Long-term effects of focal, cortical injuries upon articulation and discrimination performance.

Residual, long-term effects of cortical injuries upon speech production are rarely examined. In this study, we examined the articulation and discrimination abilities in twelve subjects who received focal, cortical injuries in Vietnam during 1968-1971. The subjects were divided into two groups based upon the hemisphere (right or left) of lesion. Data revealed the left-hemisphere injured group produced a greater number of articulation and discrimination errors than the right-hemisphere injured group. Articulation errors occurred more often than discrimination errors in both groups. However, a feature analysis revealed the left-hemisphere injured group made predominantly combination errors and the right-hemisphere injured group made predominantly place errors. Taken overall, the data suggest the left-hemisphere injured group may experience residual difficulties with the encoding of phonological units while the right-hemisphere injured group appears to have residual problems that may be related to the spatial correlates of speech.

The correlation between surgical and CT estimates of brain damage following missile wounds.

The occurrence of distant brain damage following an apparent focal missile injury to the brain has not been well documented until computerized tomography scanning demonstrated this phenomenon. Mechanisms of additional or distant damage within the brain may include a high deposit of kinetic energy from the penetrating missile, additional vascular damage, and possibly neuronal and axonal degeneration. Widespread and distant brain changes may explain some instances of late neuropsychological and psychiatric dysfunction or rehabilitation failure following a brain wound. Brain imaging should be used to properly evaluate the full extent of brain damage following wounding.

Preoperative functional assessment of auditory cortex in adult cochlear implant users.

OBJECTIVES: To explore functional neuroanatomical responses to auditory stimulation before and after implantation. STUDY DESIGN: A prospective study of three cochlear implant candidates (pure-tone averages of 90 dB HL or greater bilaterally and hearing in noise test [HINT] performances of <40%) in which regional cerebral blood flow (rCBF) was assessed using single photon emission computed tomography (SPECT). METHODS: Candidates watched a 15-minute videotaped story under four conditions: audio presented monaurally in the right and left ears (aided), audio presented binaurally (aided), and visual-only presentation of the story. Five minutes into each story, 20 to 25 mCi of technetium 99m (99mTc) hexamethyl-propyleneamine-oxime (HMPAO) (Ceratec; Nycomed Amersham, Princeton, NJ, U.SA) was injected over a 30-second period to ensure that subjects were unaware of tracer administration. Subjects were scanned for 20 minutes using a PRISM 3000 gamma camera (Picker International, Cleveland, OH, U.S.A.). Data were normalized and co-registered, and subtraction images were compiled. Subtraction images contrasted activation patterns generated under the visual-only control condition to the auditory activation states acquired monaurally and binaurally. RESULTS: Right and left ear monaural stimulation in normal hearing subjects resulted in significant bilateral activation of Brodmann areas 41, 42, 21, 22, and 38. Although substantial intersubject response variability was noted, subjects generally failed to bilaterally activate these areas under monaural hearing aid presentations; however, bilateral activation of areas 41 and 22 was noted under binaural presentations. CONCLUSIONS: Despite relatively similar hearing losses in each ear, significant differences in preoperative auditory cortex activation were observed between ears. These data suggest that functional brain imaging provides a useful tool for exploring the responsiveness of the auditory cortex in cochlear implant candidates.

Developmental aspects of dichoptic viewing.

Age-related performance changes on a dichoptic viewing task were examined with twenty-five (25) individuals in a cross-sectional design. Using a double-report procedure, subjects were asked to identify two different consonant-vowel graphemes presented separately to the same foveal area of each eye (i.e., dichoptic stimulation). Stimuli were presented at stimulus-onset asynchronies (SOAs) ranging from 0 to 300 msec in 50-msec steps. Results indicated that the number of both-correct trials (i.e., correct reports of both stimuli in a dichoptic pair) significantly increased with age, while single-correct trials (a correct report of only one stimulus in the pair) significantly decreased with age. In addition, the shape of the masking functions indicated lagging stimuli were reported more accurately than leading stimuli at SOAs of 50-300 msec for all subjects. Younger subjects exhibited peak masking effects for synchronous presentations (0-msec SOA) while older individuals showed peak masking at SOAs of 50 msec. Results suggest developmental performance changes noted in processing visual information parallel, to a remarkable degree, those observed in processing auditory information.

