Data from: In-vivo analysis of medial perforant path-evoked excitation and inhibition in dentate granule cells

Across brain regions and species, the dynamics and balance of excitation
and inhibition critically determine neuronal firing. The hippocampal
dentate gyrus is a brain area thought to be strongly regulated by
inhibition. In vivo, it exhibits remarkably sparse activity, a
characteristic proposed to underlie computational tasks like pattern
separation. Several populations of interneurons mediate strong feedforward
as well as feedback inhibition onto granule cells. However, the dynamics
of inhibition control granule cell activity in vivo are insufficiently
studied. Using two-photon in vivo Ca2+ imaging in mice of either sex, we
show that sensory stimulation activates only a small number of dentate
gyrus granule cells, while inducing widespread inhibition across the
remaining granule cell population. Dual-color imaging of both bulk medial
perforant path activity and individual granule cell activity allowed us to
probe input–output conversion in this pathway. To examine the interplay of
MPP-evoked excitation and inhibition at the cellular level, we used in
vivo whole-cell patch-clamp recordings while simultaneously
photo-activating MPP inputs. Our findings reveal that MPP-triggered
inhibition is fast, significantly larger than excitation, and
long-lasting. These results reveal specific properties of inhibition in
the dentate gyrus that are likely crucial for its computational functions,
in maintaining sparse activity with a high signal-to-noise ratio.