The transient-evoked potential-analysis approach provides a broadly accepted way to identify and measure component auditory evoked potentials (AEPs). However, for purposes of looking across normal brain development/aging, there is a need for a paradigm shift toward a process that objectifies AEP interpretation. Toward this goal, a shift toward a more analytical method to the evoked response has been developed from the use of a steady-state-analysis approach, which potentially provides a more analytical and objective approach and whose advantages may well serve such interests as tracking aging changes and/or effects of brain injury, that is- if the approach is extended to incorporate a more comprehensive representation of the AEP component waves. This new method has been applied, and findings in young children and adults demonstrate efficacy of the method, namely in a unified test and analysis, rather than several different transient tests with response identification and measurement more-or-less idiosyncratic to each component test. The proposed study builds logically on this previous research, and serves as a backdrop to explore this unified test and analysis across the adult lifespan (i.e., three age groups). Steady-state response amplitudes will be assessed over a wide range of stimulus repetition rates embracing the traditionally measured transient AEPs. Of particular interest are ASSRs dominated by activity from the auditory cortices (<20 Hz) and the age- dependent distribution and spectral patterns at three midline, two lateral and two temporal electrodes. In addition, steady-state recording parameters and subject-related characteristics will be examined to determine if they behave similarly to their transient-AEP counterparts.
The effect of sound rate on hearing responses will be assessed in individuals ranging from 20 to 79 years of age. The proposed study builds logically on previous research, and serves as a backdrop to explore a new analysis approach. Electrical responses produced by the auditory system will be measured from a small microphone in the ear canal and from small disks located in a Lycra cap on the head. Responses to tones will be assessed at different pitches, volumes, and at the different rates at which they are presented.