During mammalian evolution, primate neocortex expanded, shifting hippocampal functional networks away from primary sensory cortices, towards association cortices. Reflecting this rerouting, human resting hippocampal functional networks preferentially include higher association cortices, while those in rodents retained primary sensory cortices. Research on human visual, auditory and somatosensory systems shows evidence of this rerouting. Olfaction, however, is unique among sensory systems in its relative structural conservation throughout mammalian evolution, and it is unknown whether human primary olfactory cortex was subject to the same rerouting. We combined functional neuroimaging and intracranial electrophysiology to directly compare hippocampal functional networks across human sensory systems. We show that human primary olfactory cortex—including the anterior olfactory nucleus, olfactory tubercle and piriform cortex—has stronger functional connectivity with hippocampal networks at rest, compared to other sensory systems. This suggests that unlike other sensory systems, olfactory-hippocampal connectivity may have been retained in mammalian evolution. We further show that olfactory-hippocampal connectivity oscillates with nasal breathing. Our findings suggest olfaction might provide insight into how memory and cognition depend on hippocampal interactions.

在哺乳动物进化过程中，灵长类动物新皮层扩张，将海马功能网络从初级感觉皮层转移到联想皮层。反映这种重新路由，人类静息海马功能网络优先包括高级关联皮层，而啮齿动物保留初级感觉皮层。对人类视觉、听觉和体感系统的研究显示了这种重新路由的证据。然而，嗅觉在整个哺乳动物进化过程中的相对结构保守性在感觉系统中是独一无二的，并且尚不清楚人类初级嗅觉皮层是否受到相同的重新路由。我们将功能性神经影像学和颅内电生理学相结合，直接比较跨人类感觉系统的海马功能网络。我们表明，与其他感觉系统相比，人类初级嗅觉皮层——包括前嗅核、嗅结节和梨状皮层——在静止时与海马网络具有更强的功能连接性。这表明，与其他感觉系统不同，嗅觉-海马连接可能在哺乳动物进化过程中得以保留。我们进一步表明嗅觉-海马连接随着鼻呼吸而振荡。我们的研究结果表明，嗅觉可能有助于深入了解记忆和认知如何依赖海马相互作用。嗅觉-海马的连通性可能在哺乳动物进化过程中得以保留。我们进一步表明嗅觉-海马连接随着鼻呼吸而振荡。我们的研究结果表明，嗅觉可能有助于深入了解记忆和认知如何依赖海马相互作用。嗅觉-海马的连通性可能在哺乳动物进化过程中得以保留。我们进一步表明嗅觉-海马连接随着鼻呼吸而振荡。我们的研究结果表明，嗅觉可能有助于深入了解记忆和认知如何依赖海马相互作用。