Compensatory Brain Activity in Older Adults.
Condition: Old Age; Dementia; Aging; Cognitive Decline
MeSH terms: Cognitive Dysfunction
Study type: Interventional

Summary: 
      There are two important aspects in which the present project will allow to enrich our
      understanding of compensatory brain activity in older adults. First, in the studies that have
      been conducted so far the compensatory brain activity in older adults was investigated
      primarily with the use of the functional magnetic resonance (fMRI) or positon emission
      tomography (PET). In order to identify compensatory activity in our study we will use
      electroencephalographic markers (observable in EEG). It will allow to confirm the assumptions
      about compensatory brain activity relying on new data, as in EEG research the brain markers
      of the same cognitive processes are different from those used in fMRI and PET research. What
      is more, in the studies conducted so far brain activity in older adults was only registered
      and interpreted, whereas the present study additionally adds the training component. The aim
      of our study is to see if it is possible to influence the compensatory brain activity through
      cognitive functions training, relying on working memory training. Theoretically, such a
      training should optimize brain activity in older adults, namely evoke compensatory brain
      activity during difficult tasks in order to make them easier, whereas in the case of easy
      tasks it should lead to the disappearance of the need to trigger compensatory activity. This
      assumption will be verified in an experimental setting.

      The participants will be divided into six groups: two experimental (the groups of young and
      old adults), and by analogy two active control groups and two passive (no-contact) control
      groups. The experiment was designed in the following way: (1) All groups will be subjected to
      pre-test measurements that will be EEG registration during a cognitive task execution at
      different difficulty levels; (2) Experimental groups will undergo working memory training.
      Over the period of 4 weeks participants in the experimental groups will take part in 12
      training sessions. In the active control groups instead of the n-back training the practice
      of tasks which do not involve working memory will be introduced. Participants of the passive
      control groups will be awaiting post-test (no-contact control); (3) In all groups post-test
      measurements will be administered analogically to the pre-test measurements in order to
      assess changes in cognitive tasks performance and related brain activity.
    

Detailed description: 
      Compensatory brain activity in older adults is an important research area concerned with
      cognitive aging and the possibilities of cognitive enhancement in late adulthood. Most
      comprehensively these issues are addressed by the STAC model - Scaffolding Theory of Aging
      and Cognition. The present study will be concerned with empirical investigations into some of
      its theoretical assumptions. The innovative character of the research solutions included in
      the present project is based, on the one hand, on new approaches to the verification of the
      STAC assumptions and, on the other hand, on the verification of the assumptions that have not
      been subjected to systematic investigations so far. Such a research agenda has been motivated
      by gaps in existing knowledge regarding some of the phenomena described in the STAC model.
      Filling these gaps will be the contribution of the project to the development of research on
      cognitive aging.

      In this context, the aims of the study are the following:

        1. The verification of the STAC model assumptions about the cognitive processes triggered
           during compensatory brain activity in older adults based on EEG time-frequency analyses.

        2. The verification of the STAC model assumption about the possible influence of cognitive
           training on the emergence and disappearance of compensatory brain activity in older
           adults, has not been investigated so far.

      Research problems justifying the aims:

      Re. 1. The cognitive interpretation of compensatory brain activity in older adults, both in
      the STAC model and in light of research findings collected until now, is based on incomplete
      premises. Compensatory brain engagement is the overactivation observed in certain brain
      regions in older adults which is linked to a better performance on cognitive tasks. Better
      performance on cognitive tasks is regarded here as evidence for ongoing compensation.
      Compensatory brain activity in older adults has been confirmed by numerous studies utilizing
      fMRI and PET scans, which are the two most dominant neuroimaging methods in this area. Models
      of compensatory brain activity in older adults, such as the STAC model, are based on these
      neuroimaging data. Theoretical interpretations in terms of cognitive processes are imposed on
      these observations only subsequently. Thus, the verification of the compensatory mechanisms
      described in these models is limited as the development and the verification of the model are
      based on the same methodology. Subsequent studies that found a positive relationship between
      the overactivation of specific brain regions and better performance on cognitive tasks
      confirmed the empirical relationship that led to the development of the theoretical model.
      However, the confirmation of the relationship alone does not suffice to verify the
      theoretical interpretation encapsulated in the model. The need to deepen the understanding of
      cognitive processes engaged in compensation was indicated by the very authors of the STAC
      model.

      The use of the EEG methods in the project (event-related oscillations, ERO), instead of the
      fMRI or PET imaging, will contribute to this goal. The reason is that the EEG-based approach
      requires hypotheses based not only on the localization of compensatory brain activity but
      also on the cognitive processes theoretically linked to the activity of interest. Since fMRI
      and PET findings cannot be directly expressed in EEG terms, the following reasoning has been
      employed to predict the results: compensatory brain overactivation observed in fMRI and PET →
      cognitive interpretation of the overactivation → determination of the EEG indicators
      (event-related synchronization, ERS and event-related desynchronization, ERD) of the
      cognitive processes specified based on the interpretation → the verification of the existence
      of the indicators in EEG signal recorded in older adults when their cognitive performance
      does not diverge from performance observed in young adults (and their lack when the older
      adults perform worse than young subjects). In other words, the aim is to identify the neural
      markers of the processes that have been proposed by the STAC model to account for
      compensatory brain activity based on the activation of certain brain structures as registered
      with the fMRI and PET but with the use of another technique that relies on alternative
      indicators of cognitive processes' engagement. Thus, thanks to the use of EEG measurements in
      the study, it will be possible to verify the compensatory role of the cognitive processes and
      not only confirm the localization of the overactivation, which has been a significant
      limitation of the studies conducted so far.

