City Research Online

Abstract

Perceptual decision-making describes the process of choosing one of at least two response alternatives based on sensory evidence. This sensorimotor process underlies a range of human behaviours and has been studied extensively by both psychologists and neuroscientists. There is now a consensus, that perceptual decision-making can be explained by sequential sampling models, which assume that we make decisions by accumulating sensory evidence over time until a decision threshold is reached and the response is executed. Although these models are designed to explain behavioural data, the accumulation-to-bound processes they predict have recently been shown to occur in the brain. In this project, we set out to explore these neural correlates of decision-making in the human brain by combining mathematical modelling with neuroimaging. We fitted sequential sampling models to human decision-making data collected in a number of paradigms and directly compared the associated accumulation profiles with neural signals, which were generated either by using electroencephalographic (EEG) recordings or through transcranial magnetic stimulation (TMS). We found that decision-related accumulation profiles can be observed using a parietal EEG signal, namely the event-related potential centroparietal positivity (CPP). Additionally, we showed that accumulation is fed forward to the motor system, where it can be measured using TMS-induced motor evoked potentials. We demonstrated that, under a number of manipulations, namely difficulty, response speed instructions, non-stationary evidence, decision biases, and number of alternatives, these signals display profiles similar to those predicted by sequential sampling models. Our findings support the notion that sequential sampling occurs in the human brain and demonstrate that a model-based approach in which sequential sampling models and neuroimaging are combined and inform each other, can shed light on the underlying mechanisms of human perceptual decision-making.

Publication Type:	Thesis (Doctoral)
Subjects:	B Philosophy. Psychology. Religion > BF Psychology R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Departments:	Doctoral Theses School of Health & Psychological Sciences > Psychology School of Health & Psychological Sciences > School of Health & Psychological Sciences Doctoral Theses

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