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Author:Nieminen, Jussi Johannes
Title:Brain activation in a complex stimulus
Aivoaktivaatio monimuotoisessa ärsykkeessä
Publication type:Master's thesis
Publication year:2010
Pages:viii + 50      Language:   eng
Department/School:Lääketieteellisen tekniikan ja laskennallisen tieteen laitos
Main subject:Laskennallinen tekniikka   (S-114)
Supervisor:Lampinen, Jouko
Instructor:
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201203131521
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  1197   | Archive
Keywords:consistency
fMRI
ICA
konsistenssi
ISC
Abstract (eng): Natural conditions are imitated by showing a movie as a stimulus.
The common brain activity caused by this kind of stimulus is studied.
The interest is to find what kind of responses brain gives to the stimulus.
The independent component analysis (ICA) and the intersubject correlation (ISC) are used to analyze the data.
Consistency and variability of the components revealed by group ICA are tested.
Similarities between the subjects are tested by ISC.
The stimuli causing the most consistent components are traced from the movie as is also done with ISC in certain brain regions.

The beginning of the movie Tulitikkutehtaan tyttö was shown to subjects whose brain activity was recorded with functional magnetic resonance imaging (fMRI).
The subjects could freely view the movie and no instructions were given.
The resulting data from fMRI was analyzed by group intersubject correlation and independent component analysis.
The stability and the consistency of ICA was tested by bootstrapping the data.
Intersubject correlation was calculated to the whole movie and windowed data separately.
The whole movie was also divided to 5 subbands to compare correlations in different frequencies.

ICA revealed stable components in the auditory and the visual processing areas and in the parietal area.
ISC showed synchronization mainly in the same regions.
The subbands showed the dominance of the auditory and the visual processing areas in high frequencies.
Frontal part of the brain had correlation in low frequencies.
Abstract (fin): Tutkimuksessa luonnollisia olosuhteita jäljitellään näyttämällä elokuvaa.
Tällaisen ärsykkeen aiheuttamaa yleistä aivoaktivaatiota tutkitaan.
Aivojen vasteita kyseiselle ärsykkeelle selvitetään.
Riippumattomien komponenttien analyysia (ICA) ja koehenkilöiden välisiä korrelaatioita (ISC) käytetään datan analysointiin.
ICA:sta saatujen komponenttien konsistenssia ja vaihtelevuutta testataan.
Koehenkilöiden samankaltaisuutta tutkitaan ISC:lla.
Stabiilimmat komponenttit aiheuttavia ärsykkeitä etsitään elokuvasta, kuten tehdään myös joidenkin aivoalueiden ISC:lla.

Elokuva Tulitikkutehtaan tyttö näytettiin koehenkilöille, joiden aivojen aktiivisuutta mitattiin toiminnallisella magneettikuvauksella (fMRI).
Koehenkilöt saivat vapaasti katsoa elokuvaa eikä erillisiä ohjeita annettu.
FMRI:sta saatu data analysoitiin ryhmä ISC:lla ja ICA:lla.
ICA:n stabiilisuutta ja konsistenssia testattiin ajamalla useita bootstrap ICA:ja.
ISC laskettiin koko elokuvalle ja ikkunoidulle datalle erikseen.
Koko elokuva jaettiin viiteen taajuuskaistaan eri taajuuksien korrelaatioiden vertailua varten.

ICA paljasti stabiileja komponentteja kuuloa ja näköä prosessoivilla alueilla sekä parietaali alueella.
ISC näytti synkronisaatiota pääosin samoilla alueilla.
Datan jako taajuuskaistoihin paljasti ääni ja kuulo alueiden hallinnan korkeilla taajuuksilla.
Aivojen etuosissa oli korrelaatiota matalilla taajuuksilla.
ED:2010-08-20
INSSI record number: 40209
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