An OpIE2-DsRed marker disrupts female blood-feeding and shortens lifespan in the malaria vector Anopheles gambiae.

The hippocampus (HPC) has long been recognized as a crucial hub for memory processes and spatial cognition (). While the same basic circuitry is maintained throughout the entire structure, there are anatomical, genetic, and functional variations along its septotemporal axis (, ). Lesions and pharmacological manipulations in the dorsal (dHPC) and ventral (vHPC) HPC in rodents (respectively, septal and temporal poles in primates) tend to have distinct impacts on spatial vs. emotional learning (–). In fear conditioning paradigms, manipulations of the dHPC impair the formation, consolidation, and retrieval of contextual, but not cued fear memory (, , ) while vHPC manipulations tend to have broader effects (, –). This provides support for the conventional view that the dHPC primarily processes spatial and contextual information, while the vHPC is more involved in emotional processing (, , ). This dichotomy is supported by neuronal recordings in rodents. First, the precision of spatial coding diminishes along the dorsoventral axis of the HPC (–). Second, neurons in more ventral parts of the HPC exhibit a stronger association with the emotional valence of locations (–) and odors (, ) as compared to the dHPC. Moreover, vHPC activity and specific pathways between the vHPC, the amygdala, and the prefrontal cortex are key players for anxiety and fear-related behaviors (, –). However, this dominant view is challenged by several results highlighting the involvement of the dHPC in emotional processing, beyond its traditional role in contextual or spatial processing. Indeed, under several experimental conditions, suppressing activity in the dHPC impairs trace fear conditioning (, ). Additionally, the modulation of fear-related dHPC engram cells impacts fear expression (, ), similarly to the manipulation of vHPC engram cells (). These results support a more nuanced view where both the vHPC and dHPC could contribute to emotional processing, and in particular to fear conditioning. Overall, while an extensive literature supports the notion that dorsal and ventral HPC play separable roles in fear conditioning, it is unknown how their relative roles are reflected in the neural activity of each subregion. Moreover, while recent literature points toward an overlap of these contributions along the hippocampal dorsoventral axis, the mechanisms allowing such integration remain unexplored.