| Abstract: | To examine the possibility that different taste qualities arerepresented by the correlative activity of cortical gustatoryneurons, we made simultaneous recordings of neuron pairs duringapplication of four basic tastes into the oral cavity of anesthetizedrats and the following observations were made: (i) in 30 of67 pairs of taste responsive neurons, peaks (troughs in a fewcases) were produced in the cross-correlograms (CCs) duringstimulation with some tastants; (ii) the correlative dischargesoccupied 6–8% of the total spikes discharged by individualneurons during taste stimulation and occurred, in a considerablenumber of cases, even during stimulation with tastants to whichone or both of the component neurons of a pair were apparentlynon-responding (often sucrose and quinine); (iii) the numberof tastants to which a neuron pair responded with a significantcorrelative activity was often greater than the number of tastantsto which the component neurons of the same pair responded withsignificant changes in discharge rate; (iv) there was no significantdifference between the correlative (formation of peaks or troughsin the CC) and individual (change in discharge rate of individualneurons) ways of coding in the sensitivity to distinguish betweentwo taste qualities ranked to be adjacent on the basis of thenumber of spikes composing the response; and (v) the peaks ortroughs appearing in two CCs during stimulations with two kindsof tastants were compared with regard to overlapping of theirdelay ranges and widths. The spikes in the non-overlapping portionof each peak (suppressed spike number in the case of troughs)are supposed to be able to contribute to two-taste discrimination:the correlated discharges occurring with a delay time that correspondsto the overlapping portion can in no way be judged differently,but the spikes falling in the non-overlapping portion may contributeto the differentiation. The ratio of the non-overlapping portionto the entire peak (or trough) was 0.35 on average. It is concludedthat temporal coding of taste qualities seems to operate effectivelyin the gustatory cortex. Chem. Senses 22: 363–373, 1997. |
