Spatiotemporal and frequency signatures of noun and verb processing: a wavelet-based beamformer study.

A total of 8 participants were tested using magnetoencephalography for investigating the spatial, temporal, and frequency signatures of noun and verb processing in the brain. Visually presented nouns and verbs both activated the occipital, left posterior temporal, and left inferior frontal cortices at a latency range of 106-329 ms in a frequency range of 24-98 Hz. Nouns activated the left posterior temporal area while verbs activated the inferior left frontal area at a latency range of 411-430 ms in a frequency range of 116-137 Hz. Nouns and verbs were processed in similar brain areas during early latency and relatively low frequency, but were processed in different brain areas during late latency and high frequency. The results indicate that there are distinct neural substrates underlying different aspects of the language system. This finding sheds light on the cerebral mechanisms of impairments of selective word categories in patients with brain damage in clinical neuropsychology.