Taste is sensed by small number of chemoreceptor types but identified by a sophisticated neural network. Analysis of the neural network concerning taste will contribute to further understanding of informational processing in the central nervous system. A marine gastropod Aplysia has large neurons and shows clear food preferences. We attempted to analyze the neural network which generates ingestive or rejective response by using fluorescent voltage dye imaging. Buccal mass and buccal ganglia of Aplysia californica were isolated with keeping their connection by buccal nerves. The neurons in the ganglia were stained with voltage sensitive dye (Di-4-ANEPPS) in the presence of tetraethylammonium (TEA) chloride. Then the responses of the stained neurons were explored after administration of 1 mM solution of _L-asparagine or _L-aspartic acid to radula inside the buccal mass. Administration of each of amino acids induced firing of neurons in S1 and S2 clusters. Additionally, the administration of _L-aspartic acid induced the firing in these clusters with shorter time lag than that of _L-asparagine. This phenomenon was also observed by electrophysiological experiments using a glass microelectrode. Then, _L-asparagine induces ingestive response of the jaws and radula, while _L-aspartic acid induces rejective response of them. Then, the result is consistent with the fact that an animal must reject wrong food immediately for survival. Furthermore, the staining and TEA treatment of neurons which are necessary to voltage imaging would not affect seriously neural response because the time lag of firing from the administration of amino acids were almost same whether these treatments were performed or not. The results suggest that voltage sensitive dye imaging is useful for an analysis of neural network for taste recognition because this method can detect neural signals in response to taste stimulation in large numbers of neurons simultaneously.