Brain regions involved in subprocesses of small-space episodic object-location memory: a systematic review of lesion and functional neuroimaging studies.

Object-location memory (OLM) enables us to keep track of the locations of objects in our environment. The neurocognitive model of OLM (Postma, A., Kessels, R. P. C., & Van Asselen, M. (2004). The neuropsychology of object-location memory. In G. L. Allen (Ed.), Human spatial memory: Remembering where (pp. 143-160). Mahwah, NJ: Lawrence Erlbaum, Postma, A., Kessels, R. P. C., & Van Asselen, M. (2008). How the brain remembers and forgets where things are: The neurocognition of object-location memory. Neuroscience & Biobehavioral Reviews, 32, 1339-1345. doi: 10.1016/j.neubiorev.2008.05.001 ) proposes that distinct brain regions are specialised for different subprocesses of OLM (object processing, location processing, and object-location binding; categorical and coordinate OLM; egocentric and allocentric OLM). It was based mainly on findings from lesion studies. However, recent episodic memory studies point to a contribution of additional or different brain regions to object and location processing within episodic OLM. To evaluate and update the neurocognitive model of OLM, we therefore conducted a systematic literature search for lesion as well as functional neuroimaging studies contrasting small-space episodic OLM with object memory or location memory. We identified 10 relevant lesion studies and 8 relevant functional neuroimaging studies. We could confirm some of the proposals of the neurocognitive model of OLM, but also differing hypotheses from episodic memory research, about which brain regions are involved in the different subprocesses of small-space episodic OLM. In addition, we were able to identify new brain regions as well as important research gaps.

Transfer after process-based object-location memory training in healthy older adults.

A substantial part of age-related episodic memory decline has been attributed to the decreasing ability of older adults to encode and retrieve associations among simultaneously processed information units from long-term memory. In addition, this ability seems to share unique variance with reasoning. In this study, we therefore examined whether process-based training of the ability to learn and remember associations has the potential to induce transfer effects to untrained episodic memory and reasoning tasks in healthy older adults (60-75 years). For this purpose, the experimental group (n = 36) completed 30 sessions of process-based object-location memory training, while the active control group (n = 31) practiced visual perception on the same material. Near (spatial episodic memory), intermediate (verbal episodic memory), and far transfer effects (reasoning) were each assessed with multiple tasks at four measurements (before, midway through, immediately after, and 4 months after training). Linear mixed-effects models revealed transfer effects on spatial episodic memory and reasoning that were still observed 4 months after training. These results provide first empirical evidence that process-based training can enhance healthy older adults' associative memory performance and positively affect untrained episodic memory and reasoning abilities. (PsycINFO Database Record

Multi-domain training enhances attentional control.

Multi-domain training potentially increases the likelihood of overlap in processing components with transfer tasks and everyday life, and hence is a promising training approach for older adults. To empirically test this, 84 healthy older adults aged 64 to 75 years were randomly assigned to one of three single-domain training conditions (inhibition, visuomotor function, spatial navigation) or to the simultaneous training of all three cognitive functions (multi-domain training condition). All participants trained on an iPad at home for 50 training sessions. Before and after the training, and at a 6-month follow-up measurement, cognitive functioning and training transfer were assessed with a neuropsychological test battery including tests targeting the trained functions (near transfer) and transfer to executive functions (far transfer: attentional control, working memory, speed). Participants in all four training groups showed a linear increase in training performance over the 50 training sessions. Using a latent difference score model, the multi-domain training group, compared with the single-domain training groups, showed more improvement on the far transfer attentional control composite. Individuals with initially lower baseline performance showed higher training-related improvements, indicating that training compensated for lower initial cognitive performance. At the 6-month follow-up, performance on the cognitive test battery remained stable. This is one of the first studies to investigate systematically multi-domain training including comparable single-domain training conditions. Our findings suggest that multi-domain training enhances attentional control involved in handling several different tasks at the same time, an aspect in everyday life that is particularly challenging for older people. (PsycINFO Database Record

No Evidence for Improved Associative Memory Performance Following Process-Based Associative Memory Training in Older Adults.

