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The largest brains are those of sperm whales, weighing about 8 kg (18 lb). An elephant's brain weighs just over 5 kg (11 lb), a bottlenose dolphin's 1.5 to 1.7 kg (3.3 to 3.7 lb), whereas a human brain is around 1.3 to 1.5 kg (2.9 to 3.3 lb). Brain size tends to vary according to body size. The relationship is not proportional, though: the ...
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 (~10 11 neurons, ~10 14 synapses) of a complex system leads to ...
Dolphins have the highest brain-to-body weight ratio of all cetaceans. [11] Monitor lizards, tegus and anoles and some tortoise species have the largest among reptiles. [citation needed] Among birds, the highest brain-to-body ratios are found among parrots, crows, magpies, jays and ravens. Among amphibians, the studies are still limited.
The cerebrum (pl.: cerebra), telencephalon or endbrain [1] is the largest part of the brain, containing the cerebral cortex (of the two cerebral hemispheres) as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In the human brain, the cerebrum is the uppermost region of the central nervous system.
Typically, Old World monkeys (paleotropical) are larger than New World monkeys (neotropical); the reasons for this are not entirely understood but several hypotheses have been generated. [3] As a rule, primate brains are "significantly larger" than those of other mammals with similar body sizes. [ 4 ]
The purpose of this part of the brain is to sustain fundamental homeostatic functions, which are self regulating processes organisms use to help their bodies adapt. The pons and medulla are major structures found there. A new region of the brain developed in mammals about 250 million years after the appearance of the hindbrain.
In some primitive fishes, such as lampreys, this region is the largest part of the brain. [43] The superior colliculus is part of the midbrain. The pallium is a layer of grey matter that lies on the surface of the forebrain and is the most complex and most recent evolutionary development of the brain as an organ. [44]
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.