Dynamic optimization of odor representations by slow temporal patterning of mitral cell activity

Mitral cells (MCs) in the olfactory bulb (OB) respond to odors with slow te mporal firing patterns. The representation of each odor by activity pattern s across the MC population thus changes continuously throughout a stimulus, in an odor-specific manner. In the zebrafish OB, we found that this distri buted temporal patterning progressively reduced the similarity between ense mble representations of related odors, thereby making each odor's represent ation more specific over time. The tuning of individual MCs was not sharpen ed during this process. Hence, the individual responses of MCs did not beco me more specific, but the odor-coding MC assemblies changed such that their overlap decreased. This optimization of ensemble representations did not o ccur among olfactory afferents but resulted from OB circuit dynamics. Time can therefore gradually optimize stimulus representations in a sensory netw ork.