right hemisphere function. The present study tested this hypothesis using dichotic listening measures of functional asymmetry. Both alcoholics and older nonalcoholics evidenced patterns of cognitive preservation and impairment similar to those seen in patients with known right hemisphere dysfunction. Nevertheless, dichotic listening findings did not reveal any selective effect on the right hemisphere, as previously proposed. The dichotic studies supported the view that both hemispheres are affected by aging and alcoholism. Patients with right hemisphere lesions demonstrated characteristic and predictable changes in dichotic asymmetries, illustrating the reliability of the dichotic measures as indices of hemispheric function.

Lateralization for the expression and perception of facial emotion as a function of age

In order to test the hypothesis of right hemisphere changes with age, this study examined lateralization for facial emotion in young, middle-aged, and older women (N = 90). For expression, subjects were photographed while posing positive and negative emotions. Composite photographs were created and rated for intensity. For perception, subjects were required to make intensity judgements about emotional chimeric faces. Overall, subjects demonstrated significant left-sided facial asymmetry for expression and significant left hemispace biases for perception. The findings for facial expression were not influenced by emotional valence or resting face asymmetries. There were no changes in lateralization as a function of age for either expression or perception. Taken together, these findings lend support to the notion that the right hemisphere mediates emotional processing across the adult life span.

Dichotic performance in elderly Italians with Italian stop consonant-vowel stimuli

Dichotic listening tests were carried out at various interaural onset asynchronies (from 0 to 500 ms) on normal-hearing young and elderly subjects using a free recall method. The stimuli were Italian stop consonant and vowel syllables computer-edited to reduce prevoicing of the consonant and vowel syllables from the original 100-120 ms to 30 ms. Results suggest that right-ear advantage is uninfluenced by age, despite a significantly lower total dichotic performance and abnormal lag effect in the older group.

Age related differences in left and right hand skill and in visuo-spatial performance: their possible relationships to the hypothesis that the right hemisphere ages more rapidly than the left

Young and old right handed people were disproportionately worse with their left hand when speed was stressed but showed no especial difficulty when accuracy of performance was emphasised. Both groups of people were also tested on the AH4 test of cognitive abilities. As frequently reported by Rabbitt, the old were disproportionately worse on the visuo-spatial part than on the verbal part compared with the young, even though both parts required "fluid" abilities and even though both were given under time constraints. There was no correlation amongst the elderly people between speed stressed deficits in their left hand performance and their deficits on the visuo-spatial part of the AH4. Both fine control of the left hand and fingers and visuo-spatial performance are likely to be mediated by the right cerebral hemisphere and the implications of these results for a variety of possible views about selective aging of the right hemisphere are discussed.

Age-related differences in brain electrical activity of healthy subjects

A combined neurophysiological (electroencephalographic [EEG] and sensory evoked potential) and neuropsychological investigation was performed on 63 healthy men ranging in age from 30 to 80 years. Although alpha frequency diminished slightly with age, neither amplitude nor frequency demonstrated a high age correlation. Alpha blocking, in contrast, did correlate with age, in the direction of reduced alpha reactivity. EEG background activity underwent significant age-correlated change, consisting of reductions in slow activity and augmentation of fast activity, i.e., EEG desynchronization. Previously reported age-related EEG slowing may be related to the presence of disease in the populations studied. Topographic analysis revealed that the greatest change occurred in the temporal lobes. More change was noted either early or late in the age span, suggesting that aging is a nonlinear process. More features were derived from the right hemisphere than from the left, suggesting that the aging process is not completely symmetrical.

Changes in cerebral lateralization in aging

To determine whether there is increasing left hemispheric lateralization for language with age and whether the right hemisphere is selectively impaired with advanced age, we tested 96 right-handed people aged 25-80 yr on verbal and non-verbal matching tasks presented tachistoscopically. Task difficulties was equalized by adjusting exposure durations. Exposure duration, error laterality and response latency laterality were analyzed. Typical field effects as well as age-related slowing and sex by task interactions were observed. However, no systematic age-related changes in lateralization were apparent.

Bimanual tactual discrimination in aging alcoholics

Somesthesis and perceptual laterality were studied in normal aging and in aging alcoholic populations. The bimanual (dichhaptic) stimulation technique that was employed required participants to recognize and identify items traced onto the palms of both hands simultaneously, thereby eliciting competition for analysis by the two cerebral hemispheres. Performance of five groups of participants was compared (younger and older alcoholics and age-matched normal controls, and alcoholic Korsakoff patients); within each of the groups, the ability to identify verbal stimuli (letters) was compared with nonverbal stimuli (lines differing in orientation) for the right and the left hands separately. The results suggest that tactile discrimination accuracy for nonverbal information is disrupted by aging, but that alcoholism per se does not have this effect. The combined effects of alcohol abuse and aging were seen only on the tactual tasks that required identification of verbal items. Lateralization measures based upon performance by the two hands separately did not differentiate among the groups.

The effect of age on hemispheric asymmetry in visual and auditory identification

On psychometric tests, spatial scores typically decline more with age than do verbal scores. Since in humans, visuo-spatial information is more efficiently processed by the right hemisphere (RH) and verbal information by the left (LH), this behavioral pattern could reflect a greater age decline in RH than in LH abilities. To test this possibility, the speed with which young and old subjects identified stimuli in their right and left visual fields was measured. Since each half field, projects to the opposite hemisphere, by presenting stimuli in one half field, RH and LH abilities can be measured relatively independently. Words were identified faster in the right field (i.e., LH), pictorial stimuli in the left (RH). This was equally true for both young and old. Similarly, a right ear advantage in the identification of dichotically presented syllables was of equal magnitude in both age groups. Thus, there was no evidence on these tasks for a selective decline with age in RH processing efficiency.

Lateralization for pure tone perception as a function of age and sex

Pure tone thresholds were obtained for right and left ears from 195 males and 82 females aged 24-84. Right ear advantages were present and increased with advanced age for the males; no ear differences were found for females. These data may explain contradictions in the dichotic listening literature testing lateralization for language across the lifespan.

Age differences in perceptual style, selective attention, and perceptual-motor reaction time

One hundred seventy-five females ranging in age from 17 to 72 years, who were placed into one of seven age groups, were administered tasks measuring perceptual style, selective attention, simple choice, and complex reaction time. Multivariate and univariate analysis indicated there were significant differences between the age groups for all dependent measures. Trends manifest in the data suggest significant declines on the investigated information-processing ability measures begin in the late-40's. This finding appears to indicate an over-all general decline on all information-processing variables rather than selective drop-out of abilities. Theoretical and applied implications of the results are discussed.

Decline of Immediate Recall with Age

Three hypotheses regarding decline of immediate recall with age were tested: (1) that chunking or receding efficiency declines with age, (2) that immediate recall declines more rapidly with age as the input sequence is lengthened, and (3) that order errors in recall increase with age because of slowness in identifying individual items as they are presented. The subjects (62 men, 106 women) were asked to recall word-pair strings that varied in length (2, 4, 6, and 8 words) and in type (associated and unassociated word pairs). Results indicated that chunking efficiency declines with age, and that immediate recall of 8-item word-strings declines more rapidly with age than does immediate recall of 6-item strings. Group differences with regard to order errors did not indicate a consistent increase of order errors with age.

A review of age changes in perceptual information processing ability with regard to driving

Age related changes in the sensory modalities of hearing and vision, along with changes in the information processing abilities of selective attention, perceptual style, and perceptual-motor reaction time, were reviewed in the context of driving behavior. Literature reported, indicated age related changes in these abilities have relevance for the understanding of the driving behavior of the older adult.