Start | basic neuroanat. | reading | zeki extracts | table of links | List of Refs | Journals
  • All vertebrate brains can be categorised into parts including the spinal cord and cerebral hemispheres (Simple diagram | mp3 audio file -135k- of arbitrary list of brain parts sung to the tune of ‘Camptown Races’)

  • Very few people, if any, would argue that there were not differences in function between these basic levels: for instance that the spinal cord has functions different from those of the cerebral hemispheres, or that the limbic system within the hemispheres has its own characteristic functions.

  • So the starting point of the argument is that the brain is composed of many different parts, and the different parts do different things.

  • Within these coarsely differentiated levels or parts, there are further differentiations of function. The limbic system itself is composed of a wide variety of parts.

  • There is also little disagreement that the left and right hemispheres of the human brain differ in their functions (example based on Sperry, 1974, after Popper and Eccles, 1977)

  • The current debates about localization of function concern the roles of different small areas of the cortex of the cerebral hemispheres.

  • There is a great amount of fine detail possible in the analysis of cortical functions, but the main important distinction for present purposes is simply that between the different lobes of the brain, and the different starting points for the several sensory modalities.

      • The position of the frontal lobes is self explanatory; the basic defining feature is motor output.
      • The occipital lobes receive visual input, but are furthest away from the eyes, at the back of the brain.
      • The parietal lobes start behind the frontal lobes, and receive primary tactile input, and spatial input via visual areas.
      • The temporal lobes are at the bottom and sides of the hemispheres, near the ears, and receive primary auditory input and semantic visual knowledge from visual areas.

    • Coloured diagram of lobes of the brain. [© University of Washington Interactive Brain Atlas reproduced with permission]

    • Black and white diagram (after Popper and Eccles, 1977) showing sensory areas.

    • The tactile homunculus [© University of Wisconsin Department of Radiology reproduced with permission]

    • The Penfield sensory and motor homunculi



Association bundles
horizontal brain section
It is an important limitation on localization of function that any identifiable part of the brain is likely to be reciprically connected to many other parts; and within cerebral cortex this takes place via large tract of white matter underneath the surface. The best known of these is the corpus callosum, which reciprocally connects many (but not all) corresponding areas in the two hemispheres. The diagram above also picks out in green some of the front to back major connections (called “bundles”, or the latin equivalent “fasciculi”).

This image shows the location of some of these association bundles in a vertical section through the brain
[The ‘coloured chalk’ diagrams above are after Jamieson, Edward Bald (1961) Illustrations of regional anatomy: Vol.1 Central nervous system 8th ed. Edinburgh : Livingstone]



Individual Differences

It is important to bear in mind that human brains, like human hands or faces, will vary a great deal while keeping to a recognizable plan. Damasio (1995) devoted a book of MRI images of actual brains to this theme. The simplest distinction is between what she calleds the most standard normal brain and a rounder or brachycephalic brain.

This variation is worth bearing in mind when observing averaged computerised reconstructions of brain scanning data from several subjects.

The sort of figure that is possible with modern techniques is this one, from a National Institute of Mental Health (Washington, DC) Press release
Figure for 640 screen  / figure for 800 screen resolution.

The full press release is reproduced here

The references for the work are —

Braver, TS, Cohen, JD, Nystrom, LE, Jonides, J, Smith, EE, Noll, DC (1997) A parametric study of prefrontal cortex involvement in human working memory . Neuroimage, Vol.5, No.1, Pp.49-62. [full-text pdf file of this is in principle available via clicking back though theIngenta - Neuroimage archives - or try this ingenta link - from Birkbeck or BK dialup but is not particularly relevant.]

Cohen, JD, Perlstein, WM, Braver, TS, Nystrom, LE, Noll, DC, Jonides, J, Smith, EE (1997) Temporal dynamics of brain activation during a working memory task. Nature, Vol.386, No.6625, Pp.604-608.

brain location for tactile stimulation of the hand
history of functional localization

last revised, 25-10-02

Start | basic neuroanat. | reading | zeki extracts | table of links | List of Refs | Journals