Magnetoencephalographic Brain Research Articles

The influence of meaning on the perception of speech sounds

As part of knowledge of language, an adult speaker possesses information on which sounds are used in the language and on the distribution of these sounds in a multidimensional acoustic space. However, a speaker must know not only the sound categories of his language but also the functional significance of these categories, in particular, which sound contrasts are relevant for storing words in memory and which sound contrasts are not. Using magnetoencephalographic brain recordings with speakers of Russian and Korean, we demonstrate that a speaker's perceptual space, as reflected in early auditory brain responses, is shaped not only by bottom-up analysis of the distribution of sounds in his language but also by more abstract analysis of the functional significance of those sounds.

The role of magnetoencephalography in pediatric epilepsy surgery

Magnetoencephalography (MEG) is a new diagnostic imaging and brain mapping device that has been recently used in the context of pediatric epilepsy, epilepsy surgery, and neuronavigation. MEG allows for the placement of magnetic spike sources on a conventional magnetic resonance imaging scan, the so-called magnetic source imaging, so that the localization of epileptiform activity in a child can be determined. Considerable effort is placed on analyzing the configuration and number of spike waves by MEG that relate to a primary epileptiform discharge. Such MEG spike clusters are corroborated now by intraoperative invasive subdural grid monitoring that show good correlation in the majority of cases. Another important role of MEG relates to the mapping of critical regions of brain function using known paradigms for speech, motor, sensory, visual, and auditory brain cortex. When linked to standard neuronavigation devices, MEG brain mapping can be extremely helpful to the neurosurgeon approaching nonlesional epilepsy cases or lesional cases where the safest and most direct route to the surgical disease can be selected. As paradigms for brain mapping improve and as MEG software upgrades become more sensitive to analyzing all types of spike sources, MEG will play an increasingly important role in pediatric neurosurgery, especially for the child with intractable epilepsy.