Abstract
Since Helmholtz, the human brain supposedly predicts upcoming information for subsequent processing. However, tracing the dynamics of a predicted information content remains challenging in neuroimaging. Here, we do so with predictions of the Spatial Frequency (SF) contents of Gabor patches. On each experimental trial, seven observers categorized the LSF vs. HSF of Gabor patches displayed in the left or right visual fields, at an eccentricity ensuring their initial contra-lateral hemispheric projections, while we concurrently measured each observer’s single trial source-reconstructed MEG activity on 12,773 voxels. In a two-stage cueing design, a first visual cue (left vs. right dot) predicted the location (left vs. right) of the incoming Gabor patch, followed by an auditory cue (a sweeping tone at 220 Hz vs. 1760 Hz) that predicted the upcoming SF contents (LSF vs. LSF) (and vs. 880Hz for an invalid cue), followed by the Gabor patch itself. As expected, valid cues reduced behavioral reaction times in all observers. We traced the dynamics of LSF vs. HSF prediction following auditory cue onset, when the Gabor location is known. Every 2 ms post stimuli, we computed the mutual information between LSF vs. HSF cues and the corresponding responses of each. voxel (N = 12,2773), separating left- and right-predicted trials. Prediction representation (i.e. LSF vs. HSF) started in auditory cortex (superior temporal gyrus, ~80ms post-cue), then frontal cortex (~100ms) then early visual cortex (~120 ms post-cue and ~1100ms prior to Gabor onset). Furthermore, MEG activity of auditory cortex and early visual cortex redundantly represented the SF prediction, separately for left and right trials, indicating they represent the same predicted contents on individual trials. In sum, our results show where, when and how predicted SF Gabor contents dynamically propagate from auditory to visual cortices, before stimulus onset, to speed up subsequent perceptual decision behavior.