Possible Changes in Information from the Primary to Higher-order Gustatory Cortices, Studied by Recording Neural Activities during a Taste Discrimination GO/NOGO Task in Monkeys

Several gustatory cortices have been identified in the macaque monkey: the primary gustatory cortices (PGC: areas G, 3 and 1–2) and the higher-order gustatory cortices (HGC), including the precentral operculum (PrCO), orbitofrontal operculum (OFO), insula and orbitofrontal cortex (OFC; area 12). So far, several studies have investigated the response characteristics of taste neurons in the PGC and HGC (Ogawa, 1994; Rolls, 1989; Scott and Plata-Salaman, 1999), and HGC taste neurons are characterized by convergence of various sensory inputs and effects of sensory satiety on taste-responsive neurons in the HGC (Rolls and Scott, 2003). However, it is still a challenge to study differences in coding of taste information between the two areas. During the last decade, we developed a saltwater discrimination GO/NOGO task for monkeys and investigated neural activities in the PGC and HGC to NaCl and water in the cue phase, and sucrose in the reward phase during the task to clarify different coding mechanism of taste perception between the PGC and HGC. We review our recent work in this article.