Attentional networks in normal aging and Alzheimer's disease

Decreased functional connectivity and structural deficit in alertness network with right-sided temporal lobe epilepsy

Patients with temporal lobe epilepsy (TLE) often suffer from alertness alterations. However, specific regions connected with alertness remain controversial, and whether these regions have structural impairment is also elusive. This study aimed to investigate the characteristics and neural mechanisms underlying the functions and structures of alertness network in patients with right-sided temporal lobe epilepsy (rTLE) by performing the attentional network test (ANT), resting-state functional magnetic resonance imaging (R-SfMRI), and diffusion tensor imaging (DTI).A total of 47 patients with rTLE and 34 healthy controls underwent ANT, R-SfMRI, and DTI scan. The seed-based functional connectivity (FC) method and deterministic tractography were used to analyze the data.Patients with rTLE had longer reaction times in the no-cue and double-cue conditions. However, no differences were noted in the alertness effect between the 2 groups. The patient group had lower FC compared with the control group in the right inferior parietal lobe (IPL), amygdala, and insula. Structural deficits were found in the right parahippocampal gyrus, superior temporal pole, insula, and amygdala in the patient group compared with the control group. Also significantly negative correlations were observed between abnormal fractional anisotropy (between the right insula and the superior temporal pole) and illness duration in the patients with rTLE.The findings of this study suggested abnormal intrinsic and phasic alertness, decreased FC, and structural deficits within the alerting network in the rTLE. This study provided new insights into the mechanisms of alertness alterations in rTLE.

Reduced distractor interference during vagus nerve stimulation

Suppressing irrelevant information in decision making is an essential everyday skill. We studied whether this ability could be improved in epileptic patients during vagus nerve stimulation (VNS). VNS is known to increase norepinephrine (NE) in the brain. NE is thought to improve several aspects of cognitive control, including the suppression of irrelevant information. Nineteen epileptic VNS patients executed the Eriksen flanker task twice, both during on and off stimulation. Distractor interference was indexed by the congruency effect, a standard empirical marker of cognitive control. We found a reduced congruency effect during stimulation, which indicates an improved ability to suppress distractor interference. This effect was only found in patients that are clinically determined VNS-responders (n = 10). As VNS increases NE in VNS-responders, our finding suggests a beneficial role of NE in cognitive control. At the same time, it suggests that VNS does not only reduce seizure frequency in epileptic patients, but also improves cognitive control.

Competition among the attentional networks due to resource reduction in Tibetan indigenous residents: evidence from event-related potentials

This study used the attention network test (ANT) to evaluate the alerting, orienting, and executive network efficiencies of attention related to indigenous residents who were born and raised until early adulthood in different high-altitude areas (2900-m, 3700-m, and 4200-m) at the same location (3700-m) where these residents had been living for approximately 2 years in Tibet. We further applied the event-related potential (ERP) method to identify the underlying neurophysiological basis. Based on the ANT, we found that, in the 4200-m residents, executive function was increased but the orienting function was decreased, and the executive and orienting network scores were oppositely correlated. The behavioral findings were supported by the ERP data, showing that the P3 amplitude changes indicated that the executive function was over-active under conflict conditions and that the N1 amplitude change indicated a decreased orienting function in the 4200-m residents. In addition, the changed P3 amplitudes were significantly correlated with intelligence performance across the residents only in the 4200-m group. The present study provided evidence for competition among the attentional networks due to high-altitude exposure in indigenous residents, and showed the existence of a threshold of the influence of high altitudes on attentional function in the brain.

Effects of age on inhibitory control are affected by task-specific features

Older adults have been argued to have impoverished inhibitory control compared to younger adults. However, these effects of age may depend on processing speed and their manifestation may furthermore depend on the type of inhibitory control task that is used. We present two experiments that examine age effects on inhibition across three tasks: a Simon arrow, static flanker and motion flanker task. The results showed overall slower reaction times (RTs) for older adults on all three tasks. However, effects of age on inhibition costs were only found for the Simon task, but not for the two flanker tasks. The motion flanker task furthermore showed an effect of baseline processing speed on the relation between age and inhibition costs. Older adults with slower baseline responses showed smaller inhibition costs, suggesting they were affected less by the flanker items than faster older adults. These findings suggest that effects of age on inhibition are task dependent and can be modulated by task-specific features such as the type of interference, type of stimuli and processing speed.

Beyond a Differential Diagnosis: Cognitive and Morphometric Decoding of Information Processing Speed in Senior Adults with DSM-5 Mild Neurocognitive Disorders

BACKGROUND

Processing speed has been highlighted as a diagnostic item for neurocognitive disorders (NCD) in DSM-5. The utility of information processing speed (IPS) enclosed with multiscale constructs in the diagnosis of NCD warrants exploration.

OBJECTIVE

We aimed to investigate the IPS with two types of measurements in the patients with NCD due to vascular disease (NCD-vascular) and NCD due to Alzheimer's disease (NCD-AD), and examine the associations between IPS measures and morphometric features.

METHODS

The IPS was evaluated using trail making test (TMT) and flanker test (n = 204). Direct scores, derived scores, and reaction time (RT) were used as IPS measures. Further, surface-based morphometry cortical volume was calculated in a subsample (n = 44) with structural MRI data.

