Information Transfer in the Brain

Transmitting fibers in the brain: Total length and distribution of lengths

The human brain’s approximately 86 billion neurons are probably connected by something like 850,000 km of axons and dendrites. Of this total, roughly 80% is short-range, local connections (averaging 680 microns in length), and approximately

Costs of human-level hardware

Computing hardware which is equivalent to the brain – in terms of FLOPS probably costs between $1 x 105 and $3 x 1016, or $2/hour-$700bn/hour. in terms of TEPS probably costs $200M – $7B, or or $4,700 – $170,000/hour

Glial Signaling

The presence of glial cells may increase the capacity for signaling in the brain by a small factor, but is unlikely to qualitatively change the nature or extent of signaling in the brain. Support Number

Scale of the Human Brain

The brain has about 10¹¹ neurons and 1.8-3.2 x 10¹⁴ synapses. These probably account for the majority of computationally interesting behavior. Support Number of neurons in the brain The number of neurons in the brain is about 10¹¹. For

Neuron firing rates in humans

Our best guess is that an average neuron in the human brain transmits a spike about 0.1-2 times per second. Support Bias from neurons with sparse activity When researchers measure neural activity, they can fail to see neurons

Metabolic Estimates of Rate of Cortical Firing

Cortical neurons are estimated to spike around 0.16 times per second, based on the amount of energy consumed by the human neocortex. They seem unlikely to spike much more than once per second on average, based on this