Aging and shifts of visual spatial attention

The modulation of expectation violation on attention: Evidence from the spatial cueing effects

The study sought to investigate whether and how expectation violation can modulate attention using the exogenous spatial cueing paradigm, under the theoretical framework of the Memory Encoding Cost (MEC) model. The MEC proposes that exogenous spatial cueing effects are mainly driven by a combination of two distinct mechanisms: attentional facilitation triggered by the presence of an abrupt cue, and attentional suppression induced by memory encoding of the cue. In current experiments, participants needed to identify a target letter that was sometimes preceded by a peripheral onset cue. Various types of expectation violation were introduced by regulating the probability of cue presentation (Experiments 1 & 5), the probability of cue location (Experiments 2 & 4), and the probability of irrelevant sound presentation (Experiment 3). The results showed that expectation violation could enhance the cueing effect (valid vs. invalid cue) in some cases. More crucially, all experiments consistently observed asymmetrical modulation of expectation violation on the cost (invalid vs. neutral cue) and benefit (valid vs. neutral cue) effects: Expectation violation increased the cost effects while did not modulate or decreased (or even reversed) the benefit effects. Furthermore, Experiment 5 provided direct evidence that violation of expectations could enhance the memory encoding of a cue (e.g., color) and this memory advantage could manifest quickly in the early stages of the experiment. The MEC better explains these findings than some traditional models like the spotlight: Expectation violation can both enhance the attentional facilitation of the cue and memory encoding of irrelevant cue information. These findings suggest that expectation violation has a general adaptive function in modulating the attention selectivity.

Overview of (f)MRI Studies of Cognitive Aging for Non-Experts: Looking through the Lens of Neuroimaging

This special issue concerning Brain Functional and Structural Connectivity and Cognition aims to expand our understanding of brain connectivity. Herein, I review related topics including the principle and concepts of functional MRI, brain activation, and functional/structural connectivity in aging for uninitiated readers. Visuospatial attention, one of the well-studied functions in aging, is discussed from the perspective of neuroimaging.

An awareness-dependent mapping of saliency in the human visual system

The allocation of exogenously cued spatial attention is governed by a saliency map. Yet, how salience is mapped when multiple salient stimuli are present simultaneously, and how this mapping interacts with awareness remains unclear. These questions were addressed here using either visible or invisible displays presenting two foreground stimuli (whose bars were oriented differently from the bars in the otherwise uniform background): a high salience target and a distractor of varied, lesser salience. Interference, or not, by the distractor with the effective salience of the target served to index a graded or non-graded nature of salience mapping, respectively. The invisible and visible displays were empirically validated by a two-alternative forced choice test (detecting the quadrant of the target) demonstrating subjects' performance at or above chance level, respectively. By combining psychophysics, fMRI, and effective connectivity analysis, we found a graded distribution of salience with awareness, changing to a non-graded distribution without awareness. Crucially, we further revealed that the graded distribution was contingent upon feedback from the posterior intraparietal sulcus (pIPS, especially from the right pIPS), whereas the non-graded distribution was innate to V1. Together, this awareness-dependent mapping of saliency reconciles several previous, seemingly contradictory findings regarding the nature of the saliency map.

Aging and Inhibition of Return to Locations and Objects

Inhibition of return (IOR) is thought to reflect a cognitive mechanism that biases attention from returning to previously engaged items. While models of cognitive aging have proposed deficits within select inhibitory domains, older adults have demonstrated preserved IOR functioning in previous studies. The present study investigated whether inhibition associated with objects shows the same age patterns as inhibition associated with locations. Young adults (18-22 years) and older adults (60-86 years) were tested in two experiments measuring location- and object-based IOR. Using a dynamic paradigm (Experiment 1), both age groups produced significant location-based IOR, but only young adults produced significant object-based IOR, consistent with previous findings. However, with a static paradigm (Experiment 2), young adults and older adults produced both location- and object-based IOR, indicating that object-based IOR is preserved in older adults under some conditions. The findings provide partial support for unique age-related inhibitory patterns associated with attention to objects and locations.

Irrelevant task suppresses the N170 of automatic attention allocation to fearful faces

Recent researches have provided evidence that stimulus-driven attentional bias for threats can be modulated by top-down goals. However, it is highlight essential to indicate whether and to what extent the top-down goals can affect the early stage of attention processing and its early neural mechanism. In this study, we collected electroencephalographic data from 28 healthy volunteers with a modified spatial cueing task. The results revealed that in the irrelevant task, there was no significant difference between the reaction time (RT) of the fearful and neutral faces. In the relevant task, we found that RT of fearful faces was faster than that of neutral faces in the valid cue condition, whereas the RT of fearful faces was slower than that of neutral faces in the invalid cue condition. The N170 component in our study showed a similar result compared with RT. Specifically, we noted that in the relevant task, fearful faces in the cue position of the target evoked a larger N170 amplitude than neutral faces, whereas this effect was suppressed in the irrelevant task. These results suggest that the irrelevant task may inhibit the early attention allocation to the fearful faces. Furthermore, the top-down goals can modulate the early attentional bias for threatening facial expressions.

