INFORMATION TRANSFER AT MOSSY FIBRE TO STRATUM LUCIDUM INTERNEURON SYNAPSES

GABAergic interneurons within the hippocampus constitute a minority, comprising approximately 10-15% of the total cell population. Despite their small number, these interneurons play a critical role in regulating both individual neuronal activity and the network-level dynamics essential for learning and memory processes. In the CA3 region, stratum lucidum interneurons are proposed to exert feedforward inhibition, resulting in sparse activation of pyramidal cells. Concurrently, these interneurons contribute to the generation of distinct firing patterns, network oscillations, and temporal constraints on information flow. Our findings suggest the presence of two distinct populations of interneurons. One group displays frequency-dependent facilitation, whereas the other exhibits consistent responses across various stimuli. We hypothesize that this dichotomy
may be attributed to the differential expression of Elfn1, a transmembrane protein known to modulate short-term plasticity at CA1 interneuron synapses. Given its widespread distribution in the CA3 region, Elfn1 likely imparts unique response properties to interneurons, whereby identical stimuli elicit disparate responses based on Elfn1 presence. This diversification in neuronal responses not only enriches single-cell electrophysiology and computational capacities but also enhances the computational capabilities of dentate gyrus (DG)-CA3 circuitry, which is pivotal for hippocampal function in memory encoding and learning. By employing electrophysiological recordings and morphological analyses of recorded cells, our study aims to characterize DG-interneuron-CA3 synapses, delineate the distinct interneuron populations, and elucidate their encoding roles within the broader context of hippocampal information processing.