Activity and excitatory amino acid receptors

1. In lower vertebrates, optic fibers form a highly ordered retinotopic projection to the contralateral midbrain. 2. The formation of fine retinotopy during development or regeneration requires patterned impulse activity in optic fibers. 3. The transmitter used by optic fibers is probably glutamate. 4. Blockade of NMDA receptors prevents the formation of fine retinotopy. 5. The available evidence leaves open several different interpretations for these NMDA effects.