Suppression of the P(b) (P(1)) component of the auditory middle latency response with contralateral masking.
OBJECTIVE
In this study, the effects of contralateral noise or speech on middle latency response (MLR) components P(a) and P(b) (P(1) or P50) were studied using high rates clicks in normal hearing awake adult subjects.


METHODS
One standard (4.88 Hz) and four jittered click sequences (24.4, 39.1, 58.6, 78.1 Hz) at different mean rates were monaurally presented to ten subjects. The contralateral ears were stimulated with continuous pink noise, recorded speech or no stimulus for control. Overlapping MLR responses to jittered click stimuli were deconvolved using the frequency domain continuous loop averaging deconvolution (CLAD).


RESULTS
The recordings show that contralateral noise or speech stimulation suppresses P(b) component greatly at rates around 40 Hz while earlier components (ABR and P(a)) are not significantly affected. The suppression of the P(b) component is about 50% with some latency reduction.


CONCLUSIONS
The results show that the P(b) component of the MLR is significantly affected by contralateral stimulus at resonance rates at around 40 Hz. It appears that the contralateral noise obliterates the amplitude enlargement due to resonance effect.


CONCLUSIONS
These findings show that the P(b) is generated very differently from the P(a) component and strongly inhibited by the contralateral ear. These results also explain the previously observed masking of the 40 Hz auditory steady-state responses (ASSR) with contralateral noise.
Özdamar
Özcan
Ö
Department of Biomedical Engineering, University of Miami, P.O. Box 248294, Coral Gables, FL 33124, USA; Departments of Otolaryngology, Pediatrics and Neuroscience, School of Medicine, University of Miami, Miami, FL, USA. Electronic address: oozdamar@miami.edu.
Bohórquez
Jorge
J
Department of Biomedical Engineering, University of Miami, P.O. Box 248294, Coral Gables, FL 33124, USA.
D000161:Acoustic Stimulation; D000328:Adult; D000704:Analysis of Variance; D004307:Dose-Response Relationship, Radiation; D004569:Electroencephalography / Q000379:methods; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009622:Noise; D010470:Perceptual Masking / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D013997:Time Factors