Fig. 6.

Sound-evoked auditory activity is required to maintain the soma size gradient in the MNTB of mice and gerbils. Normal-hearing gerbils and mice both show a soma size gradient. If auditory activity is eliminated through cochlear ablation (gerbil) or TTX treatment (gerbil), DT treatment (mouse), or genetic mutation (mouse) the cell size gradient is absent. If auditory activity returns after a period of deprivation (TTX treatment) the cell size gradient will be restored. The dotted outline of the presumptive PMCA2 gradient indicates expression in the calyces as suggested by the electrophysiological data rather than in MNTB neurons. HF, high frequency; LF, low frequency.