RESULTS

All IPS measures showed a significant value to differentiate NCD patients from healthy subjects. Only mean RT could distinguish NCD-AD from NCD-vascular groups. TMT-B score and difference score were correlated with gray matter volume (GMV) of inferior frontal gyrus, precuneus and superior temporal cortex. Mean RT was associated with the GMV of post-central gyrus (r = -0.327, p = 0.035), and executive speed was associated with inferior frontal cortex (r = -0.475, p = 0.001), cingulate gyrus (r = -0.497, p = 0.001), and superior temporal gyrus (r = -0.36, p = 0.019).

CONCLUSION

The cognitive and morphometric correlates of IPS measures indicate that complex IPS might be decomposed into the domain-specific components with corresponding neural underpinnings. Our findings may also provide essential insights into the diagnostic item of NCD.

The P3 Parietal-To-Frontal Shift Relates to Age-Related Slowing in a Selective Attention Task

Abstract. Older adults recruit relatively more frontal as compared to parietal resources in a variety of cognitive and perceptual tasks. It is not yet clear whether this parietal-to-frontal shift is a compensatory mechanism, or simply reflects a reduction in processing efficiency. In this study we aimed to investigate how the parietal-to-frontal shift with aging relates to selective attention. Fourteen young and 26 older healthy adults performed a color Flanker task under three conditions (incongruent, congruent, neutral) and event-related potentials (ERPs) were measured. The P3 was analyzed for the electrode positions Pz, Cz, and Fz as an indicator of the parietal-to-frontal shift. Further, behavioral performance and other ERP components (P1 and N1 at electrodes O1 and O2; N2 at electrodes Fz and Cz) were investigated. First young and older adults were compared. Older adults had longer response times, reduced accuracy, longer P3 latencies, and a more frontal distribution of P3 than young adults. These results confirm the parietal-to-frontal shift in the P3 with age for the selective attention task. Second, based on the differences between frontal and parietal P3 activity the group of older adults was subdivided into those showing a rather equal distribution of the P3 and older participants showing a strong frontal focus of the P3. Older adults with a more frontally distributed P3 had longer response times than participants with a more equally distributed P3. These results suggest that the frontally distributed P3 observed in older adults has no compensatory function in selective attention but rather indicates less efficient processing and slowing with 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.

Efficiency of Attentional Components in Elderly with Mild Neurocognitive Disorders Shown by the Attention Network Test

AIMS

Complex attention, serving as a main diagnostic item of mild neurocognitive disorders (NCD), has been reported to be susceptible to pathological ageing. This study aimed to evaluate the attention network functions in older adults with subtypes of NCD.

METHODS

36 adults with NCD due to Alzheimer's disease (NCD-AD), 31 adults with NCD due to vascular disease (NCD-vascular) and 137 healthy controls were recruited. Attention Network Test (ANT) was conducted to assess the efficiency of alerting, orienting and executive control.

RESULTS

Significant between-group differences were found in executive control (conventional score: F = 11.472, p < 0.001; ratio score: F = 8.430, p < 0.001) and processing speed (F = 4.958, p = 0.008). NCD subgroups demonstrated poorer performance on the ANT, particularly on executive control (healthy 59.9 ± 45.9, NCD-vascular 88.9 ± 44.8, NCD-AD 97.0 ± 53.9). Moreover, the NCD-AD group showed both less efficient executive control and prominent slowing processing speed (reaction time: healthy 687.5 ± 106.0 ms, NCD-vascular 685.3 ± 97.1 ms, NCD-AD 750.6 ± 132.6 ms).

CONCLUSIONS

The NCD-vascular group appeared to be less efficient in executive control, while the NCD-AD group demonstrated less effective executive control and also slower processing speed. These results suggest that the characterized performance of ANT, processing speed and executive control in particular, might help differentiate adults at risk of different forms of cognitive impairment.

Alzheimer's Disease: Prototype of Cognitive Deterioration, Valuable Lessons to Understand Human Cognition

It is important for neurologists to become more familiar with neuropsychological evaluation for Alzheimer disease. The growth of this method in research, as an available, inexpensive, and noninvasive diagnostic approach, which can be administered even by non-specialist-trained examiners, makes this knowledge more necessary than ever. Such knowledge has a basic role in planning national programs in primary health care systems for prevention and early detection of Alzheimer disease. This is more crucial in developing countries, which have higher rates of dementia prevalence along with cardiovascular risk factors, lack of public knowledge about dementia, and limited social support. In addition compared to the neurological hard signs which are tangible and measurable, the concept of cognition seems to be more difficult for the neurologists to evaluate and for the students to understand. Dementia in general and Alzheimer's disease as the prototype of cognitive disorders specifically, play an important role to explore all domains of human cognition through its symptomatology and neuropsychological deficits.

