Development of the visual pathways: Effects of neural activity

Very early in the development of neural connections in the brain, axons find their targets without the aid of neural activity. In subsequent stages of development, however, neural activity plays an important role. The visual pathway has provided important clues to the role of activity in brain development. The development of the precise point-to-point connections that underlie a functionally normal visual system requires patterned neural activity that in some cases is generated by the nervous system itself. Thereafter, neural activity generated by visual stimuli is required for the development and maintenance of precise connectivity. Lastly, neural activity must lead to long-term changes that mediate visual learning and memory. A good deal of evidence suggests that the mechanisms involved in the activity-dependent development of neural connections are similar to those underlying long-term changes in synaptic strength in the adult brain. MRDD Research Reviews 1999; 5:51–59. © 1999 Wiley-Liss, Inc.