Table 1. Implementation of the neurochemical interaction matrix and the neurochemical mobile system^%.

Entity	Implementation
Equations$	DA'  =  ACh0.5 · HT0.2 · Glu0.5 · NA0.5 · GABA−0.3 – 7.901101 · DA
	ACh'  =  DA−0.3 · HT−0.3 · Glu0.5 · NA−0.3 · GABA−0.3 – 0.0004985258 · Ach
	HT'  =  DA−0.2 · ACh0.5 · Glu0.5 · NA−0.3 · GABA−0.3 – 0.03145485 · HT
	Glu'  =  DA−0.3 · ACh0.5 · HT0.5 · NA0.5 · GABA−0.3 – 0.2793461 · Glu
	NA'  =  DA0.5 · ACh0.5 · HT0.5 · Glu0.5 · GABA−0.3 – 31.45485 · NA
	GABA'  =  DA−0.3 · ACh0.5 · HT−0.3 · Glu0.5 · NA−0.3 – 0.01494252 · GABA
Initial values#	HT  = 100; DA  = 100; NA  = 100;
	Glu  = 200; GABA  = 150; ACh  = 100;
Mobile configuration (Lever length)&	Lever_HT  = 1; Lever_DA  = 1; Lever_NA  = 2;
	Lever_HT_DA  = 1; Lever_HT_DA_NA  = 1;
	Lever_Glu  = 1; Lever_GABA  = 1.3333; Lever_ACh  = 3.5;
	Lever_Glu_GABA  = 1; Lever_ACh_Glu_GABA  = 0.6667;

^%:This implementation of the system uses the categorized weighting scheme, which assumes that the contributions of the different neurotransmitters to alcohol dependence are of comparable impact. Specifically, the concentrations are categorized into classes and transformed into low (100), medium (150), and high (200) values. A Matlab file of the system is presented in Supplement S2.

^$:Apostrophes on the left-hand sides of the equations indicate derivatives with respect to time.

^#:Relative signal intensities of neurotransmitters.

^&:Lever lengths in the mobile for the various neurotransmitters. Please see the Figure 2 for the corresponding positions of levers within the mobile.