Subject: Re: Pitch orientation-discriminating feature detectors? From: Martin Braun <nombraun(at)POST.NETLINK.SE> Date: Wed, 25 Sep 2002 12:58:29 +0200Daniel Pressnitzer wrote: > The next question is of course why would it be useful in the real > world to process differently upward vs. downward frequency > movements... Thanks, Daniel, for introducing this question to the thread. It's a highly interesting one. Before coming to the biological background, let me start with a short musical introduction. For some strange reasons, frequency sweeps had been banned almost totally from classical European music. This has changed in recent decades, and people like Yannis Xenakis have written most fascinating pieces where frequency sweeps (musicians call them glissandi) are quite dominant. In other musical cultures these techniques have a much longer tradition, like in Japanese flute und string music. Several years ago I did some engineering on musical wind instruments that can produce slides. The only wind instrument in classical European music which can do this is the trombone. So I developed, and let build, a slide flute in the same size as the common concert flute. After that I also developed a slide bassoon. Recently I saw, and heard, in a professional Swedish Jazz band a guitar-like zither that was plucked with one hand while sliding a steel hand over the strings with the other hand. A most sophisticated instrument. Nothing like the old Hawaii guitar. In short, I have some experience how frequency sweeps sound like. The difference between rising and falling pitch sweeps is striking. Upwards raises tension, even alarm. Downwards evokes relaxation. Now to the biology. In the vocalization of probably all mammals we have more slides than steady states. Upslide is associated with an increased lung pressure, and downslide with a decreased one. Further, increased lung pressure and upslides are associated with the animal's excitation, the reverse with its relaxation. Therefore the former is a sign of alarm, the latter a sign of calm. Perhaps we should also remember our police car and air raid signals. The terrifying parts are the upslides. No wonder at all, that there are plenty of neurons that respond direction-specific to frequency modulation. Martin ------------------------------------------- Martin Braun Neuroscience of Music S-671 95 Klässbol Sweden e-mail: nombraun(at)post.netlink.se web site: http://hem.netlink.se/~sbe29751/home.htm