From the Discussion in the paper A subset of broadly responsive Type III taste cells contribute to the detection of bitter, sweet and umami stimuli [1]:
> Our data suggest that BR cells are a subset of Type III cells that are capable of responding to multiple taste stimuli, except sodium chloride. Since the BR cells always responded to sour, 100% of these cells responded to multiple taste qualities and approximately 80% of these cells responded to either three or four modalities (Fig 3D). This is in contrast to Type II cells that are usually narrowly tuned to a single taste quality.
It appears that broadly responsive (BR) cells make the taste response slightly more complicated than original thought. Salty seems to be the odd man out and conforms to the original model; I'm not sure which observation I find more intriguing.
Primarily, one should note that these cells were identified in mice where they found a subset of cells that potentially respond to multiple taste stimuli including bitter, sweet, sour, and umami.
There are already existing classes of cells that respond to bitter, sweet, and umami taste and those that respond to sour and salty stimuli. The cells identified here (BR- Broadly Responsive cells) respond to bitter, sweet, sour, and umami. But if you look at Fig. 3D, even within these BR cells, there is separation between cells that uniquely respond to specific tastes so it is not clear to me how they are all classified into "Broadly Responsive".
> Our data suggest that BR cells are a subset of Type III cells that are capable of responding to multiple taste stimuli, except sodium chloride. Since the BR cells always responded to sour, 100% of these cells responded to multiple taste qualities and approximately 80% of these cells responded to either three or four modalities (Fig 3D). This is in contrast to Type II cells that are usually narrowly tuned to a single taste quality.
It appears that broadly responsive (BR) cells make the taste response slightly more complicated than original thought. Salty seems to be the odd man out and conforms to the original model; I'm not sure which observation I find more intriguing.
[1] https://journals.plos.org/plosgenetics/article?id=10.1371/jo...