Abstract

Speaker: Visiting in person – Dr Matan Mazor, University of Oxford, UK.

Title: Playing with dice: two unusual use cases for experimental randomisation in fMRI.

Abstract: Randomisation is a defining feature of scientific experiments. In functional neuroimaging, randomising the order and timing of events allows researchers to identify activations that are causally linked to particular stimuli or cognitive processes. In this talk, I will share two additional use cases for experimental randomisation in fMRI: as a tool for identifying functional selectivity in a model-free way, and as a mechanism for time-locking of study plans as part of the pre-registration process. First, I will present TWISTER randomisation, where specific stimulus features are selectively randomised to produce differences in the similarity between experimental runs along specific dimensions in task space. This way, differences in between-run, within-voxel correlations can be taken as a measure of functional selectivity even without knowledge of the underlying data-generating model (for example, without knowing how neuronal activation is linked to the measured BOLD signal). Second, I will present a randomisation-based, cryptographic approach to pre-registration: by setting the seed of the pseudorandom number generator to a fingerprint of the pre-registered documents, we make the order and timing of events causally dependent on the pre-registered plans and hypotheses, time-locking data collection with respect to pre-registration.

Venue: MRC CBU West Wing Seminar Room and Zoom https://us02web.zoom.us/j/82385113580?pwd=RmxIUmphQW9Ud1JBby9nTDQzR0NRdz09 (Meeting ID: 823 8511 3580; Passcode: 299077)