Fig. 5.

Neural discrimination between nicotine and quinine in the GC. (A) Representative example of a broadly tuned chemosensory GC neuron that responded to nicotine, quinine, and sucrose. Shown are the responses to particular stimuli, with raster plots of action potentials and peri-stimulus time histograms depicted respectively in the upper and lower sections. Reinforced licks occur at time 0 and are marked as a single red line on the raster plot. Previous and following dry licks are visible as red triangles at ± 0.15 s. (B) Correct predictions of nicotine and quinine stimuli (white and black bars respectively) across all ensembles were compared with chance (red bars). Because 1 or 2 concentrations of each tastant were presented in different recording sessions, a weighted chance level was calculated for each stimulus from the number of presentations at each chance level (50 or 25%–see methods). Nicotine (3 mM) was predicted at chance levels. All other stimuli were predicted above chance levels.