[2] By using extracellular unit recording techniques, scientists have elucidated that neurons in the AI/FO respond to sweetness, saltiness, bitterness, and sourness, and they code the intensity of the taste stimulus.
This nucleus projects in turn to several regions of the neocortex which includes the gustatory cortex (the frontal operculum and the insula), which becomes activated when the subject is consuming and experiencing taste.
[8] Furthermore neurons in the orbitofrontal cortex respond to the visual, and/or olfactory stimuli in addition to the gustatory stimulus.
These results suggest that gustatory neurons in the orbitofrontal cortex may play an important role in food identification and selection.
Importantly, early evidence in rodent models pointed to the existence of a gustotopic map;[14] however, recent studies in both mice, through two-photon calcium imaging,[15][16] and humans, through fMRI,[13][17][18] indicated distributed population coding in GC.
[19][20] Some researchers have noted that the AI/FO neurons are intrinsically multimodal, that is, they respond to other modalities in addition to taste (often to olfaction and/or somatosensation).
[21] These findings could imply that GC is not strictly involved in taste perception but also in more domain general functions, such as decision making regarding consummatory behaviors[21] and valence processing.
Studies using the Gustatory cortex of the rat model have shown that GC neurons exhibit complex responses to changes in concentration of tastant.
In studies of chemosensory GC neurons, it was evident that few chemosensory GC neurons monotonically increased or decreased their firing rates in response to changes in concentration of tastants (such as MSG, NaCl, and sucrose), the vast majority of them responded to concentration changes in a complex manner.
This persistent cortical representation of taste familiarity requires slow post-acquisition processing to develop.
This process may be related to the activation of neurotransmitter receptors, modulation of gene expression, and posttranslational modifications detected in the insular cortex in the first hours after the consumption of an unfamiliar taste.