The dark side of the alpha rhythm: FMRI evidence for induced alpha modulation during complete darkness

Eti Ben-Simon, Ilana Podlipsky, Hadas Okon-Singer, Michal Gruberger, Dean Cvetkovic, Nathan Intrator, Talma Hendler

Research output: Contribution to journalArticlepeer-review

Abstract

The unique role of the EEG alpha rhythm in different states of cortical activity is still debated. The main theories regarding alpha function posit either sensory processing or attention allocation as the main processes governing its modulation. Closing and opening eyes, a well-known manipulation of the alpha rhythm, could be regarded as attention allocation from inward to outward focus though during light is also accompanied by visual change. To disentangle the effects of attention allocation and sensory visual input on alpha modulation, 14 healthy subjects were asked to open and close their eyes during conditions of light and of complete darkness while simultaneous recordings of EEG and fMRI were acquired. Thus, during complete darkness the eyes-open condition is not related to visual input but only to attention allocation, allowing direct examination of its role in alpha modulation. A data-driven ridge regression classifier was applied to the EEG data in order to ascertain the contribution of the alpha rhythm to eyes-open/eyes-closed inference in both lighting conditions. Classifier results revealed significant alpha contribution during both light and dark conditions, suggesting that alpha rhythm modulation is closely linked to the change in the direction of attention regardless of the presence of visual sensory input. Furthermore, fMRI activation maps derived from an alpha modulation time-course during the complete darkness condition exhibited a right frontal cortical network associated with attention allocation. These findings support the importance of top-down processes such as attention allocation to alpha rhythm modulation, possibly as a prerequisite to its known bottom-up processing of sensory input. In order to examine the effects of sensory processing vs. attention allocation on alpha rhythm modulation, this EEG-fMRI study used eyes open\close paradigm in light and complete darkness conditions. Using A ridge regression classifier and selective fMRI activations we were able to show that the alpha rhythm modulation is closely linked to the change in the direction of attention regardless of the presence of visual sensory input. These findings support the importance of top down processes to alpha rhythm modulation possibly as a prerequisite to its known bottom up processing of sensory input.

Original languageEnglish
Pages (from-to)795-803
Number of pages9
JournalEuropean Journal of Neuroscience
Volume37
Issue number5
DOIs
StatePublished - Mar 2013
Externally publishedYes

Keywords

  • EEG classification
  • Inhibition hypothesis
  • Intrinsic alertness
  • Simultaneous EEG-fMRI
  • The idle rhythm

ASJC Scopus subject areas

  • Neuroscience (all)

Fingerprint

Dive into the research topics of 'The dark side of the alpha rhythm: FMRI evidence for induced alpha modulation during complete darkness'. Together they form a unique fingerprint.

Cite this