Figure 2.

Schematic diagrams of neuroscience experiments that address commanding or “misapplied-sufficient” function of neurons. (A) An example of a feeding command neuron in a fly brain (Flood et al., 2013b). Various signals such as food or starvation flow into a pair of feeding command neurons (Feeding neuron), and the Feeding neuron makes the decision to trigger the whole feeding behavior. The Feeding neuron fulfills the “rigid” requirements of misapplied-N&S. See text. (B) A hypothetical case with redundancy, where a second imaginary feeding command neuron (Feeding 2) can substitute the first command neuron (Feeding 1). Feeding 1 fulfills the sufficient condition in misapplied-N&S, but it does not fulfill the necessary condition in misapplied-N&S. (C) A group of neurons are triggering a whole pattern of behavior such as aggression (Lin et al., 2011). The group of neurons fulfills requirements of misapplied-N&S (pale magenta represents the area tested for “sufficiency” and pale green represents “necessity”). However, it is possible that only a fraction of the cells (circles with deep colors) are responsible for the behavior. The deep magenta represents “sufficiency” and deep green for “necessity”. (D) Another possible scenario; the group of neurons fulfills requirements of misapplied-N&S, but the cells responsible for “necessity” might be different from the cells responsible for “sufficiency”. Color code is the same as that of C. This situation allows a group of redundant cells (right) to have a potential to be “sufficient” for triggering the behavior as well. The “necessity” experiment does not check if it is a natural function or not either. It is far from the true N&S shown in Fig.1A and the words “necessary and sufficient” are misleading here. See text.