Functional-structural degeneration in dorsal and ventral attention systems for Alzheimer's disease, amnestic mild cognitive impairment

Growing evidence of attention related failures in patients with amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD) has already been proposed by previous studies. However, previous studies lacked of systematic investigation on the functional and structural substrates for attention function for patients with AD and aMCI. In this work, we investigated the functional connectivity and gray matter density in dorsal and ventral attention networks (DAN, VAN) of normal participants (n = 15) and patients with aMCI (n = 12) and AD (n = 16) by applying group independent component analysis (ICA) and voxel-based morphometry (VBM) analysis. Using ICA, we extracted the functional patterns of DAN and VAN which are respectively responsible for the "top-down" attention process and "bottom-up" process. One-way analysis of variance (ANOVA) revealed significant group-differed functional connectivity in bilateral frontal eye fields (FEF) area and intraparietal sulcus (IPS) area, as well as posterior cingulate cortex and precuneus in the dorsal system. With regard to the ventral system, group-effects were significantly focused in right orbital superior/middle frontal gyrus, right inferior parietal lobule, angular gyrus, and supramarginal gyrus around the temporal-parietal junction area. Post hoc cluster-level comparisons revealed totally impaired functional substrates for both attentional networks for patients with AD, whereas selectively impaired attention systems for patients with aMCI with impaired functional patent of DAN but preserved functional pattern of VAN. Correspondingly, VBM analysis revealed gray matter loss in right ventral and dorsal frontal cortex was in the AD group, whereas preserved gray matter density was in aMCI, even a little extent of expansion of gray matter density in several participants. Using multivariate regression analysis we found discrepant couplings of functional-structural degenerations between both patient groups. Specifically, positive coupling of structural-functional degeneration was found in right dorsal and ventral frontal cortex in the AD group, whereas inverse coupling in dorsal frontal cortex was found in the aMCI group. These findings suggested discrepant functional-structural degenerations in both attention systems between both patient groups, widening avenues to better understanding the attentional deficits in patients with aMCI and AD.

Measuring the Performance of Attention Networks with the Dalhousie Computerized Attention Battery (DalCAB): Methodology and Reliability in Healthy Adults

Attention is an important, multifaceted cognitive domain that has been linked to three distinct, yet interacting, networks: alerting, orienting, and executive control. The measurement of attention and deficits of attention within these networks is critical to the assessment of many neurological and psychiatric conditions in both research and clinical settings. The Dalhousie Computerized Attention Battery (DalCAB) was created to assess attentional functions related to the three attention networks using a range of tasks including: simple reaction time, go/no-go, choice reaction time, dual task, flanker, item and location working memory, and visual search. The current study provides preliminary normative data, test-retest reliability (intraclass correlations) and practice effects in DalCAB performance 24-h after baseline for healthy young adults (n = 96, 18-31 years). Performance on the DalCAB tasks demonstrated Good to Very Good test-retest reliability for mean reaction time, while accuracy and difference measures (e.g., switch costs, interference effects, and working memory load effects) were most reliable for tasks that require more extensive cognitive processing (e.g., choice reaction time, flanker, dual task, and conjunction search). Practice effects were common and pronounced at the 24-h interval. In addition, performance related to specific within-task parameters of the DalCAB sub-tests provides preliminary support for future formal assessment of the convergent validity of our interpretation of the DalCAB as a potential clinical and research assessment tool for measuring aspects of attention related to the alerting, orienting, and executive control networks.

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.

The effects of varying contextual demands on age-related positive gaze preferences

Despite many studies on the age-related positivity effect and its role in visual attention, discrepancies remain regarding whether full attention is required for age-related differences to emerge. The present study took a new approach to this question by varying the contextual demands of emotion processing. This was done by adding perceptual distractions, such as visual and auditory noise, that could disrupt attentional control. Younger and older participants viewed pairs of happy-neutral and fearful-neutral faces while their eye movements were recorded. Facial stimuli were shown either without noise, embedded in a background of visual noise (low, medium, or high), or with simultaneous auditory babble. Older adults showed positive gaze preferences, looking toward happy faces and away from fearful faces; however, their gaze preferences tended to be influenced by the level of visual noise. Specifically, the tendency to look away from fearful faces was not present in conditions with low and medium levels of visual noise but was present when there were high levels of visual noise. It is important to note, however, that in the high-visual-noise condition, external cues were present to facilitate the processing of emotional information. In addition, older adults' positive gaze preferences disappeared or were reduced when they first viewed emotional faces within a distracting context. The current results indicate that positive gaze preferences may be less likely to occur in distracting contexts that disrupt control of visual attention.

Conflict-Specific Aging Effects Mainly Manifest in Early Information Processing Stages-An ERP Study with Different Conflict Types

Aging is usually accompanied by alterations of cognitive control functions such as conflict processing. Recent research suggests that aging effects on cognitive control seem to vary with degree and source of conflict, and conflict specific aging effects on performance measures as well as neural activation patterns have been shown. However, there is sparse information whether and how aging affects different stages of conflict processing as indicated by event related potentials (ERPs) such as the P2, N2 and P3 components. In the present study, 19 young and 23 elderly adults performed a combined Flanker conflict and stimulus-response-conflict (SRC) task. Analysis of the reaction times (RTs) revealed an increased SRC related conflict effect in elderly. ERP analysis furthermore demonstrated an age-related increase of the P2 amplitude in response to the SRC task. In addition, elderly adults exhibited an increased P3 amplitude modulation induced by incongruent SRC and Flanker conflict trials.

