Fig. 2.

a, If we assume the left and right eyes may be treated equivalently, and likewise for the ON and OFF cells, then the 16 correlation functions C^EC,E′C′, E, E′ ∈ {R, L}, C, C′ ∈ {N, F}, reduce to only four distinct functions C^XY, as shown. Here X ∈ {S_E, O_E}, where S_E means same eye and O_E means opposite eye; and Y ∈ {S_C, O_C}, where S_C means same center type and O_C means opposite center type. b–d, Development is most easily described in terms of four composite synaptic weights or modes, S^μ, and four corresponding composite correlation functions, C^μ, μ ∈ {SUM, OD, ORI+, ORI−}. b, On the left, the four synaptic weight variables S^EC are shown in a square grid with columns labeled by eye, E, and center type, C. c, Similarly, the four correlation functions of a are also arranged in a square grid. d, To the right, there is one small grid for each μ. The symbols inside the grids define both S^μ and C^μ as sums of positively and negatively weighted entries in the corresponding positions in the larger grids to the left. For example, S^OD ≡ S^RN + S^RF− S^LN − S^LF, and C^ORI+ = C^S_ES_C − C^S_EO_C + C^O_ES_C − C^O_EO_C. Explicit definitions are in Table 1.