1. Plasticity of primary cortical areas suggests that there are procedure-like "sharping " or "tuning" mechanisms that operate throughout the life time of the animal to change the receptivity of the individual processing units within the basic processors of the brain.
    1. restricting early visual experience in kitten, by arranging for input to be provided by one eye only
      1. Cells in primary visual cortex show a preference in the relative balance given to input from the two eyes, see Fig. 3-8
      2. The remaining eye takes over the cortical target area
    2. restricting early visual experience in kitten to contours of certain orientation, see Fig. 3-9
      1. Individual visual cortex neurons change their orientation selectivity in conformance with their experience, see Fig. 3-10
    1. A rapidly growing literature reveals a very large degree of short- and long-term modification of receptive field and reorganization of representation maps
    2. Gilbert et al: Receptive field dynamics in adult primary visual cortex
      1. Background information
        1. the concept of receptive field
        2. sensory cortex is topographically mapped, with retinal coordinates (or body surface) mapped systematically on the visual (or somatosensory) cortex
      2. In visual cortex, retinal lesions lead to reorganization of cortical topography in the long term recoveries, see Fig. 3-11
      3. Within minutes of the lesion procedure, cortical cells with receptive fields located near the boundary of the lesion expand in size, see Fig. 3-12.
      4. After a few months even the cortical areas that were initially silenced by the lesion recover visual activity, representing retinotopic loci surrounding the lesion, see Fig. 3-13.
      5. Cortical changes under normal sensory and behavioural experience
        1. "artificial scotoma": the area surrounding the receptive field was stimulated visually, but the receptive field itself was masked with a visual occluder, see Fig. 3-14.
        2. After a 10-minute period of conditioning the cell with this stimulus, its receptive field expanded severalfold in length, see Fig. 3-15, 3-16, 3-17.
        3. The results suggested an ongoing process of modulation of receptive field size, adapting in different ways to different scenes.
      6. the short-term plasticity must involve in some way a change in the synaptic weight of existing connections, altering the patterns of activation of intrinsic cirtuits.
      7. It seems likely that mutability of receptive fields and cortical architectures is associated with normal sensory experience, not just peripheral lesions, and that the changes can take place on a brief time scale of minutes.
    3. Merzenich et al: rearrangements of the somatotopic representation (Fig. 3-18, 3-19) in primary somatosensory cortex of monkeys following a variety of traumatic and more natural interventions in somatosensory input.
      1. Following digit removal, the cortical representation of neighbouring digits invades the cortical zone whose afferents have been removed, see Fig. 3-20
      2. Surgical joining of the digits results in the establishment of a continuous somatic representation of formerly discontinuous zones for each digit.
      3. Tactile discrimination training (for several weeks) results in altered sensory receptive fields in the somatosensory cortex (larger cortical represenations of the stimulated digits, and larger receptive fields in the expanded areas)
      4. Synchronization of cortical physiology acquired during training is well correlated with the behavioural performance in a discrimination task.


  1. Visual pathway,see Fig. 3-21
  2. Kluver and Bucy (1937): psychic blindness
    1. Removal of temporal lobe of the monkey led to the lost of ability to recognize familiar objects and their biological significance
  3. Human defect: visual agnosia
    1. Patients with visual agnosia can see all parts of the visual field, but the objects they see mean nothing to them
    2. Poor picture memory, difficulty learning new faces
  4. Face cells in inferotemporal cortex
    1. Gross et al (1972), Response to hands and faces, see Fig. 3-22, 3-23