Is silence golden? Effects of auditory stimuli and their absence on adult hippocampal neurogenesis

• Type of Material: Article
• Authors: Imke Kirste, CRTD, DFG Research Center for Regenerative Therapies Dresden; Zeina Nicola, CRTD, DFG Research Center for Regenerative Therapies Dresden; Golo Kronenberg, Charité- Universitätsmedizin Berlin; Tara L. Walker, CRTD, DFG Research Center for Regenerative Therapies Dresden; Robert Liu, Emory University; Gerd Kempermann, CRTD, DFG Research Center for Regenerative Therapies Dresden
• Language: English
• Date: 2015-03
• Publisher: Springer Verlag (Germany)
• Publication Version: Final Published Version
• Copyright Statement: © The Author(s) 2013
• License: Creative Commons Attribution 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1007/s00429-013-0679-3
• Title of Journal or Parent Work: Brain Structure and Function
• ISSN: 1863-2653
• Volume: 220
• Issue: 2
• Start Page: 1221
• End Page: 1228
• Grant/Funding Information: This study was financed from basic institutional funds, with support from NIH DC008343.
• Keywords: Hippocampus; Stem cells; Plasticity; Mouse; Learning
• Research Categories: Biology, General; Biology, Neuroscience

Abstract

We have previously hypothesized that the reason why physical activity increases precursor cell proliferation in adult neurogenesis is that movement serves as non-specific signal to evoke the alertness required to meet cognitive demands. Thereby a pool of immature neurons is generated that are potentially recruitable by subsequent cognitive stimuli. Along these lines, we here tested whether auditory stimuli might exert a similar non-specific effect on adult neurogenesis in mice. We used the standard noise level in the animal facility as baseline and compared this condition to white noise, pup calls, and silence. In addition, as patterned auditory stimulus without ethological relevance to mice we used piano music by Mozart (KV 448). All stimuli were transposed to the frequency range of C57BL/6 and hearing was objectified with acoustic evoked potentials. We found that except for white noise all stimuli, including silence, increased precursor cell proliferation (assessed 24 h after labeling with bromodeoxyuridine, BrdU). This could be explained by significant increases in BrdU-labeled Sox2-positive cells (type-1/2a). But after 7 days, only silence remained associated with increased numbers of BrdU-labeled cells. Compared to controls at this stage, exposure to silence had generated significantly increased numbers of BrdU/NeuN-labeled neurons. Our results indicate that the unnatural absence of auditory input as well as spectrotemporally rich albeit ethological irrelevant stimuli activate precursor cells—in the case of silence also leading to greater numbers of newborn immature neurons—whereas ambient and unstructured background auditory stimuli do not.