Changes in lymphocyte subsets in the intestine and mesenteric lymph nodes in caprine paratuberculosis

In five normally hearing subjects and seven subjects with damaged cochleas, detection thresholds for sinusoidal frequency modulation (FM) and amplitude modulation (AM) were measured using 1 s stimuli with a 500 Hz carrier frequency (Fc) at a 'comfortable' loudness (given by subject-dependent SPLs and SLs). The modulation frequency (Fmod) was 2 Hz or 10 Hz. FM (but not AM) detection was poorer in the hearing-impaired group, especially when the hearing loss at Fc exceeded 50 dB. Fmod had a different effect on FM and AM detection. The corresponding interaction was essentially identical for the two groups of subjects. Previous studies strongly suggested that normal listeners use mainly neural phase-locking cues for the detection of FM when Fmod = 2 Hz, but mainly tonotopic cues when Fmod = 10 Hz. The present results suggest that cochlear damages reduce the usefulness of these two types of cues to an approximately equal degree.