Abstract
In this study, the evoked responses to 70% CO2 and the odor of strawberry essence were recorded from 16 electrode positions on the human scalp according to the international 10-20 system. The experiment was carried out in 10 subjects with normal olfaction. The superficial component was calcu lated from these responses using the source derivation method and a deep component was obtained by subtracting the superficial component from the common average referenced waveforms. Three peaks were observed at latencies of 420 msec (Plc), 590 msec (P2c), and 870 msec (P3c) in the superficial component to CO2 gas. A peak in the deep component, however, was only recognized at the same la tency as P2c. A topographic analysis of the deep component in P2c showed a symmetric pattern. In contrast, a peak to the strawberry essence stimuli was only observed at a latency of 595 msec (P2s) in the superficial component. The topographic characteristics were similar to those of CO2 gas. The topographic analysis of the deep component to strawberry essence thus showed an asymmetric pattern. These results suggest that a generator of the response to strawberry essence is located in the somatosensory cortex and asymmetrically in part of the deep brain such as the orbit-frontal cortex.
