The Organization of Mouse and Human Cortico-Hippocampal Networks Estimated by Intrinsic Functional Connectivity

Abstract

While the hippocampal memory system has been relatively conserved across mammals, the cerebral cortex has undergone massive expansion. A central question in brain evolution is how cortical development affected the nature of cortical inputs to the hippocampus. To address this question, we compared cortico-hippocampal connectivity using intrinsic functional connectivity MRI (fcMRI) in awake mice and humans. We found that fcMRI recapitulates anatomical connectivity, demonstrating sensory mapping within the mouse parahippocampal region. Moreover, we identified a similar topographical modality-specific organization along the longitudinal axis of the mouse hippocampus, indicating that sensory information arriving at the hippocampus is only partly integrated. Finally, comparing cortico-hippocampal connectivity across species, we discovered preferential hippocampal connectivity of sensory cortical networks in mice compared with preferential connectivity of association cortical networks in humans. Supporting this observation in humans but not in mice, sensory and association cortical networks are connected to spatially distinct subregions within the parahippocampal region. Collectively, these findings indicate that sensory cortical networks are coupled to the mouse but not the human hippocampal memory system, suggesting that the emergence of expanded and new association areas in humans resulted in the rerouting of cortical information flow and dissociation of primary sensory cortices from the hippocampus.

Individual structural features constrain the mouse functional connectome

“…Mouse Connectivity Atlas to study structure-function relations at the group level using voltage-sensitive dyes (35) and FC (6,22,36). In addition, a recent work in rats (37) used TVB to simulate FC based on SC and found strong correlation at the group level.…”

“…All procedures were conducted in accordance with the ethical guidelines of the National Institutes of Health and were approved by the institutional animal care and use committee (IACUC) at Technion. 19 male first generation hybrid mice (B6129PF/J1, [9][10][11][12] weeks old) were implanted with MRI compatible head-posts using dental cement as previously described (22). After 3 days of recovery, the animals were acclimatized to Experiments involving mice were approved by the Institutional Animal Care and Use…”

“…fMRI data preprocessing procedure was validated in a previous study (22). Briefly, the first two time points were removed for T1-equilibration effects, slice-dependent time shifts were compensated, head motion was corrected using rigid body correction, volumes were registered to a downsampled version of the Allen Mouse Brain Atlas, and data underwent intensity normalization.…”

Connectomic imaging reveals Huntington‐related pathological and pharmaceutical effects in a mouse model

“…Previous studies also reported that the resting-state network is elucidated more by rsFC parameters than by non-rsFC parameters. 49 The comparison between the axonal projection and rsFC was explored recently in selected regions particularly around DMN, 62 in the cortical networks 63 and the whole brain. 58 Consistent with previous study, 58 high overlap between rsFC and axonal projection was found with seeds in cortical areas but was much lower in subcortical areas like CPu, suggesting involvement of multisynaptic projection for subcortical rsFC.…”

Functional network study on the wild type and DISC1 transgenic mice

“…The long-lasting effects of repeated brief anaesthesia is not well-understood. Although Bergmann et al (2016) reported that there was no abnormal breathing rate (as an indicator of stress levels) in the trained awake rats and that body temperature was maintained, direct physiological recordings were not reported (Bergmann et al, 2016). Jonkers et al (2014) reported that oxygen saturation could not be performed in awake mice due to the encumbrance of this measurement.…”