Cognitive training and transcranial electrical stimulation for working memory enhancement

Student thesis: Phd


Working memory (WM) underpins the successful performance of goal-directed behaviours, such as following instructions. Healthy older adults free of underlying neurological disease often present with WM deficits. At the other end of the developmental spectrum, WM can be impaired in childhood. For instance, impaired WM is a frequent complaint of individuals presenting with Neurofibromatosis Type 1 (NF1), a genetic disorder that can affect cognition in early development. Impaired WM can negatively impact many aspects of an individual's life, including their everyday functioning, academic/occupational performance, and quality of life. The development of therapeutic interventions that may enhance WM or delay/prevent the onset or progression of its deterioration is therefore important. Non-pharmacological techniques commonly administered to enhance WM include cognitive training (CT) and transcranial electrical stimulation (tES). However, there is a lack of clarity concerning their effectiveness, and how beneficial effects can be maximised. For that reason, the overarching motivation of this thesis was to advance understanding of non-pharmacological approaches for modulating WM in healthy (older) adults and a paediatric population with NF1. The first empirical chapter (chapter 2) details a systematic review of the effects of transcranial alternating current stimulation (tACS) on memory in healthy adults. Findings indicate a small-to-medium effect of tACS on WM and long-term memory, suggesting that it is possible to modulate memory using tACS. Additionally, results suggest frequency-specific effects of tACS on cortical oscillatory activity. The second empirical study (chapter 3) investigated the effect of training schedule on home-based CT targeting WM in healthy older adults. Significant training gains were observed on the training task, but there was no evidence of transfer to untrained tasks. Results suggest that intensive training is as effective as distributed training. The final two empirical chapters (chapters 4 and 5) focused on advancing the WM-related literature with respect to NF1. Specifically, study 3 presents an electroencephalography (EEG) study of resting state and WM (chapter 4). Findings point to aberrant resting state oscillatory activity in adolescents with NF1. Finally, study 4 details an exploratory investigation of the effects of combined CT and transcranial direct current stimulation (tDCS) on oscillatory activity in NF1 (chapter 5). Theta-range activity was susceptible to modulation following CT. Furthermore, preliminary findings suggest that tDCS does not augment CT effects on oscillatory activity, although replication using a larger sample size is required before strong conclusions can be drawn. Collectively, this empirical research advances the understanding of non-pharmacological approaches for WM modulation.
Date of Award31 Dec 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorGorana Pobric (Supervisor), Jason Taylor (Supervisor) & Laura Brown (Supervisor)


  • Transcranial alternating current stimulation
  • Non-invasive brain stimulation
  • Neurofibromatosis type 1
  • Cognitive training
  • Cortical oscillations
  • Electroencephalography
  • Transcranial direct current stimulation

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