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

Abstract

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.

Quality Time: Representation of a Multidimensional Sensory Domain through Temporal Coding

“…However, previous work has shown that taste-like sensations of an identifiable quality were evoked when the temporal patterns of NTS responses to either sucrose or quinine were played back (as electrical pulse trains) into the NTS in awake rats (Di Lorenzo and Hecht, 1993: Di Lorenzo et al, 2003, 2009). Specifically, rats with electrodes implanted in the rostrocentral NTS learned to avoid licking water when licking was paired with delivery of an electrical pulse train with the temporal characteristics of a sucrose Di Lorenzo et al, 2003) or quinine Di Lorenzo et al, 2009) response when it was paired with an injection of LiCl. Trained animals actually generalized the conditioned aversions specifically to real sucrose or quinine respectively.…”

“…Trained animals actually generalized the conditioned aversions specifically to real sucrose or quinine respectively. Lick-contingent patterns of electrical pulses based on quinine responses predictably produced avoidance without prior training (Di Lorenzo and Hecht, 1993;Di Lorenzo et al, 2009) while control patterns of pulses that contained a randomly presented sequence of interpulse intervals equivalent to the original effective pattern was not avoided (Di Lorenzo et al, 2003). Collectively, these data imply that the information about taste conveyed by temporal coding in NTS responses (Di Lorenzo and Victor, 2003, 2007; Roussin et al, 2008) is indeed functionally relevant.…”

The Languages of Neurons: An Analysis of Coding Mechanisms by Which Neurons Communicate, Learn and Store Information

“…When the S/P cellular quinine word response was mimicked by patterned electrical pulse trains, the electronically generated pulse trains sent to the CNS were found to elicit the same behavioral avoidance response as the cell-generated S/P word trains, underscoring the functional significance of temporal S/P coding [21]. These results also suggest that knowledge of specific neuronal codes might be a useful adjunct in treatment of certain human neuropathies, perhaps similar to the methodologies currently used in cardiac pacemaker technology where an electronic message at 1.13 Hz translates into 68 heartbeats/min.…”

The nature of neuronal words and language

“…Importantly, using artificial electronically generated frequencies that mimic the frequencies of recorded natural neuronal words, it has been demonstrated that it is possible not only to record these neuronal words, but also to communicate directly with the central nervous system (CNS) of rats. Where this has been done, the manufactured words have been shown to elicit the same behavioral responses in rats that would have been generated by exposure to a specific environmental stimulus [9].…”