Studies attempting to improve episodic memory performance with strategy instructions and training have had limited success in older adults: their training gains are limited in comparison to those of younger adults and do not generalize to untrained tasks and contexts. This limited success has been partly attributed to age-related impairments in associative binding of information into coherent episodes. We therefore investigated potential training and transfer effects of process-based associative memory training (i.e., repeated practice). Thirty-nine older adults (Mage = 68.8) underwent 6 weeks of either adaptive associative memory training or item recognition training. Both groups improved performance in item memory, spatial memory (object-context binding) and reasoning. A disproportionate effect of associative memory training was only observed for item memory, whereas no training-related performance changes were observed for associative memory. Self-reported strategies showed no signs of spontaneous development of memory-enhancing associative memory strategies. Hence, the results do not support the hypothesis that process-based associative memory training leads to higher associative memory performance in older adults.

Does working memory training have to be adaptive?

This study tested the common assumption that, to be most effective, working memory (WM) training should be adaptive (i.e., task difficulty is adjusted to individual performance). Indirect evidence for this assumption stems from studies comparing adaptive training to a condition in which tasks are practiced on the easiest level of difficulty only [cf. Klingberg (Trends Cogn Sci 14:317-324, 2010)], thereby, however, confounding adaptivity and exposure to varying task difficulty. For a more direct test of this hypothesis, we randomly assigned 130 young adults to one of the three WM training procedures (adaptive, randomized, or self-selected change in training task difficulty) or to an active control group. Despite large performance increases in the trained WM tasks, we observed neither transfer to untrained structurally dissimilar WM tasks nor far transfer to reasoning. Surprisingly, neither training nor transfer effects were modulated by training procedure, indicating that exposure to varying levels of task difficulty is sufficient for inducing training gains.

Multi-domain training in healthy old age: Hotel Plastisse as an iPad-based serious game to systematically compare multi-domain and single-domain training.

Finding effective training interventions for declining cognitive abilities in healthy aging is of great relevance, especially in view of the demographic development. Since it is assumed that transfer from the trained to untrained domains is more likely to occur when training conditions and transfer measures share a common underlying process, multi-domain training of several cognitive functions should increase the likelihood of such an overlap. In the first part, we give an overview of the literature showing that cognitive training using complex tasks, such as video games, leisure activities, or practicing a series of cognitive tasks, has shown promising results regarding transfer to a number of cognitive functions. These studies, however, do not allow direct inference about the underlying functions targeted by these training regimes. Custom-designed serious games allow to design training regimes according to specific cognitive functions and a target population's need. In the second part, we introduce the serious game Hotel Plastisse as an iPad-based training tool for older adults that allows the comparison of the simultaneous training of spatial navigation, visuomotor function, and inhibition to the training of each of these functions separately. Hotel Plastisse not only defines the cognitive functions of the multi-domain training clearly, but also implements training in an interesting learning environment including adaptive difficulty and feedback. We propose this novel training tool with the goal of furthering our understanding of how training regimes should be designed in order to affect cognitive functioning of older adults most broadly.

Potentials and limits of plasticity induced by working memory training in old-old age.

BACKGROUND: Old-old age (80+ years) is associated with substantial cognitive decline. In this population, training-induced cognitive plasticity has rarely been studied. While earlier findings on strategy trainings suggested reduced training gains in old-old age, recent results of an extensive process-based working memory (WM) training have been more positive. OBJECTIVE: Following up on previous research, the present study aimed at examining the effects of a short WM training in old-old adults and the influence of baseline WM capacity on training gains. METHODS: A training group (mean age: 86.8 years) and a matched control group (mean age: 87.1 years) participated in the study. The WM training consisted of five tasks that were trained in each of 10 sessions. To evaluate possible transfer effects, executive functions were assessed with two tests before and after training. The training group was divided via median split in high- and low-capacity individuals to determine the influence of baseline WM capacity on training gains. RESULTS: The training group improved in four of the trained tasks (medium-to-large effects). Training gains were significantly larger in the training group than in the control group in only two of those tasks. The training effects were mainly driven by the low-capacity individuals who improved in all trained tasks. No transfer effects were observed. CONCLUSIONS: These positive effects of a short WM training, particularly for low-capacity individuals, emphasize the potential for cognitive plasticity in old-old age. The absence of transfer effects may also point to its limits.

