Neuronal activity in the monkey fronto-opercular and adjacent insular/prefrontal cortices during a taste...

The neural coding of taste information in the fronto-opercular cortex (Fop) and the orbitofrontal area (OFA) was investigated by recording neural activities in monkeys performing a NaCl-water discrimination GO/NOGO task. Responses to GO (NaCl) and NOGO cues (water) were recorded from 160 neurons, of which 118 differentially responded to two cues (differential, Dif neurons), and 42 showed the same response (non-differential, ND neurons). Differential neurons included equal numbers of GO- and NOGO-dominant subtypes. Dif and ND neurons may code for different cues, e.g., taste and touch, as shown by our previous study [Jpn. J. Physiol. 44 (1994) 141]. The response latency of neurons in the exposed Fop was distributed with two modes, one at the shortest bin (100 ms) and one at the bin of 400-800 ms, but neurons in the buried Fop and OFA all had long latency. Such a difference between the two cortical groups of neurons suggests different roles in taste discrimination tasks. Most neurons did not show changes in the discharges or latency with varying concentrations of NaCl. The results indicate that neurons in the areas surveyed code for taste information differently in the task-performing state compared with the non-behaving state examined in previous studies.