Language-related brain activity revealed by independent component analysis.
OBJECTIVE
When an individual engages in a cognitive task, a multitude of diverse processes are activated in his/her brain and it is reasonable to assume that multiple brain sources are simultaneously active at any one time. Magnetoencephalographic (MEG) data recorded in such circumstances provide a picture of spatial distribution and time course of the sum of the magnetic fields generated by all these sources. Thus, the experimenter faces the challenge of separating the multiple contributions to the total recorded signal before attempting a localization of their sources and studying their functional roles.


METHODS
We describe in this paper how independent component analysis of MEG data collected in a word/pseudo-word reading experiment elegantly solves this problem.


RESULTS
Using a few statistical assumptions, independent component analysis resolved simultaneously active brain sources in the right-frontal, left-parietal and left-frontal areas, all showing well defined dipolar field distributions.


CONCLUSIONS
We describe the characteristics of these contributions and discuss the language-related functional roles that appear to be associated to some of the independent sources. We report in particular on one source, localized near Broca's area, which showed to be affected by reading words but not pseudo-words.
Salustri
Carlo
C
Institute of Cognitive Science and Technology (CNR) - Unità MEG, Ospedale San Giovanni Calibita Fatebenefratelli - Isola Tiberina, 00186 Rome, Italy. salustri@iess.rm.cnr.it
Kronberg
Eugene
E
D000161:Acoustic Stimulation; D000704:Analysis of Variance; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D004569:Electroencephalography / Q000379:methods; D004574:Electromagnetic Fields; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007802:Language; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D011897:Random Allocation; D011930:Reaction Time; D012660:Semantics; D013997:Time Factors