Hippocampal coding during visual deliberation in freely moving birds

The circuit mechanisms that transform sensory input into the observed firing patterns in the hippocampus are unclear. Like primates, birds almost exclusively depend on vision to navigate. However, birds primarily direct gaze using head saccades, rather than eye saccades, and gaze can therefore be readily measured during free movement. We leveraged these features to ask how visual input during navigational decisions is encoded by the hippocampus. We developed a system to estimate gaze in freely moving birds, and designed a task to behaviorally dissociate physical location (“place”) from viewed location (“gaze”). We found neural signals related to vision in the avian hippocampus, including robust modulation of firing during gaze saccades, with putative excitatory and inhibitory neurons active at different phases of the saccade. This temporal pattern suggests a similar role of saccades in visually dependent animals to rodent theta oscillations. We also found that hippocampal activity coordinates the coding of both place and gaze locations. These results yield insight into how visual perception informs hippocampal representations of space and guides behavior.