Researcher(s)
- Ellie Hoppe, Neuroscience, University of Delaware
Faculty Mentor(s)
- Joshua Neunuebel, Psychological and Brain Sciences, University of Delaware
Abstract
The hippocampus is critically involved in episodic memory, with its subregions responsible for different functions in memory formation. The dorsal CA2 (dCA2) subregion is essential for social recognition memory (Hiiti & Siegelbaum, 2014). However, how CA2 encodes naturalistic social experiences when multiple mice freely interact remains unclear. To capture the dynamic nature of behavior in different contexts, we simultaneously recorded behaviors and dCA2 activity in freely interacting mice. Male mice (n = 3) implanted with a 32-channel silicon probe interacted with three social partners (one male, two females) or three objects for one hour, over four consecutive days. The order of social and object days was pseudorandomized, with social days and object days interleaved. We extracted social (411.1 ± 73.5) and object interactions (77.3 ± 48.3) per session using custom detection programs, including only the first social and object days for neural data analyses. For each neuron, firing rate during interaction bouts was compared to duration-matched non-interaction control windows. Modulation was quantified as the natural-log firing-rate ratio (LRR), and a neuron was classified as significantly modulated (‘up’ or ‘down’) using a circular-shift permutation test (p < 0.05). During social interactions, 33/124 neurons (26.6%) significantly increased, and 6/124 (4.8%) decreased their firing rate. Interestingly, during object interactions, this pattern reversed; 15/136 (11%) increased, and 28/136 (20.6%) decreased their firing rate significantly. Comparing modulation across all neurons, the LRR was significantly increased during social compared to object interactions (p < 0.001, Wilcoxon rank-sum test). Both trends were consistent across all animals. Together, these results suggest that dCA2 activity may be differentially modulated by social versus object context. Future analyses probing activity during specific social behaviors and vocalizations may shed light on how dCA2 encodes sensory cues related to social experiences.