Behavioral and Hemodynamic Changes Following Dichotic Training in Patients with Neurological Deficits of the Auditory Nervous System: A Case Series.

BACKGROUND: Dichotic listening occurs when one attends to different acoustical messages presented simultaneously to both ears. This is important for understanding speech in compromised listening situations, such as background noise. Deficits in dichotic listening can be remediated by participating in auditory training. We present two patients with binaural integration deficits who underwent dichotic interaural intensity difference (DIID) training. PURPOSE: The purpose of this investigation is to demonstrate improvement of dichotic listening deficits following DIID training in neurological patients seen clinically for hearing issues. RESEARCH DESIGN: This was a case series utilizing a pre- and posttreatment design. STUDY SAMPLE: This case series utilized two female participants who demonstrated binaural integration deficits during an auditory processing evaluation. INTERVENTION: The participants underwent a pretraining auditory processing evaluation and functional magnetic resonance imaging (fMRI). Participants then underwent 12, 30-minute DIID training sessions followed by posttreatment auditory processing evaluations and fMRI. DATA COLLECTION AND ANALYSIS: Data was collected at the pretreatment appointment and then immediately following the completion of the training. RESULTS: Each patient demonstrated varying degrees of improvement on the posttreatment assessment. Case 1 showed significant improvement on the Speech-in-Noise-Revised (SPIN-R) test. fMRI showed changes in activation patterns following training. Case 2 demonstrated improved scores on the Dichotic Digits Test and SPIN-R and increased activation of the calcarine sulcus following training. CONCLUSION: Dichotic training can be an efficacious treatment for binaural integration deficits and may show evidence of improving speech understanding in noise. This case series demonstrates a promising therapy to help patients improve auditory function by improving dichotic listening skills.

Hormones and Hearing: Central Auditory Processing in Women.

BACKGROUND: Estrogen has been identified as playing a key role in many organ systems. Recently, estrogen has been found to be produced in the human brain and is believed contribute to central auditory processing. After menopause, a low estrogen state, many women report hearing loss but demonstrate no deficits in peripheral hearing sensitivity, which support the notion that estrogen plays an effect on central auditory processing. Although animal research on estrogen and hearing loss is extensive, there is little in the literature on the human model. PURPOSE: The aim of this study was to evaluate relationships between hormonal changes and hearing as it relates to higher auditory function in pre- and postmenopausal (Post-M) females. RESEARCH DESIGN: A prospective, group comparison study. STUDY SAMPLE: Twenty eight women between the ages of 18 and 70 at the University of Kentucky were recruited. DATA COLLECTION AND ANALYSIS: Participants were separated into premenopausal and peri-/Post-M groups. Participants had normal peripheral hearing sensitivity and underwent a behavioral auditory processing battery and electrophysiological evaluation. An analysis of variance was performed to address the aims of the study. RESULTS: Results from the study demonstrated statistically significant difference between groups, where Post-M females had difficulties in spatial hearing abilities as reflected on the Listening in Spatialized Noise Test-Sentences test. In addition, measures on the auditory brainstem response and the middle latency response reflected statistically significant differences between groups with Post-M females having longer latencies. CONCLUSIONS: Results from the present study demonstrated significant differences between groups, particularly listening in noise. Females who present with auditory complaints in spite of normal hearing thresholds should have a more extensive audiological evaluation to further evaluate possible central deficits.

Enhancement of the Auditory Late Response (N1-P2) by Presentation of Stimuli From an Unexpected Location.

