Comparison of neuronal activity during cocaine and heroin self-administration in the heroin-first, cocaine-second sessions. The format of the table is the same as Table 2. A, Comparison of mPFC neuronal activity during heroin and cocaine self-administration trials. Similar to what was observed in cocaine-first, heroin-second sessions in Table 2, most neuron-response cases responded to heroin and cocaine self-administration differently (84.1%), whereas only 15.9% of neuron-response cases shared the same response during heroin and cocaine self-administration trials. B, Comparison of the data obtained from NAc. Again, only 22.4% of neurons responded in the same way to both heroin and cocaine self-administration; the majority of neuron-response cases (77.6%) responded differently during heroin and cocaine self-administration trials.