Neuroscience

Structure of brain networks is not fixed, study finds

The shape and connectivity of brain networks—discrete areas of the brain that work together to perform complex cognitive tasks—can change in fundamental and recurring ways over time, according to a study led by Georgia ...

Neuroscience

Breakthrough in understanding how human eyes process 3-D motion

Scientists at the University of York have revealed that there are two separate 'pathways' for seeing 3-D motion in the human brain, which allow people to perform a wide range of tasks such as catching a ball or avoiding moving ...

Neuroscience

Researchers grow active mini-brain-networks

Cerebral organoids are artificially grown, 3-D tissue cultures that resemble the human brain. Now, researchers from Japan report functional neural networks derived from these organoids in a study publishing June 27 in the ...

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Human brain

The human brain is the center of the human nervous system and is a highly complex organ. Enclosed in the cranium, it has the same general structure as the brains of other mammals, but is over three times as large as the brain of a mammal with an equivalent body size. Most of the expansion comes from the cerebral cortex, a convoluted layer of neural tissue that covers the surface of the forebrain. Especially expanded are the frontal lobes, which are involved in executive functions such as self-control, planning, reasoning, and abstract thought. The portion of the brain devoted to vision is also greatly enlarged in humans.

Brain evolution, from the earliest shrewlike mammals through primates to hominids, is marked by a steady increase in encephalization, or the ratio of brain to body size. The human brain has been estimated to contain 50–100 billion (1011) neurons[citation needed], of which about 10 billion (1010) are cortical pyramidal cells.[citation needed] These cells pass signals to each other via approximately 100 trillion (1014)[citation needed] synaptic connections.

In spite of the fact that it is protected by the thick bones of the skull, suspended in cerebrospinal fluid, and isolated from the bloodstream by the blood-brain barrier, the delicate nature of the human brain makes it susceptible to many types of damage and disease. The most common forms of physical damage are closed head injuries such as a blow to the head, a stroke, or poisoning by a wide variety of chemicals that can act as neurotoxins. Infection of the brain is rare because of the barriers that protect it, but is very serious when it occurs. More common are genetically based diseases[citation needed], such as Parkinson's disease, multiple sclerosis, and many others. A number of psychiatric conditions, such as schizophrenia and depression, are widely thought to be caused at least partially by brain dysfunctions, although the nature of such brain anomalies is not well understood.

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