Fig. 7. Timeline of developmental milestones in the visual system; comparison of the ferret to the cat. Developmental milestones in the visual cortex, LGN, and retina are displayed for both species. The development of the ferret’s visual system has been thought to proceed with the same postconception time course as that of the cat. Several events, however, occur earlier in the ferret than in the cat. In addition to an earlier beginning to the critical period and ocular dominance segregation, cortical horizontal connections begin to cluster earlier, most cortical cells are born earlier, and LGN lamination, axonal growth, and cortical invasion occur earlier in the ferret than in the cat. Other subcortical developmental time points are more closely matched between the two species. OD, Ocular dominance; MD, monocular deprivation; GC,ganglion cell; C-I, contralateral-ipsilateral. References: 1,Hubel and Wiesel (1970);2,Finney and Shatz (1998); 3,Ruthazer et al. (1999); 4,LeVay et al. (1978); 5,Durack and Katz (1996); 6,Ruthazer and Stryker (1996);7,Callaway and Katz (1990); 8,Chapman and Stryker (1993); 9,Albus and Wolf (1984);10,Jackson et al. (1989); 11,Luskin and Shatz (1985); 12,Valverde and Facal-Valverde (1988);13,Hermann et al. (1994); 14,Johnson and Casagrande (1993); 15,Shatz and Luskin (1986);16,Ghosh and Shatz (1992); 17,Weliky and Katz (1998); 18,Peduzzi (1989); 19,Linden et al. (1981); 20,Hickey and Hitchcock (1984);21,Kalil (1978); 22,Shatz (1983);23,Reese et al. (1994); 24,Meister et al. (1991); 25,Wong et al. (1993); 26,Walsh et al. (1983); 27,Walsh and Polley (1985).