Functional source separation applied to induced visual gamma activity

Barbati, Giulia, Porcaro, Camillo, Hadjipapas, Avgis, Adjamian, Peyman, Pizzella, Vittorio, Romani, Gian Luca, Seri, Stefano, Tecchio, Franca and Barnes, Gareth R. (2008). Functional source separation applied to induced visual gamma activity. Human Brain Mapping, 29 (2), pp. 131-141.


Objective of this work was to explore the performance of a recently introduced source extraction method, FSS (Functional Source Separation), in recovering induced oscillatory change responses from extra-cephalic magnetoencephalographic (MEG) signals. Unlike algorithms used to solve the inverse problem, FSS does not make any assumption about the underlying biophysical source model; instead, it makes use of task-related features (functional constraints) to estimate source/s of interest. FSS was compared with blind source separation (BSS) approaches such as Principal and Independent Component Analysis, PCA and ICA, which are not subject to any explicit forward solution or functional constraint, but require source uncorrelatedness (PCA), or independence (ICA). A visual MEG experiment with signals recorded from six subjects viewing a set of static horizontal black/white square-wave grating patterns at different spatial frequencies was analyzed. The beamforming technique Synthetic Aperture Magnetometry (SAM) was applied to localize task-related sources; obtained spatial filters were used to automatically select BSS and FSS components in the spatial area of interest. Source spectral properties were investigated by using Morlet-wavelet time-frequency representations and significant task-induced changes were evaluated by means of a resampling technique; the resulting spectral behaviours in the gamma frequency band of interest (20-70 Hz), as well as the spatial frequency-dependent gamma reactivity, were quantified and compared among methods. Among the tested approaches, only FSS was able to estimate the expected sustained gamma activity enhancement in primary visual cortex, throughout the whole duration of the stimulus presentation for all subjects, and to obtain sources comparable to invasively recorded data.

Publication DOI:
Divisions: Life & Health Sciences > Psychology
Life & Health Sciences
Life & Health Sciences > Basic & Applied Neurosciences research group
Life & Health Sciences > Neurosciences research group
Life & Health Sciences > Applied Health Research Group
?? NABC ??
Uncontrolled Keywords: functional source separation,blind source separation,synthetic aperture magnetometry,magnetoencephalography,induced gamma activity,Clinical Neurology,Neuroscience(all),Radiological and Ultrasound Technology
Full Text Link:
Related URLs:
Published Date: 2008-02
Authors: Barbati, Giulia
Porcaro, Camillo
Hadjipapas, Avgis
Adjamian, Peyman
Pizzella, Vittorio
Romani, Gian Luca
Seri, Stefano
Tecchio, Franca
Barnes, Gareth R.


Item under embargo

Export / Share Citation


Additional statistics for this record