Frequency Patterns in Cochlear, Brainstem, and Cerebral Lesions: Reconnaissance mélodique dans les lésions cochléaires, bulbaires et corticales

Implications of blast exposure for central auditory function: A review

“…The involvement of multiple cortical areas is consistent with Musiek and Pinheiro's hypothesis that good performance on this task requires not only the effective processing of frequency at the level of the cochlea and the brainstem but also the faithful transmission of this information to the primary auditory cortex for coding as a series of discrete auditory objects with unique frequency content [39]. The task does not end there, however, since the subject must identify the order in which three tones differing in frequency have been presented (i.e., "lowlow-high" or "low-high-low").…”

“…No participant had more than a mild peripheral hearing loss, and most had normal hearing. Five behavioral tests were administered to the participants: the Dichotic Digits test [61], the Staggered Spondaic Words test [62], the Gapsin-Noise test [63], the Masking Level Difference test [64], and the Frequency Patterns test [39]. Each test has been used in the general population in the diagnosis of central auditory dysfunction and has been shown to discriminate between participants with brain injuries and control participants of similar age and peripheral hearing status without brain injury.…”

“…On the other hand, the frequencies used in the test are so different from each other (880 Hz and 1,122 Hz) that even a distorted representation might still be identified accurately, as Musiek and Pinheiro reported for their subjects with hearing impairment [39]. Despite the high probability that such a group would have substantially increased pitch discrimination thresholds [37], only 12 percent of Musiek and Pinheiro's cochlear hearing loss group actually had difficulty identifying the patterns.…”

“…While Musiek and Pinheiro showed that brainstem lesions are associated with an increased chance of making errors in a test of frequency-pattern identification (45% of subjects with brainstem lesions as compared with 12% of those with cochlear hearing loss but no brainstem or cortical dysfunction) [39], the strongest relationship was found in subjects with cortical lesions, where 89 percent of the patients tested made errors on 25 percent or more of the identification trials. The distributed nature of the information needed to perform this task is indicated by the diversity of cortical lesions exhibited by the patients who performed poorly in Musiek and Pinheiro's study [39]. Not only were there patients with temporal lobe lesions in one or both hemispheres, but there were subjects with frontal and/or parietal lobe lesions with damage to the insular cortex.…”

“…This dichotomy suggests that the right hemisphere would perform the sequencing task and the left hemisphere would be involved in the verbal response. Such transfer of information would require intact communication between the hemispheres as well, implicating an important role for the corpus callosum [39].…”