High-fidelity dendritic sodium spike generation in human layer 2/3 neocortical pyramidal neurons

Dendritic computations have a central role in rodent neocortical circuit function, which are signaled into neuronal output by the initiation and propagation of regenerative dendritic spikes. However, it remains poorly explored whether these mechanisms are operational in the human neocortex. To directly examine the dendritic computational properties of the most numerous class of pyramidal neuron in the human and rat neocortex we made simultaneous electrical recordings from the soma and apical dendrites of layer 2/3 pyramidal neurons maintained in acute brain slices of analogous cortical areas under identical experimental conditions. In both species correlated dendritic excitatory input led to the initiation of sodium channel-mediated dendritic spikes with conserved biophysical properties. Dendritic sodium spikes in human and rat layer 2/3 pyramidal neurons could be generated across a similar wide input range, exhibited a similar frequency range of activation, and forward propagated with high fidelity to drive neuronal output to implement stereotyped computations. Our findings therefore reveal that the dendritic computational properties of human layer 2/3 pyramidal neurons are phylogenetically conserved.