BACKGROUND: Passive electrophysiological protocols, such as the middle latency response and speech auditory brainstem response, are often advocated in the objective assessment of central auditory processing disorder (CAPD). However, few established electrophysiological protocols exist for CAPD assessment that have patients participate in active tasks which more closely approximate real-world listening. To this end, the present study used a discrimination task (i.e., oddball paradigm) to measure an enhancement of the auditory late response (N1-P2) that occurs when participants direct their auditory attention toward speech arising from an unexpected spatial location. PURPOSE: To establish whether N1-P2 is enhanced when auditory attention is directed toward an unexpected location during a two-word discrimination task. In addition, it was also investigated whether any enhancements in this response were contingent on the stimulus being counted as part of the oddball paradigm. RESEARCH DESIGN: Prospective study with a repeated measures design. STUDY SAMPLE: Ten normal hearing adults, with an age range of 18-24 years. DATA COLLECTION AND ANALYSIS: The N1 and P2 latencies and peak-to-peak amplitudes were recorded during a P300 paradigm. A series of repeated measures of analysis of variance and a correlation analysis was performed. RESULTS: There was a significant effect of stimulus location, in which words arising from the unexpected location showed a larger N1-P2 peak-to-peak amplitude and an earlier N1 latency. This effect was seen regardless of whether or not participants had to count the word total in memory. CONCLUSIONS: These findings suggest that spatial enhancement of the N1-P2 is a fairly robust phenomenon in normal hearing adult listeners. Additional studies are needed to determine whether this enhancement is absent or reduced in patients with CAPD.

Otoacoustic emission suppression in children diagnosed with central auditory processing disorder and speech in noise perception deficits.

OBJECTIVE: The present study was designed to test the hypothesis that medial olivocochlear system functionality is associated with speech recognition in babble performance in children diagnosed with central auditory processing disorder. METHOD: Children diagnosed with central auditory processing disorder who specifically demonstrated speech in noise deficits were compared to children diagnosed with central auditory processing disorder without these deficits. Suppression effects were examined across 15 time intervals to examine variability. Analysis of right and left ear suppression was performed separately to evaluate laterality. STUDY SAMPLE: 52 children diagnosed with central auditory processing disorder, aged 6-14 years were divided into normal or abnormal groups based on SinB performance in each ear. Cut-off value was set at SNR = 1.33 dB. Transient otoacoustic emissions suppression was measured. RESULTS: The abnormal Speech in Babble Right Ear group showed significant negative correlations with suppression levels for 7 of the 15 time intervals measured. No significant correlations with SinBR performance were observed for the remaining time intervals, as was the case for the typically evaluated R8-18 time interval and the Speech in Babble Left Ear. CONCLUSIONS: Results indicate that suppression is influenced by the time window analysed, and ear tested, and is associated with speech recognition in babble performance in children with central auditory processing disorder.

The Relationship between Central Auditory Processing, Language, and Cognition in Children Being Evaluated for Central Auditory Processing Disorder.

BACKGROUND: Pediatric central auditory processing disorder (CAPD) is frequently comorbid with other childhood disorders. However, few studies have examined the relationship between commonly used CAPD, language, and cognition tests within the same sample. PURPOSE: The present study examined the relationship between diagnostic CAPD tests and "gold standard" measures of language and cognitive ability, the Clinical Evaluation of Language Fundamentals (CELF) and the Wechsler Intelligence Scale for Children (WISC). RESEARCH DESIGN: A retrospective study. STUDY SAMPLE: Twenty-seven patients referred for CAPD testing who scored average or better on the CELF and low average or better on the WISC were initially included. Seven children who scored below the CELF and/or WISC inclusion criteria were then added to the dataset for a second analysis, yielding a sample size of 34. DATA COLLECTION AND ANALYSIS: Participants were administered a CAPD battery that included at least the following three CAPD tests: Frequency Patterns (FP), Dichotic Digits (DD), and Competing Sentences (CS). In addition, they were administered the CELF and WISC. Relationships between scores on CAPD, language (CELF), and cognition (WISC) tests were examined using correlation analysis. RESULTS: DD and FP showed significant correlations with Full Scale Intelligence Quotient, and the DD left ear and the DD interaural difference measures both showed significant correlations with working memory. However, ∼80% or more of the variance in these CAPD tests was unexplained by language and cognition measures. Language and cognition measures were more strongly correlated with each other than were the CAPD tests with any CELF or WISC scale. Additional correlations with the CAPD tests were revealed when patients who scored in the mild-moderate deficit range on the CELF and/or in the borderline low intellectual functioning range on the WISC were included in the analysis. CONCLUSIONS: While both the DD and FP tests showed significant correlations with one or more cognition measures, the majority of the variance in these CAPD measures went unexplained by cognition. Unlike DD and FP, the CS test was not correlated with cognition. Additionally, language measures were not significantly correlated with any of the CAPD tests. Our findings emphasize that the outcomes and interpretation of results vary as a function of the subject inclusion criteria that are applied for the CELF and WISC. Including participants with poorer cognition and/or language scores increased the number of significant correlations observed. For this reason, it is important that studies investigating the relationship between CAPD and other domains or disorders report the specific inclusion criteria used for all tests.

