Inhibitory Control of Linear and Supralinear Dendritic Excitation in CA1 Pyramidal Neurons

The transformation of dendritic excitatory synaptic inputs to axonal action potential output is the fundamental computation performed by all principal neurons. We show that in the hippocampus this transformation is potently controlled by recurrent inhibitory microcircuits. However, excitatory input on highly excitable dendritic branches could resist inhibitory control by generating strong dendritic spikes and trigger precisely timed action potential output. Furthermore, we show that inhibition-sensitive branches can be transformed into inhibition-resistant, strongly spiking branches by intrinsic plasticity of branch excitability. In addition, we demonstrate that the inhibitory control of spatially defined dendritic excitation is strongly regulated by network activity patterns. Our findings suggest that dendritic spikes may serve to transform correlated branch input into reliable and temporally precise output even in the presence of inhibition. ⺠Dendritic excitatory integration is dynamically controlled by recurrent inhibition ⺠Recurrent inhibition reduces EPSP and weak dendritic spike dependent output ⺠Strong dendritic spikes provide reliable I/O coupling in the presence of inhibition ⺠Plasticity of branch excitability modulates inhibitory resistance of branch input