Spatial and frequency differences of neuromagnetic activities in processing concrete and abstract words

This study investigated the neuromagnetic spatial and frequency differences between recognizing concrete and abstract words using a 275 channel whole head magnetoencephalography (MEG) system. The stimuli consisted of 100 concrete words and 100 abstract words which were presented visually and auditorily simultaneously. The data of 12 right-handed healthy subjects in six different frequency bands were analyzed with synthetic aperture magnetometry (SAM) which can identify the frequency-dependent volumetric distribution of the evoked magnetic field. Concrete and abstract words evoked a very similar neuromagnetic activation pattern in the primary visual and auditory cortices. However, concrete words evoked stronger synchronization in the right hemisphere and abstract words evoked stronger synchronization in the left hemisphere in 1-8 Hz. In addition, concrete words evoked more desynchronization in the left posterior temporal and parietal cortex; while abstract words evoked a clear synchronization in the left posterior temporal cortex and desynchronization in the left inferior frontal cortex in 70-120 Hz. Furthermore, concrete words evoked clear desynchronization in the left inferior frontal cortex while abstract words evoked strong synchronization in the left posterior temporal cortex in 200-300 Hz. These findings suggested that concrete words and abstract words are processed differently in the brain not only in anatomical substrates, but also in the frequency band of neural activation.