Abstract
The advanced cognitive capabilities of the human brain are often attributed to our recently evolved neocortex. However, it is not known whether the basic building blocks of the human neocortex, the pyramidal neurons, possess unique biophysical properties that might impact on cortical computations. Here we show that layer 2/3 pyramidal neurons from human temporal cortex (HL2/3 PCs) have a specific membrane capacitance (Cm) of ~0.5 µF/cm2, half of the commonly accepted 'universal' value (~1 µF/cm2) for biological membranes. This finding was predicted by fitting in vitro voltage transients to theoretical transients then validated by direct measurement of Cm in nucleated patch experiments. Models of 3D reconstructed HL2/3 PCs demonstrated that such low Cm value significantly enhances both synaptic charge-transfer from dendrites to soma and spike propagation along the axon. This is the first demonstration that human cortical neurons have distinctive membrane properties, suggesting important implications for signal processing in human neocortex.
Highlights
Since the beginnings of modern neuroscience the neocortex has attracted special attention because it is considered to play a key role in human cognition
We found that the peak somatic excitatory postsynaptic potential (EPSP) is larger by ~84% to ~93% when Cm = 0.45 mF/cm2 as compared to the case with Cm = 0.9 mF/cm2
We showed that layer 2/3 pyramidal neurons from human temporal cortex have a specific membrane capacitance (Cm) of ~0.5 mF/cm2, half of the commonly accepted ‘universal’ value (~1 mF/cm2) for biological membranes
Summary
Since the beginnings of modern neuroscience the neocortex has attracted special attention because it is considered to play a key role in human cognition. Comparison of human and rodents cortices shows that the human cortex is thicker (in particular layer 2/3 [DeFelipe et al, 2002; Elston et al, 2001]), contains more white matter (Herculano-Houzel et al, 2010), its neurons are larger (Mohan et al, 2015), and its cortical pyramidal cells have more synaptic connections per cell (15,000–30,000 for layer 2/3 pyramidal neurons [DeFelipe, 2011; DeFelipe et al, 2002]) It seems that the human neocortex, and especially its neurons, is anatomically unique.
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