Early Hearing-Impairment Results in Crossmodal Reorganization of Ferret Core Auditory Cortex
Figure 1
Auditory brainstem response (ABR) data for ferrets with early hearing loss (a–c) or normal hearing (d). For each panel, the auditory stimulus was a calibrated click (90 dB SPL; 0.1 ms square-wave click, rarefaction), delivered through a speaker positioned directly in front of one ear (RE = right; LE = left). Each waveform represents the average of 2000 trials; overlapped dual waveforms indicate that the test was repeated. Scale, indicated in panel (a), is the same for each panel. As evidenced by comparison of panels “a–c” with that of the hearing control in (d), all ferrets with early hearing loss demonstrated profoundly reduced ABRs to 90 dB SPL stimuli. However, some residual auditory response was apparent in each of the treated animals, as demonstrated by the small but repeatable peaks at approximately 3 ms latency. Further tests (not depicted) indicated that hearing thresholds for the treated animals ranged from 65 to 85 dB SPL (see Table 1).
