الفهرس 
Psychophysics of the Auditory PathwayOnly 14 pages are availabe for public view
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Abstract
Auditory Brainstem Response (ABR) provides an
objective measure of hearing threshold in neonates and children, allowing appropriate intervention
if auditory sensitivity is impaired. When ABR waves are absent at high intensity levels, it is
usually associated with severe or profound hearing loss (Cohen and Rapin, 1978).
Paradoxically, some authors reported cases with totally absent ABR waves inspite of the presence of
mild or moderate degree of hearing loss m
· radiologically-free patients (Davis and Hirch, 1979;
Worthington and Peter, 1980 and Lenhardt, 1981).
In a more recent study, Soliman (1987) reported on 11 patients with mild hearing loss, mostly low
frequency m configuration, with poor speech discrimination out of proportion to the hearing loss
together with highly distorted ABRs. This audiological profile was termed ”Low Frequency
Sensori-Neural Hearing Loss Syndrome”. The author recommended further research in order to identify
the exact site of lesion and the specific etiological factor(s) causing this low frequency hearing
disorder
Recently, there has been an increasing body of
literature demonstrating similar audiological profile for which the name ”Auditory Neuropathy”
was coined (Starr et al., 1996). There is now a well established criteria for auditory neuropathy
which are hearing loss for pure tones, impaired word discrimination out of proportion to pure tone
loss, absent or abnormal Auditory Brainstem Response (ABR) and normal outer hair cell function as
measured by Otoacoustic Emissions (OAEs) and Cochlear Microphonics (CM) (Sininger et al., 1997;
Doyle et al., 1998 and Deltenre et al., 1999).
The exact site(s) oflesion and nature of pathology in AN patients is no yet known. The site of the
disorder is likely to be in the eighth nerve or at the synapse between the hair cells and the
eight nerve. The synapses at the inner hair cell (IHC) rather than that at the outer hair cell
(OHC) were likely to be affected (Starr et al., 1991; Starr et al., 1996,; Berlin et al., 1999;
Deltenre et al., 1999 and Rance et al., 1999)..
In an attempt to explore the underlying pathology and the possible site of lesion in such
disorder, Starr et al., (1991) examined one patient using a long battery of psychophysical
tests which
. quantified perception of acoustic signals based on frequency, intensity and
temporal cues. Results suggested that, in such patient, the prominent finding
was affection of the temporal auditory features. Taking
into consideration that such a finding was based on
evaluation of only one subject, more research studies
are needed to address the underlying issues of such
auditory affection.
Accordingly, this study is conducted to evaluate
· the psychophysical auditory abilities in a larger
population of auditory neuropathy patients.