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In the primary visual cortex of macaques, the timing of the first spike relative to the start of the stimulus was found to be more important than the interval between spikes. However, the interspike interval could be used to encode more information, which is especially important when the spike rate reaches its limit, as in high-contrast situations. For this reason, temporal coding may play a part in coding defined edges rather than gradual transitions.<ref>Victor, Johnathan D. (2005). [http://dx.doi.org/10.1016/j.conb.2005.08.002 "Spike train metrics"]. <i>Current Opinion in Neurobiology</i>, 15(5):585–592.</ref>
Similarly, in mitral/tufted cells in the olfactory bulb of mice, first-spike latency relative to the start of a sniffing action seemed to encode much of the information about an odor. This strategy of using spike latency allows for rapid identification of and reaction to an odorant. In addition, some mitral/tufted cells have specific firing patterns for given odorants. This type of extra information maycould help in recognizing a certain odor, but is not completely necessary, as average spike count over the course of the animal's sniffing was also a good identifier.<ref>Wilson, Rachel I. (2008). [http://www.sciencedirect.com/science/article/pii/S0959438808000883 "Neural and behavioral mechanisms of olfactory perception"]. <i>Current Opinion in Neurobiology</i>, 18(4):408–412.</ref> Along the same lines, experiments done with the olfactory system of rabbits showed distinct patterns which correlated with different subsets of odorants, and a similar result was obtained in experiments with the locust olfactory system. <ref>Theunissen F, Miller JP. ''Temporal Encoding in Nervous Systems: A Rigorous Definition''. Journal of Computational Neuroscience, 2, 149—162; 1995.</ref>
==Implications==
The specificity of temporal coding requires highly refined technology to create informative, reliable experimental data. In 2009, advances made in [[optogenetics]] allowed neurologists to control spikes in individual neurons, offering electrical- and spatial- single-cell resolution. For example, a [[channelrhodopsin|channel rhodopsin]] in pond scum opens when it senses blue light, depolarizesdepolarizing the cell, and producesproducing a spike. When blue light is not sensed, the channel closes and the neuron ceases to spike. The pattern of the spikes matches the pattern of the blue light stimuli. By inserting channel rhodopsin DNA into mouse DNA, researchers can control spikes and therefore certain behaviors of the mouse (iei.e., making the mouse turn left).<ref> Karl Diesseroth, Lecture. “Personal Growth Series: Karl Diesseroth on Cracking the Neural Code.” Google Tech Talks. November 21, 2008. http://www.youtube.com/watch?v=5SLdSbp6VjM</ref> Researchers, through optogenetics, have the tools to effect different temporal codes in a neuron while maintaining the same mean firing rate, and thereby can test whether or not temporal coding occurs in specific neural circuits. <ref>Han X, Qian X, Stern P, Chuong AS, Boyden ES. “Informational lesions: optical perturbations of spike timing and neural synchrony via microbial opsin gene fusions.” Cambridge, MA: MIT Media Lad, 2009. PubMed.</ref>
</ref> Researchers, through optogenetics, have the tools to effect different temporal codes in a neuron while maintaining the same mean firing rate, and thereby can test whether or not temporal coding occurs in specific neural circuits. <ref>Han X, Qian X, Stern P, Chuong AS, Boyden ES. “Informational lesions: optical pertubatons of spike timing and neural synchrony via microbial opsin gene fusions.” Cambridge, MA: MIT Media Lad, 2009. PubMed.</ref>
==See also==
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