(A) A previous study (Vo et al, 2017) compared voxel receptive fields (vRFs) between different attention conditions (yellow dashed circle). vRFs were mapped with flickering checkerboard stimuli (depicted as white circles) presented at different locations on different trials. fMRI responses to these stimuli can be used to compute vRFs for each condition (right; white dashed circle; example voxel shown), demonstrating effects of attention on vRF position. (B) I propose to manipulate several stimulus properties: contrast (bright vs dim), size (small vs large), and the number of stimuli (single stimulus vs. several). (C) Within these stimulus manipulations, I will also manipulate the location of attention: participants will attend to fixed locations on the screen (as in A), or one or more visual stimuli presented. In all experiments gaze will be fixed.
This project aims to leverage recently-developed computational neuroimaging methods whereby mathematical models are used to predict brain responses according to known sensory input and cognitive task conditions to characterize and quantify limitations inherent in visual information processing within the visual and parietal cortex of healthy human participants (civilians). Rather than identifying which brain regions ‘light up’ or which are more or less strongly activated between task conditions, this approach requires building a comprehensive and predictive understanding of neural information processing, and probing this understanding with novel ‘challenges’—new types of visual stimuli or task conditions and their combinations.
Thus far, we have successfully implemented a massively-accelerated model-fitting procedure using GPU-optimized computing that will vastly improve our ability to carry out the objectives of this project within a tractable timeframe, we have made progress towards a capable stimulus and task design for efficiently testing and comparing models of neural information processing, and we have successfully applied our new analysis procedure to existing datasets to show proof-of-concept feasibility for the proposed analysis approach.