Neuroscience has been described as the last great
 frontier of human biology - in fact NASA's most recent
 mission, Neurolab, was devoted to investigations
 involving the nervous system. Australian
 neuroscientists are among the leaders in brain
 research.
 

 If an animal has a backbone it also has a brain. Dogs,
 lizards, frogs, fish: even birds have brains. But none of
 these creatures demonstrate the same capacity for
 learning, language, emotion and abstract thought that
 distinguishes the human species.

 What is it about the human brain that gives us the
 edge? Neuroscientists (scientists who study the brain
 and nervous system) and philosophers have learned
 plenty about the functioning of the brain. But they
 admit there are aspects of brainpower that remain
 among humanity's most enduring mysteries.

 An introduction to the brain

 The basic facts about the brain are well known.
 Weighing in at around 1.3 kilograms, it is one of the
 largest organs in the human body. It is nothing
 remarkable to look at - a wrinkled object about the size
 of a number 13 chicken - but it consists of a complex
 and apparently hopelessly tangled mass of nerve cells,
 or neurons. It sits inside the skull immersed in a fluid
 that cushions it from sudden impacts to the head.

 Neurons are the basic unit that makes up the brain and
 nervous system. They are specialised cells that act like
 telegraph wires carrying messages in the form of
 electrochemical impulses throughout the body. These
 impulses travel very quickly, although not as quickly as
 an electric current would travel: it takes about one
 hundredth of a second for a pain in your little toe to
 register in your brain. This is quite remarkable, given
 that the impulse travels a complex path through many
 neurons and across the gaps (synapses) between
 neurons to reach its destination (Box 1).

 Brain functions

 The brain performs a number of functions, many of
 which are related to the physical needs and actions of
 the body. For these functions, the brain can be thought
 of as the command centre of the human nervous
 system, much like the headquarters of a military unit. It
 receives information from its vast network of neurons
 throughout the body. Based on this information, it
 makes decisions and issues commands that stimulate
 muscles and give the body movement.

 Other brain functions are more like those of a university
 than a military headquarters. These functions give us
 the ability to read, write, talk and think about issues
 more broad than where the next meal is coming from.

 Structure of the brain - an overview

 The brain is shaped like two fists standing side by side
 on a single wrist. The 'wrist' is the brainstem,
 connecting the brain to the spinal column, and the 'fists'
 constitute the left and right hemispheres of the largest
 part of the brain, the cerebrum. At the back of the
 brain, below the cerebrum, is the cerebellum: its main
 function is to synchronise the muscles of the body.

 The cerebral cortex: Control centre

 The cerebrum has an outer layer of grey matter
 arranged in folds. This layer, the cerebral cortex, is
 just a few millimetres thick but because of its numerous
 folds constitutes 40 per cent of the entire brain mass.

 Different areas of the cerebral cortex play specific roles
 in human thought and activity. For example: the frontal
 lobes control behaviour, intellect and emotion; the
 speech area controls talking; specific sections of the
 motor area control voluntary muscles in different parts
 of the body, and so on.

 In general, the right side of the brain controls
 movement in the left side of the body and the left side
 controls the right. However, there is some
 specialisation. For example, language is more a function
 of the left hemisphere and recognition of shapes is more
 a function of the right (Box 2).

 Humans have large brains

 When body weights are taken into account, the brain is
 much larger in mammals than in other vertebrates and
 reaches its greatest size in monkeys, apes and humans.

 The unusual size of the cerebral cortex in the human
 brain may partly explain its unique abilities. If the
 cerebral cortex of a frog is damaged or destroyed, there
 is no obvious change in the behaviour of the animal. A
 rat without a cerebral cortex can still move about.
 Human beings, though, are totally paralysed and unable
 to see, although internal functioning continues.

 More to learn

 It is not so long ago that the only way scientists could
 study the human brain was to dissect it after a person
 died. Now scientists and clinicians have access to
 several imaging techniques that open a window on the
 living, conscious brain. These techniques are powerful
 tools for research into normal brain function and for
 locating tumours or blocked blood vessels in the brain
 (Box 3).

 Australian research

 Australian neuroscience boasts a Nobel laureate - the
 late Sir John Eccles. He was awarded the prize in 1963
 for research that explained how impulses were
 transmitted between neurons. Eccles was also the first
 to record electrical signals from the interior of neurons
 within the central nervous system.

 Australian researchers have continued to be leaders in
 the field of neuroscience, particularly in the area of
 neurotransmitters, the chemical messengers that
 convey impulses between neurons. Their studies have
 led to advances in the treatment of neurological
 diseases and may lead to the development of drugs that
 help improve memory

An Australian Academy of Science project, supported by the Science and
   Technology Awareness Program of the Commonwealth Department of
     Industry, Science and Resources and the Australian Foundation for
                                  Science.

   This topic is sponsored by the Howard Florey Institute of Experimental
                          Physiology and Medicine.
        © Australian Academy of Science | Email: aas@science.org.au