Management of hearing loss in infants: the UTD/Callier Center position statement.

As infants are being identified earlier and earlier by universal newborn hearing screening programs, there is a need to establish principles for professionals involved in habilitative processes. Recently, a panel of experts was convened for a 2-day conference entitled "Habilitative Issues for Infants with Hearing Loss," the Bruton Conference on Audiology/Communication Sciences, UTD/Callier Center for Communication Disorders. The purpose of this document was to summarize the panel's discussions on habilitative principles, state-of-the-art practices, and future needs for infants with hearing loss.

Recall performance of children failing memory portions of a speech-language-memory screening battery.

Recall performance of first- and third-grade children who failed memory portions of a speech-language-memory screen was examined using digit and consonant-vowel (CV) stimulus sets. Children passing the screening battery had more accurate recall performance than children failing the screening battery. Systematic variations in performance as a function of stimulus set (i.e., digit vs CV) were noted in the groups: significantly lower recall was noted for CV items than for digit items in all groups passing or failing the screening battery. Data indicate children failing the screening battery differed quantitatively, rather than qualitatively, from children passing the screening battery. These data further suggest the difficulties experienced by children failing the screening battery may be related to deficits in the initial coding of auditory information.

Acoustic analyses of speech changes after maxillectomy and prosthodontic management.

Acoustic speech patterns of five maxillofacial surgery patients were examined before and after prosthodontic reconstruction to determine the effectiveness of a maxillary prosthesis for eliminating (or reducing) nasal resonances. Vowel formant frequencies were measured for /i/ (as in seep) and /u/ (as in in soup). Within-subject, across test-session comparisons were made by using analysis of variance techniques. Prosthodontic restoration significantly reduced the nasal resonances in all patients by either (1) completely eliminating the resonances, (2) reducing the amplitude of the resonances, or (3) changing the frequency of the resonances to more nearby regions of the vowels.

Temporal integration of tone glides by children with auditory-memory and reading problems.

Temporal auditory integration for short-duration, frequency-varying signals was examined in children with deficits in auditory memory and reading. Signals were similar to those previously used: a fixed-frequency tone, a tone glide rising in frequency, and a tone glide falling in frequency. No significant differences were found between the Experimental and Control groups' thresholds as a function of signal class (i.e., fixed-frequency or tone glide) or duration. In addition, a significant asymmetry in the thresholds of short-duration rising and falling tone glides was found for both groups. Falling tone glides were detected at higher intensities than were rising tone glides. Data from this study indicated this particular group of children with auditory memory and reading problems was able to detect simple and complex short-duration signals in a manner similar to normal children.

Effect of different types of auditory stimulation on vowel formant frequencies in multichannel cochlear implant users.

Two experiments investigating the effects of auditory stimulation delivered via a Nucleus multichannel cochlear implant upon vowel production in adventitiously deafened adult speakers are reported. The first experiment contrasts vowel formant frequencies produced without auditory stimulation (implant processor OFF) to those produced with auditory stimulation (processor ON). Significant shifts in second formant frequencies were observed for intermediate vowels produced without auditory stimulation; however, no significant shifts were observed for the point vowels. Higher first formant frequencies occurred in five of eight vowels when the processor was turned ON versus OFF. A second experiment contrasted productions of the word "head" produced with a FULL map, OFF condition, and a SINGLE channel condition that restricted the amount of auditory information received by the subjects. This experiment revealed significant shifts in second formant frequencies between FULL map utterances and the other conditions. No significant differences in second formant frequencies were observed between SINGLE channel and OFF conditions. These data suggest auditory feedback information may be used to adjust the articulation of some speech sounds.

