[bottom of page 17 of handout]

Mechanisms involved in normal and abnormal brain development, including some invoved in Adult Plasticity

(cf pp249-250 of Elman et al, 1996)


  1. Growth of new connections

  2. Elimination of normal connections

  3. Retention of exuberant connections

  4. Reprogramming of existing connections (synaptic changes aka learning especially “Hebbian Learning”)

  5. Compensation/redistribution of function

  6. Plus, since 1996, evidence has been accumulating for neurogenesis in adult primate brains. (See the abstracts for Gould et al. 1999 - hippocampus, Gould et al. 1999 - cortex, Hastings et al. 2000 and Gross, 2000)

Florence et al 1997

Florence, SL, Jain, N and Kaas, JH (1997) Plasticity of somatosensory cortex in primates. Seminars in the Neurosciences, Vol.9, No.1- 2, Pp.3-12.

“Over recent years, we have come to the suprising realization that sensory cortex is highly plastic in functional organization, even in adult brains.”

  1. LIMITED CORTICAL CHANGES OCCUR SOON AFTER INJURY

  2. CORTICAL CHANGES MAY REFLECT SUBCORTICAL MODIFICATIONS.

  3. NEW AXON GROWTH MAY FOLLOW MASSIVE INJURY (AMPUTATION)

However, Ramachandran and Hirstein (1998) and Borsook et al (1998) add a further mechanism, that of UNMASKING of already present but not noticeable mappings.

This also applies to the paper by Zangaladze et al (1999) which showed that visual cortex is used for tactile discrimnations of some kinds in normal subjects.

-- Start --


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