Associative Plasticity at Excitatory Synapses Facilitates Recruitment of Fast-Spiking Interneurons in the Dentate Gyrus

Abstract

Fast-spiking perisomatic-inhibitory interneurons (PIIs-permeable AMPARs and do not show plasticity on associative activation. Thus, precise recruitment of PIIs requires excitation through MF-PII synapses during feedforward activation. We propose that associative plasticity at these synapses is a central mechanism that adjusts inhibition levels to maintain sparse activity and to improve signal-to-noise ratio in the DG network.

Synaptic Kainate Receptors in Interplay with INaP Shift the Sparse Firing of Dentate Granule Cells to a Sustained Rhythmic Mode in Temporal Lobe Epilepsy

“…DGCs use a sparse and specific firing for efficient discrimination of incoming information (Leutgeb et al, 2007). This results in part from their coincidence detector function due to the fast kinetics of synaptic inputs (Schmidt-Hieber et al, 2007), and from a dynamic recruitment of perisomatic-inhibitory interneurons (Sambandan et al, 2010). In TLE, we show that the interplay between aberrant KARs and I NaP , by expanding the temporal window for synaptic integration, promotes a switch from a sparse to a sustained and rhythmic firing pattern in DGCs.…”

Adult neurogenesis in the mammalian hippocampus: Why the dentate gyrus?

“…For example, perisomatic targeting basket cells residing near, or within, the GCL receive excitatory drive from both EC afferents (Zipp et al 1989) and GCs (Geiger et al 1997). Therefore, these basket cells mediate both (what would classically be defined as) feedforward and feedback inhibition (Sambandan et al 2010). Other INs mediate dendritic BOX 1.…”

LTP and LTD in cortical GABAergic interneurons: Emerging rules and roles

“…That is, when an induction protocol is delivered to one population of excitatory axons, this can result in an increase in synaptic strength that is confined to the same pathway, leaving unchanged a second, control, pathway that was not stimulated (Lamsa et al, 2005(Lamsa et al, , 2007bSambandan et al, 2010; although see also Cowan et al, 1998). Whether LTD also shows synapse specificity is less clear, with some reports arguing that this form of plasticity spreads to other synapses converging on the same interneurons (McMahon and Kauer, 1997;Cowan et al, 1998).…”

“…Further evidence that the identity of the presynaptic bouton (and by implication its innervating axon and parent cell body) is a major determinant of the type of plasticity comes from a comparison of mossy fiber and perforant path inputs to fastspiking interneurons at the border of the dentate hilus and granule cell layer (Sambandan et al, 2010). Some of the studied neurons were anatomically analyzed and shown to project axons back to the granule cell layer.…”

“…NMDA receptorindependent LTP was elicited at mossy fiber (but not perforant path) synapses by pairing presynaptic trains of action potentials with postsynaptic depolarization (see also Alle et al, 2001). The synapses that exhibited LTP were further shown to be equipped with rectifying AMPA receptors, blockade of which prevented LTP induction (Sambandan et al, 2010).…”