NEMOlab - Neuroelectromagnetic Oscillations Laboratory

The Neuroelectromagnetic Oscillations Laboratory (NEMOlab) is an ERC-funded research group at Aarhus University. We are part of the multi-disciplinary Center of Functionally Integrative Neuroscience (CFIN), and are physically located at Aarhus University Hospital.

Cognition, memory, and perceptual processes are all facilitated by the electrical activity of various neural structures. The faint signatures of this activity in cerebral cortex can be detected with both electroencephalography (EEG) and magnetoencephalography (MEG), and in the retina with electroretinography (ERG). Our research group is dedicated to unraveling how neural oscillations communicate information across the cerebral cortex, as well as between the retina and cerebral cortex.


News

We are recruiting postdocs and PhD students as part of an ERC Starting Grant that will investigate the neural interaction between the retina and cortex. Please contact Sarang if you are interested to apply!

Sarang Dalal, group leader; Monika Zeiller, PhD student; Tommy Clausner, Hiwi; Wibke Naumann, Hiwi; Claudia Leupold, Hiwi (Erlangen); Britta Westner, PhD student; Sabine Leske, postdoc; Maité Crespo García, postdoc.
September 2015.


Retinal-Cortical Oscillations and Coupling

The retina is known to substantially preprocess visual stimuli, and some consider it to be an extension of the brain due to the sophistication of its neural circuitry. The electrical activity of the retina, or the electroretinogram (ERG), can be measured using special electrodes placed on or near the eye. While the ERG is widely used as a clinical diagnostic technique in ophthalmology, it is less known in human neuroscience research. Studies examining information transfer between retina and cerebral cortex in humans remain especially rare. This nascent project records ERG simultaneously with MEG, with the aim of examining oscillatory interactions between retina and visual cortex.


NEMO Members

  • Sarang Dalal
  • Mathis Kaiser
  • Britta Westner

Funding

  • European Research Council
  • Zukunftskolleg
  • Ministerium für Wissenschaft, Forschung und Kunst, Baden-Württemberg

 

 

 

A camera dome for fast and accurate measurements of MEG coils and EEG electrodes

Measuring the locations of MEG sensors and EEG electrodes on the head is a necessary procedure for neural source localization, i.e., determining precisely which brain structures generated which signals. This is typically performed using an electromagnetic or infrared digitizer system; however, the procedure is relatively cumbersome, time-consuming, and ultimately, less accurate than one would hope. In fact, the measurement errors are sufficient to impair source localization performance and possibly prevent the detection of weaker or deeper brain sources (Dalal et al., 2014).

However, the proliferation of affordable digital cameras has made feasible an affordable, faster, and more accurate solution: by taking photographs of a subject from a variety of angles, a 3D computer model of it can be created using a technique called photogrammetry. This strategy has been used to create several familiar 3D applications, such as the 3D views of buildings featured in Google Maps and the iconic “bullet time” sequence featured in the film The Matrix.

With the aim of measuring the positions of MEG coils and EEG electrodes, our research assistant, Tommy Clausner, spent the summer constructing a dome containing an array of 35 cameras. This included writing the software to control it and assemble the resulting data, which is now released as the open source janus3D (available at https://janus3d.github.io/janus3D_toolbox/ ).

EEG session, while the post-processing of the images will be less error-prone than the current MRI coregistration procedure and ultimately result in more reliable neural source localization. A participant simply stands underneath the dome, after the MEG coils or EEG cap have been fitted. In an instant, the cameras simultaneously capture all 35 different viewpoints around the head, and the participant is then immediately ready for the MEG or EEG recording. Offline, the different photographs are assembled into a 3D representation of the participant’s head, together with the MEG or EEG positions. The participant’s facial landmarks are then semi-automatically matched to their corresponding structural MRI, yielding the precise coordinates of the MEG sensors or EEG electrodes relative to the brain. 

We greatly look forward to integrating the camera dome into our standard laboratory protocol for MEG and EEG recordings.

