Structural complexity supports computational richness in human hippocampal CA1 pyramidal neurons

The hippocampus is essential for memory acquisition and spatial navigation. The organizational principles have been mapped from cellular characteristics to cognition in rodent but not human brain. Here, we investigate the electrical, morphological and computational properties of individual CA1 pyramidal neurons in human living brain slices. Human CA1 pyramidal neurons have extensive dendritic trees and consistently exhibit a preferred resonance frequency of 2.9 Hz, which maps accurately onto theta-oscillations found in humans. Using unbiased cluster analysis, we find three main cell classes that differ in morpho-electric properties, including apical dendrite early bifurcations. The consequence of early apical bifurcations and extensive oblique dendrite formation in human CA1 pyramidal neurons is computationally independent dendritic compartments and preferential routing of oblique activity to either the soma/axon (proximal obliques) or to the main apical branches (distal obliques). These morpho-electrical properties increase the computational complexity of input-output transformations of CA1 pyramidal neurons in human hippocampus.