Figure 1.

ECochG waveform and energy spectra characteristics of CI subjects. All stimuli were presented at 90 dB nHL.

A. ECochG response and to 500 Hz and the corresponding FFT spectrum. Red portion of the waveform at the onset of the response indicates a CAP. Blue portion within the blue background indicates the ongoing, or steady-state portion of the ECochG response containing the CM and ANN. The red circles in the spectrum indicate the level required for the peaks to be significant (see Methods).

B. ECochG recordings with increasing evidence of neural activity in the form of CAP and ANN. From top to bottom panel the visually apparent magnitudes of CAP and ANN increase resulting in a higher scores noted on the left of the panels.

(Left) The ANN was determined using the ‘average cycle’ to low frequency tones. The average cycle is the average of all cycles in the ongoing portion of the response, as in the blue box in A. The responses shown are to different cases, and were to 500 (top two and bottom tracing), 750 (third from top), and 250 Hz (fourth and fifth from top). The degree that the average cycle deviated from the best-fit sinusoid (red dashed line) was used to determine the score for the ANN.

(Right) The CAP was most apparent in the sum of the responses to alternating phase stimuli (blue lines). The score for the CAP is given at the left. The top and the bottom two panels are responses to 2000 Hz tone bursts, and the third and fourth panels are the responses to 500 Hz tone bursts.