Brain

:For other articles about other subjects named brain see brain (disambiguation). For information about the human brain in specific, please see its article.

A smart device

Brains in nature

Three groups of animals, with some exceptions, have notably complex brains: the arthropods (for example, insects and crustaceans), the cephalopods (octopuses, squid, and similar mollusks), and craniates (vertebrates and their cousins). The brain of arthropods and cephalopods arise from twin parallel nerve cords that extend through the body of the animal. The arthropod brain consists of large optical lobes behind each eye for visual processing and a central brain with three divisions.

Related Topics:
Complex - Arthropod - Insect - Crustacean - Cephalopod - Octopus - Squid - Mollusk - Craniate - Vertebrate - Eye

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The brains of craniates develop from the anterior section of a single dorsal nerve cord, which later becomes the spinal cord. In craniates, the brain is protected by the bones of the skull. Vertebrates are characterized by increasing complexity in the cerebral cortex as one moves up the phylogenetic and evolutionary tree. Primitive vertebrates, like fish, reptiles, and amphibians have cortices with less than six layers of neurons, a structure known as allocortex (Martin, 1996). More complex vertebrates like mammals have developed six-layered neocortex in addition to having some parts of the brain that are allocortex (Martin, 1996). In mammals, increasing convolutions of the brain, called gyri, are characteristic of animals with more advanced brains. These convolutions evolved to provide more surface area for a greater number of neurons while keeping the volume of the brain compact enough to fit inside the skull.

Related Topics:
Nerve cord - Spinal cord - Skull - Complexity - Cerebral cortex - Phylogenetic - Evolutionary tree - Allocortex - Neocortex

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Brains in medicine

The brain, along with the heart, is one of the two most important organs in the human body. Loss of function in this organ fulfills some definitions of death. Injuries to the brain tend to affect large areas of the brain, sometimes causing major deficits in intelligence, memory and control of the body. Head trauma, caused by automobile accidents or other blows to the skull, is a leading cause of death. Often in these cases, more damage is caused by swelling, or edema, than by the impact itself. Stroke, caused by blockage of blood vessels in the brain, is another major cause of death and brain damage.

Related Topics:
Heart - Death - Intelligence - Edema - Stroke - Blood vessel

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Other problems in the brain can be more accurately classified as diseases rather than injuries. Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, motor neurone disease, and Huntington's disease, are caused by the gradual death of individual neurons leading to decrements in movement control, memory, and thinking abilities. Currently, only the symptoms of these diseases can be treated, but stem cell research may offer a cure. Mental illnesses, such as clinical depression, schizophrenia, bipolar disorder, and post-traumatic stress disorder, are theorized as having a biological basis in the brain. These disorders may be treated by psychiatric therapy, by drugs, or by a combination of treatments, but the effectiveness of the therapy varies with the individual and any comorbid organic diseases.

Related Topics:
Neurodegenerative disease - Alzheimer's disease - Parkinson's disease - Motor neurone disease - Huntington's disease - Stem cell - Mental illness - Clinical depression - Schizophrenia - Bipolar disorder - Post-traumatic stress disorder - Psychiatric therapy - Drug

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Some infectious diseases affecting the brain are caused by viral or bacterial infection(s). Infection of the meninges, the membrane that covers the brain, can lead to meningitis. Bovine spongiform encephalopathy, also known as mad cow disease, is a deadly disease among cattle and is linked to prions. Kuru is a similar prion-borne degenerative brain disease affecting humans. Both are linked to the ingestion of neural tissue from animals of the same species, and are often theorized to be an evolutionary defense against cannibalism. Viral or bacteria causes have been substantiated in multiple sclerosis, Parkinson's disease, and Lyme disease, as well as in encephalopathy and encephalomyelitis.

Related Topics:
Viral - Bacterial - Meningitis - Bovine spongiform encephalopathy - Mad cow disease - Cattle - Prion - Kuru - Evolution - Cannibalism - Multiple sclerosis - Parkinson's disease - Lyme disease

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Some brain disorders are congenital. Tay-Sachs disease, Fragile X syndrome, Down syndrome, and Tourette syndrome are all linked to genetic or chromosomal errors. Malfunctions in the embryonic development of the brain can be caused by genetic factors or by drug use or disease in the mother.

Related Topics:
Congenital - Tay-Sachs disease - Fragile X syndrome - Down syndrome - Tourette syndrome - Gene - Chromosomal - Development

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Brains in philosophy

Some philosophers consider that "brain" is synonymous with "mind", while others (strong AI theorists) believe that the mind is the software of the hardware-brain. This issue, related to the mind-body problem, and many others are the subject of the philosophy of mind: what is consciousness? Do non-human animals have consciousness?

Related Topics:
Mind - Software - Mind-body problem - Philosophy of mind - Consciousness

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Artificial brains

Computer scientists have produced computer systems called neural networks that are loosely based on the structure of neuron connections in the brain. Artificial intelligence seeks to replicate brain function (although not necessarily brain mechanisms) more exactly, but this has not yet proven successful. Creating an algorithm to mimic a biological brain is extremely difficult because the brain is not a static arrangement of circuits, but a network of vastly interconnected neurons that are constantly changing their connectivity and sensitivity. More recent work in both neuroscience and artificial intelligence models the brain using the mathematical tools of chaos theory and dynamical systems.

Related Topics:
Neural network - Artificial intelligence - Algorithm - Chaos theory - Dynamical systems

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Interfacing brains with machines

The activity of a brain can be detected by electrodes, raising the possibility of "brain-computer interface".

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The reverse path has also been demonstrated; brain implants have been used to generate artificial hearing and (crude and experimental) artificial vision for deaf and blind people, and brain pacemakers are now common to regulate brain activity in conditions such as Parkinson's disease.

Related Topics:
Brain implant - Brain pacemaker - Parkinson's disease

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Both of these avenues of research have potentially serious ethical implications.

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For example, using electrodes in a brain and a remote control, researchers have been able to remotely control the movements of a rat. This offers the possibility to create an electronically-controlled biological "ratbot" that could go in dangerous places.

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