Multimodal MEG and Microstructure-MRI Investigations of the Human Hippocampal Scene Network

Although several studies have demonstrated that perceptual discrimination of complex scenes relies on an extended hippocampal posteromedial system, we currently have limited insight into the specific functional and structural properties of this system in humans. Here, combining electrophysiological (magnetoencephalography) and advanced microstructural (multishell diffusion magnetic resonance imaging; quantitative magnetization transfer) imaging in healthy human adults (30 females/10 males), we show that both theta power modulation of the hippocampus and fiber restriction/hindrance (reflecting axon packing/myelination) of the fornix (a major input/output pathway of the hippocampus) were independently related to scene, but not face, perceptual discrimination accuracy. Conversely, microstructural features of the inferior longitudinal fasciculus (a long-range occipitoanterotemporal tract) correlated with face, but not scene, perceptual discrimination accuracy. Our results provide new mechanistic insight into the neurocognitive systems underpinning complex scene discrimination, providing novel support for the idea of multiple processing streams within the human medial temporal lobe.