Brain-wide activation and deactivation maps during smooth and saccadic tracking in humans

This study aimed to identify brain activity modulations associated with different types of visual tracking using advanced functional magnetic resonance imaging techniques developed by the Human Connectome Project (HCP) consortium. Magnetic resonance imaging data were collected from 27 healthy volunteers using a 3-T scanner. During a single run, participants either fixated on a stationary visual target (fixation block) or tracked a smoothly moving or jumping target (smooth or saccadic tracking blocks), alternating across blocks. Data were preprocessed and analyzed using the HCP Pipelines. Compared to fixation, both smooth and saccadic tracking elicited significant activation across widespread cortical regions previously reported, along with deactivation in several others. Smooth tracking predominantly activated the occipital visual cortex, posterior cingulate cortex, retroinsular cortex, and postcentral gyrus. Saccadic tracking showed a similar activation-deactivation pattern but with broader cortical involvement, including the medial and basal surfaces of the occipital cortex, intraparietal sulcus, inferior parietal lobule, and the premotor and supplementary oculomotor areas. Subcortically, saccadic tracking involved greater activation of cerebellar lobules (up to VII) and the putamen. These findings support known regional contributions to eye movements and expand our understanding of the large-scale functional architecture of the visuo-oculomotor system, highlighting distinct neural circuits engaged by different types of eye movements.