Custom-built dome containing an array of 35 digital cameras, located in CFIN’s MEG laboratory.
Screenshot of janus3D showing a 3D reconstruction derived from photographs of a volunteer wearing an EEG cap (left) and the corresponding electrode locations matched to the volunteer’s MRI scan (right).

BrainCycles

In this project we will have the rare opportunity to record brain activity directly from the basal ganglia in Parkinson’s disease patients. These patients have been implanted electrodes for deep brain stimulation at the Düsseldorf Movement Disorders Clinic at the Heinrich Heine University (Prof. Alfons Schnitzler). These implants provide unique access to directly record neuronal activity while patients are engaged in performing controlled tasks such as walking. 

https://www.mmsp.uni-konstanz.de/research/finished-projects/braincycles/

    

Contribution of Deep Brain Structures to Cortical Processing

Cognition, memory, and perceptual processes are all facilitated by the electrical activity of various brain structures. The faint signatures of this activity can be detected with both electroencephalography (EEG) and magnetoencephalography (MEG), with most research aiming to resolve activity near the brain surface. However, neural processing inevitably involves deeper brain structures such as the hippocampus, which plays important roles in memory encoding and spatial navigation. 

Intracranial EEG can allow reliable detection of the hippocampus in certain patient populations. However, only noninvasive EEG and MEG can provide a “whole brain” view of neural dynamics. More accurate representation of recording parameters as well as improved physics models of the head may facilitate the detection of weaker brain signals, and by extension, deeper brain sources. Simultaneous recording of noninvasive MEG and intracranial EEG is another technique to provide information on the functional connections between deep brain structures and cortical processing, as well as provide clues for noninvasive detection of deep sources.


NEMO Members

  • Maité Crespo-García
  • Monika Zeiller
  • Sarang Dalal

External Partners

  • Stefan Rampp & Hajo Hamer (Universitätsklinikum Erlangen)
  • Carsten Wolters (University of Münster)

Funding

  • DFG grant DA1485/1

 

 

 

Simultaneous MEG or fMRI and Intracranial EEG

This transnational project aims to address this important limitation by performing icEEG recording 
of high frequency brainwaves with simultaneous MEG and functional magnetic resonance 
imaging (fMRI). The two latter imaging methods can explore the function of the entire brain 
noninvasively, and if coupled with icEEG, provide information regarding changes occurring in 
virtually every brain region when local high-frequency brainwaves are detected by intracerebral 
electrodes. Ultimately, this will allow us to develop new methods to accurately infer the location 
and extent of high-frequency activity within the brain purely from noninvasive imagery.


NEMO Members

  • Daniel Wong
  • Britta Westner
  • Sarang Dalal

External Partners

  • Carolina Ciumas, Jean-Philippe Lachaux, Philippe Ryvlin (Lyon Neuroscience Research Center, France)
  • Gustavo Deco (Universitat Pompeu Fabra, Barcelona, Spain)

Funding

 

 

 

Hemispheric dominance in single-sided postlingual deafness and changes/plasticity induced by cochlear implants

The suppression of auditory alpha oscillations during speech processing has been shown to be correlated with the level of comprehension of spectrally and temporally degraded words. Since cochlear implants (CIs) present the wearer with spectrally degraded speech while leaving the temporal envelope intact, it is expected that processing of spectral and temporal speech degradation will be affected by CI implantation. This project shall examine the effects of cochlear implantation on healthy ear comprehension of degraded speech in patients with single-sided deafness (SSD) using behavioral and electrophysiological measures.


NEMO Members

  • Daniel Wong
  • Sarang Dalal

External Partners

  • Jonas Obleser (Max Planck Institute Leipzig)
  • Tobias Kleinjung (Universitätsspital Zürich)
  • Nathan Weisz (University of Trento)

Funding

  • Erasmus Mundus Auditory Cognitive Neuroscience network
  • Zukunftskolleg
Associate Professor
Sarang S. Dalal