Crossmodal spatial distraction across the lifespan

The ability to resist distracting stimuli whilst voluntarily focusing on a task is fundamental to our everyday cognitive functioning. Here, we investigated how this ability develops, and thereafter declines, across the lifespan using a single task/experiment. Young children (5-7 years), older children (10-11 years), young adults (20-27 years), and older adults (62-86 years) were presented with complex visual scenes. Endogenous (voluntary) attention was engaged by having the participants search for a visual target presented on either the left or right side of the display. The onset of the visual scenes was preceded - at stimulus onset asynchronies (SOAs) of 50, 200, or 500 ms - by a task-irrelevant sound (an exogenous crossmodal spatial distractor) delivered either on the same or opposite side as the visual target, or simultaneously on both sides (cued, uncued, or neutral trials, respectively). Age-related differences were revealed, especially in the extreme age-groups, which showed a greater impact of crossmodal spatial distractors. Young children were highly susceptible to exogenous spatial distraction at the shortest SOA (50 ms), whereas older adults were distracted at all SOAs, showing significant exogenous capture effects during the visual search task. By contrast, older children and young adults' search performance was not significantly affected by crossmodal spatial distraction. Overall, these findings present a detailed picture of the developmental trajectory of endogenous resistance to crossmodal spatial distraction from childhood to old age and demonstrate a different efficiency in coping with distraction across the four age-groups studied.

Predictivity and Manifestation Factors in Aging Effects on the Orienting of Spatial Attention

OBJECTIVE

Prior attention research has asserted that endogenous orienting of spatial attention by willful focusing may be differently influenced by aging than exogenous orienting, the capture of attention by external cues. However, most such studies confound factors of manifestation (locational vs symbolic cues) and the predictivity of cues. We therefore investigated whether age effects on orienting are mediated by those factors.

METHOD

We measured accuracy and response times of groups of younger and older adults in a discrimination task with flanker distracters, under three spatial cueing conditions: nonpredictive locational cues, predictive symbolic cues, and a hybrid predictive locational condition.

RESULTS

Age differences were found to be related to the factor of cue predictivity, but not to the factor of spatial manifestation. These differences were not modulated by flanker congruency.

DISCUSSION

The results indicate that the orienting of spatial attention in healthy aging may be adversely affected by less effective perception or utilization of the predictive value of cues, but not by the requirement to voluntarily execute a shift of attention.

Normative data of neuropsychological tests of attention and executive functions in Ecuadorian adult population

OBJECTIVE

The purpose of this study was to generate normative data for five tests of attention and executive functions (M-WCST, Stroop test, TMT, BTA, and SDMT), in a group of 322 Ecuadorian adults from Quito between the ages of 18 and 85.

METHOD

Multiple regression analyzes taking into account age, education, and gender were used to generate the normative data.

RESULTS

Age and education were significantly related to test performance such that scores decreased with age and improved as a function of education. An online calculator is provided to generate normative test scores.

CONCLUSIONS

This is the first study that presents normative data for tests of executive functions and attention in an Ecuadorian adult population. This data will improve the clinical practice of neuropsychology and help to develop the field in the country.

Visual attention, biological motion perception, and healthy ageing

Biological motion perception is the ability of the visual system to perceive complex human movement patterns. The previous studies have shown a direct link between attentional abilities and performance on biological motion tasks, both of which have been shown to deteriorate with age. However, it is not known whether there is a direct link between age-related deficits in biological motion processing and attention. Here, we investigated whether age-related changes in biological motion perception are mediated by impaired attentional abilities. To assess basic biological motion performance, we asked 42 younger (M = 21 years) and 39 older adults (M = 69 years) to indicate the facing direction of point-light actions. Performance did not differ between age groups. We assessed visual spatial and selective attentional abilities, using a range of tasks: conjunctive visual search, spatial cueing, and the Stroop task. Across all tasks, older adults were significantly slower to respond and exhibited larger interference/cueing effects, compared to younger adults. To assess attentional demands in relation with biological motion perception, participants performed a biological motion search task for which they had to indicate the presence of a target point-light walker among a varied number of distracters. Older adults were slower, and generally worse than younger adults at discriminating the walkers. Correlations showed that there was no significant relationship between performance in attention tasks and biological motion processing, which indicates that age-related changes in biological motion perception are unlikely to be driven by general attentional decline.

The link between reading ability and visual spatial attention across development

Interacting with a cluttered and dynamic environment requires making decisions about visual information at relevant locations while ignoring irrelevant locations. Typical adults can do this with covert spatial attention: prioritizing particular visual field locations even without moving the eyes. Deficits of covert spatial attention have been implicated in developmental dyslexia, a specific reading disability. Previous studies of children with dyslexia, however, have been complicated by group differences in overall task ability that are difficult to distinguish from selective spatial attention. Here, we used a single-fixation visual search task to estimate orientation discrimination thresholds with and without an informative spatial cue in a large sample (N = 123) of people ranging in age from 5 to 70 years and with a wide range of reading abilities. We assessed the efficiency of attentional selection via the cueing effect: the difference in log thresholds with and without the spatial cue. Across our whole sample, both absolute thresholds and the cueing effect gradually improved throughout childhood and adolescence. Compared to typical readers, individuals with dyslexia had higher thresholds (worse orientation discrimination) as well as smaller cueing effects (weaker attentional selection). Those differences in dyslexia were especially pronounced prior to age 20, when basic visual function is still maturing. Thus, in line with previous theories, literacy skills are associated with the development of selective spatial attention.

