Computational capacity of pyramidal neurons

Electric activities of cortical pyramidal neurons are supported by structurally stable, morphologically complex axo-dendritic trees. Anatomical differences between axons and dendrites in regard to their length or caliber reflect the underlying functional specializations, for input or output of neural information, respectively. To properly assess the computational capacity of cortical pyramidal neurons, various morphometric measures of their axons and dendrites need to be precisely quantified from available three-dimensional digital reconstructions.

In our recent article published in Brain Research, we estimate the total number and type of ions involved in neuronal electric spiking based on the obtained morphometric data, which when combined with energetics of neurotransmitter release and signaling fueled by glucose consumed by the active brain, support highly efficient cerebral computation performed at the thermodynamically allowed Landauer limit for implementation of irreversible logical operations. We also show that individual proton tunneling events in voltage-sensing S4 protein α-helices of Na+, K+ or Ca2+ ion channels are ideally suited to serve as single Landauer elementary logical operations that are then amplified by selective ionic currents traversing the open channel pores. This miniaturization of computational gating allows the execution of over 1.2×1021 logical operations per second in the human cerebral cortex without combusting the brain by the released heat.