Single synaptic inputs drive high-precision action potentials in parvalbumin expressing GABA-ergic cortical neurons in vivo

By J. Jouhanneau, Jens Kremkow, J. Poulet. 2018

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A defining feature of cortical layer 2/3 excitatory neurons is their sparse activity, often firing in singlets of action potentials. Local inhibitory neurons are thought to play a major role in regulating sparseness, but which cell types are recruited by single excitatory synaptic inputs is unknown. Using multiple, targeted, in vivo whole-cell recordings, we show that single uEPSPs have little effect on the firing rates of excitatory neurons and somatostatin-expressing GABA-ergic inhibitory neurons but evoke precisely timed action potentials in parvalbumin-expressing inhibitory neurons. Despite a uEPSP decay time of 7.8 ms, the evoked action potentials were almost completely restricted to the uEPSP rising phase (~0.5 ms). Evoked parvalbumin-expressing neuron action potentials go on to inhibit the local excitatory network, thus providing a pathway for single spike evoked disynaptic inhibition which may enforce sparse and precisely timed cortical signaling. In superficial layers of the cortex, excitatory neurons often fire single action potentials. Here, using multiple whole-cell recordings in vivo, the authors show that single excitatory synaptic events can drive GABA-ergic parvalbumin neurons to fire, triggering inhibition of other pyramidal neurons.

Subfields: Cellular and Molecular Neuroscience, Cognitive Neuroscience