The following are two lists of animals ordered by the size of their nervous system. The first list shows number of neurons in their entire nervous system. The second list shows the number of neurons in the structure that has been found to be representative of animal intelligence. [1] The human brain contains 86 billion neurons, with 16 billion neurons in the cerebral cortex. [2] [1]
Neuron counts constitute an important source of insight on the topic of neuroscience and intelligence: the question of how the evolution of a set of components and parameters (~1011 neurons, ~1014 synapses) of a complex system leads to the phenomenon of intelligence. [3]
Neurons are the cells that transmit information in an animal's nervous system so that it can sense stimuli from its environment and behave accordingly. Not all animals have neurons; Trichoplax and sponges lack nerve cells altogether.
Neurons may be packed to form structures such as the brain of vertebrates or the neural ganglions of insects.
The number of neurons and their relative abundance in different parts of the brain is a determinant of neural function and, consequently, of behavior.
All numbers for neurons (except Caenorhabditis and Ciona), and all numbers for synapses (except Ciona) are estimations.
Proxies for animal intelligence have varied over the centuries. One early suggestion was brain size (or weight, which provides the same ordering.) A second proposal was brain-to-body-mass ratio, and a third was encephalization quotient, sometimes referred to as EQ. The current best predictor is number of neurons in the forebrain, based on Herculano-Houzel's improved neuron counts. [1] This accounts for variation in the number of neurons in the rest of the brain, for which no link to intelligence has been established. Elephants, for example, have an exceptionally large cerebellum, while birds make do with a much smaller one.
Differing methods have been used to count neurons, and these may differ in degree of reliability. The primary methods are the optical fractionator, an application of stereology and the isotropic fractionator, a recent methodological innovation. Most numbers in the list are the result of studies using the newer isotropic fractionator. [1] [40] [29] [44] [45] [47] [48] [49] [50] [55] [56] [57] [59] [60] [62] [64] A variation of the optical fractionator was responsible for the previous total human brain neuron count of 100,000,000,000 neurons, which has been revised down to 86,000,000,000 by the use of the isotropic fractionator. This is in part why it may be considered to be less reliable. Finally, some numbers are the result of estimations based on correlations observed between number of cortical neurons and brain mass within closely related taxa.
The following table gives information on the number of neurons estimated to be in the sensory-associative structure: the cerebral cortex (aka pallium) for mammals, the dorsal ventricular ridge ("DVR" or "hypopallium") of the pallium for birds, and the corpora pedunculata ("mushroom bodies") for insects.
Common name | Average number of sensory-associative structure neurons [a] | Intraspecific variation [b] | Method [c] | Sensory-associative structure | Binomial nomenclature | Image | Source |
---|---|---|---|---|---|---|---|
Common fruit fly | 2,500* | Optical fractionator | Corpora pedunculata | Drosophila melanogaster | [65] | ||
House cricket | 50,000* | Optical fractionator | Corpora pedunculata | Acheta domesticus | [65] | ||
Honey bee | 170,000* | Optical fractionator | Corpora pedunculata | Genus: Apis | [65] | ||
Common cockroach | 200,000* | Optical fractionator | Corpora pedunculata | Genus: Periplaneta | [65] | ||
African sheath-tailed bat | 5,000,000 | Isotropic fractionator | Pallium (cortex) | Coleura afra | [41] | ||
