Gustatory pathway in humans: A review of models of taste perception and their potential lateralization

The focus of this review is to interpret recent advances in human gustatory pathways with respect to the laterality of gustatory responses. Psychophysical, neuroimaging, and clinical anatomical studies published in peer reviewed scientific journals were examined. From the anatomical and neuroimaging studies a total of six models are outlined and discussed in the light of some recent psychophysical and clinical results. In the specific of the salt condition and right preferred hand the outcomes have revealed a predominant left ipsilateral pathway with evidences of ipsilateral projection from the left primary gustatory cortex (PGC) to the orbitofrontal cortex, while a bilateral projection from the right oral cavity to the left and right insula seems to be more consistent. Also, the right side predominance of the chemosensory perception is objected. Additionally, the gustatory response appears to be dependent on the taste quality, supporting the idea of a chemotopical organization of the PGC as well as the Labelled-Line Model theory of peripheral taste quality encoding. However, where the fibers branch along the ascending pathway is not unequivocally established. Interestingly, factors like handedness appear to be remarkable when studying the lateralization of brain functions. Finally we suggest that further studies must include handedness and taste quality as distinctive factors that can help to interpret the results in a unique way.