Seeing through the skull: Advanced EEGs use MRIs to accurately measure cortical activity from the scalp

Alan Gevins, Jian Le, Paul Brickett, Bryan Reutter, John Desmond

Research output: Contribution to journalArticlepeer-review


There is a vast amount of untapped spatial information in scalp- recorded EEGs. Measuring this information requires use of many electrodes and application of spatial signal enhancing procedures to reduce blur distortion due to transmission through the skull and other tissues. Recordings with 124 electrodes are now routinely made, and spatial signal enhancing techniques have been developed. The most advanced of these techniques uses information from a subject's MRI to correct blur distortion, in effect providing a measure of the actual cortical potential distribution. Examples of these procedures are presented, including a validation from subdural recordings in an epileptic patient. Examples of equivalent dipole modeling of the somatosensory evoked potential are also presented in which two adjacent fingers are clearly separated. These results demonstrate that EEGs can provide images of superficial cortical electrical activity with spatial detail approaching that of O15 PET scans. Additionally, equivalent dipole modeling with EEGs appears to have the same degree of spatial resolution as that reported for MEGs. Considering that EEG technology costs ten to fifty times less than other brain imaging modalities, that it is completely harmless, and that recordings can be made in naturalistic settings for extended periods of time, a greater investment in advancing EEG technology seems very desirable.

Original languageEnglish (US)
Pages (from-to)125-131
Number of pages7
JournalBrain Topography
Issue number2
StatePublished - Dec 1 1991
Externally publishedYes


  • Deblurring
  • Evoked potential
  • Finite element model
  • High-resolution EEG
  • Laplacian derivation
  • MRI
  • Spatial signal enhancement

ASJC Scopus subject areas

  • Anatomy
  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging
  • Neurology
  • Clinical Neurology


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