BRAIN Facts

Apr 03, 2018 08:22 PM

See Suzanna Herculano TED talk... wonderful.

Jan 17, 2013 12:11 AM

Look at Alex Huth study of cerebral cortex in Neuron 2012.

30,000 voxels each about 2 by 2 by 4 mm deep.

I think that is for both hemispheres, but need to check.

04:06 PM, August 10, 2007

Brain Facts from faculty.washington.edu/chudler/facts.html and other sources.

adult human weight of brain = 1300 to 1400 grams = 3 lbs.  (= about 1.5 liters or quarts)

% of body weight = 2% of weight (150lbs * .02)

Number of neurons total = 100 billion = 1011. This is a CASUAL estimate.

The actual number in the average adult male brain is 86B +/- 8 B

(so 100B is somewhat high but memorable).

Jeff Hawkins frequently says the Cerebral cortex has an area of 1000 cm2  (say abt 33 by 33 like a dinner napkin

or large pizza).   That = 1000 * 100 mm2 per cm2 =  100,000  mm2.

If the thickness of the CEREBRAL CORTEX = (say 2 mm (it prob. somewhat more) but that makes the math easy).

then the total volume of the CORTEX = 200,000  mm3.

The cortex in an adult male (see Herculano below) has on avg 16B neurons  (call it 20B).

So, 20B  divided by 200,000 mm3 =  100,000 neurons per mm3 in cortex.

I use a typical branching factor of 10,000 synapses per neuron for cortex (no one knows exactly: no studies).

Then you get 10,000 synapses *100,000 neurons per mm3 =  1B synapses per mm3

(I've seen casual estimates of 800M, so 1B is a good casual estimate.)

(Note:  branching factor is 100,000 synapses per neuron in cerebellum and perhaps 1000 in other regions).

But note:  cerebral cortex is 82% of the WEIGHT of the human brain even though it contains only

16B neurons (of a total of 86B neurons):  16/82 = 19% of  total neurons.  So,  where's the remaining weight:

it must be in glials cells (2:1 ratio and in white matter:  massive corticocortical connex and thalamocort. connex).

Note:  the oft-cited 10 to 1 for glial cells to neurons is simply WRONG!!!

(see Herculano-Houzel below (Brazilian study))  it is exactly 1 to 1  (avg adult male has 85B glial cells)

but the ratio varies wildly depending upon region of brain.  Cerebellum has huge numbers of neurons

(perhaps 3X as many as cerebral cortex:  all those granule cells and perhaps only

1 glial cell per 25 neurons).   Compare that to < 2 glial cells per neuron in cortex.

And 17 glial cells per neuron in thalamus and in ventral pallidum (basal ganglia by 12 glial cells to 1 neuron).

(My guess is those neurons are firing like mad and need a lot of support, but that's my guess.)

The average cortical cell is prob. quiet most of the time (due to sparse coding) and

even more so for the cerebellum  ( idling most of the time).

Gray to white matter in cerebral hemispheres in a 20 year old = 1.3

In a 50 year old = 1.1. => 20% loss of neurons.

Patricia Churchland (see the computational brain) estimates the total wiring to be 100,000 km.

Brian Wandell in his visual field map paper estimates wiring in 1 mm3 to be abt 3 km ...

this would give a total length  3km * 1500 cc * 1000 mm3 per cc as over 1 million km of wiring!!!!

packed into 1.5 quart brain case.

Average number of glial cells in brain = 10-50 times the number of neurons

Number of neocortical neurons (females) = 19.3 billion (Pakkenberg, B., Pelvig, D., Marner,L., Bundgaard, M.J., Gundersen, H.J.G., Nyengaard, J.R. and Regeur, L. Aging and the human neocortex. Exp. Gerontology, 38:95-99, 2003 and Pakkenberg, B. and Gundersen, H.J.G. Neocortical neuron number in humans: effect of sex and age. J. Comp. Neurology, 384:312-320, 1997.)

Number of   neocortical neurons (males) = 22.8 billion (Pakkenberg et al., 1997; 2003)

Average loss of neocortical neurons = 85,000 per day (₃₁ million per year) (Pakkenberg et al., 1997; 2003)

Average loss of neocortical neurons = 1 per second (Pakkenberg et al., 1997; 2003)

Average number of neocortical glial cells (young adults ) = 39 billion (Pakkenberg et al., 1997; 2003)

Average number of neocortical glial cells (older adults) =36 billion (Pakkenberg et al., 1997; 2003)

Length of myelinated nerve fibers in brain = 150,000-180,000 km (Pakkenberg et al., 1997; 2003)

Number of synapses in cortex = 0.15 quadrillion (Pakkenberg et al., 1997; 2003)

Difference number of neurons in the right and left hemispheres = 186 million MORE neurons on left side than right side (Pakkenberg et al., 1997; 2003)

Total surface area of the cerebral cortex =  2,500 cm2 (2.5 ft2 ; A. Peters, and E.G. Jones,  Cerebral Cortex , 1984 ) = pizza or unfolded dinner napkin.

