<p><span>Entorhinal–hippocampal circuits in the mammalian brain are crucial for an animal’s spatial and episodic experience, but the neural basis for different spatial computations remain unknown. Medial entorhinal cortex layer II contains pyramidal island and stellate ocean cells. Here, we performed cell type-specific Ca</span>²⁺<span> imaging in freely exploring mice using cellular markers and a miniature head-mounted fluorescence microscope.