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. Author manuscript; available in PMC: 2019 Feb 21.
Published in final edited form as: Neuroscience. 2017 Dec 23;372:97–113. doi: 10.1016/j.neuroscience.2017.12.018

Figure 7.

Figure 7

An illustration of the idea of interaction among efferent and afferent signals leading to iso-perceptual manifold, IPM. A: The UCM in the space of two efferent variables, {E1; E2}, corresponding to stabilization of their sum: E1 + E2 = RC. B: A subspace in the space of afferent variables, {A1; A2}, corresponding to their constant sum A1 + A2 = S (the thick solid line). Stability of a percept (P) is defined by the sum (RC + S) illustrated as a plane (IPM) in the three-dimensional space spanned by RC, A1, and A2. Motion along the IPM is perceptually equivalent (PE) motion (the dashed trajectory from point 1 to point 2). A change in the efferent process without a change in afferent signals (point 3) is an example of non-perceptually equivalent (nPE) motion to a new IPM. The figure is simplified in two aspects. First, it shows linear manifolds. Second, it assumes sharing of elemental variables between the UCM and IPM.