Rufous trident bat | 6,000,000 | Isotropic fractionator | Pallium (cortex) | Triaenops persicus | [41] | ||
Naked mole-rat | 6,000,000 | ± 1,065,587 [43] | Isotropic fractionator | Pallium (cortex) | Heterocephalus glaber | [40] | |
Little free-tailed bat | 6,000,000 | Isotropic fractionator | Pallium (cortex) | Chaerephon pumilus | [41] | ||
Common bent-wing bat | 6,000,000 | Isotropic fractionator | Pallium (cortex) | Miniopterus schreibersii | [41] | ||
Commerson's roundleaf bat | 8,000,000 | Isotropic fractionator | Pallium (cortex) | Hipposideros commersoni | [41] | ||
Heart-nosed bat | 10,000,000 | Isotropic fractionator | Pallium (cortex) | Cardioderma cor | [41] | ||
Ansell's mole-rat | 10,000,000 | Isotropic fractionator | Pallium (cortex) | Fukomys anselli | [46] | ||
Smoky shrew | 10,000,000 | ± 352,000 [43] | Isotropic fractionator | Pallium (cortex) | Sorex fumeus | [43] | |
Short-palated fruit bat | 10,000,000 | Isotropic fractionator | Pallium (cortex) | Casinycteris argynnis | [41] | ||
Mashona mole-rat | 12,000,000 | Isotropic fractionator | Pallium (cortex) | Fukomys darlingi | [46] | ||
Woermann's bat | 12,000,000 | Isotropic fractionator | Pallium (cortex) | Megaloglossus woermanni | [41] | ||
Northern short-tailed shrew | 12,000,000 | ± 1,569,000 [43] | Isotropic fractionator | Pallium (cortex) | Blarina brevicauda | [43] | |
Zenker's fruit bat | 13,000,000 | Isotropic fractionator | Pallium (cortex) | Scotonycteris zenkeri | [41] | ||
House mouse | 14,000,000 | ± 2,242,257 [43] | Isotropic fractionator | Pallium (cortex) | Mus musculus | [43] | |
Hairy-tailed mole | 16,000,000 | ± 2,611,000 [43] | Isotropic fractionator | Pallium (cortex) | Parascalops breweri | [43] | |
Star-nosed mole | 17,000,000 | ± 3,105,000 [43] | Isotropic fractionator | Pallium (cortex) | Condylura cristata | [43] | |
Golden hamster | 17,000,000 | ± 3,619,934 [43] | Isotropic fractionator | Pallium (cortex) | Mesocricetus auratus | [43] | |
Diamond dove | 18,209,000 | Isotropic fractionator | Pallium (DVR) | Geopelia cuneata | [34] | ||
King quail | 20,523,000 | Isotropic fractionator | Pallium (DVR) | Synoicus chinensis | [34] | ||
Damaraland mole-rat | 21,000,000 | Isotropic fractionator | Pallium (cortex) | Fukomys damarensis | [46] | ||
Hottentot golden mole | 22,000,000 | ± 2,154,000 [43] | Isotropic fractionator | Pallium (cortex) | Amblysomus hottentotus | [43] | |
Gray mouse lemur | 22,310,000 | Isotropic fractionator | Pallium (cortex) | Microcebus murinus | [49] | ||
Common quail | 22,568,000 | Isotropic fractionator | Pallium (DVR) | Coturnix coturnix | [34] | ||
Mechow's mole-rat | 23,000,000 | Isotropic fractionator | Pallium (cortex) | Fukomys mechowii | [46] | ||
Franquet's epauletted fruit bat | 23,000,000 | Isotropic fractionator | Pallium (cortex) | Epomops franqueti | [41] | ||
Hammer-headed bat | 24,000,000 | Isotropic fractionator | Pallium (cortex) | Hypsignathus mostrosus | [41] | ||
Hedgehog | 24,000,000^ | Estimated | Pallium (cortex) | Subfamily Erinaceinae, various species | [66] | ||
Silvery mole-rat | 25,000,000 | Isotropic fractionator | Pallium (cortex) | Heliophobius argenteocinereus | [46] | ||
Wahlberg's epauletted fruit bat | 26,000,000 | Isotropic fractionator | Pallium (cortex) | Epomophorus wahlbergi | [41] | ||
Cape mole-rat | 26,000,000 | Isotropic fractionator | Pallium (cortex) | Georychus capensis | [46] | ||
Guyenne spiny rat | 26,000,000 | ± 2,155,723 [43] | Isotropic fractionator | Pallium (cortex) | Proechimys cayennensis | [43] | |
Eastern rock elephant shrew | 26,000,000 | ± 4,020,000 [43] | Isotropic fractionator | Pallium (cortex) | Elephantulus myurus | [43] | |
Eastern mole | 27,000,000 | ± 5,113,000 [43] | Isotropic fractionator | Pallium (cortex) | Scalopus aquaticus | [43] | |
