| The nucleus of the solitary tract (NTS) is the first neural relay in the central gustatory system of mammals. As such, it receives and processes information from a number of peripheral nerves innervating taste buds within the oropharyngeal area. To gain insight into how taste-related information is integrated within the NTS, a network of "neurons" was constructed based on the neuron's physiological and morphological features using computational modeling techniques. Twelve neurons, 3 in each of classes (salt, sweet, sour, or bitter best), in the model NTS received simulated input from peripheral nerves (based on extant literature) and, in some simulations, from centrifugal structures. Ten types of network structures, which included excitatory and/or inhibitory intra- and inter-class connections were constructed. Additionally, variations in the arrangement of inputs, i.e. concentrated or dispersed along a dendrite, and the size of dendritic fields were varied systematically and the effects on the breadth of tuning were noted. Results provided several insights into the coding mechanisms in the NTS: (1) A dispersed distribution of the excitatory connections on the NTS dendrites can make the transmission of taste information from dendrite to axon less susceptible to blockage by inhibition. (2) Randomly distributed inhibitory connections have the effect of narrowing the tuning of already narrowly tuned cells, but degrade the organization of cells into best stimulus groups, as assessed by hierarchical cluster analysis. (3) Results of our simulations suggest that the dendritic fields of narrowly tuned NTS neurons are likely smaller, and their primary dendrites shorter, than more broadly tuned cells. (4) Inter-class inhibitory connections can enhance the contrast among different taste stimuli, and the intra-class inhibitory connections may affect temporal coding in the gustatory system. |
