Different chemosensory EEG signals of human brain in elemental and configural odor mixtures

Abstract

Most of the odors we encounter in our daily lives are odor mixtures. Odor mixtures can be perceived either elementally, meaning each component is still discernible, or configurally, which means the single odorants blend together to form a new unity. This study explores whether the brain signals of single odorants within a mixture are more similar to those of elementally perceived mixtures or configurally perceived mixtures. Previous studies in humans showed that as the number of single odorants within the mixtures increases, the mixtures are perceived more configurally. However, how the brain processes these mixtures when the odor mixtures are perceived configurally has yet to be thoroughly explored in humans. Therefore, this thesis aims to investigate the brain processes of configural odor mixtures in humans by analyzing the behavior responses and brain activities with EEG measurement. Consistent with previous studies, I found that as the number of single odorants within the mixtures increased, identifying the single odorants within the mixtures became more difficult, especially when the number exceeded three. As such, I classified mixtures with two single odorants as being perceived elementally and mixtures with three or more odorants as being perceived configurally. When measuring brain signals for single odorants and odor mixtures, I found that the brain signals for single odorants were more similar to those of elemental mixtures than those of configural mixtures. This suggests that within the olfactory system, there are differences between elemental and configural odor mixtures at olfactory processing.