Making time count: functional evidence for temporal coding of taste sensation.

Although the temporal characteristics of neural responses have been proposed as a mechanism for sensory neural coding, there has been little evidence thus far that this type of information is actually used by the nervous system. Here the authors show that patterned electrical pulses trains that mimic the response to the taste of quinine can produce a bitterlike sensation when delivered to the nucleus tractus solitarius of behaving rats. Following conditioned aversion training using either "quinine simulation" patterns of electrical stimulation or natural quinine (0.1 mM) as a conditioned stimulus, rats specifically generalized the aversion to 2 bitter tastants: quinine and urea. Randomization of the quinine simulation patterns resulted in generalization patterns that resembled those to a perithreshold concentration (0.01 mM) of quinine. These data provide strong evidence that the temporal pattern of brainstem activity may convey information about taste quality and underscore the functional significance of temporal coding. (c) 2009 APA, all rights reserved.