Subject: Re: Rationale for Critical Bands From: Martin Braun <nombraun@xxxxxxxx> Date: Tue, 15 Jun 2010 16:16:48 +0200 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Dear Peter, and list, it looks we can learn a lot from your two references. As to your question if we could adapt to something like 1 critical bands (CB) per octave, I would say no. The number of around 4 CBs per octave in the most important hearing range that humans and cats have, and probably also rats and mice, appears to be a kind of optimum adaptation. More CBs would not add significantly to spectral integration, such as pitch synthesis. Less CBs would weaken the basis for spectral integration. As to neural plasticity, it is more probable to occur within a neural lamina, and between adjacent laminae, than across several laminae. The brain has a great capability to invest into improved spectral filtering, as we see in musicians. But there are also anatomical limits. To shift the number of CBs per octave by training does not seem realistic at all. Martin --------------------------------------------------------------------- Martin Braun Neuroscience of Music S-671 95 Klässbol Sweden email: nombraun@xxxxxxxx web site: http://www.neuroscience-of-music.se/index.htm ----- Original Message ----- From: "Peter Meijer" <feedback@xxxxxxxx> To: <AUDITORY@xxxxxxxx> Sent: Tuesday, June 15, 2010 8:58 AM Subject: Re: Rationale for Critical Bands > Thank you for these very interesting references, Martin. > > To the extent that critical bands find their origin in the ICC, one could > conjecture that critical bands may be subject to (some) neural plasticity. > Are there any studies with, say, young animals to see if the distribution > of critical bands can be modified through suitable exposure and training > with sounds, e.g., aimed at narrowing the critical bands? Natural settings > for critical bands would likely already be "optimal" in some sense for > natural sounds, but it would be interesting to know if adaptation is > possible > in (artificial) situations where an optimal setting would be different. > Perhaps even a dynamic modulation of critical bands depending on momentary > needs would be possible in cases where that serves the optimality > condition. > > A quick web search turns up references like > > http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2474628/ > http://jn.physiology.org/cgi/content/full/93/1/71 > > The second of these two references does seem to get close to addressing my > question, but I'm not sure if it is the most representative example. I am > personally most interested in possible effects of plasticity with complex > sounds that are non-harmonic, with close to 20 tones - or more - per > octave > in a log distribution. Standard critical bands cause a within-band > temporal > "roughness" that might play a role in guiding effects of plasticity for a > better spectral envelope discrimination with complex sounds, but I am not > aware of much literature on this so would appreciate to learn more about > it. > > Thanks and best regards, > > Peter Meijer > > > Seeing with Sound - The vOICe > http://www.seeingwithsound.com > >> Date: Mon, 14 Jun 2010 15:12:16 +0200 >> From: Martin Braun<nombraun@xxxxxxxx> >> Subject: Re: Rationale for Critical Bands >> >> Dear Dan, and list, >> >> You are quite right. The level independence of the critical bandwidths >> (C= >> B)=20 >> over wide sound level ranges excludes an origin in the cochlea. >> >> There are compelling data indicating that the origin is in the central=20 >> nucleus of the inferior colliculus (ICC). >> >> http://www.ncbi.nlm.nih.gov/pubmed/3975613 >> >> http://www.ncbi.nlm.nih.gov/pubmed/7677631 >> >> http://www.ncbi.nlm.nih.gov/pubmed/9237756 >> >> http://www.ncbi.nlm.nih.gov/pubmed/10190753 >> >> http://www.ncbi.nlm.nih.gov/pubmed/10867285 >> >> Enjoy, >> >> Martin