An entorhinal-like region in food-caching birds

The mammalian entorhinal cortex routes inputs from diverse sources into
the hippocampus. This information is mixed and expressed in the activity
of many specialized entorhinal cell types, which are considered
indispensable for hippocampal function. However, functionally similar
hippocampi exist even in non-mammals that lack an obvious entorhinal
cortex, or generally any layered cortex. To address this dilemma, we
mapped extrinsic hippocampal connections in chickadees, whose hippocampi
are used for remembering numerous food caches. We found a well-delineated
structure in these birds that is topologically similar to the entorhinal
cortex and interfaces between the hippocampus and other pallial regions.
Recordings of this structure revealed entorhinal-like activity, including
border and multi-field grid-like cells. These cells were localized to the
subregion predicted by anatomical mapping to match the dorsomedial
entorhinal cortex. Our findings uncover an anatomical and physiological
equivalence of vastly different brains, suggesting a fundamental nature of
entorhinal-like computations for hippocampal function.