Cross-correlation analysis was made in the taste-sensitive neuron pairs recorded simultaneously from the parabrachial nucleus (PBN) of rats. Three indexes were adopted to evaluate the activities of the taste neurons; namely, 1) spike response density (RD value), which is the net spike density to stimulation with the four basic tastes; 2) the frequency of correlated discharges (FC value in spikes per second), which was determined by measuring the area of the peak appearing in the cross-correlogram (CC) during application of the test fluids; and 3) the weight of correlated discharge (WC = FC/RD), which shows the relative importance of correlated discharges in the taste signals delivered by a component neuron of a given pair. 2. In 11 of 23 pairs, the CCs exhibited peaks during stimulation with tastants. These 11 pairs, which were recorded in the pontine taste area, were composed of 18 NaCl-best (most sensitive to NaCl) and 4 HCl-best neurons. In eight pairs, the best-stimulus of both of the component neurons was NaCl, and it was HCl in one pair (homo-type pairs). The remaining two pairs were composed of an NaCl-best and an HCl-best neuron (hetero-type pairs). 3. In eight homo-type pairs (7 NaCl-best pairs and 1 HCl-best pair), each pair exhibited the maximal FC value during stimulation with the best-stimulus of the component neurons (2.3 less than or equal to maximal FC less than or equal to 26.6 Hz). In the remaining three pairs, the maximal FC values were low (0.8-1.9 Hz).(ABSTRACT TRUNCATED AT 250 WORDS)