Opossum | 27,000,000^ | Estimated | Pallium (cortex) | Didelphis virginiana | [66] | ||
Egyptian fruit bat | 29,000,000 | Isotropic fractionator | Pallium (cortex) | Rousettus aegyptiacus | [41] | ||
Brown Rat | 31,000,000 | + 3,034,654 [43] | Isotropic fractionator | Pallium (cortex) | Rattus norvegicus | [43] | |
Four-toed elephant shrew | 34,000,000 | ± 5,840,000 [43] | Isotropic fractionator | Pallium (cortex) | Petrodromus tetradactylus | [43] | |
Grey partridge | 36,882,000 | Isotropic fractionator | Pallium (DVR) | Perdix perdix | [34] | ||
Ferret | 38,950,000 | Isotropic fractionator | Pallium (cortex) | Mustela putorius furo | [51] | ||
Northern bobwhite | 39,112,000 | Isotropic fractionator | Pallium (DVR) | Colinus virginianus | [34] | ||
African collared dove | 39,997,000 | Isotropic fractionator | Pallium (DVR) | Streptopelia roseogrisea | [34] | ||
Cape dune mole-rat | 43,000,000 | Isotropic fractionator | Pallium (cortex) | Bathyergus suillus | [46] | ||
Guinea pig | 43,510,000 | ± 3,169,924 [43] | Isotropic fractionator | Pallium (cortex) | Cavia porcellus | [40] | |
Quebracho crested tinamou | 48,292,000 | Isotropic fractionator | Pallium (DVR) | Eudromia formosa | [34] | ||
Common wood pigeon | 51,325,000 | Isotropic fractionator | Pallium (DVR) | Columba palumbus | [34] | ||
Elegant crested tinamou | 51,384,000 | Isotropic fractionator | Pallium (DVR) | Eudromia elegans | [34] | ||
Eurasian blackcap | 52,000,000 | Isotropic fractionator | Pallium (DVR) | Sylvia atricapilla | [47] | ||
Prairie dog | 53,770,000 | ± 6,044,322 [43] | Isotropic fractionator | Pallium (cortex) | Genus:Cynomys | [40] | |
Zebra finch | 55,000,000 | Isotropic fractionator | Pallium (DVR) | Taeniopygia guttata | [47] | ||
Chilean tinamou | 59,130,000 | Isotropic fractionator | Pallium (DVR) | Nothoprocta perdicaria | [34] | ||
Common treeshrew | 60,000,000 | ± 26,510,000 [43] | Isotropic fractionator | Pallium (cortex) | Tupaia glis | [43] | |
Red junglefowl | 61,000,000 | Isotropic fractionator | Pallium (DVR) | Gallus gallus | [47] | ||
Goldcrest | 64,000,000 | Isotropic fractionator | Pallium (DVR) | Regulus regulus | [47] | ||
European rabbit | 71,450,000 | Isotropic fractionator | Pallium (cortex) | Oryctolagus cuniculus | [40] | ||
Rock dove | 72,000,000 | Isotropic fractionator | Pallium (DVR) | Columba livia | [47] | ||
Eastern gray squirrel | 77,330,000 | ± 2,634,444 [43] | Isotropic fractionator | Pallium (cortex) | Sciurius carolinensis | [40] | |
Reeves's pheasant | 80,688,000 | Isotropic fractionator | Pallium (DVR) | Syrmaticus reevesii | [34] | ||
Great tit | 83,000,000 | Isotropic fractionator | Pallium (DVR) | Parus major | [47] | ||
Eurasian sparrowhawk | 87,832,000 | Isotropic fractionator | Pallium (DVR) | Accipiter nisus | [34] | ||
Western tree hyrax | 99,000,000 | Isotropic fractionator | Pallium (cortex) | Dendrohyrax dorsalis | [43] | ||
Green-rumped parrotlet | 103,000,000 | Isotropic fractionator | Pallium (DVR) | Forpus passerinus | [47] | ||
Wild turkey | 105,654,000 | Isotropic fractionator | Pallium (DVR) | Meleagris gallopavo | [34] | ||
Mallard | 112,255,000 | Isotropic fractionator | Pallium (DVR) | Anas platyrhynchos | [34] | ||
Black-rumped agouti | 113,000,000 | ± 2,576,768 [43] | Isotropic fractionator | Pallium (cortex) | Dasyprocta prymnolopha | [1] | |
Banded mongoose | 115,770,000 | Isotropic fractionator | Pallium (cortex) | Mungos mungo | [51] | ||
Victoria crowned pigeon | 118,445,000 | Isotropic fractionator | Pallium (DVR) | Goura victoria | [34] | ||
Yellow-knobbed curassow | 124,624,000 | Isotropic fractionator | Pallium (DVR) | Crax daubentoni | [34] | ||
Indian peafowl | 129,621,000 | Isotropic fractionator | Pallium (DVR) | Pavo cristatus | [34] | ||