The protective role of long-term meditation on the decline of the executive component of attention in aging: a preliminary cross-sectional study

Life expectancy is constantly increasing. However, a longer life not always corresponds to a healthier life. Indeed, even normal aging is associated with a decline in different cognitive functions. It has been proposed that a central mechanism that could contribute to this widespread cognitive decline is an ineffective inhibitory attentional control. Meditation, to the other hand, has been associated, in young adults, to enhancement of several attentional processes. Nevertheless, attention is not a unitary construct. An influent model proposed the distinction of three subsystems: the alerting (the ability to reach and maintain a vigilance state), the orienting (the capacity of focusing attention on a subset of stimuli), and the conflict resolution or executive component (the ability to resolve conflict or allocate limited resources between competing stimuli). Here, we investigated, employing the Attentional Network Task (ANT), the specific impact of age on these three subcomponents, and the protective role of long-term meditation testing a group of older adults naïve to meditation, a group of age-matched adults with long-term practice of meditation, and a group of young adults with no previous meditation experience. We reported a specific decline of the efficiency of the executive component in elderly that was not observed in age-matched meditators. Our results are encouraging for the investigation of the potential beneficial impact of meditation on other cognitive processes that decline in aging such as memory. Moreover, they could inform geriatric healthcare prevention and intervention strategies, proposing a new approach for cognitive remediation in elderly populations.

Bilingual effects on deployment of the attention system in linguistically and culturally homogeneous children and adults

We investigated the impact of early childhood and adulthood bilingualism on the attention system in a group of linguistically and culturally homogeneous children (5- and 6-year olds) and young adults. We administered the child Attention Network Test (ANT) to 63 English monolingual and Korean-English bilingual children and administered the adult ANT to 39 language- and culture-matched college students. Advantageous bilingual effects on attention were observed for both children and adults in global processing levels of inverse efficiency, response time, and accuracy at a magnitude more pronounced for children than for adults. Differential bilingualism effects were evident at the local network level of executive control and orienting in favor of the adult bilinguals only. Notably, however, bilingual children achieved an adult level of accuracy in the incongruent flanker condition, implying enhanced attentional skills to cope with interferences. Our findings suggest that although both child and adult bilinguals share cognitive advantages in attentional functioning, age-related cognitive and linguistic maturation differentially shapes the outcomes of attentional processing at a local network level.

Selective impairment of attention networks during propofol anesthesia after gynecological surgery in middle-aged women

BACKGROUND

Postoperative cognitive dysfunction is a common complication of anesthesia and surgery. Attention networks are essential components of cognitive function and are subject to impairment after anesthesia and surgery. It is not known whether such impairment represents a global attention deficit or relates to a specific attention network. We used an Attention Network Task (ANT) to examine the efficiency of the alerting, orienting, and executive control attention networks in middle-aged women (40-60 years) undergoing gynecologic surgery. A matched group of medical inpatients were recruited as a control.

METHODS

Fifty female patients undergoing gynecologic surgery (observation group) and 50 female medical inpatients (control group) participated in this study. Preoperatively patients were administered a mini-mental state examination as a screening method. The preoperative efficiencies of three attention networks in an attention network test were compared to the 1st and 5th post-operative days.

RESULTS

The control group did not have any significant attention network impairments. On the 1st postoperative day, significant impairment was shown in the alerting (p=0.003 vs. control group, p=0.015 vs. baseline), orienting (p<0.001 vs. both baseline level and control group), and executive control networks (p=0.007 vs. control group, p=0.002 vs. baseline) of the observation group. By the 5th postoperative day, the alerting network efficiency had recovered to preoperative levels (p=0.464 vs. baseline) and the orienting network efficiency had recovered partially (p=0.031 vs. 1st post-operative day), but not to preoperative levels (p=0.01 vs. baseline). The executive control network did not recover by the 5th postoperative day (p=0.001 vs. baseline, p=0.680 vs. 1st post-operative day).

CONCLUSIONS

Attention networks of middle-aged women show a varying degree of significant impairment and differing levels of recovery after surgery and propofol anesthetic.

Disturbance of attention network functions in Chinese healthy older adults: an intra-individual perspective

BACKGROUND

Intra-individual variability (IIV) and the change of attentional functions have been reported to be susceptible to both healthy ageing and pathological ageing. The current study aimed to evaluate the IIV of attention and the age-related effect on alerting, orienting, and executive control in cognitively healthy older adults.

METHOD

We evaluated 145 Chinese older adults (age range of 65-80 years, mean age of 72.41 years) with a comprehensive neuropsychological battery and the Attention network test (ANT). A two-step strategy of analytical methods was used: Firstly, the IIV of older adults was evaluated by the intraindividual coefficient of variation of reaction time (ICV-RT). The correlation between ICV-RT and age was used to evaluate the necessity of subgrouping. Further, the comparisons of ANT performance among three age groups were performed with processing speed adjusted.

