Neuromagnetic localization of higher order brain processing

To localize and ultimately image higher-order processing in the human brain, the neuromagnetic field evoked under a special oddball auditory stimulation paradigm (1-kHz frequent tone, 80% probability; 1.2-kHz rare tone, 20% probability) has been measured with a 37-channel SQUID (superconducting quantum interference device) neuromagnetometer. The field in response to the rare presentation, to which the subject is attentive, shows a clear peak at about 300 ms poststimulus. This peak is analogous to the P3 peak studied in evoked potentials to evaluate cognitive function. Using a neuromagnetic localization algorithm and superposing the results on corresponding MR (magnetic resonance) images after registration, the authors have localized the neural generators of the P3 wave to a site approximately 1.8 cm from the contralateral hippocampus in one subject. Thus, the feasibility of localizing higher-order function in the human brain using neuromagnetic and magnetic resonance imaging has been shown.<>