The relationship between glutamate and oscillatory activity in a repetition suppression paradigm – a combined MR-spectroscopy and EEG study
Bangor University, United Kingdom
University College London, United Kingdom
University of Nottingham, United Kingdom
Institute of Psychology, University Osnabrueck, Germany
Philips Medical, United Kingdom
Department of Psychology City University, Spain
The formation and sharpening of cortical object representations requires the activation of neuronal cell assemblies and has been correlated to synchronized neuronal activity in the gamma band range using the repetition suppression paradigm. There is also evidence that magnetic resonance spectroscopy (MRS) can be used to measure the relationship between synchronised oscillatory activity and neurometabolites. However, the temporal relationship between MRS and gamma band activity has not yet been investigated. We present here event-related MRS (ER-MRS) from the lateral occipital cortex and concurrently acquired electroencephalography (EEG) results collected during a repetition suppression paradigm in twelve healthy subjects. Subjects were presented repeatedly with line drawings of real and abstract objects. ER-MRS data was collected using a Philips 3T after each stimulus, and averaged to produce one set of MRS data per stimulus type. jMRUI software was used to provide concentration estimates for Glutamate (Glu) as well as the other major neurometabolites. EEG data was acquired continuously at 5 kHz and analyzed using custom routines in MATLAB. EEG data showed decreasing evoked gamma band activity (eGBA) with increasing repetition of real stimuli and the opposite pattern for abstract stimuli. Average Glu was lower after real stimuli presentation compared to abstract stimuli (p = .02), with the opposite effect seen for GABA. A significant correlation between Glu levels and the eGBA was also found for real stimuli. These results provide the first in-vivo evidence of changes in neuronal electrical activity with related changes in simultaneously measured Glu concentrations, and provide a window into the underlying neurochemical substrates of neuronal network activity. Funding: Supported by WICN Grant WBI31.
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Poster Sessions: Multimodal Integration of EEG, MEG and fMRI data
(2011). The relationship between glutamate and oscillatory activity in a repetition suppression paradigm – a combined MR-spectroscopy and EEG study.
Front. Hum. Neurosci.
XI International Conference on Cognitive Neuroscience (ICON XI).
16 Nov 2011;
25 Nov 2011.
Dr. Paul Mullins, Bangor University, Bangor, United Kingdom, email@example.com