1 Introduction
Electroencephalogram (EEG) signals are an important source of information for studying brain activity, and its current research is mainly focused on visual [1], auditory [2], and motor imagery [3]. As an essential sense, the olfactory can directly stimulate memory and trigger strong emotions [4]. Due to the great potential of the olfactory, there have been substantial studies devoted to exploring olfactory EEG signals. Previous research has shown that the classification of olfactory EEG signals plays a vital role in many fields, including neuroscience research [5], disorder treatment [6], multimedia [7], and brain-computer interfaces [8].