Marbled duck | 130,142,000 | Isotropic fractionator | Pallium (DVR) | Marmaronetta angustirostris | [34] | ||
Pygmy falcon | 131,898,000 | Isotropic fractionator | Pallium (DVR) | Polihierax semitorquatus | [34] | ||
Common blackbird | 136,000,000 | Isotropic fractionator | Pallium (DVR) | Turdus merula | [47] | ||
Wood duck | 138,206,000 | Isotropic fractionator | Pallium (DVR) | Aix sponsa | [34] | ||
Red-breasted goose | 148,617,000 | Isotropic fractionator | Pallium (DVR) | Branta ruficollis | [34] | ||
Budgerigar | 149,000,000 | Isotropic fractionator | Pallium (DVR) | Melopsittacus undulatus | [47] | ||
Eurasian teal | 167,287,000 | Isotropic fractionator | Pallium (DVR) | Anas crecca | [34] | ||
Rock hyrax | 198,000,000 | ± 29,082,000 [43] | Isotropic fractionator | Pallium (cortex) | Procavia capensis | [43] | |
Northern greater galago | 226,000,000 | ± 87,570,000 [43] | Isotropic fractionator | Pallium (cortex) | Otolemur garnettii | [43] | |
Common starling | 226,000,000 | Isotropic fractionator | Pallium (DVR) | Sturnus vulgaris | [47] | ||
Common kestrel | 237,903,000 | Isotropic fractionator | Pallium (DVR) | Falco tinnunculus | [34] | ||
Raccoon dog | 240,180,000 | Isotropic fractionator | Pallium (cortex) | Nyctereutes procyonoides | [54] | ||
Common marmoset | 245,000,000 | ± 81,180,000 [43] | Isotropic fractionator | Pallium (cortex) | Callithrix jacchus | [43] | |
House cat | 249,830,000 | Isotropic fractionator | Pallium (cortex) | Felis catus | [51] | ||
Brown bear | 250,970,000 | Isotropic fractionator | Pallium (cortex) | Ursus arctos | [51] | ||
Cockatiel | 258,000,000 | Isotropic fractionator | Pallium (DVR) | Nymphicus hollandicus | [47] | ||
Greylag goose | 258,650,000 | Isotropic fractionator | Pallium (DVR) | Anser anser | [34] | ||
Capybara | 306,500,000 | ± 62,726,120 [43] | Isotropic fractionator | Pallium (cortex) | Hydrochoerus hydrochaeris | [40] | |
Tarsius | 310,000,000 | Estimated | Pallium (cortex) | Genus: Tarsius, unknown species | [67] | ||
Mute swan | 323,661,000 | Isotropic fractionator | Pallium (DVR) | Cygnus olor | [34] | ||
Greater rhea | 330,342,000 | Isotropic fractionator | Pallium (DVR) | Rhea americana | [34] | ||
Eastern rosella | 333,000,000 | Isotropic fractionator | Pallium (DVR) | Platycercus eximius | [47] | ||
Common buzzard | 351,700,000 | Isotropic fractionator | Pallium (DVR) | Buteo buteo | [34] | ||
Red fox | 355,010,000 | Isotropic fractionator | Pallium (cortex) | Vulpes vulpes | [54] | ||
Goeldi's marmoset | 357,130,000 | Isotropic fractionator | Pallium (cortex) | Callimico goeldii | [49] | ||
Eurasian pygmy owl | 364,000,000 | Isotropic fractionator | Pallium (DVR) | Glaucidium passerinum | [34] | ||
Western grey kangaroo | 370,170,000 | Isotropic fractionator | Pallium (cortex) | Macropus fuliginosus | [68] | ||
Golden jackal | 393,620,000 | Isotropic fractionator | Pallium (cortex) | Canis aureus | [54] | ||
Monk parakeet | 396,000,000 | Isotropic fractionator | Pallium (DVR) | Myiopsitta monachus | [47] | ||
Springbok | 396,900,000 | Isotropic fractionator | Pallium (cortex) | Antidorcas marsupialis | [55] | ||
Black vulture | 398,899,000 | Isotropic fractionator | Pallium (DVR) | Coragyps atratus | [34] | ||
Azure-winged magpie | 400,000,000 | Isotropic fractionator | Pallium (DVR) | Cyanopica cyanus | [47] | ||
Little owl | 400,822,000 | Isotropic fractionator | Pallium (DVR) | Athene noctua | [34] | ||
Common hill myna | 410,000,000 | Isotropic fractionator | Pallium (DVR) | Gracula religiosa | [47] | ||
Domesticated pig | 425,000,000* | Optical fractionator | Pallium (cortex) | Sus scrofa domesticus | [69] | ||
Barn owl | 437,000,000 | Isotropic fractionator | Pallium (DVR) | Tyto alba | [47] | ||
Emu | 439,000,000 | Isotropic fractionator | Pallium (DVR) | Dromaius novaehollandiae | [47] | ||
