Is it possible to measure non-invasively brain conductivity fluctuations during reactions to external stimuli with the use of microwaves?

Based on the focused microwave radiometry imaging method, a novel microwave radiometry imaging system (MiRaIS) has been developed in order to explore the possibility of non-invasively measuring variations of brain activation associated with specific psychophysiological tasks. The radiometric output voltage fluctuations could be attributed to electrical conductivity variations of excitable cell clusters, detected at microwave frequencies. Specifically, in the present study the activation of the left frontal areas under well standardized experimental conditions was investigated, utilizing this technique. An adaptation of the Hayling test was performed on seventeen human volunteers, while the possibly involved or affected activations of the respective brain areas, associated with the verbal inhibition and initiation, were mapped using the MiRaIS. The results showed that both the inhibition and the initiation tasks are associated with significantly higher cerebral activity in the left frontal areas, compared to the control condition, with the inhibition processes being in the longest arm. These findings indicate the potential value of using focused microwave radiometry to identify brain activation possibly involved or affected in operations induced by particular psychophysiological tasks such as the Hayling test. Potential limitations to the generalization of the present observations are discussed. Keywords— brain conductivity variation imaging, left frontal area, focused microwave radiometry, verbal inhibition and initiation