Helena M. Blumen

Neuroimaging of Mobility in Aging: A Targeted Review

BACKGROUND The relationship between mobility and cognition in aging is well established, but the relationship between mobility and the structure and function of the aging brain is relatively unknown. This, in part, is attributed to the technological limitations of most neuroimaging procedures, which require the individual to be immobile or in a supine position. Herein, we provide a targeted review of neuroimaging studies of mobility in aging to promote (i) a better understanding of this relationship, (ii) future research in this area, and (iii) development of applications for improving mobility. METHODS A systematic search of peer-reviewed studies was performed using PubMed. Search terms included (i) aging, older adults, or elderly; (ii) gait, walking, balance, or mobility; and (iii) magnetic resonance imaging, voxel-based morphometry, fluid-attenuated inversion recovery, diffusion tensor imaging, positron emission tomography, functional magnetic resonance imaging, electroencephalography, event-related potential, and functional near-infrared spectroscopy. RESULTS Poor mobility outcomes were reliably associated with reduced gray and white matter volume. Fewer studies examined the relationship between changes in task-related brain activation and mobility performance. Extant findings, however, showed that activation patterns in the cerebellum, basal ganglia, parietal and frontal cortices were related to mobility. Increased involvement of the prefrontal cortex was evident in both imagined walking conditions and conditions where the cognitive demands of locomotion were increased. CONCLUSIONS Cortical control of gait in aging is bilateral, widespread, and dependent on the integrity of both gray and white matter.

Influence of re-exposure and retrieval disruption during group collaboration on later individual recall

This research examined the influence of prior group collaboration on later individual recall. We considered the negative effects of retrieval disruption and the potentially positive effects of re-exposure to additional items during group recall in the context of three hypotheses: the individual-strategy hypothesis, the combined-strategy hypothesis, and the group-strategy hypothesis. After a study phase and a brief delay, participants completed three successive recall trials in four different recall sequence conditions: III (individual-individual-individual), ICI (individual-collaborative-individual), CII (collaborative-individual-individual), and CCI (collaborative-collaborative-individual). Results show that repeated group recalls (CCI), and securing individual retrieval organisation prior to group recall (ICI), benefit later individual recall more than repeated individual recalls (III). These findings support the group-strategy hypothesis and the individual-strategy hypothesis, and have important implications for group versus individual learning practices in educational settings.

Space Fortress game training and executive control in older adults: A pilot intervention

ABSTRACT We investigated the feasibility of using the Space Fortress (SF) game, a complex video game originally developed to study complex skill acquisition in young adults, to improve executive control processes in cognitively healthy older adults. The study protocol consisted of 36 one-hour game play sessions over 3 months with cognitive evaluations before and after, and a follow-up evaluation at 6 months. Sixty participants were randomized to one of three conditions: Emphasis Change (EC) – elders were instructed to concentrate on playing the entire game but place particular emphasis on a specific aspect of game play in each particular game; Active Control (AC) – game play with standard instructions; Passive Control (PC) – evaluation sessions without game play. Primary outcome measures were obtained from five tasks, presumably tapping executive control processes. A total of 54 older adults completed the study protocol. One measure of executive control, WAIS-III letter–number sequencing, showed improvement in performance from pre- to post-evaluations in the EC condition, but not in the other two conditions. These initial findings are modest but encouraging. Future SF interventions need to carefully consider increasing the duration and or the intensity of the intervention by providing at-home game training, reducing the motor demands of the game, and selecting appropriate outcome measures.

Behavioral and neural correlates of imagined walking and walking-while-talking in the elderly.

Cognition is important for locomotion and gait decline increases the risk for morbidity, mortality, cognitive decline, and dementia. Yet, the neural correlates of gait are not well established, because most neuroimaging methods cannot image the brain during locomotion. Imagined gait protocols overcome this limitation. This study examined the behavioral and neural correlates of a new imagined gait protocol that involved imagined walking (iW), imagined talking (iT), and imagined walking‐while‐talking (iWWT). In Experiment 1, 82 cognitively‐healthy older adults (M = 80.45) walked (W), iW, walked while talking (WWT) and iWWT. Real and imagined walking task times were strongly correlated, particularly real and imagined dual‐task times (WWT and iWWT). In Experiment 2, 33 cognitively‐healthy older adults (M = 73.03) iW, iT, and iWWT during functional magnetic resonance imaging. A multivariate Ordinal Trend (OrT) Covariance analysis identified a pattern of brain regions that: (1) varied as a function of imagery task difficulty (iW, iT and iWWT), (2) involved cerebellar, precuneus, supplementary motor and other prefrontal regions, and (3) were associated with kinesthetic imagery ratings and behavioral performance during actual WWT. This is the first study to compare the behavioral and neural correlates of imagined gait in single and dual‐task situations, an issue that is particularly relevant to elderly populations. These initial findings encourage further research and development of this imagined gait protocol as a tool for improving gait and cognition among the elderly. Hum Brain Mapp 35:4090–4104, 2014.

Gait phenotype from mild cognitive impairment to moderate dementia: results from the GOOD initiative

The differences in gait abnormalities from the earliest to the later stages of dementia and in the different subtypes of dementia have not been fully examined. This study aims to compare spatiotemporal gait parameters in cognitively healthy individuals, patients with amnestic mild cognitive impairment (MCI) and non‐amnestic MCI, and patients with mild and moderate stages of Alzheimers disease (AD) and non‐Alzheimers disease (non‐AD).

