Neuronal activities in the monkey primary and higher-order gustatory cortices during a taste discrimination delayed GO/NOGO task and after reversal.

The correlation between different gustatory areas in the frontal operculum, orbitofrontal area, and insula and the representation of different aspects of cues during a salt-water discrimination delayed GO/NOGO task was studied in a Japanese monkey. Four groups were identified among 169 neurons responding to cues before/after task reversal. Group I (n=78) responded to the physicochemical nature of the cue, Group II (n=8) responded to both the physicochemical nature of the cue and the subsequent behavior, Group III (n=51) (three subgroups) produced discharges related to the subsequent behavior, and Group IV (n=32) produced non-differential responses probably related to attention. The primary gustatory areas (area G and the oral part of area 3) almost exclusively contained Group I neurons, whereas the so-called secondary gustatory areas (the PrCO and area 12) contained most of the Group III neurons. Group IIIc showed discharges accelerating to the LED onset, probably representing preparation for subsequent behavior, and the response differed between the PrCO and area 12. The PrCO also contained Group IV neurons. The primary gustatory areas process pure gustatory signals, whereas the PrCO and area 12 may be involved in gustatory perception, attention, or behavior.