Explicit and implicit timing in aging

Explicit and implicit measures of timing were compared between young and older participants. In both tasks, participants were initially familiarized with a reference interval by responding to the second of two beeps separated by a fixed interval. During the subsequent testing phase, this inter-stimulus interval was variable. In the explicit task, participants were instructed to judge interval duration, whereas in the implicit task they were told to respond as quickly as possible to the second beep. Cognitive abilities were assessed with neuropsychological tests. Results showed that in both explicit and implicit timing tasks, temporal performance peaked around the reference interval and did not differ between young and older participants. This indicates an accurate representation of duration that did not decline with normal aging. However, some age-related differences were observed in performance depending on the task used. In the explicit timing task, the variability of duration judgments was greater in older than young participants, though this was directly related to older participants' lower attentional capacity. In the implicit timing task, young participants' reaction times (RTs) were slower to targets appearing either earlier or later than the trained interval. Conversely, while older participants RTs were also slowed by early targets, their RTs to late targets were as fast as those to targets appearing at the trained interval. We hypothesize that with age, and irrespective of cognitive ability, there is increasing reliance on temporal information conveyed by the probability of target appearance as a function of elapsing time ("hazard function") than that conveyed by the statistical likelihood of previously experienced temporal associations.

Strategy variability in numerosity comparison task: a study in young and older adults

We investigated strategies used by young and older adults in dot comparison tasks to further our understanding of mechanisms underlying numerosity discrimination and age-related differences therein. The participants were shown a series of two dot collections and asked to select the largest collection. Analyses of verbal protocols collected on each trial, solution times, and percentages of errors documented the strategy repertoire and strategy distribution in young and older adults. Based on visual features of dot collections, both young and older adults used a set of 9 strategies and selected strategies on a trial-by-trial basis. The findings also documented age-related differences (i.e., strategy preferences) and similarities (e.g., number of strategies used by individuals) in strategies and performance. Strategy variability found here has important implications for understanding numerosity comparison and contrasts with previous findings suggesting that participants use a single strategy when they compare dot collections.

Value-driven attentional capture in neglect

OBJECTIVE

Recent studies suggest that motivational cues such as rewards may be a powerful determinant of attentional selection, both in healthy subjects and in brain-damaged patients suffering from neglect. However, the exact brain mechanisms underlying these effects and their relation to other well-known attentional systems are still poorly known.

METHODS

We designed a visual search paradigm to examine how value-based attentional priority could modulate spatial orienting in patients with pathological biases due to neglect after right hemispheric stroke. Targets were preceded by exogenous valid or invalid spatial cues, in the presence or absence of distractors that were associated with high reward values subsequent to an initial reinforcement training phase.

RESULTS

We found that the learned reward value of distractors interfered with spatial reorienting toward the left (neglected) side when neglect patients were invalidly cued to the right side. Moreover, the presence of reward-associated distractors in the contralesional field interfered most with the detection of task-relevant targets on the same side, and this interference was exaggerated with more severe neglect. Voxelwise anatomical lesion analysis indicated that damage to the right angular gyrus, as well as lateral occipital and inferior temporal areas of the right hemisphere, were associated with stronger value-driven attentional effects.

CONCLUSIONS

Visual stimuli previously associated with rewards receive higher attentional priority during visual search despite pathological spatial biases due to neglect, and thus interfere with orienting to contralesional targets, presumably by competing with top-down mechanisms controlling exogenous spatial attention. Reward signals may bias neural activity evoked by visual stimuli, independent of conscious control, through a common priority map integrating several different attentional influences. These results do not only provide novel insights to link spatial orienting and motivational signals within current models of attention, but also open new perspectives that may usefully be exploited for neurological rehabilitation strategies in patients suffering from attentional deficits and neglect.

Enhancing Spatial Attention and Working Memory in Younger and Older Adults

Daily experiences demand both focused and broad allocation of attention for us to interact efficiently with our complex environments. Many types of attention have shown age-related decline, although there is also evidence that such deficits may be remediated with cognitive training. However, spatial attention abilities have shown inconsistent age-related differences, and the extent of potential enhancement of these abilities remains unknown. Here, we assessed spatial attention in both healthy younger and older adults and trained this ability in both age groups for 5 hr over the course of 2 weeks using a custom-made, computerized mobile training application. We compared training-related gains on a spatial attention assessment and spatial working memory task to age-matched controls who engaged in expectancy-matched, active placebo computerized training. Age-related declines in spatial attention abilities were observed regardless of task difficulty. Spatial attention training led to improved focused and distributed attention abilities as well as improved spatial working memory in both younger and older participants. No such improvements were observed in either of the age-matched control groups. Note that these findings were not a function of improvements in simple response time, as basic motoric function did not change after training. Furthermore, when using change in simple response time as a covariate, all findings remained significant. These results suggest that spatial attention training can lead to enhancements in spatial working memory regardless of age.