Temporal resolution in individuals with neurological disorders.

OBJECTIVE: Temporal processing refers to the ability of the central auditory nervous system to encode and detect subtle changes in acoustic signals. This study aims to investigate the temporal resolution ability of individuals with mesial temporal sclerosis and to determine the sensitivity and specificity of the gaps-in-noise test in identifying this type of lesion. METHOD: This prospective study investigated differences in temporal resolution between 30 individuals with normal hearing and without neurological lesions (G1) and 16 individuals with both normal hearing and mesial temporal sclerosis (G2). Test performances were compared, and the sensitivity and specificity were calculated. RESULTS: There was no difference in gap detection thresholds between the two groups, although G1 revealed better average thresholds than G2 did. The sensitivity and specificity of the gaps-in-noise test for neurological lesions were 68% and 98%, respectively. CONCLUSIONS: Temporal resolution ability is compromised in individuals with neurological lesions caused by mesial temporal sclerosis. The gaps-in-noise test was shown to be a sensitive and specific measure of central auditory dysfunction in these patients.

Temporal resolution in individuals with neurological disorders

OBJECTIVE:Temporal processing refers to the ability of the central auditory nervous system to encode and detect subtle changes in acoustic signals. This study aims to investigate the temporal resolution ability of individuals with mesial temporal sclerosis and to determine the sensitivity and specificity of the gaps-in-noise test in identifying this type of lesion.METHOD:This prospective study investigated differences in temporal resolution between 30 individuals with normal hearing and without neurological lesions (G1) and 16 individuals with both normal hearing and mesial temporal sclerosis (G2). Test performances were compared, and the sensitivity and specificity were calculated.RESULTS:There was no difference in gap detection thresholds between the two groups, although G1 revealed better average thresholds than G2 did. The sensitivity and specificity of the gaps-in-noise test for neurological lesions were 68% and 98%, respectively.CONCLUSIONS:Temporal resolution ability is compromised in individuals with neurological lesions caused by mesial temporal sclerosis. The gaps-in-noise test was shown to be a sensitive and specific measure of central auditory dysfunction in these patients.

Characteristics of Pediatric Performance on a Test Battery Commonly Used in the Diagnosis of Central Auditory Processing Disorder.

BACKGROUND: Although central auditory processing disorder (CAPD) test battery performance has been examined in adults with neurologic lesions of the central auditory nervous system (CANS), similar data on children being referred for CAPD evaluations are sparse. PURPOSE: This study characterizes CAPD test battery performance in children using tests commonly administered to diagnose the disorder. Specifically, this study describes failure rates for various test combinations, relationships between CAPD tests used in the battery, and the influence of cognitive function on CAPD test performance and CAPD diagnosis. A comparison is also made between the performance of children with CAPD and data from patients with neurologic lesions of the CANS. RESEARCH DESIGN: A retrospective study. STUDY SAMPLE: Fifty-six pediatric patients were referred for CAPD testing. DATA COLLECTION AND ANALYSIS: Participants were administered four CAPD tests, including frequency patterns (FP), low-pass filtered speech (LPFS), dichotic digits (DD), and competing sentences (CS). In addition, they were given the Wechsler Intelligence Scale for Children (WISC). Descriptive analyses examined the failure rates of various test combinations, as well as how often children with CAPD failed certain combinations when compared with adults with CANS lesions. A principal components analysis was performed to examine interrelationships between tests. Correlations and regressions were conducted to determine the relationship between CAPD test performance and the WISC. RESULTS: Results showed that the FP and LPFS tests were most commonly failed by children with CAPD. Two-test combinations that included one or both of these two tests and excluded DD tended to be failed more often. Including the DD and CS test in a battery benefited specificity. Tests thought to measure interhemispheric transfer tended to be correlated. Compared with adult patients with neurologic lesions, children with CAPD tended to fail LPFS more frequently and DD less frequently. Both groups failed FP with relatively equal frequency. CONCLUSIONS: The two-test combination that showed the highest failure rate for children with CAPD was LPFS-FP. Comparison with adults with CANS lesions, however, suggests that the mechanisms underlying LPFS performance in children need to be better understood. The two-test combination that showed the next highest failure rates among children with CAPD and did not include LPFS was CS-FP. If it is desirable to use a dichotic measure that has a lower linguistic load than CS then DD can be substituted for CS despite the slightly lower failure rate of the DD-FP battery.

