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| Figure 1 |
We view the gustatory system as a dynamic unit made up of interacting elements, and predict that gustatory processing will be reflected in coherent shifts of activity among neural populations (see Seidemann, et al., 1996). Basic support for this view can be found in taste-specific cross-correlations between simultaneously recorded GC neurons. This figure shows cross-correlations between a pair of GC neurons-one of which did not appear taste-specific on its own (see also Adachi et al 1989, Nakamura & Ogawa 1997, Yokota & Satoh 2001). Note that the cross-correlation was significant when NaCl was on the tongue (maroon trace) but not when any other tastant was present.
We performed extensive simulations to probe the source of the significant cross-correlations. These analyses revealed that the lack of independence between the firing of the two neurons was specifically related to time-varying aspects of the firing rate responses (and not to synchrony, across-session variations in isolation, or common input), consistent with theories and data suggesting that coherent rate modulations, and not individual spike arrival times, may be the currency of population coding both in the gustatory system and elsewhere (Baker & Lemon 2000, Di Lorenzo & Victor 2003, Friedrich & Laurent 2001, Seidemann et al 1996, Wiener & Richmond 2003).
When both the dynamics of single-unit taste responses and taste-specific between-neuron interactions are taken into account, the percentage of GC neurons involved in gustation can be seen to be an order of magnitude larger than that previously supposed (see Table).
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| Table 1 |
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