Fractal dimension analysis of gustatory electroencephalograms in humans

To quantify the neural dynamics of the brain responsible for gustatory recognition and discrimination, fractal dimensions (FDs) of electroencephalograms (EEGs), which were measured under resting and three gustatory stimulation states, were investigated. The seven normal subjects sat on a chair with the chin resting on a frame made of plaster bandage and eyes closed. Distilled water (DW), high concentrated taste (HCT) solution (300 mM NaCl, 1 mM quinine-HCl, 40 mM acetic acid and 500 mM sucrose) and low concentrated taste (LCT) solution (51 mM NaCl, 0.026 mM quinine-HCl, 3 mM acetic acid and 14 mM sucrose) were randomly delivered to the anterior region of the tongue which was protruded slightly out of the mouth. FDs of EEGs from Cz in the resting and in the DW stimulation state were 5.43±1.01 and 4.94±1.03, respectively. In the HCT stimulation state, FD significantly decreased to 4.20±1.08 as compared with that in the resting (P < 0.001). While, in the LCT stimulation state, FD significantly increased to 5.77±1.02 as compared with that in the HCT stimulation state (P < 0.001). These results suggest that information processing of the brain is relatively simple when easily recognized tastes are applied.