RESULTS

Person's correlation revealed significant positive correlations between age and IIV (r = 0.185, p = 0.032), age and executive control (r = 0.253, p = 0.003). Furthermore, one-way ANOVA comparisons among three age groups revealed a significant age-related disturbance on executive control (F = 4.55, p = 0.01), in which oldest group (group with age >75 years) showed less efficient executive control than young-old (group with age 65-70 years) (Conventional score, p = 0.012; Ratio score, p = 0.020).

CONCLUSION

Advancing age has an effect on both IIV and executive attention in cognitively healthy older adults, suggesting that the disturbance of executive attention is a sensitive indicator to reflect healthy ageing. Its significance to predict further deterioration should be carefully evaluated with prospective studies.

Age differences in the Attention Network Test: Evidence from behavior and event-related potentials

The Attention Network Test (ANT) is widely used to capture group and individual differences in selective attention. Prior behavioral studies with younger and older adults have yielded mixed findings with respect to age differences in three putative attention networks (alerting, orienting, and executive control). To overcome the limitations of behavioral data, the current study combined behavioral and electrophysiological measures. Twenty-four healthy younger adults (aged 18-29years) and 24 healthy older adults (aged 60-76years) completed the ANT while EEG data were recorded. Behaviorally, older adults showed reduced alerting, but did not differ from younger adults in orienting or executive control. Electrophysiological components related to alerting and orienting (P1, N1, and CNV) were similar in both age groups, whereas components related to executive control (N2 and P3) showed age-related differences. Together these results suggest that comparisons of network effects between age groups using behavioral data alone may not offer a complete picture of age differences in selective attention, especially for alerting and executive control networks.

Neural correlates of attention-executive dysfunction in lewy body dementia and Alzheimer's disease

Attentional and executive dysfunction contribute to cognitive impairment in both Lewy body dementia and Alzheimer's disease. Using functional MRI, we examined the neural correlates of three components of attention (alerting, orienting, and executive/conflict function) in 23 patients with Alzheimer's disease, 32 patients with Lewy body dementia (19 with dementia with Lewy bodies and 13 with Parkinson's disease with dementia), and 23 healthy controls using a modified Attention Network Test. Although the functional MRI demonstrated a similar fronto-parieto-occipital network activation in all groups, Alzheimer's disease and Lewy body dementia patients had greater activation of this network for incongruent and more difficult trials, which were also accompanied by slower reaction times. There was no recruitment of additional brain regions or, conversely, regional deficits in brain activation. The default mode network, however, displayed diverging activity patterns in the dementia groups. The Alzheimer's disease group had limited task related deactivations of the default mode network, whereas patients with Lewy body dementia showed heightened deactivation to all trials, which might be an attempt to allocate neural resources to impaired attentional networks. We posit that, despite a common endpoint of attention-executive disturbances in both dementias, the pathophysiological basis of these is very different between these diseases.

Age Differences in Reaction Times and a Neurophysiological Marker of Cholinergic Activity

RÉSUMÉ La détérioration du système cholinergique lors du vieillissement normal semble contribuer au déclin de l'attention avec l'âge. Nous avons examiné l'effet potentiel de l'âge sur la performance au « Attention Network Test » (ANT) ainsi que sur la variabilité intra-individuelle dans la vitesse des réponses à une tâche go/no-go et à une tâche de temps de réaction (TR) à choix multiples chez un groupe de jeunes adultes et de personnes âgées en santé. Nous avons ensuite examiné si un marqueur neurophysiologique de l'activité cholinergique dérivé de la stimulation magnétique transcrânienne (i.e., inhibition afférente à courte latence; IACL) était associé à la performance. Les personnes âgées montraient un ralentissement au ANT ainsi qu'une plus grande variabilité intra-individuelle que les jeunes adultes à la tâche de TR à choix multiples, mais il n'y avait pas de différence liée à l'âge dans les scores reflétant les réseaux attentionnels du ANT (vigilance, orientation aux stimuli et contrôle exécutif). Les niveaux de IACL étaient diminués chez les personnes âgées, mais ils n'étaient pas associés à la performance. Il est possible que des relations entre le marqueur de l'activité cholinergique et l'attention émergent seulement en cas de déficits de neurotransmission sévères. D'autres mécanismes corticaux pourraient aussi être plus fortement associés aux fonctions liées à l'attention.

Not just scenery: viewing nature pictures improves executive attention in older adults

BACKGROUND/STUDY CONTEXT: Attention Restoration Theory (Kaplan, 1995, Journal of Environmental Psychology, 15, 169-182) suggests that exposure to nature improves attention. Berman, Jonides, and Kaplan (2008, Psychological Science, 19, 1207-1212) showed that simply viewing nature pictures improves executive attention in young adults. The present study is the first to investigate this Nature Effect in older adults. The authors investigated whether executive attention could be improved in healthy older adults following brief exposure to nature pictures.

METHODS

Thirty healthy older adults (64-79 years old) and 26 young university students (18-25 years old) participated. They completed the Attention Network Test before and after 6 min of viewing either nature or urban pictures, with random assignment into a picture type. Attention immediately before (most fatigued) and after (most restored) picture viewing was measured, and change in attention was compared between age groups and picture types.