Functional connectivity associated with gait velocity during walking and walking-while-talking in aging: a resting-state fMRI study

Gait decline is common among older adults and is a risk factor for adverse outcomes. Poor gait performance in dual‐task conditions, such as walking while performing a secondary cognitive interference task, is associated with increased risk of frailty, disability, and death. Yet, the functional neural substrates that support locomotion are not well established. We examined the functional connectivity associated with gait velocity in single‐ (normal pace walking) and dual‐task (walking while talking) conditions using resting‐state functional Magnetic Resonance Imaging (fMRI). We acquired 6 minutes of resting‐state fMRI data in 30 cognitively healthy older adults. Independent components analyses were performed to separate resting‐state fMRI data into group‐level statistically independent spatial components that correlated with gait velocity in single‐ and dual‐task conditions. Gait velocity in both task conditions was associated with similar functional connectivity in sensorimotor, visual, vestibular, and left fronto‐parietal cortical areas. Compared to gait velocity in the single‐task condition, the networks associated with gait velocity in the dual‐task condition were associated with greater functional connectivity in supplementary motor and prefrontal regions. Our findings show that there are partially overlapping functional networks associated with single‐ and dual‐task walking conditions. These initial findings encourage the future use of resting‐state fMRI as tool in developing a comprehensive understanding of age‐related mobility impairments. Hum Brain Mapp 36:1484–1493, 2015.

Effects of repeated collaborative retrieval on individual memory vary as a function of recall versus recognition tasks

Our research examines how prior group collaboration modulates later individual memory. We recently showed that repeated collaborative recall sessions benefit later individual recall more than a single collaborative recall session (Blumen & Rajaram, 2008). Current research compared the effects of repeated collaborative recall and repeated collaborative recognition on later individual recall and later individual recognition. A total of 192 participants studied a list of nouns and then completed three successive retrieval sessions in one of four conditions. While two collaborative recall sessions and two collaborative recognition sessions generated comparable levels of individual recall (CRecall-CRecall-I Recall ∼ CRecognition-CRecognition-I Recall , Experiment 1a), two collaborative recognition sessions generated greater levels of individual recognition than two collaborative recall sessions (CRecognition-CRecognition- IRecognition > CRecall-CRecall- I Recognition , Experiment 1b). These findings are discussed in terms of two opposing mechanisms that operate during collaborative retrieval—re-exposure and retrieval disruption—and in terms of transfer-appropriate processing across collaborative and individual retrieval sessions.

Training Cognitive Control in Older Adults with the Space Fortress Game: The Role of Training Instructions and Basic Motor Ability

This study examined if and how cognitively healthy older adults can learn to play a complex computer-based action game called the Space Fortress (SF) as a function of training instructions [Standard vs. Emphasis Change (EC); e.g., Gopher et al., 1989] and basic motor ability. A total of 35 cognitively healthy older adults completed a 3-month SF training program with three SF sessions weekly. Twelve 3-min games were played during each session. Basic motor ability was assessed with an aiming task, which required rapidly rotating a spaceship to shoot targets. Older adults showed improved performance on the SF task over time, but did not perform at the same level as younger adults. Unlike studies of younger adults, overall SF performance in older adults was greater following standard instructions than following EC instructions. However, this advantage was primarily due to collecting more bonus points and not – the primary goal of the game – shooting and destroying the fortress, which in contrast benefited from EC instructions. Basic motor ability was low and influenced many different aspects of SF game learning, often interacted with learning rate, and influenced overall SF performance. These findings show that older adults can be trained to deal with the complexity of the SF task but that overall SF performance, and the ability to capitalize on EC instructions, differs when a basic ability such as motor control is low. Hence, the development of this training program as a cognitive intervention that can potentially compensate for age-related cognitive decline should consider that basic motor ability can interact with the efficiency of training instructions that promote the use of cognitive control (e.g., EC instructions) – and the confluence between such basic abilities and higher-level cognitive control abilities should be further examined.

The role of group configuration in the social transmission of memory: Evidence from identical and reconfigured groups

Collaborating with others during recall shapes both group and individual memories. Individuals contribute less when recalling in groups than when recalling alone, a phenomenon called collaborative inhibition. In contrast, collaboration improves post-collaborative individual memory by providing re-exposure to information that would have been otherwise forgotten. Collaboration also influences collective memory—the overlap in post-collaborative memory among group members. We examined the role of group configuration on such transmission of memory by varying group configuration across repeated recalls. Participants (N = 162) studied words and completed three recall sessions in one of three conditions (N = 54/condition): Individual–Individual–Individual (Control), Collaborative–Collaborative (Identical group)–Individual and Collaborative–Collaborative (Reconfigured group)–Individual. Collaborative inhibition occurred in both the Identical and Reconfigured groups during the first recall but disappeared in the Reconfigured groups during the second recall. Post-collaborative individual memory was greater following Reconfigured than Identical group collaboration. This pattern reversed for collective memories; repeated collaboration increased overlap in the remembered and forgotten items in Identical groups compared to Reconfigured groups. Finally, Reconfigured groups provided a quantifiable index of the influence of distal partners (i.e., no direct collaboration involved) on post-collaborative individual memory. We conclude that group configuration has powerful consequences on the amount, the similarity and the variety of memory representations.

Neural networks associated with the speed-accuracy tradeoff: Evidence from the response signal method

This functional neuroimaging (fMRI) study examined the neural networks (spatial patterns of covarying neural activity) associated with the speed-accuracy tradeoff (SAT) in younger adults. The response signal method was used to systematically increase probe duration (125, 250, 500, 1000 and 2000 ms) in a nonverbal delayed-item recognition task. A covariance-based multivariate approach identified three networks that varied with probe duration--indicating that the SAT is driven by three distributed neural networks.