TEMPORAL PATTERN-DISCRIMINATION AND SPEECH RECOGNITION UNDER ELECTRICAL-STIMULATION

Discrimination of temporal patterns has been suggested as a relevant p rocess in speech recognition by subjects with normal hearing [Sorkin, J. Acoust. Soc. Am. 87, 1695-1701 (1990)]. This paper investigates whe ther performance of Nucleus multichannel cochlear implant subjects on a temporal pattern discrimination task is an efficient and valid psych ophysical measure of speech recognition ability. Stimuli consisted of temporal sequences defined by twelve 35-ms tones and eleven randomly g enerated temporal gaps separating the tones. A fixed-level same/differ ent paradigm was used to measure the discriminability of these sequenc es as a function of their average correlation across a block of trials . On each trial, the ''standard'' sequence was generated randomly by d rawing gap durations from a Gaussian distribution. The gaps of the com parison sequence were generated in a similar fashion with a specified average correlation with the gaps of the first sequence. Performance o f implanted and normal hearing subjects decreased monotonically with i ncreasing average sequence correlation. However, performance across im planted subjects ranged from that observed for acoustically stimulated subjects with audiometrically normal hearing to levels near chance. C omparing these data with measures of speech recognition in the same su bjects, we have found that performance on standard speech recognition tests correlates with ability to discriminate among such random tempor al patterns.