Investigating the Neural Correlates in Memory Retrieval After HD-tDCS
Condition: Healthy Adults
Study type: Interventional

Summary: 
      The overall objective of this study is to investigate the neural correlate in retrieval
      memory task.

      The aim of the study is to understand the undergoing changes in late positive ERP component
      during retrieval memory task when stimulating the posterior cingulate cortex (PCC) with High
      Definition Transcranial Direct Current Stimulation (HD-tDCS).
    

Detailed description: 
      Retrieval memory is supported by distinct retrieval process known as recollection and
      familiarity. These two process have been associated with distinct event related potentials
      (ERPs). At the time of retrieval, familiarity is associated with modulation of the FN400, an
      enhanced positivity for old items relative to new items observed from approximately 400-600ms
      post stimulus onset. The FN400 tends to have mid-frontal scalp distribution which can extend
      to left and right frontal areas and central midline regions. In contrast, recollection has
      been linked with modulation of positive going waveform that emerges approximately 600ms post
      stimulus and is typically maximal over parietal sites and referred to as late positive
      component (LPC). In addition, FN400 is found to increase gradually as a function of item
      retrieval confidence whereas LPC is limited to high confidence retrieval response.

      High Definition transcranial Direct Current Stimulation (HD-tDCS ) is a non-invasive
      neuromodulation technique. Compared to the standard bipolar montage used by the conventional
      tDCS, it uses arrays of smaller, specially designed electrodes to deliver a constant and low
      current directly to the cortical brain areas to increase the spatial focality. Studies show
      that the cortical area undergoing stimulation with HD-tDCS is more restricted compared to the
      standard bipolar montage of conventional tDCS. Moreover, tDCS has been proposed as a
      therapeutic procedure in various diseases and tDCS in healthy adults have demonstrated to
      improve cognitive and memory performance, but information regarding the effects of HD-tDCS
      targeting the PCC and its impact on memory retrieval is scarce. By targeting the PCC area by
      HD-tDCS, we want to introduce a safer, easier-to-use and more accurate non-invasive
      neuromodulation procedure. The dysfunctions of posterior cingulate cortex hav been linked to
      a range of psychiatric and neurological condition such as Alzheimer's disease, schizophrenia,
      autism, depression and attention deficit hyperactivity disorder, as well as aging. It shows
      increased activity when subject retrieve autobiographical memories suggests its internal
      orientated function. PET and ERP combined studies have shown greater blood flow medial
      temporal lobe with a brief late positive ERP component in PCC. Therefore, in this study we
      aim to understand whether HD-tDCS targeting the PCC can modulate the late positive ERP
      component.
    

Intervention name(s): active anodal HD-tDCS; sham HD-tDCS; active cathodal HD-tDCS
Intervention type(s): Device; Device; Device
Intervention description(s): 1) active anodal HD-tDCS with memory task; 2) sham HD-tDCS with memory task; 3) active cathodal HD-tDCS with memory task
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: Participants will be randomly assigned to one of three groups: (1) active HD-tDCS with retrieval memory task, (2) sham HD-tDCS with retrieval memory task, (3) active cathodal HD-tDCS with retrieval memory task
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Basic Science