Morphological changes in the middle latency response using maximum length sequence stimuli.
BACKGROUND
The middle latency response (MLR) can be a powerful tool for assessing integrity of cortical and subcortical auditory structures. Most research on the MLR, however, is constrained to relatively slow repetition rates by the time window necessary for response acquisition. Maximum length sequence (MLS) paradigms enable the recording of the MLR at high repetition rates, which could reduce test time and provide information about the behavior of auditory structures at rapid rates of stimulation.


OBJECTIVE
To examine potential timing advantages and differences in waveforms between an MLS-MLR paradigm compared to a conventional MLR paradigm (Experiment 1), and to examine effects of rate on MLR morphology within the MLS paradigm (Experiment 2).


METHODS
A repeated measures study. All subjects within each experiment underwent every condition for that experiment.


METHODS
Ten young adult female subjects participated in each experiment of this study. All subjects had normal hearing and negative neurological history.


METHODS
Latency and amplitude values as well as the presence/absence of Na, Pa, Nb, and Pb components of the MLR were measured. Comparisons were made between the MLS-MLR and conventional MLR paradigms, as well as between repetition rates within the MLS-MLR paradigm.


RESULTS
Significant latency and amplitude differences were found between MLS and conventional MLR paradigms. The late components of the MLR (Nb, Pb) were present significantly more often when the MLS paradigm was used. No timing advantage was found with the MLS-MLR paradigm. Within the MLS paradigm, as repetition rate increases, latency becomes significantly shorter and amplitude significantly lower.


CONCLUSIONS
Middle latency responses evoked by the MLS-MLR paradigm show significant differences from those evoked by a conventional MLR paradigm. The MLS-MLR paradigm can reliably evoke the late components (Nb, Pb) of the MLR and may be an important clinical tool for future investigation of these elements.
Nagle
Stephanie
S
University of Connecticut, Department of Communication Disorders, Neuroaudiology Lab, 850 Bolton Road, Unit 1085, Storrs, CT 06269, USA. Stephanie.nagle@Uconn.edu
Musiek
Frank E
FE
D000161:Acoustic Stimulation; D000328:Adult; D001300:Audiometry, Evoked Response / Q000379:methods*; D001303:Auditory Cortex / Q000502:physiology*; D001309:Auditory Threshold / Q000502:physiology*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006309:Hearing / Q000502:physiology*; D006801:Humans; D011930:Reaction Time / Q000502:physiology*; D015203:Reproducibility of Results; D055815:Young Adult