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This paper
started showing the previous literatures compare ABR and ASSR and the
advantages and disadvantage of each one in frequency specificity, effect and modulation
frequency and, automatic detection. With brief description for both of them.

The first study:
is a retrospective study to compare c-ABR with ASSRs in estimating audiometric
threshold. Infants and children were tested using visual reinforcement
audiometry or play procedures to estimate behavioral thresholds. ABR thresholds
were determined using click stimuli and threshold was determined at the lowest
level at which an ABR was present. ASSR thresholds were determined using pure
tones and threshold was determined as the lowest stimulus level that met the
phase-locked response criterion. Results: show that both c-ABR and ASSR have strong and
statistically significant correlations with the pure-tone audiogram in infants
and children with various degrees of hearing loss. The pure tone-ABR
correlation was higher than ASSR at 1 and 2 kHz and, higher for ASSR at 500 Hz
compared to c-ABR. whereas at 4 kHz, the correlations were identical. The
discrepancy between behavioral and evoked potential threshold was generally
smaller for ASSR than for ABR, but the standard deviation of the difference was
essentially the same for both measures. Discussion: unlike previous
analyses of the study, the ABR data were also used, and at 1 and 2 kHz, the
pure tone-ABR correlation slightly exceeded those for the ASSR. This was
unexpected because it was thought that ASSRs, evoked by AM + FM tones, would
yield higher correlations with behavioral thresholds at the same frequencies.
However, several factors may contribute to these results including: synchronous
differences, the instantaneous rise time, frequency specificity, the response
detection methods used, the “test performance” (sensitivity and
specificity of response judgments) and, nature of pure tone test results.

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The second study:
a prospective study comparing ASSR and tb-ABR using and automatic detection
algorithm for threshold detection in normal-hearing adults. About visual
detection, seven stimulus levels were recorded and plotted in hardcopy for post
hoc judging. The presence or absence of responses is judged by reviewing all
responses. Threshold was judged to be the lowest stimulus level at which a wave
V was visually detected. About automatic detection, calculation of the Fsp and
PC2 was used to determine whether a response was present for ASSR
tests. Results: Thresholds
for 500 Hz were elevated relative to those for 4000 Hz, and all
thresholds were in accordance with previously published data. There are
Differences in thresholds as a function of test type (visually detected ABR,
Fsp detected ABR, ASSR at 41 Hz, and ASSR at 74 Hz) at 500 Hz. Discussion: this study showed that tone-ABR and
ASSR could both be used to estimate hearing threshold but that the stimulus
used (tone burst versus AM + FM tone) and detection method (algorithm versus
visual detection) affected the threshold determination.

and weaknesses:

-In this article
I learned that an audiologist can estimate audiometric thresholds using both
clinical instruments (ASSR and c-ABR). However, there are advantages using ASSR
over ABR and vice versa. –also, I learned that an audiologist can estimate
hearing threshold using different stimulus (tb-ABR or FM+AM ASSR) and can
detect responses either visually or objectively using algorithms. However different stimulus and detection
methods will affect the results.    

article provides information in a systematic way, enabling the reader to review
previous published studies and compare the results easily.-The results
of the studies are in a good agreement with some published studies and confirm
them.-The present studies investigated and highlighted the limitations
of some previous studies.-Results obtained were explained in details.

-The behavioral
thresholds included in the first study were all reliable.-This article compared
both ASSR and ABR thresholds with behavioral thresholds unlike the previous
studies which compare behavioral thresholds with only one electrophysiological

Limitations: -I
can notice that the selection criteria (sampling procedure) of the first study
affect the results.-Gender of participants in first study were not specified. -In
the first study they didn’t investigate the correlation between behavioral
thresholds and electrophysiological thresholds in more profound cases so,
further investigations are needed. -They didn’t mention the reliability of the
electrophysiological thresholds.-ASSR considered as a new clinical
method so that audiologists are not familiar with yet. However, this article is
published in 2002, nowadays most of audiologists are familiar with the ASSR.

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