Cell

Neuroscience

Pyramidal cell

Subiculum

Biology

Hippocampal formation

Cytoarchitecture

Cell type

Dentate gyrus

Hippocampus

Genetics

Nature reviews. Neuroscience

The mechanistic operation of brain regions is often interpreted by partitioning constituent neurons into ‘cell types’. Historically, such cell types were broadly defined by their correspondence to gross features of the nervous system (such as cytoarchitecture). Modern-day neuroscientific techniques, enabling a more nuanced examination of neuronal properties, have illustrated a wealth of heterogeneity within these classical cell types. Here, we review the extent of this within-cell-type heterogeneity in one of the simplest cortical regions of the mammalian brain, the rodent hippocampus. We focus on the mounting evidence&nbsp;that the classical CA3, CA1 and subiculum pyramidal cell types all exhibit prominent&nbsp;and spatially patterned within-cell-type heterogeneity, and suggest these cell&nbsp;types&nbsp;provide a model system for exploring the organization and function of such heterogeneity. Given that the hippocampus is structurally simple and evolutionarily ancient,&nbsp;within-cell-type heterogeneity is likely to be a general and crucial feature of the&nbsp;mammalian brain. It is now clear that most classical ‘cell types’ are composed of collections of cells with heterogeneous features. Cembrowski and Spruston describe the heterogeneity of hippocampal pyramidal cells and argue that these cells can act as a model of within-cell-type heterogeneity in the brain.

Heterogeneity within classical cell types is the rule: lessons from hippocampal pyramidal neurons