Mode of recording and modulation frequency effects of auditory steady state response thresholds.
BACKGROUND
The performance of auditory steady state response (ASSR) in threshold testing when recorded ipsilaterally and contralaterally, as well as at low and high modulation frequencies (MFs), has not been systematically studied.


OBJECTIVE
To verify the influences of mode of recording (ipsilateral vs. contralateral) and modulation frequency (40Hz vs. 90Hz) on ASSR thresholds.


METHODS
Fifteen female and 14 male subjects (aged 18-30 years) with normal hearing bilaterally were studied. Narrow-band CE-chirp®stimuli (centerd at 500, 1000, 2000, and 4000Hz) modulated at 40 and 90Hz MFs were presented to the participants' right ear. The ASSR thresholds were then recorded at each test frequency in both ipsilateral and contralateral channels.


RESULTS
Due to pronounced interaction effects between mode of recording and MF (p<0.05 by two-way repeated measures ANOVA), mean ASSR thresholds were then compared among four conditions (ipsi-40Hz, ipsi-90Hz, contra-40Hz, and contra-90Hz) using one-way repeated measures ANOVA. At the 500 and 1000Hz test frequencies, contra-40Hz condition produced the lowest mean ASSR thresholds. In contrast, at high frequencies (2000 and 4000Hz), ipsi-90Hz condition revealed the lowest mean ASSR thresholds. At most test frequencies, contra-90Hz produced the highest mean ASSR thresholds.


CONCLUSIONS
Based on the findings, the present study recommends two different protocols for an optimum threshold testing with ASSR, at least when testing young adults. This includes the use of contra-40Hz recording mode due to its promising performance in hearing threshold estimation.
Universiti Sains Malaysia, School of Health Sciences, Audiology Programme, Kelantan, Malaysia; Iran University of Medical Sciences, Department of Audiology, Tehran, Iran. Electronic address: mojtajal@gmail.com.
Bahram
B
Jalaei
University of Social Welfare and Rehabilitation Sciences, Department of Audiology, Tehran, Iran.
Moslem
M
Shaabani
Universiti Sains Malaysia, School of Health Sciences, Audiology Programme, Kelantan, Malaysia.
Mohd Normani
MN
Zakaria
D000161:Acoustic Stimulation / Q000379:methods*; D000293:Adolescent; D000328:Adult; D001309:Auditory Threshold / Q000502:physiology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D012016:Reference Values; D055815:Young Adult
Auditory steady state response; Contralateral recording; Hearing threshold; Ipsilateral recording; Limiar auditivo; Registro contralateral; Registro ipsilateral; Resposta auditiva de estado estável