Instruments for comprehensive needs assessment in individuals with cognitive complaints, mild cognitive impairment or dementia: a systematic review.

OBJECTIVE: In recent years, it has become more common to complement the objective assessment of symptoms with an assessment of individual needs patterns that are created by the individual pattern of symptoms. However, little is known on needs patterns in individuals with subjective cognitive impairment, mild cognitive impairment and dementia. Thus, on the basis of an analysis of the development of needs in the course of cognitive decline, we provide an overview of the existing needs assessment instruments with respect to feasibility, validity and reliability. METHOD: We conducted a literature search in PsycINFO and PubMed including all publications up to September 2009. We included needs assessment instruments for use in older individuals with mental or cognitive disorders and dementia. RESULTS: We identified 17 needs assessment instruments for individuals with mental disorders, cognitive impairment or dementia. The analysis of selected articles demonstrated a wide range of needs indicators within different subgroups. Validity and reliability range between moderate and good. CONCLUSIONS: Even though a wide range of needs assessment instruments is available, most instruments assess the needs of individuals with subjective cognitive impairment, mild cognitive impairment and dementia on a general level rather than on a more concrete level that may serve better to inform interventions for this growing population. In addition, we suggest basing the development of instruments firmly on an adequate theoretical framework and standardised procedural guidelines.

Plasticity and imaging research in healthy aging: core ideas and profile of the International Normal Aging and Plasticity Imaging Center (INAPIC).

The key objective of the International Normal Aging and Plasticity Imaging Center (INAPIC) at the University of Zürich is to facilitate research on normal healthy behavioral and neural development and aging to explore the potential for plasticity and compensation across the lifespan. The INAPIC invites international research groups to submit proposals for collaborative projects on these subjects. It is unique in Europe in giving partner groups 'plug and play' access to state-of-the-art neuroimaging techniques, technical support, and assistance in data collection. This article introduces the core ideas of the INAPIC, its key research areas, and the available infrastructure.

Measuring compensation and its plasticity across the lifespan.

PURPOSE: The present paper integrates two important aspects when studying compensation: (1) the knowledge about specific compensational mechanisms and (2) the consideration of lifelong changes in these mechanisms (i.e., plasticity of compensation). Hence, the paper addresses the questions (a) which neural networks are supporting successful cognitive performance across development, (b) what are the associated compensational mechanisms and (c) are these compensational mechanisms plastic across the lifespan. METHODS: To answer these questions, we suggest to integrate behavioural and neuroimaging methods and present specific methods and their advantages and disadvantages. RESULTS: We will illustrate the relevance of this integration by presenting data using ERPs and (s)LORETA to study compensational processes across the lifespan in a higher order cognitive function, i.e., delayed intentional behaviour. A higher activation in old adults or adolescents in successful trials compared to young adults is considered compensatory as specialized cortical regions are selectively recruited in response to task demands. CONCLUSIONS: Findings show that whereas the performance outcome might be the same across age groups, underlying processes and activations might be fundamentally different. We conclude with a discussion about specific implications of this integrative approach when studying the adaptive potentials and limits of human cognition.

Motor brain regions are involved in the encoding of delayed intentions: a fMRI study.

