Abstract
Behavioral and electrophysiological studies suggest that rats can identify a taste stimulus with a single lick, in <200 ms. However, the conditions under which these conclusions were drawn varied widely across experiments. We designed a series of experiments to assess the effects of the number of licks of a tastant that are available, tastant concentration and prior learning experience on the speed with which a tastant can modify behavior. To accomplish this we tested exemplars of four basic taste qualities (quinine, 0.1 mM; NaCl, 100 mM; saccharin, 4 mM, or sucrose, 100 mM; citric acid, 10 mM) in rats that were conditioned to avoid quinine. Taste stimuli were available for one, two, or three licks on separate days. All tastants were presented in a randomized order interspersed with water rinse licks presented on a variable ratio schedule. A tastant-specific significant increase in the proportion of long pauses in licking following quinine presentation was defined as evidence of “behavioral identification.” Rats with aversion training given three licks of all taste stimuli paused significantly more often after quinine by the fourth interlick interval, ~580 ms. Control rats showed no evidence of quinine (0.1 mM) identification. When rats in all conditioning groups were tested with a high concentration of quinine (10 mM), a single lick was sufficient to produce significant pausing after quinine, but not until the fourth interlick interval, i.e., ~580 ms. Testing rats with only two tastants rather than four in a session had no effect on the speed of quinine identification. Present data confirm that a single lick is sufficient for rats to identify a taste stimulus, but that additional licks occur before evidence of identification is apparent. Furthermore, learning, tastant concentration and motivation to drink can all modify the speed of behavioral identification.
Highlights
In the visual and auditory systems, rapid encoding of stimuli and decision-making is a well-known feature of neural processing
Since the task required a comparison of taste stimuli in order to identify quinine, we defined the selective emergence of these long interlick intervals (ILIs) as evidence of behavioral identification of quinine
We estimate the time for behavioral identification of quinine by the ILI number where the proportion of ILIs >350 ms is significantly larger than this proportion for all other tastants and water
Summary
In the visual and auditory systems, rapid encoding of stimuli and decision-making is a well-known feature of neural processing. There is long standing evidence that the identification of a visual or auditory stimulus can occur within ∼200–300 ms (Valls-Sole et al, 1999; Fabre-Thorpe et al, 2003; Carlsen et al, 2011). Taste and olfaction, which many consider “slow” senses, there is evidence that stimuli can be identified with similar rapidity. Fast identification of tastes and smells has a clear evolutionary advantage to an animal. Recognition of smells that signal danger or the taste of deadly poisons can and do trigger relatively fast evasive action while, finding, and ingesting foodstuffs speaks to the very essence of survival skills. Rapid encoding of taste and smell is supported by a powerful evolutionary mandate
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
