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

Four years and I bet your doctor and stroke hospital have done nothing to create a silence protocol. Are they that fucking incompetent? Yes they are. What are you going to do about that? 

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

Brain Struct Funct. 2015; 220(2): 1221–1228.

Published online 2013 Dec 1. doi:  10.1007/s00429-013-0679-3

Imke Kirste, Zeina Nicola, Golo Kronenberg, Tara L. Walker, Robert C. Liu, and Gerd Kempermann

Author information ► Article notes ► Copyright and License information ►

This article has been cited by other articles in PMC.

Go to:

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.

Neuroscience Reveals the Nourishing Benefits That Silence Has on Your Brain

I bet your doctor hasn't even come up with this simple stroke protocol in the 3 years since it came out. A fireable offense in my book, including the stroke department head and the hospital president. The contradictions between this and enriched environment will need to be answered by your doctor. Do not try silence on your own, that would be too dangerous unless your doctor has prescribed it. 

Neuroscience Reveals the Nourishing Benefits That Silence Has on Your Brain

When's the last time you sat in total, utter silence? While it's not easy to find true peace and quiet, there's now evidence you may want to find more opportunities to embrace noiselessness throughout your day.
We already know too much noise is not a good thing for our brains or our bodies. Research has linked noise pollution to increased blood pressure, sleep loss, and heart disease. These results have led to even more research on the long-term effects of noise. Along the way, almost by accident, scientists who study noise are uncovering benefits of its absence.
A recent piece in Nautilus explores in detail the positive effects that silence can have on our brains. Journalist Daniel A. Gross elaborates on several studies in which researchers set out to study the effects of various types of noise--such as music, short bursts of sound, and white noise--only to discover the silence in between the sounds they were studying produced interesting results. Here are a few gems this body of research has revealed.

Growth of new brain cells

In exposing groups of mice to a selection of sounds, Duke University regenerative biologist Imke Kirste was trying to see which one might spark the creation of new brain cells. She used silence as her control.
She found that two hours of silence a day produced new cell creation in the hippocampus, the main part of the brain associated with memory. In reviewing the results, Kirste concluded that silence could have been such a strange departure from the norm that it heightened the mice's alertness.
"We saw that silence is really helping the new generated cells to differentiate into neurons and integrate into the system," Kirste said.

Activation of your brain's memory

Even when the world around us is completely quiet, our brains are extremely adequate at filling in the silence. Take the example of listening to your favorite song, when it suddenly cuts out halfway through. If you know the song well, you'll continue to hear it play in your head.
By retrieving the memory of the song's music and lyrics, your brain is creating an illusion of sound. The Nautilus piece explains that this is because your brain's auditory cortex remains hard at work. Even if your ears are not being stimulated by external sounds, your brain always finds a way to muscle its way into staying active.

Encouragement of self-reflection

Without stimulation and distraction, your brain need not focus and goes into a default mode of sorts. That doesn't mean it completely turns off. Quite the opposite. Your brain at rest will sort and gather information. This is where the self-reflection comes in.
Auditory stimulation forces your brain to process sound and listen to what's going on around you. Without that external noise, your brain is forced to listen to what's going on inside of it.

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

I bet your doctor hasn't even come up with this simple stroke protocol in the 2.5 years since it came out. A fireable offense in my book, including the stroke department head and the hospital president. The contradictions between this and enriched environment will need to be answered by your doctor. Do not try silence on your own, that would be too dangerous unless your doctor has prescribed it. Is silence golden? 

Effects of auditory stimuli and their absence on adult hippocampal neurogenesis

From http://www.lifehack.org/377243/science-says-silence-much-more-important-our-brains-than-thought

Imke Kirste, Zeina Nicola, Golo Kronenberg, Tara L. Walker, Robert C. Liu, and Gerd Kempermann

Author information ► Article notes ► Copyright and License information ►

This article has been cited by other articles in PMC.

Go to:

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.

Keywords: Plasticity, Stem cells, Hippocampus, Mouse, Learning

Go to:

Introduction

Adult neurogenesis adds plasticity to the dentate gyrus of the hippocampus and is involved in key functions such as pattern separation (Aimone et al. 2010; Clelland et al. 2009) and avoidance of catastrophic interference (Appleby and Wiskott 2009; Wiskott et al. 2006) by adding flexibility to the network in situations where novel information has to be integrated into established representations (Garthe et al. 2009; Dupret et al. 2008). Adult neurogenesis is regulated by behavioral activity. Both physical activity and exposure to a challenging environment increase adult neurogenesis but do so by different means (Kronenberg et al. 2003). Non-specific stimuli like physical activity enhance the proliferation of precursor cells and lead to an increased potential in form of a larger pool of “neuroblasts” and immature neurons that can be recruited in case of a cognitive challenge. In contrast, exposure to an enriched environment promotes the survival of newborn neurons. Accordingly, the two interventions turned out to be additive in their effect (Fabel et al. 2009).

The new immature neurons own particular functionality in that they are more likely to generate action potentials in response to incoming stimuli due to their particular balance between excitatory and inhibitory input (Marin-Burgin et al. 2012). The threshold for LTP induction is reduced in these neurons (Schmidt-Hieber et al. 2004; Snyder et al. 2001). In fact, the LTP that is measurable in the dentate gyrus under physiological conditions is contributed by the newborn neurons during this critical period of their development (Garthe et al. 2009; Saxe et al. 2006). Thus, the immature new neurons are assumed to be more easily excitable than older cells, biasing the input towards the more plastic subpopulation of cells (Marin-Burgin et al. 2012). The hypothesis is that this mechanism allows flexible adaptation and learning of new information in previously established contexts. Non-specific stimuli would increase precursor cell proliferation to increase a pool of cells that can be recruited if cognitive demand arises (for detailed discussion see: Fabel et al. 2009).

The finding that exercise would have this effect on proliferation raised the question, whether other non-specific stimuli would also lead to an increased availability of potentially recruitable cells. Presumably, the intrinsic stimulus during physical activity essentially consists of proprioception and vision. Likewise, there are numerous reports on links between the vestibular system and hippocampal function [(Brandt et al. 2005); see Ref. Smith et al. (2010) for review] even though effects on adult neurogenesis have not yet been specifically addressed. In order to identify relevant sensory stimuli independent of locomotion, we here focused on auditory input as a potential signal to affect adult hippocampal neurogenesis.

Noise trauma with inner ear hair cell loss has led to a reduction of precursor cell proliferation in the hippocampus of rats (Kraus et al. 2010). A potential positive regulatory effect of sound on the early steps of adult hippocampal neurogenesis, however, has not yet been explored. We asked how different types of auditory stimuli would affect the baseline regulation of adult hippocampal neurogenesis (Fig. 1a).

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 ...

We used ambient noise in the animal facility (animal house noise) as baseline and exposed our mice to four different conditions: (1) white noise as unstructured auditory stimulus; (2) mouse pup calls as structured stimulus that is for mice common and relevant; (3) Mozart piano music as a structured stimulus, unknown and presumably irrelevant to mice; and (4) silence.

More at link.