Modulating Prospective Memory in Older Adults With Non-invasive Brain Stimulation
Condition: Healthy Aging
Study type: Interventional

Summary: 
      Prospective memory is the ability to remember to carry out intentions with a certain delay
      (e.g. remember to buy stamps when passing a postal office). Prospective memory tasks require
      a large degree of self-initiated retrieval and in the absence of a prompt to recall, people
      must 'remember to remember' by their own volition. Thus, prospective memory is a challenge -
      especially in old age with increasing health-related prospective memory demands.

      Previous studies reported links between neural activity in specific brain regions and
      prospective memory performance. Yet, the mere occurrence of a change in brain activity in
      concomitance with performance of a behavioral task is not sufficient to confirm a causal
      relationship between the two phenomena. Therefore, this study aims to apply non-invasive
      brain stimulation to facilitate or inhibit activity in different brain regions presumed to be
      functionally associated with prospective memory. Additional to the prospective memory tasks,
      the investigators will implement control tasks (i.e., attention) to assess whether
      stimulation will specifically enhance prospective memory performance or whether other
      cognitive functions will be modulated additionally.

      It is hypothesized that stimulation will lead to changes in prospective memory functioning.
      Further, the investigators expect that facilitation of attentional processes might be linked
      to prospective memory improvements.
    

Detailed description: 
      This study aims to modulate neural activity in the left and right inferior frontal lobe as
      well as in the right superior parietal lobe via high-definition transcranial direct current
      stimulation (HD-tDCS) in older adults. There is evidence from functional magnetic resonance
      imaging (fMRI) studies that these areas are involved in prospective memory performance in
      younger and older adults but a causal relation between activity in these areas and responses
      in prospective memory tasks has not been established so far.

      A double blind, sham-controlled, parallel group design will be applied. Healthy older adults
      (n=105) will participate in two separate sessions: During the first baseline session, no
      stimulation is applied. For the second session, participants will then be randomly assigned
      to one of seven experimental groups (cathodal vs. anodal right inferior frontal lobe (rIFL);
      cathodal vs. anodal left inferior frontal lobe (lIFL); cathodal vs. anodal right superior
      parietal lobe (rSPL); or sham). Real stimulation will be applied during 20 minutes with one
      Milliamp (mA). In case of sham stimulation (i.e., control intervention), the electrode
      positions and the attachment procedures correspond to those of real tDCS but the electrical
      current will only be ramped up to one mA and switched off completely after 30 s of
      stimulation.

      The primary objective of this study is the modulation of prospective memory performance in a
      computer-based task via tDCS. Further, this study aims to clarify the role of attentional
      control for prospective memory performance, as both processes seem to recruit similar neural
      structures. Additionally, naturalistic and self-rated prospective memory performance will be
      assessed.

      It is hypothesized that stimulation of the right inferior frontal lobe will lead to changes
      in prospective memory performance and attentional processes. Whether cathodal or anodal
      stimulation will enhance performance is not clear yet, since previous fMRI studies were
      inconsistent about activity changes in older adults. Further, the investigators expect that
      anodal stimulation of the left inferior frontal cortex may lead to faster responses to
      prospective memory stimuli, whereas cathodal stimulation of the same area may lead to
      prolonged reaction times. It is hypothesized that attentional control will not be affected by
      stimulation of the left inferior frontal lobe. Finally, the investigators expect that anodal
      stimulation of the right superior parietal cortex will lead to better prospective memory and
      attentional control performance, whereas cathodal stimulation will have detrimental effects
      on both functions.
    

Intervention name(s): Non-invasive brain stimulation; Sham stimulation
Intervention type(s): Device; Device
Intervention description(s): Stimulation will be applied once per subject with one mA for 20 minutes over either the left inferior frontal lobe, the right inferior frontal lobe or the right superior parietal lobe.; The electrode positions and the attachment procedures correspond to those of real tDCS but the electrical current will only be ramped up to 1 mA and switched off completely after 30 s of stimulation.
Other intervention name(s): high-definition transcranial direct current stimulation; HD-tDCS; Soterix medical
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science