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Browsing by Subject "http://www.yso.fi/onto/yso/p3328"

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  • Kasvojen identiteetin, ilmeen ja ilmeen voimakkuuden vaikutus tapahtumasidonnaisiin jännitevasteisiin 
    Miettinen, Johanna (2017)
    Objectives. This study aimed to clarify the brain-level processing of face stimuli by examining event related potentials. The purpose was to examine whether it is appropriate to make conclusions about the localization of brain-level processing of face expression and identity. Additionally, the study wanted to clarify whether there are observable differences between expression processing and does the intensity of the expression affect on the brain-level differentiation of expressions. Prior studies about the perception of face stimuli have been heavily focused on the modular view of the information processing system, in which every cognitive function has its own anatomical correlates and where the modules are clearly distinguishable from each other. The opposing view to this is the network-assumption in which the confines between modules are vague. Knowledge about these cognitive processes is crucial when new rehabilitation forms are being developed for people, from whom face perception is abnormal. Methods. 17 healthy test subjects took part in the study. In total, subjects were presented with 112 face stimuli, in which face expression and identity varied systematically. Based on prior studies, the event related potentials, which are known to be present in the perception of face stimuli were especially studied: the positive or negative fluctuations that occur 100, 170 and 250 milliseconds after the presentation of face stimulus (so called P1, N170 and N250 components). The effects of expressions and identities on the event related potentials were examined with traditional one-variable analysis (comparison of averages) as well as with multiple variable methods (comparison of correlations of distributions), which better expose the changes caused by face stimuli manipulations. Results and conclusions. The average amplitude and latency of event related potentials did not differe across conditions. The complex interactions between test conditions were exposed by forming 112 x 112 dissimilarity matrices of event related potentials. General linear model, which included eight regressors, was fitted into dissimilarity matrices. Fitted models were also compiled. In those, every every regressor was weighted with beta-coefficients at the time points of P1, N170 and N250 components. Based on the results, it is possible to assume that expression processing happens in an earlier phase than identity processing. Additionally, there was a robust interaction between expression and identity, which clarified the variation in the data. These results give support to the network-assumption in the perception of faces. However, the network-assumption does not deny modularity completely.
  • Perinnöllisen lukivaikeusriskin yhteys vastasyntyneen aivojen kuuloerotteluvasteisiin 
    Ala-Kurikka, Iina (2016)
    Dyslexia affects reading speed and accuracy. Developmental dyslexia is a heritable learning disability related to structural changes in the brain and deficits in sound discrimination. Dyslexia and its’ genetic risk have been studied with auditory event-related potentials (ERPs) from babies to adults. Dyslexia has been associated with changes in the cortical change detection response called the mismatch negativity (MMN). Dyslexic adults and children elicit attenuated MMN responses compared to the control group. The controls’ MMN responses to speech sounds are more pronounced on the left hemisphere than the at-risk group’s responses. Interventions targeting the sound discrimination and phonological awareness have resulted in better reading and writing skills. Rehabilitation is most efficient already before school-age but research on early markers of dyslexia is still insufficient. We studied the relation between inherited dyslexia risk and newborn brain responses by recording ERPs from 38 babies. Half of them were controls. Newborns in the at-risk group had one parent with diagnosed dyslexia. During the ERP recordings we used a speech sound stream consisting of the repetitive pseudoword /ta-ta/. The latter syllable contained infrequent duration, frequency and vowel changes. The sound stream also contained distinct and surprising sounds. We also included a control paradigm to investigate how acoustic variance in the speech sounds affects the brain responses. The speech sound ERPs were small in amplitude. Duration and frequency changes elicited significant MMN responses in both the at-risk and control groups. The strongest MMN response in both groups was due to duration change. The onset of this MMN response seemed to be delayed in the at-risk group. The profiles for standard responses and frequency-MMN responses differed between the groups but these differences didn’t reach statistical significance. Acoustic variance had no effect on the MMN amplitude. Background factors including sex, duration of the pregnancy and birth weight correlated with the response amplitudes. Overall these results show that inherited dyslexia risk contributes to sound discrimination skills soon after birth. Hence studying auditory discrimination interventions at an early age is well-grounded.

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