RESULTS

Results showed that viewing nature, but not urban, pictures significantly improved executive attention in both older and young adults as measured by the Attention Network Test, with similar effects seen in the two age groups. Alerting and orienting attention scores were not affected by picture viewing.

CONCLUSION

This was the first study to show that viewing nature pictures improves attention in older adults, and to show that it is executive attention, specifically, that is improved. Among a growing number of interventions, nature exposure offers a quick, inexpensive, and enjoyable means to provide a temporary boost in executive attention.

Information processing speed and attention in multiple sclerosis: Reconsidering the Attention Network Test (ANT)

OBJECTIVE

The Attention Network Test (ANT) assesses attention in terms of discrepancies between response times to items that differ in the burden they place on some facet of attention. However, simple arithmetic difference scores commonly used to capture these discrepancies fail to provide adequate control for information processing speed, leading to distorted findings when patient and control groups differ markedly in the speed with which they process and respond to stimulus information. This study examined attention networks in patients with multiple sclerosis (MS) using simple difference scores, proportional scores, and residualized scores that control for processing speed through statistical regression.

METHOD

Patients with relapsing-remitting (N = 20) or secondary progressive (N = 20) MS and healthy controls (N = 40) of similar age, education, and gender completed the ANT.

RESULTS

Substantial differences between patients and controls were found on all measures of processing speed. Patients exhibited difficulties in the executive control network, but only when difference scores were considered. When deficits in information processing speed were adequately controlled using proportional or residualized score, deficits in the alerting network emerged. The effect sizes for these deficits were notably smaller than those for overall information processing speed and were also limited to patients with secondary progressive MS.

CONCLUSIONS

Deficits in processing speed are more prominent in MS than those involving attention, and when the former are properly accounted for, differences in the latter are confined to the alerting network.

The boundary condition for observing compensatory responses by the elderly in a flanker-task paradigm

This study aimed to establish a baseline condition to observe ERP responses for older adults in a conventional flanker-task paradigm, in which neither a reversal response rule toward a target nor a color-coded target was employed. In addition, this study aimed to examine whether the previous finding of the compensatory responses reflected on event-related potential (ERP) for older adults in performing a flanker task was due to the specific demand of the reversal response rule toward a target or simply due to the pop-out effect with a singleton target manipulation. The results of the current study showed that (1) some of the previously thought-to-be compensatory ERP responses might not really reflect compensatory responses; (2) the previous finding of age-related ERP compensatory responses was mainly due to the manipulation of the reversal response rule condition; and (3) in some scenarios of flanker-task paradigms, older adults were just as capable as younger adults in conquer with the flanker interference even though no ERP compensatory responses were found.

Discourse intervention strategies in Alzheimer's disease: Eye-tracking and the effect of visual cues in conversation

Objective

The goal of this study was to investigate whether on-topic visual cues can serve as aids for the maintenance of discourse coherence and informativeness in autobiographical narratives of persons with Alzheimer's disease (AD).

Methods

The experiment consisted of three randomized conversation conditions: one without prompts, showing a blank computer screen; an on-topic condition, showing a picture and a sentence about the conversation; and an off-topic condition, showing a picture and a sentence which were unrelated to the conversation. Speech was recorded while visual attention was examined using eye tracking to measure how long participants looked at cues and the face of the listener.

Results

Results suggest that interventions using visual cues in the form of images and written information are useful to improve discourse informativeness in AD.

Conclusion

This study demonstrated the potential of using images and short written messages as means of compensating for the cognitive deficits which underlie uninformative discourse in AD. Future studies should further investigate the efficacy of language interventions based in the use of these compensation strategies for AD patients and their family members and friends.

Neural correlates of alerting and orienting impairment in multiple sclerosis patients

BACKGROUND

A considerable percentage of multiple sclerosis patients have attentional impairment, but understanding its neurophysiological basis remains a challenge. The Attention Network Test allows 3 attentional networks to be studied. Previous behavioural studies using this test have shown that the alerting network is impaired in multiple sclerosis. The aim of this study was to identify neurophysiological indexes of the attention impairment in relapsing-remitting multiple sclerosis patients using this test.

RESULTS

After general slowing had been removed in patients group to isolate the effects of each condition, some behavioral differences between them were obtained. About Contingent Negative Variation, a statistically significant decrement were found in the amplitude for Central and Spatial Cue Conditions for patient group (p<0.05). ANOVAs showed for the patient group a significant latency delay for P1 and N1 components (p<0.05) and a decrease of P3 amplitude for congruent and incongruent stimuli (p<0.01). With regard to correlation analysis, PASAT-3s and SDMT showed significant correlations with behavioral measures of the Attention Network Test (p<0.01) and an ERP parameter (CNV amplitude).

CONCLUSIONS

Behavioral data are highly correlated with the neuropsychological scores and show that the alerting and orienting mechanisms in the patient group were impaired. Reduced amplitude for the Contingent Negative Variation in the patient group suggests that this component could be a physiological marker related to the alerting and orienting impairment in relapsing-remitting multiple sclerosis. P1 and N1 delayed latencies are evidence of the demyelination process that causes impairment in the first steps of the visual sensory processing. Lastly, P3 amplitude shows a general decrease for the pathological group probably indexing a more central impairment. These results suggest that the Attention Network Test give evidence of multiple levels of attention impairment, which could help in the assessment and treatment of relapsing-remitting multiple sclerosis patients.

