Fig. 1.

Regulation of adult hippocampal neurogenesis in dependency of auditory stimuli. a We used two different approaches to address both proliferation and survival/differentiation by injection of BrdU either 24 h before daily sounds exposure or after daily sound exposure (see “Materials and methods” for details). During the auditory stimulation for 2 h each day, animals were kept in anechoic sound isolation box to prevent outside interference (c). Auditory brain stem responses were measured in mice at the experimental age of 8 weeks to control for hearing abilities during the experiments and to adjust the dB levels (b). While white noise did not show any effect on the number of proliferating cells in the adult dentate gyrus, all other stimuli significantly increased the size of the population of BrdU+ cells (d, e, a). In case of exposure to silence as well as Mozart's piano music (KV 448), we found particular increase in the population of BrdU-marked Sox2-positive precursor cells (f, g). The side length of the box in the large panel of (f) equals 150 μm. Differentiation, in contrast, was only significantly affected by silence (h, k) with a slight increase in the number of BrdU/NeuN double-positive new Neurons (i)