In 1974 one of the first major symposia on auditory processing took place at the University of Nebraska Medical Center by and was organized by Marsha Sullivan. The proceedings of this conference was published a year later. Though this meeting was relatively early in the history of CAPD, there were many important ideas and concepts critical to our understanding of this emerging discipline. Fortunately, some of these understandings have been mainstays of practice and research but unfortunately some have been forgotten. Therefore, a cursory review of some of the key presentations seemed appropriate for this issue of Pathways.
The first presentation was by Charles Speaks on dichotic listening. Using newly developed synthetic sentences and at that time, the then popular consonant- vowels (CVs) test. These sentences were designed to reduce linguistic cues making the test more purely “auditory”. An example of a synthetic sentence is: A SMALL BOAT WITH A PICTURE HAS BECOME. Speaks presentation solidified the concept of the contralateral ear effect. He also introduced the theory of dichotic interference. This was when the stimulus in the strong ear interfered with perception in the weak or poorer ear hence the reason for the reduced performance in that ear. Another speaker was Chuck Berlin who at that time was heavy into dichotic research. He relayed several principles related to dichotic listening. (1) In normal participants their performance for listening to one channel to one ear at a time, was better than listening in the dichotic mode. (2) In dichotic listening the right ear performs better than the left. (3) In temporal lobectomies, as the poorer ear declines in performance, the better ear improves. Berlin also addressed several fundamental aspects of dichotic listening such as the influence of intensity and temporal alignment on performance. If the intensity is not essentially equal in both ears the ear receiving the greater intensity will perform better (tangential to hearing loss). The onsets of dichotic stimuli should be highly similar—if not, the task becomes easier and the lagged ear will perform better. —- For these and other details of Berlin’s critical early work see (Berlin & Cullen. 1975; Berlin et al., 1974).
George Lynn and John Gilroy an audiologist and neurologist respectively, reported some important site of lesion information.in this symposium. Using filtered speech and dichotic tests these authors reported key trends. Patients with lesions in the posterior temporal lobe performed more poorly than those with lesions in the frontal lobe, anterior temporal lobe and parietal lobe. Though those with deep parietal lobe lesions often showed left ear deficits (likely corpus callosum involvement). This early data was of critical importance as it showed the differential capability of central auditory tests. That is when the auditory areas are involved the tests yield low scores compared to involvement of other (non-auditory) areas of the brain.
By 1974 Jack Katz’s SSW test had been in use for over 10 years and at this conference he reported on some data that he had been collecting for some time. Interestingly by acquiring data in competing and non-competing conditions, his data supported Berlin’s principle of listening dichotically is more difficult than monaural listening to one channel. Katz’s competing condition (dichotic) yielded scores consistently lower than non-competing conditions in his data on control or normal participants. Katz reported on patients with cerebral lesions with the SSW yielding decreased scores in the competing condition in the ear contralateral to the lesioned hemisphere. Katz also commented on the interpretation of reversals and other permutations of SSW patterns.
Perhaps one of the most unique and novel presentations at this conference was by Donnell Johns. Johns introduced auditory evoked potentials as a possible use in defining central auditory processing deficits. This speaker focused on the N1 and P2 responses. Johns was, at this stage, concerned about the variability of these responses in normal adult subjects. He conceded that the N1 and P2 yielded variability on the waveform morphology but that other measures such as latency and amplitude could be refined enough to be potentially useful in central auditory disorders. Johns showed some interesting data on evoked potentials derived from stutterers and controls back up his view of possible applications of evoked potentials.
Other speakers spoke on a variety of topics. The emphasis, however, was clearly on adult participants with lesions that affected the central auditory nervous system. The presentations were in concert with the clinical research started by Bocca and his colleagues in Italy in the 1950s. Interestingly, there no presentations on children, but in couple years later another symposium on CAPD headed by Bob Keith, would focus on Jack Willeford’s and Marilyn Pinheiro’s pediatric presentations.
Sullivan, M. (Ed.) (1975) Proceedings of a Symposium on Central Auditory Processing Disorders, University of Nebraska Medical Center, May, 1974
Cullen, J. K., Jr., Thonpson, C-L-, & Samson, D. S. The effects of varied acoustic parameters on performance in dichotlc speech perception tasks. Brain and Language, 1974, 1, 307-322
Berlin, C. I. & Cullen, J. K. Acoustic problems in dichotic listening tasks. In C. I. Berlin (Ed.), Brainand language development:acoustic problems in dichotic listening tasks. New York: Academic Press, 1975