İyi – kötü koku uyartılarının EEG aktivitesine etkisinin Welch metodu ile incelenmesi

It is known that odor stimulus has effects on brain electrical activity. The odor effects on human emotions, behaviors and mood can not be denied. In contrast to other external stimulus, odor perception is a complex event due to its sensory and cognitive manners, so there is no exact statement for the effects of odors on human central nervous system. Some odor dysfunctions may appear as a result of some neurologic disease (Parkinson, Alzheimer, motor neuron disease, etc.). The sense of odor, ability to distinction different odors and recognizing odors can be decreased in these diseases. This situation is sometimes ignored in clinical treatment. In literature, bunch of electro-physiological methods can be seen to analyse brain electrical avtivity. One of these method is Electroencehalogram (EEG) that is known as a good source to comment about functioning of brain. There are some external stimulus such as visual, audial and odor has effects on brain activity. Beside there are many studies releated to visual and audial issues, the effects of odor stimuli, which is more complex than others, on nerveous system are not well known. The aims of this study are to analyse how pleasantunpleasant odors affect fluctiation of EEG singals and find out relations between odors and brain activities. 14 channelled EMOTIV EPOC headset is used with 6 participants whose eyes are closed and 8 different odors(4 of them are pleasant, the rest is unpleasant) are applied to receive EEG datasets. The datum, which has already been preprocessed by embeded fillters (5th order sinc filter to notch out 50 Hz network frequency, 0.5-45 Hz bandpass filter) in headset, are analysed independently by looking power spectral density graphs in respect to channels by help of Welch’s method. In Welch’s method, hamming window with %50 overlap was used. By the help of surveys belong to participant and graphs of power spectrum density, most dominant pleasant – unpleasant (two of each) odors were determined. The odors belonging pleasant ones are vanilin and rose and unpleasant ones are onion and garlic. This argument is compatible with power spectrum graphs. In most graphs, these odors play dominant roles. Delta band consists of 50-70 percent of whole bands and releated power accumulates on lower frequencies. In general, pleasant odors oscillates close by high band power and unpleasant odors oscillates around lower band power. When 14 channels of EEG is analysed, Cortical asymmetry appears for almost all participants. In other words, pleasant odors have dominant character on left hemisphere of brain. Same thing can be said for unpleasant odors on right hemisphere of brain. We can say that odor is a subjective concept and same odor can not show same effects on different people. The discrimination of different odors through graphs brings an idea whether these odors can be classified successfully each other or not. In future works, these odors can be applied to a classification problem.