Subject: Auditory stimulation for fMRI From: Leon Deouell <deouell(at)SOCRATES.BERKELEY.EDU> Date: Thu, 26 Oct 2000 15:44:14 -0700I am working with the group of Erv Hafter in UC Berkeley, trying to figure out what the state-of-the art is for auditory stimulus delivery in functional MRI experiments. As we see it, the requirements of such a system would be at least : 1. To provide attenuation of the scanner noise so as a) to defend the subject's hearing from being damaged by the scanner noise, which can get, apparently, higher that 135dB at 3Tesla (we intend to use 4T) and b) to minimize the masking of the stimuli by the scanner noise 2. Having a flat (ideally) or predictable frequency response over the widest range of frequencies possible, or at least in the speech range 3. Having a reliable inter-aural balance, that will allow manipulations of inter-aural parameters. 4. Being compatible with the magnetic field requirements so that as little disruption of the MR signal will occur The major questions are: Air tube vs. Electrostatic/ Piezoelectric earphones. Any one of the above - what make? Are there any good on the shelf products? Regarding electrostatic earphones we know that the group from IHR in Nottingham has modified a set of Senheiser earphones to the degree that (if we correctly understand) they can be used without earplugs. There is an extensive description of their system in http://www.ihr.mrc.ac.uk/caf/caf.shtml There are also KOSS Earphones that are apparently MR compatible which the group in Wisconsin helped modifying (Model 'medical ESP 900' ). The KOSS company sales person told me that they sold about 20 of those and that some modification was needed by the user to make it really usable in MRI studies. He could not say what these modifications were - we would appreciate any tip on this. It also seems that these headphones need to used together with earplugs. What is the experience with these systems? Are there any major solution that we missed? Leon Deouell ----------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------- Dr. Leon Y Deouell, M.D. IPSR Department of Psychology 4143 Tolman Hall #5050 University of California Berkeley, CA 94720-5050 Tel: (510) 6439744 Fax:(510) 6421196 e-mail: deouell(at)socrates.berkeley.edu