Which evidence supports labeled line coding in the taste system?Group of answer choicesIncreasing concentrations of tastants can overcome a genetic mutation that results in a deficiency of taste receptors.The same behavioral responses are observed in response to all tastants when specific taste receptors are inactivated.No change in cranial nerve activity is observed when specific taste receptors are inactivated.Mice re-expressing PLCb2 in T2-expressing taste cells in a PLCb2 mutant mouse are able to respond to bitter tastes.Receptor proteins re-expressing are expressed broadly in taste cells and not in subsets

To determine which evidence supports labeled line coding in the taste system, let's analyze each of the provided options step by step:

1. Increasing concentrations of tastants can overcome a genetic mutation that results in a deficiency of taste receptors.

   • This suggests that higher concentrations of tastants can compensate for the lack of specific receptors, which implies that the system might be more flexible and not strictly dependent on specific labeled lines. This does not support labeled line coding.

2. The same behavioral responses are observed in response to all tastants when specific taste receptors are inactivated.

   • If inactivating specific taste receptors leads to the same behavioral response for all tastants, it suggests that the system is not using distinct pathways (labeled lines) for different tastes. This does not support labeled line coding.

3. No change in cranial nerve activity is observed when specific taste receptors are inactivated.

   • If inactivating specific taste receptors does not change cranial nerve activity, it implies that the taste system might be using a more integrated or redundant coding mechanism rather than distinct labeled lines. This does not support labeled line coding.

4. Mice re-expressing PLCb2 in T2-expressing taste cells in a PLCb2 mutant mouse are able to respond to bitter tastes.

   • This indicates that reintroducing a specific signaling molecule (PLCb2) in specific taste cells (T2 cells) restores the ability to detect bitter tastes. This supports the idea that specific cells and pathways (labeled lines) are responsible for detecting specific tastes. This supports labeled line coding.

5. Receptor proteins re-expressing are expressed broadly in taste cells and not in subsets.

   • If receptor proteins are expressed broadly and not in specific subsets of taste cells, it suggests a more distributed coding mechanism rather than distinct labeled lines. This does not support labeled line coding.

Based on the analysis, the evidence that supports labeled line coding in the taste system is:

Mice re-expressing PLCb2 in T2-expressing taste cells in a PLCb2 mutant mouse are able to respond to bitter tastes.