West Highland White Terrier | 440,160,000 | Isotropic fractionator | Pallium (cortex) | Canis lupus familiaris | [54] | ||
Three-striped night monkey | 442,000,000 | ± 111,310,000 [43] | Isotropic fractionator | Pallium (cortex) | Aotus trivirgatus | [1] | |
Saker falcon | 442,946,000 | Isotropic fractionator | Pallium (DVR) | Falco cherrug | [34] | ||
Eurasian magpie | 443,000,000 | Isotropic fractionator | Pallium (DVR) | Pica pica | [47] | ||
Raccoon | 453,000,000 | Isotropic fractionator | Pallium (cortex) | Procyon lotor | [64] | ||
Chow Chow | 471,500,000 | Isotropic fractionator | Pallium (cortex) | Canis lupus familiaris | [54] | ||
Common ostrich | 479,410,000 | Isotropic fractionator | Pallium (DVR) | Struthio camelus | [34] | ||
Western jackdaw | 492,000,000 | Isotropic fractionator | Pallium (DVR) | Coloeus monedula | [47] | ||
Striped hyena | 495,280,000 | Isotropic fractionator | Pallium (cortex) | Hyaena hyaena | [51] | ||
Chihuahua | 513,330,000 | Isotropic fractionator | Pallium (cortex) | Canis lupus familiaris | [54] | ||
Eurasian jay | 529,000,000 | Isotropic fractionator | Pallium (DVR) | Garrulus glandarius | [47] | ||
White-tailed eagle | 542,926,000 | Isotropic fractionator | Pallium (DVR) | Haliaeetus albicilla | [34] | ||
Lion | 545,240,000 | Isotropic fractionator | Pallium (cortex) | Panthera leo | [51] | ||
Blesbok | 570,670,000 | Isotropic fractionator | Pallium (cortex) | Damaliscus pygargus phillipsi | [55] | ||
Yorkshire Terrier | 572,140,000 | Isotropic fractionator | Pallium (cortex) | Canis lupus familiaris | [54] | ||
Alexandrine parakeet | 575,000,000 | Isotropic fractionator | Pallium (DVR) | Psittacula eupatria | [47] | ||
Tanimbar corella | 599,000,000 | Isotropic fractionator | Pallium (DVR) | Cacatua goffiniana | [47] | ||
Golden retriever | 627,000,000 | Isotropic fractionator | Pallium (cortex) | Canis lupus familiaris | [51] | ||
Long-eared owl | 673,000,000 | Isotropic fractionator | Pallium (DVR) | Asio otus | [34] | ||
Transylvanian Hound | 725,760,000 | Isotropic fractionator | Pallium (cortex) | Canis lupus familiaris | [54] | ||
Greater kudu | 762,570,000 | Isotropic fractionator | Pallium (cortex) | Tragelaphus strepsiceros | [55] | ||
Crab-eating macaque | 800,960,000 | Isotropic fractionator | Pallium (cortex) | Macaca fascicularis | [49] | ||
Rook | 820,000,000 | Isotropic fractionator | Pallium (DVR) | Corvus frugilegus | [47] | ||
Beagle | 844,410,000 | Isotropic fractionator | Pallium (cortex) | Canis lupus familiaris | [54] | ||
Grey parrot | 850,000,000 | Isotropic fractionator | Pallium (DVR) | Psittacus erithacus | [47] | ||
Komondor | 883,380,000 | Isotropic fractionator | Pallium (cortex) | Canis lupus familiaris | [54] | ||
German Shepherd | 885,460,000 | Isotropic fractionator | Pallium (cortex) | Canis lupus familiaris | [54] | ||
Sulphur-crested cockatoo | 1,135,000,000 | Isotropic fractionator | Pallium (DVR) | Cacatua galerita | [47] | ||
Tufted capuchin | 1,140,000,000 | Isotropic fractionator | Pallium (cortex) | Sapajus apella | [43] [1] | ||
Tawny owl | 1,153,000,000 | Isotropic fractionator | Pallium (DVR) | Strix aluco | [34] | ||
Harp seal | 1,168,000,000^ 6,100,000,000* | Estimated Optical fractionator | Pallium (cortex) | Pagophilus groenlandicus | [70] [71] | ||
Horse | 1,200,000,000^ | Estimated | Pallium (cortex) | Equus ferus caballus | [72] | ||
Raven | 1,204,000,000 | Isotropic fractionator | Pallium (DVR) | Corvus corax | [47] | ||
Snowy owl | 1,270,000,000 | Isotropic fractionator | Pallium (DVR) | Bubo scandiacus | [34] | ||
Kea | 1,281,000,000 | Isotropic fractionator | Pallium (DVR) | Nestor notabilis | [47] | ||
Eurasian eagle-owl | 1,328,000,000 | Isotropic fractionator | Pallium (DVR) | Bubo bubo | [34] | ||
