Center for Neuroplasticity and Pain

Ph.D. defence by Ali Asghar Zarei

Ali Asghar Zarei will defend his Ph.D. thesis “Modulation of Sensory Perceptions and Cortical Responses Following TENS” on Tuesday 17 August 2021 at 13.00.

Last modified: 03.08.2021


13.00 Opening by the Moderator Winnie Jensen
13.05 Ph.D. lecture by Ali Asghar Zarei
13.50 Break
14.00 Questions and comments from the Committee
          Questions and comments from the audience at the Moderator’s discretion
16.00 Conclusion of the session by the Moderator


The Faculty Council has appointed the following adjudication committee to evaluate the thesis and the associated lecture: 

Dr. Aleksandra Vuckovic, Senior Lecturer, University of Glasgow, Scotland
Dr. André Mouraux, Professor, Universite Catholique de Louvain, Belgium


Dr. Laura Petrini, Aalborg University, Denmark


Dr. Winnie Jensen, Aalborg University, Denmark



Recent increasing awareness of diminishing quality of life and societal impact of phantom limb pain (PLP) pose an increasing burden on rehabilitation within the health care system. Amputation deprives the nervous system of sensory input leading to anatomical and physiological changes at the peripheral and central level, contributing to the mechanisms generating PLP. Transcutaneous electrical nerve stimulation (TENS) has been suggested as a possible non-invasive, drug-free pain treatment for chronic and neuropathic pain (e.g., PLP and back pain). However, the underlying mechanism of TENS's analgesic effect on the central nervous system (CNS) in amputees to induce phantom limb pain relief is not yet understood. The objective of this Ph.D. project was therefore to investigate possible altered cortical responses following TENS in amputees and healthy subjects. 

The Ph.D. thesis was based on a series of three studies. Study I was conducted to evaluate the effect of TENS on perceived sensation and induced changes in SEP waves since the SEP waves have been reported as a verified biomarker for assessing pain and sensory processing. The results showed significant cortical inhibition in somatosensory evoked potentials (SEPs) for at least up to an hour following TENS intervention which was associated with a suppression in theta and alpha oscillation and perceived intensity. The brain functional network alternation following TENS was investigated in Study II. Functional brain network from eight brain areas corresponding to pain and sensation across five frequency bands was examined. The results of Study II demonstrated significant changes in local and global brain network indices following the application of TENS. The induced changes following TENS in the brain and associated PLP relief were evaluated in PLP patients and compared with healthy subjects in Study III. The finding of Study III reported the same changes in SEP pattern and FC features. At the same time, a meaningful PLP reduction following TENS was found.

In conclusion, the underlying CNS mechanism of TENS on pain and sensation was found to affect both the sensory-motor cortex and the functional connectivity between brain regions involved in pain and sensory processing.