Information processing and magnetic resonance imaging indices of brain pathology in multiple sclerosis

Accumulation of central nervous system (CNS) pathology affects cognitive processing speed and efficiency and is thought to underlie attentional and executive deficits in multiple sclerosis (MS). Most clinical neuropsychological tests are multifactorial and are limited in their sensitivity to specific cognitive processes. This may, in part, account for the low to moderate correlations between clinical test results and magnetic resonance imaging (MRI) indices of brain pathology. We compared the ability of a clinical and an experimental test of cognitive processing speed to differentiate domain-specific cognitive changes in MS, and examined relations between test performance and MRI measures of brain pathology. Twelve MS patients and 12 controls completed the Paced Auditory Serial Addition Test (PASAT) and the Attention Networks Test-Interactions (ANT-I), a computerized response latency task. Subjects also had MRI scans that included T1, T2, and fluid-attenuated inversion recovery (FLAIR) sequences that provided global and localized volumetric measures. Patients made more errors on the PASAT and were slower on the ANT-I. The ANT-I also revealed specific deficits in response inhibition. In addition, ANT-I performance was associated with changes in a number of MRI measures, which was not the case for the PASAT. Reaction time paradigms that manipulate within-task demands on distinct cognitive functions may provide meaningful markers of brain disease burden in MS.

Spontaneous neuronal activity predicts intersubject variations in executive control of attention

Executive control of attention regulates our thoughts, emotion and behavior. Individual differences in executive control are associated with task-related differences in brain activity. But it is unknown whether attentional differences depend on endogenous (resting state) brain activity and to what extent regional fluctuations and functional connectivity contribute to individual variations in executive control processing. Here, we explored the potential contribution of intrinsic brain activity to executive control by using resting-state functional magnetic resonance imaging (fMRI). Using the amplitude of low-frequency fluctuations (ALFF) as an index of spontaneous brain activity, we found that ALFF in the right precuneus (PCUN) and the medial part of left superior frontal gyrus (msFC) was significantly correlated with the efficiency of executive control processing. Crucially, the strengths of functional connectivity between the right PCUN/left msFC and distributed brain regions, including the left fusiform gyrus, right inferior frontal gyrus, left superior frontal gyrus and right precentral gyrus, were correlated with individual differences in executive performance. Together, the ALFF and functional connectivity accounted for 67% of the variability in behavioral performance. Moreover, the strength of functional connectivity between specific regions could predict more individual variability in executive control performance than regionally specific fluctuations. In conclusion, our findings suggest that spontaneous brain activity may reflect or underpin executive control of attention. It will provide new insights into the origins of inter-individual variability in human executive control processing.

Look out-it's your off-peak time of day! Time of day matters more for alerting than for orienting or executive attention

BACKGROUND/STUDY CONTEXT: Older adults' peak performance on memory and cognitive inhibition tasks tends to be in the morning, whereas younger adults' peak performance tends to be in the afternoon. Although these tasks require efficient attentional processes for optimal performance, previous research examining age differences in the effects of time of day has not measured the distinct aspects of attention quantified by the Attention Network Test (ANT; Fan, McCandliss, Sommer, Raz, & Posner, 2002, Journal of Cognitive Neuroscience, 14, 340-347).

METHODS

The authors examined the relationship between time of testing and the efficiency of alerting, orienting, and executive attention networks by randomly assigning younger (18-28 years; n = 27, M = 21.37 years, SD = 2.39) and older (65-85 years; n = 32, M = 73.34 years, SD = 5.18) adults to morning (AM) or afternoon (PM) testing of alerting, orienting, and executive attention. Mean reaction times for each network were analyzed with a univariate analysis of variance (ANOVA) with age (younger, older) and time of day (AM, PM) as between-subjects factors.

RESULTS

Consistent with the authors' hypotheses, although time of day had little effect on orienting or executive attention, it affected alerting in opposite ways for younger and older adults, with alerting cues benefiting performance most at participants' off-peak times of day. A larger benefit from alerting cues was observed when participants were tested at their off-peak (M = 30.11 ± 15.66) relative to their peak (M = 2.18 ± 15.97) time.

CONCLUSION

These findings show that age-related circadian patterns influence the alerting component of attention, with both age groups showing the largest benefit from alerting cues when testing occurs at nonoptimal times of day. Overall, these findings underscore the importance of controlling for time of day in investigations of attention and add to our understanding of how age differences in circadian patterns impact attention.

