Erratum: Top-down suppression deficit underlies working memory impairment in normal aging

Getting Lost Behavior in Patients with Mild Alzheimer's Disease: A Cognitive and Anatomical Model

Background

Getting lost behavior (GLB) in the elderly is believed to involve poor top-down modulation of visuospatial processing, by impaired executive functions. However, since healthy elderly and elderly with Alzheimer's disease (AD) experience a different pattern of cognitive decline, it remains unclear whether this hypothesis can explain GLB in dementia.

Objective

We sought to identify whether poor executive functions and working memory modulate the relationship between visuospatial processing and prevalence of GLB in healthy elderly and patients with AD. Complementary to this, we explored whether brain regions critical for executive functions modulate the relationship between GLB and brain regions critical for visuospatial processing.

Method

Ninety-two participants with mild AD and 46 healthy age-matched controls underwent neuropsychological assessment and a structural MRI. GLB was assessed using a semistructured clinical interview. Path analysis was used to explore interactions between visuospatial deficits, executive dysfunction/working memory, and prevalence of GLB, in AD and controls independently.

Results

For both healthy controls and patients with mild AD, visuospatial processing deficits were associated with GLB only in the presence of poor working memory. Anatomically, GLB was associated with medial temporal atrophy in patients with mild AD, which was not strengthened by low frontal gray matter (GM) volume as predicted. Instead, medial temporal atrophy was more strongly related to GLB in patients with high frontal GM volumes. For controls, GLB was not associated with occipital, parietal, medial temporal, or frontal GM volume.

Conclusion

Cognitively, a top-down modulation deficit may drive GLB in both healthy elderly and patients with mild AD. This modulation effect may be localized in the medial temporal lobe for patients with mild AD. Thus, anatomical substrates of GLB in mild AD may not follow the typical top-down modulation mechanisms often reported in the healthy aging population. Implications advance therapeutic practices by highlighting the need to target both working memory and visuospatial deficits simultaneously, and that anatomical substrates of GLB may be disease specific.

The effects of aging on the working memory processes of multimodal information

Normal aging is associated with deficits in working memory processes. However, the majority of research has focused on storage or inhibitory processes using unimodal paradigms, without addressing their relationships using different sensory modalities. Hence, we pursued two objectives. First, was to examine the effects of aging on storage and inhibitory processes. Second, was to evaluate aging effects on multisensory integration of visual and auditory stimuli. To this end, young and older participants performed a multimodal task for visual and auditory pairs of stimuli with increasing memory load at encoding and interference during retention. Our results showed an age-related increased vulnerability to interrupting and distracting interference reflecting inhibitory deficits related to the off-line reactivation and on-line suppression of relevant and irrelevant information, respectively. Storage capacity was impaired with increasing task demands in both age groups. Additionally, older adults showed a deficit in multisensory integration, with poorer performance for new visual compared to new auditory information.

Aging effects on the resting state motor network and interlimb coordination

Both increases and decreases in resting state functional connectivity have been previously observed within the motor network during aging. Moreover, the relationship between altered functional connectivity and age-related declines in bimanual coordination remains unclear. Here, we explored the developmental dynamics of the resting brain within a task-specific motor network in a sample of 128 healthy participants, aged 18-80 years. We found that age-related increases in functional connectivity between interhemispheric dorsal and ventral premotor areas were associated with poorer performance on a novel bimanual visuomotor task. Additionally, a control analysis performed on the default mode network confirmed that our age-related increases in functional connectivity were specific to the motor system. Our findings suggest that increases in functional connectivity within the resting state motor network with aging reflect a loss of functional specialization that may not only occur in the active brain but also in the resting brain.

Crowdsourcing for cognitive science--the utility of smartphones

By 2015, there will be an estimated two billion smartphone users worldwide. This technology presents exciting opportunities for cognitive science as a medium for rapid, large-scale experimentation and data collection. At present, cost and logistics limit most study populations to small samples, restricting the experimental questions that can be addressed. In this study we investigated whether the mass collection of experimental data using smartphone technology is valid, given the variability of data collection outside of a laboratory setting. We presented four classic experimental paradigms as short games, available as a free app and over the first month 20,800 users submitted data. We found that the large sample size vastly outweighed the noise inherent in collecting data outside a controlled laboratory setting, and show that for all four games canonical results were reproduced. For the first time, we provide experimental validation for the use of smartphones for data collection in cognitive science, which can lead to the collection of richer data sets and a significant cost reduction as well as provide an opportunity for efficient phenotypic screening of large populations.

Mindfulness and the aging brain: a proposed paradigm shift

There has been a proliferation of cognitive training studies investigating the efficacy of various cognitive training paradigms as well as strategies for improving cognitive control in the elderly. While some have found support for the transfer of training, the majority of training studies show modest to no transfer effects. When transfer effects have been observed, the mechanisms contributing to enhanced functioning have been difficult to dissociate. In this review, we provide a theoretical rationale for the study of mindfulness in older adults as a particular type of training program designed to improve cognitive control by capitalizing on older adults’ acquired behavioral orientation toward higher socioemotional goals. Given the synergistic relationship between emotional and cognitive control processes, the paradoxical divergence in older adults’ functional trajectory in these respective domains, and the harmonious interplay of cognitive and emotional control embedded in the practice of mindfulness, we propose mindfulness training as an opportunistic approach to cultivating cognitive benefits in older adults. The study of mindfulness within aging, we argue, capitalizes on a fundamental finding of the socioemotional aging literature, namely the preferential change in motivational goals of older adults from ones involving future-oriented wants and desires to present-focused emotion regulation and gratification.

Similar behaviour, different brain patterns: age-related changes in neural signatures of ignoring

We measured behavioural performance and fMRI activity whilst old and young adults performed a temporal segmentation task ('preview search'). Being able to select parts of the visual world to be attended or ignored is a critical visual skill. Both old and young adults were able to improve their performance on a difficult search task when some of the distracter items were presented earlier than the remainder. Comparisons of brain activity and functional connectivity, however, suggested that the underlying mechanisms are quite different for the two age groups. Older adults' activation patterns do not correspond to those predicted by simple increased involvement of frontal regions reflecting higher demand with age but seem to suggest that changes in brain activation patterns propagate throughout the cortex.