Abstract
An important variable in the field of taste research is the relative palatability of tastants. Historically, individual tastant lick-counts collected during an active tastant delivery protocol have been used to establish relative palatability rank ordering, but there are many other metrics (first bout-length, orofacial behaviors) that can also be used to define palatability in rats. A concern with all of these measures is variability—while behavior is typically averaged across groups of subjects, rodents, like humans, appear to show individual differences in preferences. This fact takes on special significance in light of unpublished work from the Katz lab showing that significant between-rat variability also exists in the activity of the gustatory cortex during the palatability encoding phase of taste responses. This variability, which has traditionally been assumed to be noise, may in fact be signal reflecting individual differences in relative palatability preferences. Here I have tested this hypothesis: using lick-microstructure metrics gathered during a brief-access task, I measured individual rats’ palatability preferences; I then recorded gustatory cortical responses from these same rats in a standard tasting/recording session. My comparison of these two datasets reveals that the dynamic activity of neurons in GC during the palatability encoding phase of taste processing is indeed better correlated with individualized rank orders than with “canonical,” across-rat average orders. This result underscores the importance of considering inter-rat variability in both brain and behavior, and is novel reinforcing evidence that the late epoch of taste processing in GC genuinely tracks taste palatability.