The average number of neurons in V1
(adult human primary visual cortex, per hemisphere)

For some reason, this information is more obscure than it ought to be (the first two articles are not freely available online). I've also put this on wikipedia.

Best estimate: 140 million

Older estimate: 114 million

Rough estimates (pooling different sources for volume and density): 205 to 285 million

an aside: how this compares to number of fibers from the retina

  • The average human retina contains 1.07 million ganglion cells
    (inter-individual variability observed: between 700e3 and 1500e3)

    Curcio, C.A. and K.A. Allen 1990 "Topography of ganglion cells in human retina." J. Comp. Neurol. 300:5-25.
  • Thus, average number of V1 neurons per fiber in optic nerve:
    • best estimate: 140e6 / 1.07e6 = 131 V1 neurons / retinal fiber
    • low estimate: 114e6 / 1500e3 = 76 V1 neurons / retinal fiber
    • high estimate: 285e6 / 700e3 = 407 V1 neurons / retinal fiber
  • Yes, 13100 cortical neurons in V1 per 10x10 patch of fibers from retina! Why?

keywords: striate cortex, V1, Brodmann Area 17, neuronal packing density, neuron density, neural density