Increased risk for age-related impairment in visual attention associated with mild traumatic brain injury: Evidence from saccadic response times

It was hypothesized that risk for age-related impairment in attention would be greater among those with remote history of mild TBI than individuals without history of head injury. Twenty-seven adults with remote history of mild TBI and a well-matched comparison group of 54 uninjured controls completed a computerized test of visual attention while saccadic and manual response times were recorded. Within the mild TBI group only, older age was associated with slower saccadic responses and poorer saccadic inhibition. Saccadic slowing was mitigated in situations where the timing and location of attention targets was fully predictable. Mild TBI was not associated with age-related increases in risk for neuropsychological impairment or neurobehavioral symptoms. These results provide preliminary evidence that risk for age-related impairment in visual attention may be higher among those with a history of mild TBI. Saccadic measures may provide enhanced sensitivity to this subtle form of cognitive impairment.

An Event-Related Potential Investigation of the Effects of Age on Alerting, Orienting, and Executive Function

The present study compared young and older adults on behavioral and neural correlates of three attentional networks (alerting, orienting, and executive control). Nineteen young and 16 older neurologically-healthy adults completed the Attention Network Test (ANT) while behavioral data (reaction time and error rates) and 64-channel event-related potentials (ERPs) were acquired. Significant age-related RT differences were observed across all three networks; however, after controlling for generalized slowing, only the alerting network remained significantly reduced in older compared with young adults. ERP data revealed that alerting cues led to enhanced posterior N1 responses for subsequent attentional targets in young adults, but this effect was weakened in older adults. As a result, it appears that older adults did not benefit fully from alerting cues, and their lack of subsequent attentional enhancements may compromise their ability to be as responsive and flexible as their younger counterparts. N1 alerting deficits were associated with several key neuropsychological tests of attention that were difficult for older adults. Orienting and executive attention networks were largely similar between groups. Taken together, older adults demonstrated behavioral and neural alterations in alerting, however, they appeared to compensate for this reduction, as they did not significantly differ in their abilities to use spatially informative cues to aid performance (e.g., orienting), or successfully resolve response conflict (e.g., executive control). These results have important implications for understanding the mechanisms of age-related changes in attentional networks.

Bistable perception in normal aging: perceptual reversibility and its relation to cognition

The effects of age on the ability to resolve perceptual ambiguity are unknown, though it depends on frontoparietal attentional networks known to change with age. We presented the bistable Necker cube to 24 middle-aged and OAs (older adults; 56-78 years) and 20 YAs (younger adults; 18-24 years) under passive-viewing and volitional control conditions: Hold one cube percept and Switch between cube percepts. During passive viewing, OAs had longer dominance durations (time spent on each percept) than YAs. In the Hold condition, OAs were less able than YAs to increase dominance durations. In the Switch condition, OAs and YAs did not differ in performance. Dominance durations in either condition correlated with performance on tests of executive function mediated by the frontal lobes. Eye movements (fixation deviations) did not differ between groups. These results suggest that OAs' reduced ability to hold a percept may arise from reduced selective attention. The lack of correlation of performance between Hold and executive-function measures suggests at least a partial segregation of underlying mechanisms.

Idiosyncratic responding during movie-watching predicted by age differences in attentional control

Much is known about how age affects the brain during tightly controlled, though largely contrived, experiments, but do these effects extrapolate to everyday life? Naturalistic stimuli, such as movies, closely mimic the real world and provide a window onto the brain's ability to respond in a timely and measured fashion to complex, everyday events. Young adults respond to these stimuli in a highly synchronized fashion, but it remains to be seen how age affects neural responsiveness during naturalistic viewing. To this end, we scanned a large (N = 218), population-based sample from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) during movie-watching. Intersubject synchronization declined with age, such that older adults' response to the movie was more idiosyncratic. This decreased synchrony related to cognitive measures sensitive to attentional control. Our findings suggest that neural responsivity changes with age, which likely has important implications for real-world event comprehension and memory.

Specificity of Age-Related Differences in Eye-Gaze Following: Evidence From Social and Nonsocial Stimuli

BACKGROUND

Eye-gaze following is a fundamental social skill, facilitating communication. The present series of studies explored adult age-related differences in this key social-cognitive ability.

METHOD

In Study 1 younger and older adult participants completed a cueing task in which eye-gaze cues were predictive or non-predictive of target location. Another eye-gaze cueing task, assessing the influence of congruent and incongruent eye-gaze cues relative to trials which provided no cue to target location, was administered in Study 2. Finally, in Study 3 the eye-gaze cue was replaced by an arrow.

RESULTS

In Study 1 older adults showed less evidence of gaze following than younger participants when required to strategically follow predictive eye-gaze cues and when making automatic shifts of attention to non-predictive eye-gaze cues. Findings from Study 2 suggested that, unlike younger adults, older participants showed no facilitation effect and thus did not follow congruent eye-gaze cues. They also had significantly weaker attentional costs than their younger counterparts. These age-related differences were not found in the non-social arrow cueing task.

