[6] ORs, which are located on the membranes of the cilia have been classified as a complex type of ligand-gated metabotropic channels.

The olfactory receptor neuron has a fast working negative feedback response upon depolarization.

When the neuron is depolarizing, the CNG ion channel is open allowing sodium and calcium to rush into the cell.

[12] The effect of this negative feedback response inhibits the neuron from further activation when another odor molecule is introduced.

Critics argued that the methodology used for the estimation was fundamentally flawed, showing that applying the same argument for better-understood sensory modalities, such as vision or audition, leads to wrong conclusions.

[15] The authors of the original study have argued that their estimate holds as long as it is assumed that odor space is sufficiently high-dimensional.