Brain Topography

, Volume 22, Issue 3, pp 185–190 | Cite as

Characteristic Changes in Brain Electrical Activity Due to Chronic Hypoxia in Patients with Obstructive Sleep Apnea Syndrome (OSAS): A Combined EEG Study Using LORETA and Omega Complexity

  • Marton TothEmail author
  • Bela Faludi
  • Jiri Wackermann
  • Jozsef Czopf
  • Istvan Kondakor
Original Paper


EEG background activity of patients with obstructive sleep apnea syndrome (OSAS, N = 25) was compared to that of normal controls (N = 14) to reflect alterations of brain electrical activity caused by chronic intermittent hypoxia in OSAS. Global and regional (left vs. right, anterior vs. posterior) measures of spatial complexity (Omega) were used to characterize the degree of spatial synchrony of EEG. Low resolution electromagnetic tomography (LORETA) was used to localize generators of EEG activity in separate frequency bands. Comparing patients to controls, lower Omega complexity was found globally and in the right hemisphere. Using LORETA, an increased medium frequency activity was seen bilaterally in the precuneus, paracentral and posterior cingulate cortex. These findings indicate that alterations caused by chronic hypoxia in brain electrical activity in regions associated with influencing emotional regulation, long-term memory and the default mode network. Global synchronization (lower Omega complexity) may indicate a significantly reduced number of relatively independent, parallel neural processes due to chronic global hypoxic state in apneic patients as well as over the right hemisphere.


LORETA Obstructive sleep apnea syndrome Omega complexity Quantitative EEG Posterior cingulate cortex Precuneus Posterior parietal cortex 



This work was supported by grant from the Hungarian Science Found (OTKA T048338). The authors thank Dr. Pascual-Marqui at the KEY Institute for Brain-Mind Research, Zurich, Switzerland for making available the LORETA-Key software and his help in the use of this program.


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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Marton Toth
    • 1
    Email author
  • Bela Faludi
    • 1
  • Jiri Wackermann
    • 2
  • Jozsef Czopf
    • 1
  • Istvan Kondakor
    • 3
  1. 1.Department of Neurology, Medical CenterUniversity of PécsPécs, Rét utca 2Hungary
  2. 2.Department of Empirical and Analytical PsychophysicsInstitute for Frontier Areas of Psychology and Mental HealthFreiburg i. Br.Germany
  3. 3.Department of NeurologyTeaching County Hospital of Bács-KiskunKecskemét, Nyíri u. 38Hungary

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