Table 1.

Classification of neuronal responses during cocaine and heroin self-administration

	AE		AI		PI		PE		NR
	n	% of total	n	% of total	n	% of total	n	% of total	n	% of total
Cocaine
mPFC	11	10	9	8.2	20	18.2	4	3.6	80	72.7
NAc	27	24.3	6	5.4	30	27.0	8	7.2	61	54.9
Heroin
mPFC	20	18.2	9	8.2	14	12.7	3	2.7	69	62.7
NAc	18	16.2	6	5.4	20	18.0	6	5.4	68	61.3

Number and distribution of different types of neuronal responses in mPFC and NAc during separate cocaine and heroin self-administration sessions. Different categories of neuronal responses are displayed at the top of table (AE, anticipatory excitatory response; AI, anticipatory inhibitory response; PI, post-drug inhibitory response; PE, post-drug excitatory response; NR, no response). Number of neuron(n) and percentage of total are indicated in each category. A total of 110 mPFC and 111 NAc neurons were tested across cocaine and heroin sessions. A single neuron sometimes exhibited more than one type of response so it could be counted in multiple categories.