Cortical ensembles based on dendritic plateau generation in the prefrontal cortex

Prefrontal cortex (PFC) performs executive functions, which require the selection of relevant information from inputs from multiple brain areas. At the cellular level, cortical pyramidal neurons in Layer 5 of the PFC can produce dendritic plateaus, sustained depolarizations with AMPAr and NMDAr activation in basal dendrites. Our embedded-ensemble encoding theory (EEE) hypothesizes that dendritic plateaus put individual cells in a Standby state. Cells in this state have reduced threshold to firing and can more readily produce synchronized firing in response to afferent synaptic activity. Cells that are firing together are in the Embedded state, in which ensemble neurons exhibit synchronized firing within the column or across columns. Dendritic plateaus have been well characterized at the cellular level, but their implications at the network level remains unknown. We hypothesize that the generation of dendritic plateaus in the pyramidal neurons will be relevant for the formation of neural ensembles. For this, we modeled and simulated a PFC columnar network with a connectivity that leads to dendritic plateaus, and studied the effects of subpopulations of neurons in Standby or Embedded states. We used the NetPyNE package, which extends the NEURON simulator to facilitate building and parallel optimization of neuronal networks. We built a network simulating the architecture of PFC in rats that includes layers 2/3, 5, and 6. A simplified excitatory pyramidal neuron model was included in L2/3 and L6. An excitatory pyramidal neuron in L5 was optimized to simulate experimental findings that generate dendritic plateaus. Interneurons were added to the model to every layer (parvalbumin, somatostatin, and VIP positive interneurons) with proportions and connectivity according to previous reports. Local excitatory connectivity included mainly AMPA receptors. Long-range input connectivity was designed to target the basal dendrites of L5 pyramidal neurons. Long-range connectivity included AMPA and NMDA receptors with different synaptic weights to obtain dendritic plateaus. L5 pyramidal neurons receiving long-range inputs were able to induce dendritic plateaus and a high frequency rate in comparison with other network subpopulations. The generation of dendritic plateaus induced standby and embedded ensembles in our PFC network model and may be essential for the processing of multimodal cortical information.