Abstract:
Stimulus intensity, as a physical quantity, can be equivalently expressed in different unit systems. Researchers implicitly expect that the inferred neural coding precision and the amount of stimulus-related information are independent of such a subjective choice. We show, however, that even under regular reparameterizations these two popular methodological lines are affected in distinct ways. First, Fisher information is not invariant and may yield incompatible conclusions about coding precision when the identical stimulation scenario is evaluated in transformed coordinates. Second, while Shannon’s mutual information is invariant, its stimulus-specific decompositions are highly non-unique and may change under coordinate transformations unless constrained. We argue that requiring coordinate invariance naturally removes the ambiguity, and we discuss the psychophysical reference frame as a candidate for meaningful coding accuracy comparisons.