Prof. Dr. Dietrich Lehmann

 

Main Goals, Keywords

Studies on the functional significance of the brain electric microstates in perception, cognition and emotion, and their pathological aberrations in schizophrenia. Studies on spatial organisation of brain electric activity during emotional states and during altered states of consciousness.

Key words: power spectral analysis, microstates, state transitions, 'atoms of thought', source modelling of the potential field, dimensional complexity

Previous and Current Research

Besides conventional power spectral analysis and computed estimates of the dimensional complexity of the EEG and ERP time series, we use analysis approaches that give equal weight to the data's temporal and spatial characteristics. In these approaches, preference is given to data-driven procedures where top-down con- straints are kept to a minimum. Three approaches are: (1) Parsing of the series of brain electric momentary maps into epochs of quasi-stable topography, the so-called microstates. Since different momentary potential maps must have been generated by the activity of different neural assemblies, it is reasonable to assume that they represent different brain functional states, i.e., different steps or modes of information processing. (2) Source modelling of the potential fields in the time domain, and source modelling in the frequency domain. (3) Computation of the global dimensional complexity of the brain electric signals. In addition to the conventional dimensional complexity single time series (after state space reconstruction following Takens' procedure), we apply computations of the 'global dimensional complexity' of the trajectory of the brain state (as assessed by the momentary maps) in state space.

Selected Publications

• Lehmann D, Faber PL, Tei S, Pascual-Marqui RD, Milz P, Kochi K. Reduced functional connectivity between cortical sources in five meditation traditions detected with lagged coherence using EEG tomography. Neuroimage. 2012 Apr 2;60(2):1574-86. Epub 2012 Jan 12.
• Lehmann D, Michel CM. EEG-defined functional microstates as basic building blocks of mental processes. Clin Neurophysiol. 2011 Jun;122(6):1073-4. Epub 2010 Dec 3.
• Lehmann D. Multimodal analysis of resting state cortical activity: what does fMRI add to our knowledge of microstates in resting state EEG activity? Commentary to the papers by Britz et al. and Musso et al. in the current issue of NeuroImage. Neuroimage. 2010 Oct 1;52(4):1173-4. Epub 2010 May 20.

URL

http://www.uzh.ch/keyinst/