Mice spontaneously exhibit taste neophobia, the reluctance to consume food with a novel taste. This increases the probability of survival by promoting avoidance of novel foods that may be toxic. Once a new food is tried, the ability to associate a taste with its positive or negative consequences is fundamental to survival.

The taste cortex is found in a relatively insulated area of the human brain known as the insular cortex. The accepted thinking was that a memory associated with a given taste is created in this area of the brain, divorced from the time or place. A new study published in Journal of Neuroscience (34, 11007–11015; 2014) challenges that idea by showing the contributions of three different areas of the hippocampus—CA1, dentate gyrus and CA3—to taste memory.

The study was led by Kobi Rosenblum (University of Haifa, Israel) in collaboration with researchers at RIKEN Brain Science Institute (Saitama, Japan). Using conditional genetics, NMDA-receptor-dependent plasticity was blocked individually in each of the three hippocampal areas in different mice. In a conditioned taste aversion paradigm, the mice were first habituated to daily water for 3 days. On the fourth day, they were given water flavored with sodium saccharin, followed by an injection of a substance that induces a stomachache. On the seventh day, mice were given a choice between the saccharin solution and regular water.

Compared with controls, which showed a normal conditioned aversion to the taste after its association with stomachache, mice lacking plasticity in the CA1 region showed impaired aversion to the taste. Previous studies showed that the loss of plasticity in CA1 leads to spatial learning deficits, suggesting that memory of context is important for taste memory.

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The dentate gyrus became more involved as more time passed between the new taste and the stomachache. Whereas mice lacking plasticity in the dentate gyrus showed impaired aversion to the taste when there was a delay of 1 h or more between ingestion of saccharin and the injection, these mice showed no such impairment when injected immediately after ingesting saccharin. This suggests that temporal context also plays a critical role in conditioned taste aversion.

The findings show that learning to associate a taste with its consequence involves not only the area of the brain responsible for taste memory but also those responsible for processing the memory of the time and location.