What are you looking at? The neural basis of eye movement guidance to objects

When you look, you look at something: your daughter’s face, a computer mouse, a road sign, etc. Yet most of our understanding of the neural guidance of eye movements is about how we look at locations in space. Consequently, little is known regarding the neural basis of how we guide eye movements to particular objects, faces, etc. in our environment. To take a first step towards addressing this gap, we recorded simultaneous intracranial electroencephalography with eye tracking in individuals with epilepsy during both free viewing of scenes and natural social interactions. In both paradigms, we could predict the category of object participants were going to look at next based on their brain activity from prior to the saccade onset even after controlling for the spatial location of the eye movement. Neural activity that allowed us to predict what a person was going to look at next came from parietal cortex regions traditionally associated with eye movement guidance, as well as category selective ventral temporal cortex regions. To assess whether this result was due to para-foveal responses to the object of the next fixation, we compared saccades traversing greater than 5 degrees of visual angle to smaller saccades and found that prediction accuracy did not diminish for the larger saccades. Preliminary results from one of our participants shows that next fixation prediction may involve theta frequency activity in category selective ventral visual cortex, putatively related to interactions with theta frequency activity in hippocampal regions involved in visual navigation. While many open questions remain, these results suggest that ventral temporal cortex may be involved in guiding what to look at next, with interactions between ventral temporal cortex, hippocampus, and parietal cortex then guiding where to look for that object.