The following points were presented and discussed at a press
conference on January 21, 1998.
Topic of press conference
The Functional Neuroanatomy of Tinnitus
Published in Neurology, January 1998.
A copy of the paper in the pdf format can be downloaded by
clicking on the link above (1.6 Mbyte pdf).
Who performed the study
Alan H. Lockwood, Richard J. Salvi, Mary Lou Coad, Mary Towsley,
David Wack, Brian Murphy
Where was it done
VA Western New York Healthcare System and SUNY, University
at Buffalo Centers for PET and Hearing Research Laboratory, Departments
of Neurology, Nuclear Medicine, and Communicative Disorders and
Sciences.
The problem
Tinnitus, the false perception of sound in the absence of an external stimulus, is a chronic condition affecting millions of adults.
There is no satisfactory treatment.
What we did
1. Hypothesis: changes in tinnitus loudness would be associated with changes in neural activity.
2. We mapped neural activity by measuring the rate blood flows
to specific brain regions using positron emission tomography (PET)
as the loudness of tinnitus changed and also when we stimulated
the auditory system with real sounds.
What we found
1. The spontaneous neural activity associated with tinnitus perceived in the right ear is localized to the auditory cortical regions in the left temporal lobe.
2. Tones played in just one ear activate the cochlea on that side and auditory cortical regions bilaterally. Since unilateral tinnitus is associated with unilateral activation, the phantom sounds of tinnitus do not come from the cochlea.
3. Tones played into one ear of tinnitus patients activate much more extensive portions of the auditory cortex than they do in normal subjects. Thus, there have been plastic transformations of the auditory system in tinnitus patients.
4. There are abnormal connections to the limbic system (an
emotion control center) in tinnitus patients that are not found
in normal subjects. This may be the means by which tinnitus causes
psychological symptoms.
Why were we successful
1. We used subjects who could control the loudness of their tinnitus and serve as their own controls.
2. We used PET.
3. We used sophisticated computer programs for image processing and statistical analysis.
Significance
1. Understanding the physiological basis of tinnitus is an important first step in the development of a scientifically-based search for a cure.
2. Data provide new insights into the development of tinnitus. Tinnitus may be due to the nature and extent of the plastic changes in the auditory system that develop as a consequence of hearing loss. Tinnitus may be the auditory system analog of phantom limb pain, now known to be associated with plastic changes in somatosensory systems.
Who provided grant support
SUNY, University at Buffalo, American Tinnitus Association
(Portland, OR), James H. Cummings Foundation, Inc. (Buffalo, NY),
National Institute on Deafness and other Communication Disorders.
For your convenience, we have enclosed electronic copies of
figures related to our tinnitus research. They are not copyrighted,
but if you use them, we would appreciate an acknowledgment of
their source.
The files were prepared in a Windows 95 format created for an IBM clone computer.
1. tinnitus activation (tinact.JPG)
contains surface rendering of neural sites that mediate tinnitus (red-yellow on brain image) and projections of active sites on cross sections of brain. The major site in the auditory cortex of the temporal lobe is referable to tinnitus. Other sites are referable to associated motor activity (jaw clench).
2. cochlear stimulation (cstim.JPG)
Contains surface rendering and cross sections of brain that depict sites activated by 2000 Hz tones played into the right ear only. Note bilateral activation when listening to real tones compared to unilateral activation due to the phantom sounds of tinnitus. This is evidence that tinnitus in these patients is not of cochlear origin.
3. abnormal tone activation in patients (toneact.JPG)
Contains surface rendering and cross sections of brain showing where tones played in right ear activates brain of tinnitus patients with sensorineural hearing loss but does not activate brain of normal subjects. This demonstrates plastic transformation of auditory circuits in these patients.
4. tinprev.JPEG
Contains graph of prevalence of tinnitus at various ages in bitmap format.
Contains graph of prevalence of impaired hearing at various ages in bitmap format.