      Re. 2. It is unknown if it is possible to influence compensatory brain activity in older
      adults through cognitive training, which is assumed in the STAC model. The STAC model assumes
      that compensatory brain activity can be stimulated by various kinds of interventions,
      including cognitive training. The authors of the model proposed that such training in the
      case of an under-activation or a deterioration of a neural network engaged in the cognitive
      task should establish new scaffolds, whereas when the performance on the tasks already relies
      on compensatory overactivation of certain brain areas, the training should decrease the
      activation in these secondary "scaffolded" regions and improve efficiency in the primary
      networks - a kind of a restoration of the brain activity characteristic to younger
      individuals.

      Assumptions about the aims of the training indicated by the authors of the STAC model have
      not been verified empirically so far. Research findings on the training-induced changes in
      neural activity have been only interpreted post facto in the context of the STAC model or
      narrower models of compensatory brain activity in older adults: CRUNCH - Compensation-Related
      Utilization of Neural Circuits Hypothesis, PASA - Posterior-Anterior Shift in Aging or HAROLD
      - Hemispheric Asymmetry Reduction in Older Adults.

      To our best knowledge, only two publications have reported so far studies that were designed
      directly to verify the assumptions of one of the models of compensatory brain activity in
      older adults - CRUNCH. The study, however, was conducted with the use of fMRI imaging, not
      EEG, and without including young adults, who constitute a reference group fundamental to the
      assessment of the specificity of brain activity characteristic to old age.

      Although some studies on the efficiency of cognitive training have been interested in the
      neuro-correlates of training, in most of them the sample consisted solely of young
      individuals, and even if older subjects were included the research agenda did not address
      hypotheses regarding compensatory scaffolding in old age, or they were to interpret in such
      context only partially.

      In the present study, the assumptions of the STAC model regarding the effects of cognitive
      training on compensatory scaffolding in older adults will be verified experimentally with the
      use of working memory (WM) training. The task employed in the training will be based on the
      n-back paradigm, which is the most common type of training employed in contemporary research.
      Although the transfer effect of n-back training is questionable, there is abundant evidence
      for its effectiveness in improving performance on the trained task.

      The project was conducted in two phases: preliminary and experimental. The preliminary phase
      has three main goals: (1) Empirical determination of three difficulty levels of the n-back
      task for the subsequent use during EEG recordings - the lowest level of difficulty should be
      easy for old adults (with no difference in accuracy compared to young adults) and two other
      levels should be increasingly (significantly) more difficult; (2) Selection of the task for
      the active control group. This task should not involve working memory but should seem to
      improve the same aspect of cognitive functioning as the n-back task, which will be verified
      by experts as well as old and young lay persons not belonging to the study sample; (3)
      Recruitment of volunteers for the study sample and the assignment of the selected
      participants to the experimental and control groups ensuring equivalence of these groups in
      terms of cognitive performance (according to the cognitive assessment in the preliminary
      phase). Moreover, the preliminary phase is devoted also to the programming of the
      computerized tasks that will be used in the study. Computerized tasks for cognitive
      assessment and training will be developed in the PsychoPy programming environment with the
      use of the Python programming language.

      The sample comprised 3 groups of older adults: experimental (n = 25), passive control (n =
      22), active control (n = 7), and young adults: experimental (n = 25), passive control (n =
      25), and active control (n = 12). Pre-test and post-test measurements were conducted in all
      groups.

      At pre-test and post-test participants in all groups performed a computerized n-back task at
      three levels of difficulty (determined beforehand in the preliminary phase) with simultaneous
      EEG signal recording. Moreover, in all groups, cognitive assessment was conducted, which will
      concern: working memory and short-term memory capacity, attentional focus and psychomotor
      speed, interference resistance, and inhibition ability. Only the n-back task will be
      performed with EEG registration.

      The experimental factor was the intervention using the n-back training, namely older and
      younger participants assigned to the experimental groups participated in a computerized
      process-based working memory training with the use of the n-back task. The training
      intervention lasted 4 weeks and consisted of 12 training sessions, about 45 minutes each. The
      n-back tasks used for the training purposes were analogous to those used at pre-test and
      post-test measurement (the same interface, instructions, and actions necessary to complete
      the task). The difference was the difficulty level because, in the case of the training, it
      was not planned but raised adaptively, according to the current progress of the particular
      participant. The other two groups (of old and young adults) will be active control groups. In
      these groups, cognitive training intervention with the use of n-back task was replaced by
      multi-domain non-adaptive training. The training schedule in active control groups will be
      the same as in the experimental groups. There were also two passive control groups (of old
      and young adults), which during the training period were not contacted by researchers, and no
      cognitive interventions were administered.
    

Intervention name(s): working memory adaptive training; multi-domain non-adaptive control training
Intervention type(s): Behavioral; Behavioral
Intervention description(s): The computerized n-back training lasted 4 weeks and consisted of 12 training sessions, 3 per week, about 45 minutes for each; The cognitive training in active control groups included cognitive tasks involving: visual-spatial functions, visual and verbal memory, reasoning on visual and verbal material, and calculia. The training schedule in active control groups was the same as in the experimental groups.
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Intervention model description: A pretest-posttest study design with one experimental group and two control (passive and active control) groups was applied.
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: cognitive intervention; cognitive training; cognitive aging; neuroplasticity; compensatory brain activity; eeg