Total number of neurons in cerebral cortex =  10 billion ( from G.M. Shepherd,  The Synaptic Organization of the Brain , 1998, p. 6) . However, C. Koch lists the total number of neurons in the cerebral cortex at  20 billion (  Biophysics of Computation. Information Processing in Single Neurons , New York: Oxford Univ. Press, 1999, page 87).

Total number of synapses in cerebral cortex =  60 trillion (yes, trillion) (from G.M. Shepherd,  The Synaptic Organization of the Brain , 1998, p. 6). However, C. Koch lists the total synapses in the cerebral cortex at  240 trillion (  Biophysics of Computation. Information Processing in Single Neurons , New York: Oxford Univ. Press, 1999, page 87).

Percentage of total cerebral cortex volume (human): frontal lobe = 41%; temporal lobe = 22%; parietal lobe = 19%; occipital lobe = 18%. (Caviness Jr., et al.  Cerebral Cortex , 8:372-384, 1998.)

Number of cortical layers = 6

Thickness of cerebral cortex = 1.5-4.5 mm

Thickness of cerebral cortex (Bottlenosed dolphin) = 1.3-1.8 mm (S.H. Ridgway,  The Cetacean Central Nervous System , p. 221)

EEG - beta wave frequency = 13 to 30 Hz

EEG - alpha wave frequency = 8 to 13 Hz

EEG - theta wave frequency = 4 to 7 Hz

EEG - delta wave frequency = 0.5 to 4 Hz

World record, time without sleep = 264 hours (11 days) by Randy Gardner in 1965. Note: In  Biopsychology (by J.P.J. Pinel, Boston: Allyn and Bacon, 2000, p. 322), the record for time awake is attributed to Mrs. Maureen Weston. She apparently spent 449 hours [18 days, 17 hours] awake in a rocking chair. The  Guinness Book of World Records [1990] has the record belonging to Robert McDonald who spent 453 hours, 40 min in a rocking chair.

Time until unconsciousness after loss of blood supply to brain = 8-10 sec

Time until reflex loss after loss of blood supply to brain = 40-110 sec

Number of fibers in human optic nerve = 1,200,000

Length of optic nerve = 50 mm

Audition

Surface area of the tympanic membrane = 85mm2 (  Hearing: Its Physiology and Pathophysiology , A.R. Moller, Amsterdam: Elsevier, 2006)

Length of the eustachian tube = 3.5 to 3.9 cm (  Hearing. Its Physiology and Pathophysiology , A.R. Moller, San Diego, Academic Press, 2000.)

Number of hair cells in cochlea = 3,500 inner hair cells; 12,000 outer hair cells (  Hearing. Its Physiology and Pathophysiology , A.R. Moller, San Diego, Academic Press, 2000.)

Number of fibers in auditory nerve = 30,000 (  Hearing: Its Physiology and Pathophysiology , A.R. Moller, Amsterdam: Elsevier, 2006)

Length of auditory nerve = 2.5 cm (  Hearing: Its Physiology and Pathophysiology , A.R. Moller, Amsterdam: Elsevier, 2006)

Number of neurons in cochlear nuclei = 8,800 (Northern, J.L. and Downs, M.P., Hearing in Children, 5th edition, Philadelphia: Lippincott Williams & Wilkins, 2002.)

Number of neurons in inferior colliculus = 392,000 (Northern, J.L. and Downs, M.P., Hearing in Children, 5th edition, Philadelphia: Lippincott Williams & Wilkins, 2002.)

Number of neurons in medial geniculate body = 570,000

Number of neurons in auditory cortex = 100,000,000

Hearing Range (young adult human) = 20 to 20,000 Hz

Hearing Range (elderly human) = 50 to 8,000 Hz (Guyton, A.C.,  Textbook of Medical Physiology , 1986

VISION FACTS

Number of retinal receptor cells = 5-6 million cones; 120-140 million rods

Number of retinal ganglion cells = 800 thousand to 1 million

Number of fibers in optic nerve = 1,200,000

Number of neurons in lateral geniculate body = 570,000

Number of cells in visual cortex (area 17) = 538,000,000

Wavelength of visible light (human) = 400-700 nm

Amount of light necessary to excite a rod = 1 photon

Amount of light necessary to excite a cone = 100 photons

Location of the greatest density of rods = 20o from fovea

Highest density of rods = 160,000 per mm2

Peak density of rods (cat) = 400,000 per mm2

Density of cones in fovea = 200,000 per mm2

Diameter of fovea = 1.5 mm

Intraocular pressure = 10-20 mm Hg

Volume of orbit = 30 ml

Area of retina = 2,500 mm2  (= abt 5 by 5 cm)

Thickness of retina = 120 microns (ranges from 100 to 230 microns)

BRAIN Facts

Attachments