Taste receptors are intermixed across the entire tongue, not localized to specific areas.

“It is a total myth, complete fiction, that different parts of your tongue harbor different taste receptors. You know, that high school textbook diagram that you know sweet is in one part of the tongue and sour is in another, and bitters in another, complete fiction, just total fiction related to very old studies that were performed in a very poorly controlled way, no serious biologists and certainly no one that works on tastes would contend that that's the way that the taste receptors are organized, they are completely intermixed along your tongue.”