Spike Rate and Spike Timing Contributions to Coding Taste Quality Information in Rat Periphery

Abstract

There is emerging evidence that individual sensory neurons in the rodent brain rely on temporal features of the discharge pattern to code differences in taste quality information. In contrast, investigations of individual sensory neurons in the periphery have focused on analysis of spike rate and mostly disregarded spike timing as a taste quality coding mechanism. The purpose of this work was to determine the contribution of spike timing to taste quality coding by rat geniculate ganglion neurons using computational methods that have been applied successfully in other systems. We recorded the discharge patterns of narrowly tuned and broadly tuned neurons in the rat geniculate ganglion to representatives of the five basic taste qualities. We used mutual information to determine significant responses and the van Rossum metric to characterize their temporal features. While our findings show that spike timing contributes a significant part of the message, spike rate contributes the largest portion of the message relayed by afferent neurons from rat fungiform taste buds to the brain. Thus, spike rate and spike timing together are more effective than spike rate alone in coding stimulus quality information to a single basic taste in the periphery for both narrowly tuned specialist and broadly tuned generalist neurons.

Anion size modulates salt taste in rats

“…5 is the typical response profile of a NaClspecialist and an acid-generalist neuron to 5-s stimulation with the standard stimuli. As shown, the NaCl-specialist neuron responds selectively to NaCl in a background of low spontaneous firing rate, whereas the acid-generalist neuron responds broadly to all five standard stimuli in a background of high spontaneous firing rate, consistent with our laboratory's recent studies (Breza et al 2010;Lawhern et al 2011). Notably, each test solution elicited a unique and consistent EGG waveform on 2 separate recording days, indicative of controlled delivery of test solutions to the tongue.…”

“…It is logical to expect that the underlying neural process for rapid taste quality and intensity discrimination must be in temporal registry with the behavior. In the present study, the most obvious response measures more in temporal registry with behavioral discrimination are response latency (Breza et al 2010;Lawhern et al 2011) and phasic response frequency (Bealer 1978). For the ENaC saltsensing pathway, NaCl-specialist neurons responded to NaCl and Na-gluconate with concentration-dependent response latency and phasic response frequency components during the first 500-ms measurement period.…”

Sensory receptor diversity establishes a peripheral population code for stimulus duration at low intensities

“…The use of multiple coding strategies is common in sensory systems (Lawhern et al, 2011). However, these distinct computations are…”

A new spike train distance measure

“…Thus to quantify the similarity or dissimilarity between two spike trains new measures have to be developed [3], [8], as difference in firing rates cannot be taken as a reliable distance measure. These distance measures find their use in diverse applications, such as, in studying the auditory system [9], [10], coding in the retinal ganglion cells [11] etc. These distance measures also play a very important role in neural prosthetics [12] and brain-machine interface [13].…”