Auditory Training for Central Auditory Processing Disorder.

Auditory training (AT) is an important component of rehabilitation for patients with central auditory processing disorder (CAPD). The present article identifies and describes aspects of AT as they relate to applications in this population. A description of the types of auditory processes along with information on relevant AT protocols that can be used to address these specific deficits is included. Characteristics and principles of effective AT procedures also are detailed in light of research that reflects on their value. Finally, research investigating AT in populations who show CAPD or present with auditory complaints is reported. Although efficacy data in this area are still emerging, current findings support the use of AT for treatment of auditory difficulties.

The influence of aging on interaural asymmetries in middle latency response amplitude.

BACKGROUND: Auditory-evoked potentials (EPs) provide a more objective assessment of central auditory nervous system (CANS) dysfunction when compared to behavioral measures because they do not require a behavioral response (Anderson and Kraus, 2010). In this regard, the middle latency response (MLR) has been considered an important component of CANS assessment (Jerger et al, 1988); however, its large within-group variability limits its usefulness (Musiek et al, 1999). It has been argued that performing intratest calculations on the MLR (e.g., difference in EP amplitude when stimulating the left ear versus the right ear) can reduce the within-group variability of the MLR and enhance its clinical usefulness (Musiek et al, 1999; Weihing et al, 2012). To date, it has not been investigated how well these MLR intratest measures reduce within-group variability in adults of various ages, nor has it been shown that these intratest measures are sensitive to aging-related changes in the CANS. PURPOSE: The two primary goals of the present study were (1) to determine if calculating an intratest MLR measure, the difference in MLR Na-Pa peak-to-peak amplitude on left versus right ear stimulation (i.e., "ear effects"), will reduce within-group variability in adults of various ages; and (2) to determine if ear effect magnitude will change as a function of aging. Ear effects were measured in both quiet and in noise to determine if the addition of noise enhanced any age-related-effects. RESEARCH DESIGN: A cross-sectional study was conducted. STUDY SAMPLE: The researchers studied 30 adults ranging in age from 20-80 yr with hearing sensitivity of 25 dB HL or better at the octave frequencies from 500-2000 Hz, and no history of neurologic issues. Adults were assigned to one of three age groups based on their chronological age, which were young adults, middle-aged adults, and older adults. DATA COLLECTION AND ANALYSIS: MLRs were acquired using a Nicolet Spirit 2000 during a single laboratory visit. To determine if within-group variability decreased significantly with ear effects, variability for absolute amplitude measures was compared to ear effect variability using the Pitman t-test. To examine potential effects of background noise and aging, data were analyzed using a mixed-factorial analysis of variance with the within-subjects factor "background noise" and the between-subjects factor "age group." RESULTS: Within-group variability was significantly reduced by calculating ear effects for the youngest group only. Additionally, the oldest adults in the present sample showed significantly larger ear effects than younger and middle-aged adults. This effect did not appear to be a result of differences in peripheral hearing sensitivity. Finally, introducing noise into the paradigm did not influence the observed effects. CONCLUSIONS: Ear effects become larger in older adults possibly as a result of age-related changes in the subcortical and/or cortical generators of the MLR. Failure of the ear effect calculation to reduce within-group variability in the middle-aged and older adults suggests that interaural asymmetries in MLR amplitude become more variable across participants who are older than 50 yr. Information obtained from this measure may benefit the development of treatment plans for older adults with hearing difficulties.

