Alessandro Benedetto, Paola Binda, Mauro Costagli, Michela Tosetti, and Maria Concetta Morrone
Voluntary action rhythmically modulates 7T BOLD visual responses in primary visual cortex
AIRMM XI Congress
Behavioral visual sensitivity varies rhythmically over time when synchronized by an attention cue, a sensory stimulus, or the onset of a voluntary action. These rhythms may emerge from phase-resetting of endogenous neuronal oscillations by motor preparation, implicating them in sensory-motor coordination. Here we measure the BOLD correlates of behavioral oscillations by monitoring activity in early visual and motor cortex, using ultra-high field fMRI (GE MR950 7T research system). METHODS Participants (21 healthy adults) made voluntary keypresses (one every 30 s on average) followed by a brief (33 ms) visual stimulus, with four possible delays between the keypress and the visual stimulus (70, 150, 230, 310 ms). The visual presentation consisted of two half-gratings with slightly different spatial frequencies; participants were instructed to report which half-grating had the higher spatial frequency, with a second keypress (different key). fMRI sequences were T2*-weighted GE-EPI with TR = 3 s and 1.5 mm isotropic voxels. Functional data were corrected for EPI distortions, motion and slice-time acquisition, and aligned to high-resolution 3D anatomies (FSPGR 1mm isotropic voxels) with FSL/Freesurfer. fMRI data were also projected to the cortical surfaces of the individual subject and to an average surface template. We defined regions of interest over primary visual cortex V1 and later visual areas using retinotopic mapping data acquired in a separate scan. We also placed regions of interest over the motor and somatosensory cortex using responses to keypresses-only events, made to perform the discrimination task. Within these visual and somatosensory/motor regions, we analyzed BOLD responses to keypress+visual events, i.e. keypresses immediately followed by the visual stimulation. RESULTS We find that visual-evoked BOLD responses in V1 are strongly modulated by voluntary actions (keypresses). V1 activity is modulated by the delay between the keypress and the visual stimulus: lower for stimuli delivered 70 ms or 230 ms after the keypress, higher for stimuli at 150 ms or 310 ms, paralleling the behavioral oscillations of visual sensitivity. A similar oscillatory pattern is seen across early visual areas, but no such effect is seen in motor and somatosensory cortex. Nevertheless, we find strong and systematic associations between M1 activity at the time of voluntary keypress and V1 modulations, suggesting that cortical connectivity between these areas drives the oscillation of visual sensitivity. Our findings are consistent with EEG and behavioral studies and suggest that motor cortex modulates the output signals from early visual cortex to prioritize the processing of information relevant for visuo-motor coordination, and that this mechanism may rely on synchronization of endogenous rhythms.