This study investigated the effect of intensity on pitch in electric hearing and its relationship to the speech perception ability of cochlear implantees. Subjects were 13 adult users of the Nucleus 22 cochlear implant system, using either the Spectra22 or ESPrit22 speech processor and the SPEAK speech processing strategy. A multidimensional scaling technique was employed. Speech perception was measured using sentences and vowels. All measurements were performed in a soundfield condition, and subjects wore their own speech processors with their normally used settings. Results showed a significant correlation between the degree of deviation of the subjects' stimulus spaces from the "ideal" space and subjects' performance with the sentences, but not with the vowels. A significant correlation was found between subjects' response variability in performing the multidimensional scaling task and their speech perception measures, suggesting that spectral smearing or underlying cognitive abilities might affect implantees' speech perception performance.
Cognitive impairment has been reported to occur in minor head injury (concussion). The value of the P300 evoked potential as a measure of cerebral concussion was studied in 20 patients with minor head injury and compared with the data from 20 normal subjects. Significant abnormalities of the P300 latency and amplitude were noted in these patients in the post-concussion period. The abnormalities improved completely on repeat testing. The correlation of the P300 to other parameters of head injury is discussed. The P300 constitutes a simple laboratory test that is sensitive measure of cerebral dysfunction in concussive head injuries.