Bronze-level articleBrain

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An artist's impression of the brain.
Brain and brain! What is brain?!

The brain is the chunk of meat that sits at the terminus of the central nervous system and helps coordinate sensory input, motor activity, and behavior. Most animals have something similar to a brain, though the level of complexity differs greatly across taxa. We've all got a brain and some of us think with it.

In humans the brain is involved in thought, emotion, desire, action, choice, memories, and sensory processing. Other parts of the nervous system can do some basic preprocessing and all parts are needed, but the brain is in charge. Many people believe that the mind is not totally reducible to the brain.[1] This idea is rejected by most neurologists as unscientific and unnecessary to explain the function of the mind.

Contents

Basic anatomy of the human brain

The first part to understanding anatomy is to understand directional terms. There are three axes: top to bottom, front to back, and left to right of center. The top is referred to as dorsal, the bottom as ventral(sometimes superior and inferior as well). The front is anterior and the back is posterior, while those areas in the center of the brain are medial and those moving to the left or right side are lateral.

The human brain is anatomically referenced based on several distinct and universal features. The most notable is the medial longitudinal fissure, which is a wide gap that separates the brain into two hemispheres (right and left). Moving from the middle of the fissure down the sides of the brain is the central sulcus. From the side view of the brain another sulcus (or gap) can be seen just below the central sulcus, running from the bottom front to about halfway back. This is the superior temporal sulcus.

The brain has two major divisions, cortical and sub-cortical. The cortical structures are on the outside of the brain and are the folds of gray and white matter that most people picture as being the brain. Below that are the sub-cortical structures.

There are four major lobes in the cortex each playing a dominant role in different functions. The frontal lobe is the whole section of the brain that is anterior to the central sulcus and ventral to the superior temporal sulcus. The parietal lobe is posterior to the central sulcus and ventral to the superior temproal sulcus. The temporal lobe is dorsal to the superior temporal sulcus. Finally, there is the occipital lobe, which is at the most posterior region of the cortex.

The frontal lobe is associated with executive function, logical thought, planning, motivation, and many of the “higher order” brain functions. The parietal lobe contains the sensory cortex, and is responsible for a large portion of sensory integration. The temporal lobe is associated with memory and learning. The occipital lobe is the visual processing center of the brain.

Evolution of the human brain

The human brain has several unique features, most notably a massively expanded frontal lobe and significant anatomical specification throughout the frontal lobe tissue. Other areas linked to language processing are also highly developed. This massive expansion of the frontal lobe does not seem to coincide with any immediate changes in survival skills for the human species. Many early hypotheses for the evolutionary pressures leading to this expansion (such as hunting, tool making, or language development) did not coincide temporally with when the expansion took place. Most current hypotheses focus on this expansion as being driven by social navigation or even sexual selection.

The brain and modern toys

Real brain scans, unfortunately, aren't this simple or conclusive.

A new era in understanding how the brain creates thought has emerged with the development of several new toys. We now have the ability to non-invasively image the anatomy of the brain and functional activation of brain areas, measure cell firing rates, and even change the firing patterns of brain areas.

MRI

Magnetic Resonance Imaging uses a strong magnetic field to align the magnetic fields of hydrogen nueclei in the body. Applying radio-frequency radiation distorts this polarisation, and as the nuclei return to their original lowest energy state they emit further radio waves that can be translated into an image. Different molecules emit different energy patterns and so different things can be imaged from the same machine.

The most common molecule to be imaged is water and fat, as these are the most abundant in the body, providing good, clear images of the anatomy.

fMRI

Functional Magnetic Resonance Imaging works the same way as any MRI, but instead of water the machine is calibrated to measure blood. It is theorized that brain areas that are undergoing increased activation will also have a corresponding increase in metabolic requirements. The need to provide oxygen to these areas will increase the blood flow. Thus the fMRI measures the blood-oxygen-level dependent (BOLD) signal.

The BOLD signal is often superimposed on an anatomical MRI. This allows figuring out which areas of the brain seemed to be activated at a particular time.

TMS

Transcranial Magnetic Stimulation is the “black art” of neuroscience. Essentially, a large coil has an electrical field pulsed through it, which (supposedly) can be used to temporarily change the firing patterns of neurons in the brain. It is not clear whether the TMS acts to excite or inhibit brain activation (or even do both). Effects from the TMS can last as long as 12-24 hours after application or as short as a few minutes.

Tasty brains

Braaaaaaiiiins!!!! Brahhhhiaaaannnnsssss.... Mrsssuuurrrrrrhhhhh.... Braaiaiaaaannnssssz....

There's good eating on a brain. While it is socially unacceptable to eat a human brain - unless you are Hannibal Lecter, a Conservapedian (providing it's your own brain), or a zombie[2] - the brain of a cow, pig, goat or, in some exotic locations, a monkey, can make a nutritious meal, although rather high in cholesterol. Problematically, ignoring social constraints, eating human brains can cause Kuru, a prion disease similar to Mad Cow Disease while eating the brains of cows and sheep, possibly also pigs etc can cause actual Mad Cow Disease, Or just cause heart attacks.

The immense similarity in reactions between creationists and zombies is, frankly, appalling, and not worth repeating.[3].

See also

The topics below are not accredited Science.

External links

Footnotes

  1. See dualism and non-materialist neuroscience.
  2. Well, the last two are the same, really.
  3. And yet we have. Several times. I guess it's just that funny.
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