Common squirrel monkey | 1,340,000,000 | ± 20,000,000 [43] | Isotropic fractionator | Pallium (cortex) | Saimiri sciureus | [43] | |
Bonnet macaque | 1,660,000,000 | Isotropic fractionator | Pallium (cortex) | Macaca radiata | [43] | ||
Rhesus macaque | 1,710,000,000 | Isotropic fractionator | Pallium (cortex) | Macaca mulatta | [43] | ||
Giraffe | 1,731,000,000 | Isotropic fractionator | Pallium (cortex) | Giraffa camelopardalis | [55] | ||
Blue and yellow macaw | 1,900,000,000 | Isotropic fractionator | Pallium (DVR) | Ara ararauna | [47] | ||
Pygmy sperm whale | 2,020,000,000* | Optical fractionator | Pallium (cortex) | Kogia breviceps | [73] | ||
Leopard seal | 2,386,000,000^ | Estimated | Pallium (cortex) | Hydrurga leptonyx | [70] | ||
Guenon | 2,500,000,000^ | Estimated | Pallium (cortex) | Genus: Cercopithecus, unknown species | [67] | ||
Pigtail Macaque | 2,531,000,000^ | Estimated | Pallium (cortex) | Macaca nemestrina | [70] | ||
Gelada baboon | 2,568,000,000^ | Estimated | Pallium (cortex) | Theropithecus gelada | [70] | ||
Red-and-green macaw | 2,646,000,000^ | Estimated | Pallium (DVR) | Ara chloropterus | [70] | ||
Harbor porpoise | 2,750,000,000* | Optical fractionator | Pallium (cortex) | Phocoena phocoena | [70] [71] | ||
Yellow baboon | 2,880,000,000 | Isotropic fractionator | Pallium (cortex) | Papio cynocephalus | [49] | ||
Hyacinth macaw | 2,944,000,000^ | Estimated | Pallium (DVR) | Anodorhynchus hyacinthinus | [70] | ||
Hamadryas baboon | 2,990,000,000^ | Estimated | Pallium (cortex) | Papio hamadryas | [70] | ||
Mandrill | 3,102,000,000^ | Estimated | Pallium (cortex) | Mandrillus sphinx | [70] | ||
Common minke whale | 3,134,000,000 12,800,000,000* | Isotropic fractionator Optical fractionator | Pallium (cortex) | Balaenoptera acutorostrata | [58] [74] | ||
Walrus | 3,929,000,000^ | Estimated | Pallium (cortex) | Odobenus rosmarus | [70] | ||
Southern elephant seal | 3,994,000,000^ | Estimated | Pallium (cortex) | Mirounga leonina | [70] | ||
Fin whale | 5,000,000,000^ 15,000,000,000^ | Estimated | Pallium (cortex) | Balaenoptera physalus | [70] [75] | ||
Blue whale | 5,000,000,000^ | Estimated | Pallium (cortex) | Balaenoptera musculus | [70] | ||
African elephant | 5,600,000,000 | Isotropic fractionator | Pallium (cortex) | Loxodonta africana | [62] | ||
Pygmy chimpanzee or bonobo | 6,250,000,000^ | Estimated | Pallium (cortex) | Pan paniscus | [70] | ||
Short-beaked common dolphin | 6,700,000,000* 4,800,000,000^ | Optical fractionator Estimated | Pallium (cortex) | Delphinus delphis | [70] [73] [58] | ||
Asian elephant | 6,775,000,000^ | Estimated | Pallium (cortex) | Elephas maximus | [70] | ||
Chimpanzee | 7,400,000,000* | Optical fractionator | Pallium (cortex) | Pan troglodytes | [76] | ||
Orangutan | 7,704,000,000^ - 8,900,000,000^ | Estimated | Pallium (cortex) | Genus: Pongo | [70] [57] | ||
Western gorilla | 9,100,000,000^ | Estimated | Pallium (cortex) | Gorilla gorilla | [70] [57] | ||
Cuvier's beaked whale | 9,100,000,000* | Optical fractionator | Pallium (cortex) | Ziphius cavirostris | [73] | ||
Beluga whale | 10,000,000,000^ | Estimated | Pallium (cortex) | Delphinapterus leucas | [70] [58] | ||
Risso's dolphin | 10,000,000,000^ | Estimated | Pallium (cortex) | Grampus griseus | [70] [58] | ||
Short-finned pilot whale | 11,850,000,000 | Isotropic fractionator | Pallium (cortex) | Globicephala macrorhynchus | [70] [58] | ||
Bottlenose dolphin | 12,700,000,000* 8,700,000,000^ | Optical fractionator Estimated | Pallium (cortex) | Tursiops truncatus | [70] [73] [58] | ||
Long-finned pilot whale | 13,966,000,000^ 37,200,000,000* | Estimated Optical fractionator | Pallium (cortex) | Globicephala melas | [77] [70] [58] | ||
