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. Author manuscript; available in PMC: 2025 Apr 15.
Published in final edited form as: Annu Rev Vis Sci. 2024 Sep 19;10(1):23–46. doi: 10.1146/annurev-vision-101623-025432

Figure 6.

Figure 6

The many meanings of optimal. (a) The visual system computes intermediate representations, c, of the input x: x ↦ c ↦ ŷ. Although only one is shown, there could be several layers of representations. Encoding is moving from x to c, while decoding is moving from c to a useful quantity ŷ, which is latent in x and c. (b) Some theories restrict optimization to the encoding or decoding step, constraining or ignoring the other step. Other theories impose fewer constraints and/or use a loss function ℒ that depends on both input and output representations. Many different optimization theories can be derived by choosing different objective functions and constraints.