DISCUSSION

Taken together these findings suggest older adults do not use eye-gaze cues to engage in joint attention, and have specific social difficulties decoding critical information from the eye region.

Reflexive orienting in response to short- and long-duration gaze cues in young, young-old, and old-old adults

Shifting visual focus on the basis of the perceived gaze direction of another person is one form of joint attention. In the present study, we investigated whether this socially relevant form of orienting is reflexive and whether it is influenced by age. Green and Woldorff (Cognition 122:96-101, 2012) argued that rapid cueing effects (i.e., faster responses to validly than to invalidly cued targets) were limited to conditions in which a cue overlapped in time with a target. They attributed slower responses following invalid cues to the time needed to resolve the incongruent spatial information provided by the concurrently presented cue and target. In the present study, we examined the orienting responses of young (18-31 years), young-old (60-74 years), and old-old (75-91 years) adults following uninformative central gaze cues that overlapped in time with the target (Exp. 1) or that were removed prior to target presentation (Exp. 2). When the cue and target overlapped, all three groups localized validly cued targets more quickly than invalidly cued targets, and validity effects emerged earlier for the two younger groups (at 100 ms post-cue-onset) than for the old-old group (at 300 ms post-cue-onset). With a short-duration cue (Exp. 2), validity effects developed rapidly (by 100 ms) for all three groups, suggesting that validity effects resulted from reflexive orienting based on the gaze cue information rather than from cue-target conflict. Thus, although old-old adults may be slow to disengage from persistent gaze cues, attention continues to be reflexively guided by gaze cues late in life.

Effect of attentional interference on balance recovery in older adults

Since most working memory (WM) tasks used in dual-task (DT) postural paradigms include both storage and processing of information, it is difficult to determine the extent to which each of these contributes to interference with balance control. In the current study, a change-detection task (changes in colored squares between two presentation events) that estimates visual working memory capacity (VWMC) was paired with tasks of increasing postural demand (stance, perturbation) in young adults (YAs) and older adults (OAs) and performance compared between the two postural conditions and across the two populations. The change-detection task was selected as it requires storage of information without updating or manipulation; 34 YAs, 34 OAs, and five frail OAs were recruited. A significant reduction in VWMC occurred with increasing postural demand during the perturbation condition for both YAs (p < 0.01) and OAs (p < 0.001). VWMC was also significantly lower for OAs than YAs in the control condition (1.8 ± 0.7 vs. 2.8 ± 0.6) (p < 0.001). OAs showed a significant increase in the number of trials in which steps or rise to toes occurred during recovery between single-task (ST) and DT (p < 0.05; p < 0.05). OAs also showed a significant increase in normalized tibialis anterior amplitude (p < 0.001) following perturbations. YAs showed an increase in normalized area under the center of pressure trajectory and in AP forces (nAcopx1: p < 0.001; nFap1: p < 0.05) during the DT condition.

The effects of healthy aging on mental imagery as revealed by egocentric and allocentric mental spatial transformations

Previous studies suggest that mental rotation can be accomplished by using different mental spatial transformations. When adopting the allocentric transformation, individuals imagine the stimulus rotation referring to its intrinsic coordinate frame, while when adopting the egocentric transformation they rely on multisensory and sensory-motor mechanisms. However, how these mental transformations evolve during healthy aging has received little attention. Here we investigated how visual, multisensory, and sensory-motor components of mental imagery change with normal aging. Fifteen elderly and 15 young participants were asked to perform two different laterality tasks within either an allocentric or an egocentric frame of reference. Participants had to judge either the handedness of a visual hand (egocentric task) or the location of a marker placed on the left or right side of the same visual hand (allocentric task). Both left and right hands were presented at various angular departures to the left, the right, or to the center of the screen. When performing the egocentric task, elderly participants were less accurate and slower for biomechanically awkward hand postures (i.e., lateral hand orientations). Their performance also decreased when stimuli were presented laterally. The findings revealed that healthy aging is associated with a specific degradation of sensory-motor mechanisms necessary to accomplish complex effector-centered mental transformations. Moreover, failure to find a difference in judging left or right hand laterality suggests that aging does not necessarily impair non-dominant hand sensory-motor programs.

Sustained attention in the elderly: what do we know and what does it tell us about cognitive aging?

The ability to achieve and maintain the focus of cognitive activity on a given stimulation source or task, in other words to sustain attention or vigilance, is a fundamental component of human cognition. Given the omnipresent need for sustained attention in people's daily lives, a precise knowledge of the effects of normal aging on sustained attention is crucial. Findings in this topic are currently not consistent since they highlight either alteration or preservation or even the two, depending on the experimental approach used. Actually, the two existing approaches do not involve bottom-up and top-down processes at the same extent, which may in part account for this inconclusiveness. This review presents and attempts to explain these results by putting them into perspective with our current knowledge on cognitive aging and the two competing vigilance decrement theories, and discusses how they could inform us on our problems with sustaining attention over time.