In studies of prospective memory, recall of the content of delayed intentions is normally excellent, probably because they contain actions that have to be enacted at a later time. Action words encoded for later enactment are more accessible from memory than those encoded for later verbal report [Freeman, J.E., and Ellis, J.A. 2003a. The representation of delayed intentions: A prospective subject-performed task? Journal of Experimental Psychology: Learning, Memory, and Cognition, 29, 976-992.]. As this higher assessibility is lost when the intended actions have to be enacted during encoding, or when a motor interference task is introduced concurrent to intention encoding, Freeman and Ellis suggested that the advantage of to-be-enacted actions is due to additional preparatory motor operations during encoding. Accordingly, in a fMRI study with 10 healthy young participants, we investigated whether motor brain regions are differentially activated during verbal encoding of actions for later enactment with the right hand in contrast to verbal encoding of actions for later verbal report. We included an additional condition of verbal encoding of abstract verbs for later verbal report to investigate whether the semantic motor information inherent in action verbs in contrast to abstract verbs activates motor brain regions different from those involved in the verbal encoding of actions for later enactment. Differential activation for the verbal encoding of to-be-enacted actions in contrast to to-be-reported actions was found in brain regions known to be involved in covert motor preparation for hand movements, i.e. the postcentral gyrus, the precuneus, the dorsal and ventral premotor cortex, the posterior middle temporal gyrus and the inferior parietal lobule. There was no overlap between these brain regions and those differentially activated during the verbal encoding of actions in contrast to abstract verbs for later verbal report. Consequently, the results of this fMRI study suggest the presence of preparatory motor operations during the encoding of delayed intentions requiring a future motor response, which cannot be attributed to semantic information inherent to action verbs.

What do subjective cognitive complaints in persons with aging-associated cognitive decline reflect?

BACKGROUND: Subjective cognitive complaints have been included in diagnostic concepts such as Aging-Associated Cognitive Decline (AACD) aiming to identify older adults with cognitive impairments at high risk of developing dementia. Although several studies in normal aging have found that subjective cognitive complaints are related to depressive affect and personality factors, little is known as to whether this is also true for older adults with AACD. METHODS: In 123 older adults diagnosed with AACD and 291 controls, the role of actual cognitive performance, depressive affect, neuroticism and conscientiousness in predicting subjective cognitive complaints was investigated. In separate ordinary least squares regression analyses for both groups with gender, age, years of schooling, cognitive performance, depressive affect, neuroticism and conscientiousness as predicting variables, in the control participants, gender, age, depressive affect and neuroticism were related to subjective cognitive complaints, whereas in the AACD participants only gender and neuroticism accounted for variance in subjective cognitive complaints. Testing for group differences in predictive power, revealed differential effects for gender, depressive affect and neuroticism. CONCLUSIONS: As subjective cognitive complaints in the AACD group were related to neuroticism and gender rather than to cognitive performance, their inclusion in diagnostic concepts such as AACD should be revaluated. However, the nature of subjective cognitive complaints might be qualitatively different in persons diagnosed with AACD compared to those stated by normal older adults.

Planning and realization of complex intentions in traumatic brain injury and normal aging.

The realization of delayed intentions (i.e., prospective memory) is a highly complex process composed of four phases: intention formation, retention, re-instantiation, and execution. The aim of this study was to investigate if executive functioning impairments are related to problems in the formation, re-instantiation, and execution of a delayed complex intention. In this context, it was another aim of the study to investigate the executive functioning hypothesis of cognitive aging in prospective memory performance. It was, therefore, explored if age-related prospective memory decline leads to similar decrements in the process of prospective remembering as executive functioning-related decline in young patients with traumatic brain injury. A group of patients with traumatic brain injury with retrospective memory within normal limits but impaired executive functions, a group of healthy older and a group of healthy younger adults completed a complex prospective memory task that allows for the separate assessment of the four phases of the prospective memory process. All groups showed a similarly high performance in the intention retention phase, whereas the patients with deficits in executive functioning and the older participants performed worse than the healthy young participants in the intention formation, re-instantiation and execution phases. The importance of executive functioning for prospective remembering in traumatic brain injury and normal aging is discussed.