Human | 16,340,000,000 21,000,000,000* | ± 2,170,000,000 [43] | Isotropic fractionator Optical fractionator | Pallium (cortex) | Homo sapiens | [43] [59] [1] [78] [79] | |
Orca | 43,100,000,000* 21,000,000,000^ | Optical fractionator Estimated | Pallium (cortex) | Orcinus orca | [70] [73] [58] |
The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for special senses such as vision, hearing and olfaction. Being the most specialized organ, it is responsible for receiving information from the sensory nervous system, processing those information and the coordination of motor control.
The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and then reaches the visual cortex. The area of the visual cortex that receives the sensory input from the lateral geniculate nucleus is the primary visual cortex, also known as visual area 1 (V1), Brodmann area 17, or the striate cortex. The extrastriate areas consist of visual areas 2, 3, 4, and 5.
The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. It is the largest site of neural integration in the central nervous system, and plays a key role in attention, perception, awareness, thought, memory, language, and consciousness. The cerebral cortex is the part of the brain responsible for cognition.
In neuroanatomy, the lateral geniculate nucleus is a structure in the thalamus and a key component of the mammalian visual pathway. It is a small, ovoid, ventral projection of the thalamus where the thalamus connects with the optic nerve. There are two LGNs, one on the left and another on the right side of the thalamus. In humans, both LGNs have six layers of neurons alternating with optic fibers.
The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language. The neocortex is further subdivided into the true isocortex and the proisocortex.
Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system and in the peripheral nervous system that do not produce electrical impulses. The neuroglia make up more than one half the volume of neural tissue in the human body. They maintain homeostasis, form myelin, and provide support and protection for neurons. In the central nervous system, glial cells include oligodendrocytes, astrocytes, ependymal cells and microglia, and in the peripheral nervous system they include Schwann cells, and satellite cells.
A cortical minicolumn (also called cortical microcolumn) is a vertical column through the cortical layers of the brain. Neurons within the microcolumn "receive common inputs, have common outputs, are interconnected, and may well constitute a fundamental computational unit of the cerebral cortex". Minicolumns comprise perhaps 80–120 neurons, except in the primate primary visual cortex (V1), where there are typically more than twice the number. There are about 2×108 minicolumns in humans. From calculations, the diameter of a minicolumn is about 28–40 μm. Minicolumns grow from progenitor cells within the embryo and contain neurons within multiple layers (2–6) of the cortex.
A cortical column is a group of neurons forming a cylindrical structure through the cerebral cortex of the brain perpendicular to the cortical surface. The structure was first identified by Vernon Benjamin Mountcastle in 1957. He later identified minicolumns as the basic units of the neocortex which were arranged into columns. Each contains the same types of neurons, connectivity, and firing properties. Columns are also called hypercolumn, macrocolumn, functional column or sometimes cortical module. Neurons within a minicolumn (microcolumn) encode similar features, whereas a hypercolumn "denotes a unit containing a full set of values for any given set of receptive field parameters". A cortical module is defined as either synonymous with a hypercolumn (Mountcastle) or as a tissue block of multiple overlapping hypercolumns.