The effect of multisensory cues on attention in aging

The attention network test (ANT) assesses the effect of alerting and orienting cues on a visual flanker task measuring executive attention. Previous findings revealed that older adults demonstrate greater reaction times (RT) benefits when provided with visual orienting cues that offer both spatial and temporal information of an ensuing target. Given the overlap of neural substrates and networks involved in multisensory processing and cueing (i.e., alerting and orienting), an investigation of multisensory cueing effects on RT was warranted. The current study was designed to determine whether participants, both old and young, benefited from receiving multisensory alerting and orienting cues. Eighteen young (M=19.17 years; 45% female) and eighteen old (M=76.44 years; 61% female) individuals that were determined to be non-demented and without any medical or psychiatric conditions that would affect their performance were included. Results revealed main effects for the executive attention and orienting networks, but not for the alerting network. In terms of orienting, both old and young adults demonstrated significant orienting effects for auditory-somatosensory (AS), auditory-visual (AV), and visual-somatosensory (VS) cues. RT benefits of multisensory compared to unisensory orienting effects differed by cue type and age group; younger adults demonstrated greater RT benefits for AS orienting cues whereas older adults demonstrated greater RT benefits for AV orienting cues. Both groups, however, demonstrated significant RT benefits for multisensory VS orienting cues. These findings provide evidence for the facilitative effect of multisensory orienting cues, and not multisensory alerting cues, in old and young adults.

Timing of reflexive visuospatial orienting in young, young-old, and old-old adults

This study examined adult age differences in reflexive orienting to two types of uninformative spatial cues: central arrows and peripheral onsets. In two experiments using a Posner cuing task, young adults (ages 18-28 years), young-old adults (60-74 years), and old-old adults (75-92 years) responded to targets that were preceded 100-1,000 ms earlier by a central arrow or a peripheral abrupt onset. In Experiment 1, the cue remained present upon target onset. Facilitation effects at short cue-target stimulus onset asynchronies (SOAs) were prolonged in duration for the two older groups relative to the young adults. At longer cue-target SOAs, inhibition of return (IOR) that was initiated by peripheral onset cues was observed in the performance of young adults but not in that of the two older groups. In Experiment 2, the cue was presented briefly and removed prior to target onset. The change in cue duration minimized age differences (particularly for young-old adults) in facilitation effects and led to IOR for all three age groups. The findings are consistent with the idea that attentional control settings change with age, with higher settings for older adults leading to delayed disengagement from spatial cues.

Repeated Measurement of the Components of Attention of Older Adults using the Two Versions of the Attention Network Test: Stability, Isolability, Robustness, and Reliability

Ishigami and Klein (2010) showed that scores of the three attention networks (alerting, orienting, and executive control) measured with the two versions of the Attention Network Test (ANT; Fan et al., 2002; Callejas et al., 2005) were robust over 10 sessions of repeated testing even though practice effects were consistently observed especially in the executive network when young adults were tested. The current study replicated their method to examine robustness, stability, reliability, and isolability of the networks scores when older adults were tested with these ANTs. Ten test sessions, each containing two versions of the ANT, were administered to 10 older adults. Participants were asked to indicate the direction of a target arrow, flanked by distractors, presented either above or below the fixation following auditory signals or/and visual cue. Network scores were calculated using orthogonal subtractions of performance in selected conditions. All network scores remained highly significant even after nine previous sessions despite some practice effects in the executive and the alerting networks. Some lack of independence among the networks was found. The relatively poor reliability of network scores with one session of data rises to respectable levels as more data is added.

Alerting, orienting, and executive attention in older adults

The Attention Network Test (ANT) assesses alerting, orienting, and executive attention. The current study was designed to achieve three main objectives. First, we determined the reliability, effects, and interactions of attention networks in a relatively large cohort of non-demented older adults (n = 184). Second, in the context of this aged cohort, we examined the effect of chronological age on attention networks. Third, the effect of blood pressure on ANT performance was evaluated. Results revealed high-reliability for the ANT as a whole, and for specific cue and flanker types. We found significant main effects for the three attention networks as well as diminished alerting but enhanced orienting effects during conflict resolution trials. Furthermore, increased chronological age and low blood pressure were both associated with significantly worse performance on the executive attention network. These findings are consistent with executive function decline in older adults and the plausible effect of reduced blood flow to the frontal lobes on individual differences in attention demanding tasks.

Aging and Shifts of Visual Attention in Saccadic Eye Movements

The authors examined age-related differences in target discrimination before the saccade to investigate the influence of aging on the facilitation of target discrimination by shifts of attention. Older and younger adults made saccades toward a peripheral stimulus after its onset and discriminated the orientation of the stimulus. Mean saccadic latency was greater for older adults than for younger adults. Facilitation of target discrimination immediately before the saccades was found both in older and younger adults. These results suggest that aging affects the properties of saccades but does not affect the properties of attentional shifts immediately before a saccade.

