EEG investigation into the neural mechanisms involved in higher order decision-making

Blignaut, Julianne (2019-04)

Thesis (MEng)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: Decision-making forms a fundamental part of executive cognition. Our lives are a series of choices: some are simple, while others require more deliberation. Unravelling the neural networks that underlie the decision-making process plays an integral part in understanding to what extent these networks are informed by conscious perception and to what extent they rely on internal neural mechanisms. Our choices are the product of an interaction between our genetic makeup and subjective experiences. Failure to understand the individual’s brain has led us to a scientific impasse. We have some understanding of what happens in the brain when making arbitrary choices, but the intricacies of higher order, deliberate decision-making remain unclear. Recent studies suggest that the choices we make are deterministically formed, prior to conscious awareness of intent. This limits the role of consciousness in the decision-making process and challenges the notion of conscious free will. However, most of these studies rely on arbitrary choices devoid of real-world relevance. In 2017, Maoz et al. introduced deliberate, higher order decisions into the existing realm of studies on free will. The aim of the current research was to further investigate the neural mechanisms underlying higher order decision-making. Moreover, this research aimed to investigate the influence of traumatic subjective experiences on neurophysiological responses. The study developed an experiment that measured participants’ electro-encephalographic potentials while performing both arbitrary and deliberate choice tasks. Thereafter, the neural correlates of both decision types were evaluated and compared. Participants were presented with legal cases and had to acquit or convict one out of two criminal offenders per choice trial. The neurophysiological data was evaluated with a specific focus on the readiness potential and the P300 potential. The readiness potential has previously been used to prove the absence of free will in self-initiated action, whereas the P300 is a potential associated with the reaction to a decision. Clear readiness potentials and P300 potentials were observed for both arbitrary and deliberate decisions. Furthermore, participants who had been victims of violent crimes showed increased readiness potential amplitudes and decreased P300 potential amplitudes. Participants with close relatives who had been victims of violent crimes also showed increased readiness potentials, however, they showed increased P300 potentials too. The spatial distribution of electrical activity demonstrated greater prefrontal cortex activation for participants with close relatives who had been victims of violent crimes, compared to participants without close relatives who had been victims of violent crimes. These findings are demonstrative of how traumatic subjective experiences influence the neuro-physiology of decision-making.

AFRIKAANSE OPSOMMING: Besluitneming is 'n belangrike deel van ons menswees. Ons lewens is 'n reeks van besluite en gevolge. Sommige besluite is maklik om te neem, terwyl ander meer oorweging verg. Dit is belangrik om te verstaan tot watter mate ons keuses onderhewig is aan neurologies prosesse en tot watter mate ons eksterne omgewing ons keuses beïnvloed. Die menslike besluitnemingsproses is ‘n fyn wisselwerking tussen ons genetika en lewenservarings. Daar is egter tans geen maatstaf om te kan kwantifiseer tot watter mate subjektiewe ondervindings die neurologiese besluitnemingsproses beïnvloed nie. Alhoewel ons tot ‘n groot mate verstaan watter neurlogiese meganismes betrokke is wanneer ons arbitrêre besluite neem, is daar steeds baie onduidelikheid oor die onderliggende netwerke betrokke by hoërorde-besluitneming. Onlangse studies stel voor dat ons besluite deterministies gevorm word voor ons bewuswording van die gekose uitkoms. Hierdie bevindinge beperk dus die rol wat ons bewussyn speel in die besluit-nemingsproses. Dit bevraagteken ook die bestaan van vrye wil. Tog het meeste van hierdie studies slegs met arbitrêre keuses te make. Die doel van die huidige studie was om the neurologiese merkers, betrokke by hoërorde-besluitneming, te ondersoek. Verder wou hierdie studie ook bewys wat die potensiële invloed van traumatise ondervindings op die neurologiese besluitnemingsproses is. Tydens die studie is daar ‘n besluitnemingstaak ontwerp waartydens deelnemers gevra is om beide arbitrêre en hoër-orde besluite te neem. Die uitkoms van die twee tipies keuses is vervolgens vergelyk. Deelnemers moes, vir verskillende gevalle, een van twee misdadigers kwyt skeld of skuldig bevind. Spesifieke neurologiese merkers wat ondersoek is, is die gereedheidspotential en die P300 breinpotensiaal. Die gereedheidspotential word geredelik in die literatuur gebruik om vrye will teen te staan en die P300 potensiaal word geassosieer met die neurologiese nagevolg van ‘n besluit. Na afloop van die eksperiment, was daar ‘n duidelike gereedsheids- en P300 potensiaal vir beide arbitrêre en hoërorde besluite. Nog ‘n merkbare tendens het gewys dat die deelnemers wat al self slagoffers van geweldsdade was, gereed-heidspotensiale met groter amplitudes vertoon het. In teenstelling, was die P300 pieke van hierdie groep deelnemers kleiner. Deelnemers met familielede wat slagoffers van geweldsdade was, se gereedheidspotentiale was ook groter. Die verspreiding van elektriese breinpotensiale vir die groep deelnemers met familielede wat slagoffers was, het meer aktivering in die prefrontale korteks van die brein vertoon as vir deelnemers sonder familielede wat slagoffers was. Hierdie bevindinge ondersteun die hipotese dat traumatise ondervindings die neuro-fisiologie van hoërorde-besluitneming beïnvloed.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106217
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