Von Economo neurons, also called spindle neurons, are a specific class of mammalian cortical neurons characterized by a large spindle-shaped soma gradually tapering into a single apical axon in one direction, with only a single dendrite facing opposite. Other cortical neurons tend to have many dendrites, and the bipolar-shaped morphology of von Economo neurons is unique here.
Encephalization quotient (EQ), encephalization level (EL), or just encephalization is a relative brain size measure that is defined as the ratio between observed and predicted brain mass for an animal of a given size, based on nonlinear regression on a range of reference species. It has been used as a proxy for intelligence and thus as a possible way of comparing the intelligence levels of different species. For this purpose, it is a more refined measurement than the raw brain-to-body mass ratio, as it takes into account allometric effects. Expressed as a formula, the relationship has been developed for mammals and may not yield relevant results when applied outside this group.
The motor cortex is the region of the cerebral cortex involved in the planning, control, and execution of voluntary movements. The motor cortex is an area of the frontal lobe located in the posterior precentral gyrus immediately anterior to the central sulcus.
The size of the brain is a frequent topic of study within the fields of anatomy, biological anthropology, animal science and evolution. Measuring brain size and cranial capacity is relevant both to humans and other animals, and can be done by weight or volume via MRI scans, by skull volume, or by neuroimaging intelligence testing.
Radial glial cells, or radial glial progenitor cells (RGPs), are bipolar-shaped progenitor cells that are responsible for producing all of the neurons in the cerebral cortex. RGPs also produce certain lineages of glia, including astrocytes and oligodendrocytes. Their cell bodies (somata) reside in the embryonic ventricular zone, which lies next to the developing ventricular system.
Pasko Rakic is a Yugoslav-born American neuroscientist, who presently works in the Yale School of Medicine Department of Neuroscience in New Haven, Connecticut. His main research interest is in the development and evolution of the human brain. He was the founder and served as Chairman of the Department of Neurobiology at Yale, and was founder and Director of the Kavli Institute for Neuroscience. He is best known for elucidating the mechanisms involved in development and evolution of the cerebral cortex. In 2008, Rakic shared the inaugural Kavli Prize in Neuroscience. He is currently the Dorys McConell Duberg Professor of Neuroscience, leads an active research laboratory, and serves on Advisory Boards and Scientific Councils of a number of Institutions and Research Foundations.
A connectome is a comprehensive map of neural connections in the brain, and may be thought of as its "wiring diagram". An organism's nervous system is made up of neurons which communicate through synapses. A connectome is constructed by tracing the neuron in a nervous system and mapping where neurons are connected through synapses.
The evolution of the brain refers to the progressive development and complexity of neural structures over millions of years, resulting in the diverse range of brain sizes and functions observed across different species today, particularly in vertebrates.
Gyrification is the process of forming the characteristic folds of the cerebral cortex. The peak of such a fold is called a gyrus, and its trough is called a sulcus. The neurons of the cerebral cortex reside in a thin layer of gray matter, only 2–4 mm thick, at the surface of the brain. Much of the interior volume is occupied by white matter, which consists of long axonal projections to and from the cortical neurons residing near the surface. Gyrification allows a larger cortical surface area, and hence greater cognitive functionality to fit inside a smaller cranium.
Michael Steven Anthony Graziano is an American scientist and novelist who is currently a professor of Psychology and Neuroscience at Princeton University. His scientific research focuses on the brain basis of awareness. He has proposed the "attention schema" theory, an explanation of how, and for what adaptive advantage, brains attribute the property of awareness to themselves. His previous work focused on how the cerebral cortex monitors the space around the body and controls movement within that space. Notably he has suggested that the classical map of the body in motor cortex, the homunculus, is not correct and is better described as a map of complex actions that make up the behavioral repertoire. His publications on this topic have had a widespread impact among neuroscientists but have also generated controversy. His novels rely partly on his background in psychology and are known for surrealism or magic realism. Graziano also composes music including symphonies and string quartets.
Suzana Herculano-Houzel is a Brazilian neuroscientist. Her main field of work is comparative neuroanatomy; her findings include a method of counting neurons in human and other animals' brains and the relation between the cerebral cortex area and the thickness and number of cortical folds.
The mouse brain refers to the brain of Mus musculus. Various brain atlases exist.
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