Age-related declines in car following performance under simulated fog conditions

The present study examined age-related differences in car following performance when contrast of the driving scene was reduced by simulated fog. Older (mean age of 72.6) and younger (mean age of 21.1) drivers were presented with a car following scenario in a simulator in which a lead vehicle (LV) varied speed according to a sum of three sine wave functions. Drivers were shown an initial following distance of 18 m and were asked to maintain headway distance by controlling speed to match changes in LV speed. Five simulated fog conditions were examined ranging from a no fog condition (contrast of 0.55) to a high fog condition (contrast of 0.03). Average LV speed varied across trials (40, 60, or 80 km/h). The results indicated age-related declines in car following performance for both headway distance and RMS (root mean square) error in matching speed. The greatest decline occurred at moderate speeds under the highest fog density condition, with older drivers maintaining a headway distance that was 21% closer than younger drivers. At higher speeds older drivers maintained a greater headway distance than younger drivers. These results suggest that older drivers may be at greater risk for a collision under high fog density and moderate speeds.

Predictive knowledge of stimulus relevance does not influence top-down suppression of irrelevant information in older adults

Our ability to focus attention on task-relevant stimuli and ignore irrelevant distractions is reflected by differential enhancement and suppression of neural activity in sensory cortices. Previous research has shown that older adults exhibit a deficit in suppressing task-irrelevant information, the magnitude of which is associated with a decline in working memory performance. However, it remains unclear if a failure to suppress is a reflection of an inability of older adults to rapidly assess the relevance of information upon stimulus presentation when they are not aware of the relevance beforehand. To address this, we recorded the electroencephalogram (EEG) in healthy older participants (aged 60-80 years) while they performed two different versions of a selective face/scene working memory task, both with and without prior knowledge as to when relevant and irrelevant stimuli would appear. Each trial contained two faces and two scenes presented sequentially followed by a 9 sec delay and a probe stimulus. Participants were given the following instructions: remember faces (ignore scenes), remember scenes (ignore faces), remember the xth and yth stimuli (where x and y could be 1st, 2nd, 3rd or 4th), or passively view all stimuli. Working memory performance remained consistent regardless of task instructions. Enhanced neural activity was observed at posterior electrodes to attended stimuli, while neural responses that reflected the suppression of irrelevant stimuli was absent for both tasks. The lack of significant suppression at early stages of visual processing was revealed by P1 amplitude and N1 latency modulation indices. These results reveal that prior knowledge of stimulus relevance does not modify early neural processing during stimulus encoding and does not improve working memory performance in older adults. These results suggest that the inability to suppress irrelevant information early in the visual processing stream by older adults is related to mechanisms specific to top-down suppression.

Age differences in mental scanning of locomotor maps

PURPOSE

To investigate whether the metric quality of mental spatial representations of the environment changes with aging, by means of mental scanning of locomotor space.

METHOD

Twenty young adults (age 21.1-30.8) and 20 old adults (age 60.4-76.4) were submitted to a battery of psychometric tests to assess the effects of aging on general cognitive functions and specific visuo-spatial abilities, and to determine which cognitive factors correlated with scanning performance. The mental scanning task followed. Participants firstly had to learn a path comprising six positions by walking and observing these; secondly, they had to use mental imagery to scan from a first to a second position, according to different distances.

RESULTS

Aging reduces the validity of the metric information incorporated by mental spatial representations. Attentional and working memory resources, ability to manipulate spatial information and a general factor of abstract visuo-spatial reasoning strongly correlated with scanning performance. Finally, aging seemed to have a selective effect on cognitive functioning.

CONCLUSIONS

Age differences emerge when demanding storage and processing of information are simultaneously required, as predicted by the Limited Resources view of aged cognition.

Age-related changes in early novelty processing as measured by ERPs

This study investigated age-related changes in the early processing of novel visual stimuli using ERPs. Well-matched old (n=30), middle-aged (n=30), and young (n=32) subjects were presented standard, target/rare, and perceptually novel visual stimuli under Attend and Ignore conditions. Our results suggest that the anterior P2 component indexes the motivational salience of a stimulus as determined by either task relevance or novelty. Its enhancement by focused attention does not decrease with age. Its responsiveness to novel stimuli is particularly striking in older adults. The age-related increase in the anterior P2 to novel visual stimuli does not appear to be due to impaired inhibitory control associated with aging. Rather, the enhanced anterior P2 to novel stimuli in older adults may be linked to age-related changes in the process of matching unusual visual stimuli to stored representations, which is indexed by the temporally overlapping anterior N2 component whose amplitude substantially decreases with age.

The effect of age on auditory spatial attention in conditions of real and simulated spatial separation

The contributions of auditory and cognitive factors to age-dependent differences in auditory spatial attention were investigated. In conditions of real spatial separation, the target sentence was presented from a central location and competing sentences were presented from left and right locations. In conditions of simulated spatial separation, different apparent spatial locations of the target and competitors were induced using the precedence effect. The identity of the target was cued by a callsign presented either prior to or following each target sentence, and the probability that the target would be presented at the three locations was specified at the beginning of each block. Younger and older adults with normal hearing sensitivity below 4 kHz completed all 16 conditions (2-spatial separation method X 2-callsign conditions X 4-probability conditions). Overall, younger adults performed better than older adults. For both age groups, performance improved with target location certainty, with a priori target cueing, and when location differences were real rather than simulated. For both age groups, the contributions of natural spatial cues were most pronounced when the target occurred at "unlikely" spatial listening locations. This suggests that both age groups benefit similarly from richer acoustical cues and a priori information in difficult listening environments.

