CA1 pyramidal cell diversity enabling parallel information processing in the hippocampus

Abstract

Hippocampal network operations supporting spatial navigation and declarative memory are traditionally interpreted in a framework where each hippocampal area, such as the dentate gyrus, CA3, and CA1, consists of homogeneous populations of functionally equivalent principal neurons. However, heterogeneity within hippocampal principal cell populations, in particular within pyramidal cells at the main CA1 output node, is increasingly recognized and includes developmental, molecular, anatomical, and functional differences. Here we review recent progress in the delineation of hippocampal principal cell subpopulations by focusing on radially defined subpopulations of CA1 pyramidal cells, and we consider how functional segregation of information streams, in parallel channels with nonuniform properties, could represent a general organizational principle of the hippocampus supporting diverse behaviors.

IGFBP2 Plays an Essential Role in Cognitive Development during Early Life

“…CA1 pyramidal neurons containing IGFBP2 may also enable parallel information processing [21] in celltype-specific firing patterns [22] since we found IGFBP2 did not interfere with CA1-interneuron spiking. We found that IGFBP2 enhanced both the evoked and spontaneous neuronal excitability and the fidelity of spike transmission of CA1 pyramidal neurons by ≈5.3 excitatory inputs.…”

“…[21,22] IGFBP2 enhanced mEPSC frequency without changing the PPR, indicating a novel role of IGFBP2 in glutamate receptor kinetics. Among the pyramidal neurons, IGFBP2 preferentially excited L cells rather than H cells.…”

Ripple‐related firing of identified deep CA1 pyramidal cells in chronic temporal lobe epilepsy in mice

“…In addition, the increased baseline firing rate could have implications for the ability of these cells to function as place cells. DPCs are more likely to participate in the generation of place fields than sPCs, and have distinct patterns of efferent projections to cortical and other subcortical areas . This alteration of limbic network function could contribute to the memory deficits seen in rodents and patients with chronic epilepsy.…”

“…Given the intense interest and considerable clinical relevance of high‐frequency oscillations in epilepsy, and the paucity of data on SWR‐related firing from rigorously identified cells in the chronically epileptic hippocampus, we carried out a series of targeted experiments to investigate the SWR‐related discharges of CA1 pyramidal cells (PCs) in an experimental model of temporal lobe epilepsy (TLE) in mice. There has been increasing recognition that CA1 PCs are heterogeneous, with respect to both firing patterns during network oscillations and limbic circuit heterogeneity . We chose to focus on the PCs located in the deep subdivision of the CA1 PC (dPC) layer in order to reduce variability and because these deep cells may be more vulnerable to seizure‐induced injury .…”

“…We chose to focus on the PCs located in the deep subdivision of the CA1 PC (dPC) layer in order to reduce variability and because these deep cells may be more vulnerable to seizure‐induced injury . Compared to superficial PCs (sPCs), dPCs are more likely to have place cells and fire at higher rates, and are more strongly modulated by slow oscillations during rapid eye movement (REM) sleep, and receive stronger innervation from the CA2 area that is thought to be important for SWR initiation . To avoid confounds from direct damage to hippocampal cells within the CA1 from chemoconvulsants or seizure‐induced apoptosis, we performed a unilateral injection of kainic acid in the amygdala to generate TLE in mice.…”