Subject: Re: pitch neurons From: Martin Braun <nombraun(at)POST.NETLINK.SE> Date: Tue, 8 Oct 2002 11:40:00 +0200Israel Nelken asked: > why is there such a pressure > to assume low-level representation (i.e. subcortical) of pitch? Dear Eli and List, the reason why physiological research focused on the exploration of subcortical mechanisms when looking for the pitch detector simply was that psychoacoustic data demanded a spectrotemporal mechanism. This ruled out the auditory cortex, because phase-coupling to pitch-relevant harmonics does not occur there. The highest level where it occurs is the auditory midbrain. During the past 15 years all necessary elements for pitch extraction have been found in the auditory midbrain (inferior colliculus, in the upper brainstem). Arrays of best-pitch neurons filter out the pitch frequency of complex sound signals, in the same way as arrays of best-frequency hair cells filter out spectral frequencies in the cochlea. Whereas the tuning properties of hair cells in the cochlea are mechanical and electrical, the tuning properties of pitch neurons are purely electrical. These neurons have tuned membrane potential oscillations, which are either intrinsic, due to unit-specific distribution of membrane channel types, or imported from input neurons. This last question is still an open one. 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