Efficacy of auditory interventions for central auditory processing disorder: a response to Fey et al. (2011).

PURPOSE: To provide a commentary on "Auditory Processing Disorder and Auditory/Language Interventions: An Evidence-Based Systematic Review" by Fey et al. (2011). METHOD: Examination of the conclusions drawn by Fey et al. (2011) in the context of the American Academy of Audiology (2010a, 2010b) and American Speech-Language-Hearing Association (2005a, 2005b, 2005c) guidelines for the diagnosis and treatment of auditory processing disorder, the evidence cited therein, and other pertinent published reports. RESULTS: The review provided by Fey et al. (2011) is limited due to the exclusion of pertinent efficacy studies from their analysis, inclusion of studies that did not employ strictly auditory-based therapies, and lack of well-defined experimental groups in many of the studies cited. Further, the questions posed by their literature review may not have addressed the efficacy of true auditory interventions in the remediation of auditory difficulties in children who have primary deficits in central auditory processing. CONCLUSION: A more comprehensive review than that done by Fey et al. (2011) would have better addressed the fundamental question of the efficacy of direct remediation activities for children with central auditory processing disorder.

Ear and electrode effects reduce within-group variability in middle latency response amplitude measures.

OBJECTIVES: To establish normative amplitude values for relative difference measurements of the middle latency response (MLR) in normal-hearing pediatrics and to determine if these measurements provided a significant reduction of within-group variability when compared to raw, absolute amplitude measures. A relative amplitude difference is defined in the present paper as the difference in Na-Pa amplitude between two electrodes (e.g. |Na-Pa at C3 minus Na-Pa at C4|, or electrode effects) or between two ears (e.g. |Na-Pa on left ear stimulation minus Na-Pa on right ear stimulation|, or ear effects). In contrast, an absolute amplitude is defined as a single Na-Pa measurement made at one electrode for stimulation of one ear (e.g. Na-Pa measured at C3 on left ear stimulation). DESIGN: Cross-sectional study. STUDY SAMPLE: 155 pediatrics with normal peripheral and central hearing, and no history of psychological, neurological, or learning disability issues. RESULTS: Within-group variability was significantly smaller for relative differences when compared to absolute amplitude measures. Electrode effects showed significantly less variability than ear effects. Normative values for ear and electrode effects were reported. CONCLUSIONS: Relative differences may provide better utility in the clinical diagnosis of central auditory pathology in pediatrics when compared to absolute amplitude measures because these difference measures show significantly lower variability when examined across subjects.

Diagnostic accuracy of established central auditory processing test batteries in patients with documented brain lesions.

PURPOSE: The sensitivity, specificity, and efficiency of commonly used behavioral central auditory processing tests and test batteries were determined for 20 individuals with known lesions of the central auditory nervous system (CANS) and related auditory symptoms. RESEARCH DESIGN: Twenty-nine individuals with no known neurological involvement served as the control group. Both groups were administered dichotic digits (DD), competing sentences (CS), frequency patterns (FP), and low-pass filtered speech (FS) tests. DATA ANALYSIS: Diagnostic indices for individual tests and test batteries comprised of two, three, or four tests were calculated both using a lax criterion in which failure on only one test in a battery led to a positive diagnosis and using a strict criterion in which failure on all tests in the battery was necessary to trigger a positive diagnosis. RESULTS: The test battery providing the best balance between sensitivity and specificity varied as a function of criterion. The two-test DD-FP battery using a strict criterion demonstrated the best balance. CONCLUSIONS: Limitations of particular tests, the advantages of larger test batteries to more broadly examine multiple auditory processes, the degree to which the present results can be generalized clinically to populations without known brain lesions, and other clinical considerations are discussed.

