How different brain rhythms contribute to human behaviour is a central question in neuroscience that has been explored extensively with electro- and magnetoencephalogram (M/EEG). Where these rhythms are generated in the brain is a question that is more difficult to answer with M/EEG. Although it is possible to identify the neural sources of brain oscillations by solving the ‘inverse problem’, the results are often unsatisfactory, as the spatial resolution of M/EEG is very poor. Efforts over the past two decades have therefore focused on refining the technique of simultaneously recording EEG and fMRI. Despite recent advances, the EEG data collected in the MRI scanner still suffers from artefacts that cannot be completely removed. Here, we test a new fMRI protocol that does not require EEG and thus could greatly simplify the research on brain rhythms and their neural generators. To further test the feasibility of this protocol, we applied it also to confidence ratings and pupillometry which, to our knowledge, have not been investigated with regard to oscillatory effects to date. Importantly, using the same experimental paradigm as in the fMRI study will allow us to link the confidence and pupillometry results to the fMRI results and thereby gain a better understanding of the neural substrates underlying these behavioural measures, which few investigations are set up to do. Furthermore, to be able to better evaluate participant performance, we included catch trials that comprised of tone targets at either supra- or sub-threshold. The inclusion of these catch trials will also allow us to apply an advanced analysis method, that is, multivariate pattern classification, to decode individual performances to threshold stimuli in auditory activations.
In summary, this research project combines measures of brain activation, pupil modulation and behavioural performance in a way that has not been done before. Therefore, we expect the results to provide new insights into perceptual and decisional mechanisms that underlie the perception of noisy auditory stimuli. There may be no direct socio-economic impact to gain from these results, however, they form an important basis for further research into the neural substrates underlying the rhythmic propagation and update of priors during the perception auditory ambiguous stimuli, which is the focus of the second part of this project.