Comparing temporal order judgments and choice reaction time tasks as indices of exogenous spatial cuing

Attentional disorders are common in individuals with neurological or psychiatric conditions and impact on recovery and outcome. Thus, it is critical to develop theory-based measures of attentional function to understand potential mechanisms underlying the disorder and to evaluate the effect of intervention. The present study compared two alternative methods to measure the effects of attentional cuing that could be used in populations of individuals who may not be able to make manual responses normally or may show overall slowing in responses. Spatial attention was measured with speeded and unspeeded methods using either manual or voice responses in two standard attention paradigms: the cued target discrimination reaction time (RT) paradigm and the unspeeded temporal order judgment (TOJ) task. The comparison of speeded and unspeeded tasks specifically addresses the concern about interpreting RT differences between cued and uncued trials (taken as a proxy for attention) in the context of drastically different baseline RTs. We found significant cuing effects for both tasks (speeded RT and untimed TOJ) and both response types (vocal and manual) giving clinicians and researchers alternative methods with which to measure the effects of attention in different populations who may not be able to perform the standard speeded RT task.

Effects of aging on voluntary and involuntary shifts of attention

This experiment examined adult age differences in the speed and accuracy of voluntary and involuntary shifts of visual attention. Younger and older adults performed two spatial cuing tasks using central cues and abrupt onset peripheral cues presented at stimulus onset asynchronies (SOAs) of 100, 150, 200, 250, and 300 ms. Analyses of the magnitudes of cuing effects revealed a similar time course for younger and older adults in the central cue condition, but not in the peripheral condition. Analyses of the Brinley plot for central cues across cue validity conditions indicated that as much as 93% of the variance could be attributed to age-related general slowing rather than to differential aging of a specific visual orienting mechanism.

Age-Related Changes and the Attention Network Task: An Examination of Alerting, Orienting, and Executive Function

The effects of aging on alerting, orienting, and executive function were examined with the use of the Attention Network Task, which combines the Posner spatial cuing task and the Eriksen flanker task into a single procedure. We found that older adults showed significantly less alerting than young adults in response to a warning cue, although there were no age differences in orienting or executive function once processing speed was taken into account. We suggest that age differences in alerting may depend in part upon the presentation duration or persistence of the warning cue.

Age-related changes in brain activation during a delayed item recognition task

To test competing models of age-related changes in brain functioning (capacity limitation, neural efficiency, compensatory reorganization, and dedifferentiation), young (n=40; mean age=25.1 years) and elderly (n=18; mean age=74.4 years) subjects performed a delayed item recognition task for visually presented letters with three set sizes (1, 3, or 6 letters) while being scanned with BOLD fMRI. Spatial patterns of brain activity corresponding to either the slope or y-intercept of fMRI signal with respect to set size during memory set encoding, retention delay, or probe stimulus presentation trial phases were compared between elder and young populations. Age effects on fMRI slope during encoding and on fMRI y-intercept during retention delay were consistent with neural inefficiency; age effects on fMRI slope during retention delay were consistent with dedifferentiation. None of the other fMRI signal components showed any detectable age effects. These results suggest that, even within the same task, the nature of brain activation changes with aging can vary based on cognitive process engaged.

Interactions Between Phasic Alerting and Spatial Orienting: Effects of Normal Aging and Alzheimer's Disease

The effects of aging and Alzheimer's disease (AD) on phasic alerting and exogenous spatial orienting were examined within a single precuing task. Phasic alerting decreased with normal aging and was completely eliminated with AD. AD patients also demonstrated an increased spatial orienting effect, attributable to an increased benefit from spatial orienting that was associated with a decreased benefit from nonselective alerting. These results suggest that performance within the precuing paradigm reflects the product of an interaction between nonselective alerting processes and spatially selective orienting processes. The results also highlight the importance of simultaneously assessing alerting and orienting within the same task, because changes attributable to alerting may otherwise be attributed incorrectly to changes in 1 or more processes associated with spatial orienting.

Age, skill, and contextual cuing in target detection

This study examined the extent to which structural regularities inherent in visual arrays help to guide target detection and reduce age-related differences in skilled visual search performance. The target-detection performance of medical laboratory technologists in 2 age groups (M = 24.3 years and M = 49.0 years) and age-matched novices was assessed using images of bacterial morphology taken from Gram's stain photomicrographs as targets and search arrays. For skilled observers, response times were longer for middle-aged adults than for young adults except when external location cues were available, or when contextual cues inherent in the array were available to guide target detection. These results demonstrate that contextual information aids the skilled search of middle-aged experts, and suggest that contextual cuing is 1 means by which middle-aged adults can circumvent the effects of normally age-deficient processes on performance in a skilled domain.