[Speech comprehension by patients with Alzheimer disease. Possibilities for improvement]

Ten patients with the Alzheimer's disease and a mild hearing loss were tested with an audiotape with speech discrimination tests. The low frequency sounds on this audiotape had a delay of respectively 1, 2, 3 and 4 milliseconds with regard to the high frequency sounds. With a delay of 3 milliseconds the patients had a significant improvement in their speech understanding compared to the normal speech discrimination test. Patients with the Alzheimer's disease have a significant loss of haircells in the basal turn of the cochlea. This loss disturbs the function of the traveling wave of sound vibration in the basilar membrane of the cochlea. The traveling wave has no inhibition on its way through this disturbed basilar membrane. When the effect of the too fast running traveling wave was compensated by presenting the above-mentioned tape, the improvement of the speech intelligibility was significant.