 These findings, however, do not exclude a role for activity-dependent processes in the maintenance or potential plasticity of the map after it is established.For example, neurons that do not express functional odorant receptors have been observed to have a significantly shorter half-life.Activity-dependent processes may therefore be essential for the survival of the olfactory neurons postnatally, and in that manner, may alter the input to individual glomeruli, altering the sensitivity to individual odors.