Effects of a Nucleus multichannel cochlear implant upon speech production in children.

The purpose of this report is to describe the speech production of children participating in the Food and Drug Administration's approved clinical trials for the Nucleus multichannel cochlear implant. A significant increase in the ability to imitate nonsegmental aspects of speech was noted after using the implant; however, nonsegmental performance did not appear to increase significantly between 12, 18, or 24 mo postimplantation. Significant increases occurred in imitative and elicited segmental performance after implantation at all measurement points. Speech intelligibility was significantly higher postimplant than preimplant; however, no significant change in mean length of utterance was observed. Data from these studies suggest a multichannel cochlear implant may provide information that is useful for assisting in the development or refinement of some aspects of spoken communication.

An acoustic-speech study of patients who received orthognathic surgery.

Several reports have suggested that orthognathic surgery may influence speech patterns. The purpose of this study was to examine the formant frequency changes of speech following orthognathic surgery in patients whose speech was considered perceptually normal preoperatively and postoperatively. Speech samples were obtained from five patients (three patients with Class II, Division 1 malocclusions and two patients with Class III malocclusions). Significant second-formant frequency shifts were found for the vowel 'e' (as in 'seat'); however, only minor second-formant frequency variations were found for the vowels 'a' (as in 'sat') and 'u' (as in 'suit'). The pattern of formant frequencies before and after surgical treatment suggested that the speakers adjusted their articulation to accommodate the orthognathic surgery. Overall, the data from this study indicate that speech patterns may be reorganized after orthognathic surgery even though speech remains perceptually "normal."

Shadowed and simple reaction times in stutterers and nonstutterers.

Stutterers may experience difficulties in preparing and executing responses. This study investigated these possibilities as well as the possibility that stutterers may experience difficulty in the selection of responses. Two reaction-time tasks were investigated: a shadowing response in which speakers exactly repeated vowel sequences they heard, and a simple response in which speakers said [u] regardless of the identity of the vowel stimulus. Two groups of six adult male subjects, stutterers and nonstutterers, participated. Stimuli consisted of vowel-vowel "syllables" whose initial duration (response foreperiod) was randomly varied from 500 to 1500 ms. Electromyographic (EMG) and acoustic measures were obtained for each response condition. The EMG response latencies, acoustic response latencies, and execution times (EMG latency less the acoustic response latency) were examined for the fluent responses. Results indicated stutterers were, on average, 34 ms slower on acoustic responses than nonstutterers regardless of the task or foreperiod. However, stutterers' and nonstutterers' EMG latencies were not significantly different. Further analysis indicated that the overall slower acoustic responses of stutterers were accounted for almost entirely by longer execution times. Stutterers' difficulties thus appear to lie after response initiation suggesting they have problems in coordination of gestures during execution of fluent responses.

Effects of stimulus-onset asynchrony on the dichotic performance of children with auditory-processing disorders.

Dichotic stop-consonant-vowel identification was investigated in two experiments using two groups of learning-disabled children demonstrating clinical manifestations of auditory-processing disorders, and two groups of matched, control subjects. Two-item, forced-choice paradigms were used in both experiments. Overall (total) dichotic performance for the two learning-disabled groups was significantly lower than that of the control subjects in all dichotic conditions. This lower performance was attributable to the number of trials in which both stimulus items were correctly identified. Analysis of trials in which only one response was correct showed no differences between the groups in terms of magnitude or direction of ear-advantage (right). In conditions where stimulus onsets were separated by 30, 90, and 150 msec, analysis of one-correct trials demonstrated more accurate identification of the temporally lagging stimulus for all subjects. However, as the onset-time separation increased, the control group's identification of leading and lagging items approached equality. The learning-disabled group, on the other hand, showed little increase in identification of temporally leading items even when stimuli were separated by 150 msec. These data suggest learning-disabled children with auditory-processing disorders may have a reduced temporal efficiency in processing rapidly varying acoustic patterns associated with stop-consonants that is observable when speech perceptual mechanisms are stressed through dichotic competition.