Analyzing the effects of pleasant and
unpleasant odor stimulus to EEG
activations by using Welch’s method
Journal Name:
- Dicle Üniversitesi Mühendislik Fakültesi Mühendislik Dergisi
Keywords (Original Language):
Author Name | University of Author |
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Abstract (2. Language):
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.
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Abstract (Original Language):
Görsel, işitsel ve koku gibi dış uyaranların beynin elektriksel aktivitesi üzerinde etkileri olduğu bilinmektedir.
Görsel ve işitsel öğelere çalışmalarda oldukça yer verilmesine karşın daha karmaşık bir yapıya sahip olan
koku uyartısının merkezi sinir sistemi üzerindeki etkileri pek az bilinmektedir. Bu çalışmanın amacı iyi-kötü
kokuların Elektroansefalografi (EEG) sinyallerindeki dalgalanmaları nasıl etkilediğini incelemek ve beyin
aktivitesi üzerinde nasıl değişimler oluşturduğunu gözlemlemektir.
Çalışmada kullanılan EEG verileri 14 kanallı EMOTIV EPOC başlığı ile 6 kişinin gözler kapalı konumdayken
8 farklı koku (4 iyi- 4 kötü) kullanılarak alınmıştır. Başlığın içindeki filtreler aracılığı ile önişleme tabi
tutulmuş halde alınan koku verilerinin Welch yöntemi kullanılarak güç spektrum yoğunluk grafikleri her kanal
için ayrı ayrı incelenmiştir.
Yapılan analizler neticesinde kokulara ait verilerin tüm bant içerisindeki bağıl gücünün yaklaşık %50-70’ını
delta bandının oluşturduğu ve yoğunluğun küçük bant frekansında biriktiği görülmüştür. Genel anlamda iyi
kokular yüksek bant gücünde salınım gösterirken, kötü kokular daha düşük seviyede salınım
gerçekleştirmişlerdir. Veriye ait 14 kanal incelendiğinde genel olarak beyin kabuğunda bir asimetri (cortical
asymmetry) olduğu görülmektedir. Kokunun subjektif bir kavram olduğu, aynı kokunun her kişide her zaman
aynı etkiyi göstermediği anlaşılmaktadır.
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