Abstract
Disinhibition of cortical excitatory cell gate information flow through and between cortical columns. The major contribution of Martinotti cells (MC) is providing dendritic inhibition to excitatory neurons and therefore they are a main component of disinhibitory connections. Here we show by means of optogenetics that MC in layers II/III of the mouse primary somatosensory cortex are inhibited by both parvalbumin (PV)- and vasoactive intestinal polypeptide (VIP)-expressing cells. Paired recordings revealed stronger synaptic input onto MC from PV cells than from VIP cells. Moreover, PV cell input showed frequency-independent depression, whereas VIP cell input facilitated at high frequencies. These differences in the properties of the two unitary connections enable disinhibition with distinct temporal features.
Highlights
Disinhibition of cortical excitatory cell gate information flow through and between cortical columns
PV and vasoactive intestinal polypeptide (VIP) cell inhibition differs in synaptic properties. These findings indicated the presence of two discrete inhibitory inputs onto Martinotti cells (MC), namely, from PV and VIP cells, which are restricted to LII/LIII
The present study demonstrates that both VIP and PV cells target MC in LII/LIII of S1 and differ strongly in unitary synaptic properties as well as short-term plasticity
Summary
Disinhibition of cortical excitatory cell gate information flow through and between cortical columns. The main, but not exclusive, cell types within these subpopulations, largely defined by morphological features, are: PV-expressing basket cells, SST-expressing Martinotti cells (MC) and cells co-expressing 5HT3aR and vasoactive intestinal polypeptide (VIP)[1,3,4] The functions of these IN are manifold. They keep excitation in check, perform gain modulation and induce synchronization and oscillations, whereas they open or close temporal or spatial windows for input control or output generation[5] Their functional impact is not restricted to their interaction with excitatory neurons, but direct interactions between IN seem to be essential for sensory information processing as well[6,7,8,9]. We found that MC in mouse primary somatosensory cortex commonly receive inhibitory inputs from local PV- and VIP-expressing interneurons These inputs differ substantially in unitary properties and short-term plasticity
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