Effects of painful stimulation and acupuncture on attention networks in healthy subjects

Pain is a subjective sensory and emotional experience, and it has been reported that many different brain regions are regulated by pain, and that pain can impact attention. Acupuncture is an important treatment component of Chinese traditional medicine, and has been used for thousands of years to treat a wide variety of conditions. Although several studies have shown that acupuncture improves consciousness, the precise impact of both acupuncture and painful stimulation on attention is unclear. Are all of the attention networks modulated, or do these stimuli act on a specific network? Is the effect of painful stimulation similar to that of acupuncture? We administered the attention network test to 30 participants (15 males) to investigate the relative efficiencies of three independent attention networks (alerting, orienting, and executive control networks) under three conditions: baseline, after painful stimulation, and after acupuncture. The degree of pain experienced was assessed on a horizontally oriented visual analogue scale. The results showed that painful stimulation and acupuncture had similar effects on the orienting and executive control networks; however, there was a significantly different effect between the three conditions on the alerting network. In conclusion, (1) painful stimulation can selectively impact attention; (2) acupuncture can also selectively impact attention; i.e., both have selective influences on the alerting and executive control networks, but not on the orienting network; (3) the effects of acupuncture and painful stimulation are not identical. The mechanisms by which painful stimulation and acupuncture influence attention warrant further research.

Distinct aging effects for two types of inhibition in older adults: a near-infrared spectroscopy study on the Simon task and the flanker task

The present study examined age-related changes in inhibitory processes among older and younger adults in the flanker and Simon tasks in terms of behavioral performance and prefrontal brain activity by functional near-infrared spectroscopy. The flanker task requires a quick identification of a central target in the presence of surrounding distracters, whereas the Simon task requires an individual to respond with left and right key presses to nonspatial features of the stimulus presented in the left and right locations. The reaction times of two age groups were longer under incongruent conditions than under congruent conditions in both tasks, indicating that the flanker effect (interference suppression) and the Simon effect (response suppression) were evident. In agreement with previous studies, the magnitude of the effect for the Simon task was greater for the older adults than for the younger adults, whereas the two groups showed equivalent flanker effects. The results suggest that older adults have difficulties in response inhibition, but not in stimulus interference suppression. Enhanced activity was found in different brain regions across the two tasks among the older adults. The older adults showed more activity in the superior and middle frontal gyri of the left hemisphere than younger adults in the flanker task; they showed more activity in the bilateral superior frontal gyri in the Simon task. These results suggest that the underlying mechanisms of the inhibition processes for the two tasks are distinct: they rely on different brain regions and have differential vulnerabilities to aging.

Functional neural correlates of attentional deficits in amnestic mild cognitive impairment

Although amnestic mild cognitive impairment (aMCI; often considered a prodromal phase of Alzheimer's disease, AD) is most recognized by its implications for decline in memory function, research suggests that deficits in attention are present early in aMCI and may be predictive of progression to AD. The present study used functional magnetic resonance imaging to examine differences in the brain during the attention network test between 8 individuals with aMCI and 8 neurologically healthy, demographically matched controls. While there were no significant behavioral differences between groups for the alerting and orienting functions, patients with aMCI showed more activity in neural regions typically associated with the networks subserving these functions (e.g., temporoparietal junction and posterior parietal regions, respectively). More importantly, there were both behavioral (i.e., greater conflict effect) and corresponding neural deficits in executive control (e.g., less activation in the prefrontal and anterior cingulate cortices). Although based on a small number of patients, our findings suggest that deficits of attention, especially the executive control of attention, may significantly contribute to the behavioral and cognitive deficits of aMCI.

Twenty-four hours of total sleep deprivation selectively impairs attentional networks

Performance decrements after sleep loss have been extensively studied and are usually attributed to generic attentional deficits. This claim, however, is based on the view of attention as a unitary construct, despite evidence that it should be considered a multidimensional cognitive ability. The aim of the present study was to evaluate the impact of one night of sleep deprivation on the efficiency of three attentional networks, defined by Posner and Raichle (1994) in anatomical and functional terms, as alerting, orienting, and executive control. Thirty participants performed the Attention Network Test at 9:00 a.m. following two different sleep conditions: baseline (a normal night of sleep) and deprivation (24 hrs of wakefulness). Results showed an overall slowing in reaction times and a significant decrease in accuracy after sleep deprivation. Sleep deprivation selectively affected the three attentional networks, given that only executive control efficacy significantly decreased after sleep deprivation. By contrast, phasic alerting and orienting showed no differences in the two sleep conditions. Thus, performance deficits following sleep deprivation do not reflect global attentional deficits.

The role of affect in attentional functioning for younger and older adults

Although previous research has shown that positive affect (PA) and negative affect (NA) modulate attentional functioning in distinct ways, few studies have considered whether the links between affect and attentional functioning may vary as a function of age. Using the Attention Network Test (Fan et al., 2002), we tested whether participants' current state of PA and NA influenced distinct attentional functions (i.e., alerting, orienting, and executive attention) and how the relationships between affective states and attentional functioning differ in younger (18-25 years) and older (60-85 years) age groups. While there were age differences in alerting efficiency, these age differences were mediated by PA, indicating that the higher state PA found in older adults may contribute to age differences in alerting. Furthermore, age group moderated the relationship between PA and orienting as well as NA and orienting. That is, higher levels of PA and lower levels of NA were associated with enhanced orienting efficiency in older adults. Neither PA nor NA had any influence on executive attention. The current results suggest that PA and NA may influence attentional functioning in distinct ways, but that these patterns may depend on age groups.

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.