Linguistics 105 * Words and Sounds
Lecture Number Fourteen
The Physical Structure of the Human Brain

  1. Cortical Cells and Their Structures

    1. Neurons in cerebral cortex (1/8"-1/4" thick)

      1. soma (body)
      2. axon
        1. myeline sheath
        2. nodes of Ranvier
      3. dendrites
      4. synapses

    2. Glial cells

      1. provide support
      2. clear the debris of dead neurons
      3. absorb excess chemical neurotransmitters
      4. source of myelin
      5. guide migration of neurons during development

    3. Operations of Neurons (8 different structural kinds)

      1. Electrochemical action (1,000 firings per second)
        1. some neurons excitatory
        2. others are inhibitory

      2. All-or-nothing response in most
        1. rest potential: rest state
        2. action potential: firing strength

      3. Reaction of potassium to sodium ions

      4. Chemical neurotransmitters cross synapses to set off action
        1. acetylcholine (facilitated by nicotine)
        2. serotonine (blocked by LSD)
        3. gamma-aminobutyric acid (promoted by Valium-R)

    4. Organization of Neurons

      1. Functional redundancy: always a surplus of neurons for the job.
      2. Plasticity: if an area is destroyed, other areas will take over its functions.
      3. Parallel operation: many mental operations simultaneously.
      4. Distributed operation: information from many locations simultaneously
      5. Modularity -- no location has access to inner workings of another
      6. Pyrimidically ordered processessing systems
        1. Limbic system
        2. Cerebellum
        3. Basal ganglia (gray matter)
        4. Cerebral cortex (higher functions)--frontal, parietal, temporal, occipital lobes
        5. Commissures connecting the two hemispheres (corpus callosum is the largest)

  2. Localization Theory

    1. Lateralization: Hemispheric specialization
      1. Left hemisphere specializes in analytic skills
      2. Right hemisphere specializes in abstract (artistic) skills

    2. Motor and Somatosensory cortices adjacent to each other
      1. Left hemisphere controls the right side of the body
      2. Right hemisphere controls the left side of the body

    3. Primary Visual Cortex (Memory Associative Area of PVC -- reading)

    4. Speech areas
      1. Broca's area (agrammatism) -- memory associative area of the Motor Control Area for the articulatory organs
      2. Wernicke's area (anomia) -- memory associative area of the Primary Auditory Cortex)
      3. Angular gyrus (conductive aphasia)
      4. Arcuate fasciculus -- connects 1-3 through the Motor Control area for the articulatory organs

  3. Cognitive Capacities of The Human Brain
    1. Detecting patterns (edges, shapes, etc.)
    2. Making approximations
    3. Concept formation (groups, categories, structures, operations relations, patterns, maps)
    4. Self-correction (adjusting to feed-back)
    5. Memory (short term, long term; storage, retrieval)
    6. Creativity

  4. Conclusion.

    There are many gaps in our knowledge of how the brain acquires and processes language. However, we do know that language processing is localized in most brains to certain areas of the left hemisphere. We also know that certain types of processing is localized to specific subdomains of those areas. We can learn more about language by examining these areas; however, because of ethical issues surrounding the exploration of a healthy brain, our research is restricted to the examination of brains which have been damaged by illness or physical insult.
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