Perspectives on dichotic listening and the corpus callosum.

The present review summarizes historic and recent research which has investigated the role of the corpus callosum in dichotic processing within the context of audiology. Examination of performance by certain clinical groups, including split brain patients, multiple sclerosis cases, and other types of neurological lesions is included. Maturational, age related, and genetic factors are also discussed. Finally, some attention is given to recent trends in audiology research to develop improved diagnostic and rehabilitation tools for individuals with dichotic deficits potentially related to callosal dysfunction.

Articulatory events are imitated under rapid shadowing.

We tested the hypothesis that rapid shadowers imitate the articulatory gestures that structure acoustic speech signals-not just acoustic patterns in the signals themselves-overcoming highly practiced motor routines and phonological conditioning in the process. In a first experiment, acoustic evidence indicated that participants reproduced allophonic differences between American English /l/ types (light and dark) in the absence of the positional variation cues more typically present with lateral allophony. However, imitative effects were small. In a second experiment, varieties of /l/ with exaggerated light/dark differences were presented by ear. Acoustic measures indicated that all participants reproduced differences between /l/ types; larger average imitative effects obtained. Finally, we examined evidence for imitation in articulation. Participants ranged in behavior from one who did not imitate to another who reproduced distinctions among light laterals, dark laterals and /w/, but displayed a slight but inconsistent tendency toward enhancing imitation of lingual gestures through a slight lip protrusion. Overall, results indicated that most rapid shadowers need not substitute familiar allophones as they imitate reorganized gestural constellations even in the absence of explicit instruction to imitate, but that the extent of the imitation is small. Implications for theories of speech perception are discussed.

Dual sensory impairment (DSI) in traumatic brain injury (TBI)--An emerging interdisciplinary challenge.

The present review characterizes dual sensory impairment (DSI) as co-existing auditory and visual deficits in TBI that can be peripherally or centrally based. Current research investigating DSI in the military population, along with applicable research which focuses on unimodal deficits, is considered. Due to the heterogenous nature of TBI lesions, an important challenge that the clinician faces is ruling out the influence of multiple sensory deficits and/or the influence of cognitive processes on diagnosis and rehabilitation of the patient. Treatment options for DSI involve remediation of the sensory deficits via existing sensory aids or training exercises.

Comparisons of P300s from standard oddball and omitted paradigms: implications to exogenous/endogenous contributions.

PURPOSE: To compare the amplitude, latency, morphology, and threshold of the auditory P300 using standard oddball and omitted paradigms. RESEARCH DESIGN: P300 waveforms were measured from the Cz electrode site. Frequent stimuli for both paradigms were 1000 Hz tone bursts. Target stimuli for the standard oddball paradigm were 2000 Hz tone bursts and an omitted stimulus, or silent gap, for the omitted paradigm. STUDY SAMPLE: Fifteen bilaterally normal-hearing young adults. RESULTS: There were significantly lower amplitudes, poorer morphology, and higher thresholds for the P300 using an omitted paradigm compared to the standard oddball paradigm. CONCLUSION: These results suggest that the auditory P300 could have a larger exogenous component than traditionally thought.

The effect of visual and audiovisual competition on the auditory N1-P2 evoked potential.

BACKGROUND: Use of a competition stimuli (e.g., video) in clinical settings is a widespread practice, yet the effects of these stimuli on evoked potentials are not well understood. PURPOSE: The present investigation acquired the click evoked auditory N1-P2 in quiet and in two types of competition: during presentation of an unrelated visual stimulus or audiovisual stimulus. Responses were acquired in each of these conditions at two click stimulus levels (i.e., 35 and 65 dBnHL) to determine if the effect of competition was greater closer to threshold. An attempt was made to quantify effect robustness by examining within- and between-session reliability. RESEARCH DESIGN: Repeated measures ANOVA. STUDY SAMPLE: 17 normal hearing female subjects. RESULTS: Findings indicated a significant effect of audiovisual competition on the amplitude of the N1-P2, and a borderline significant effect of visual competition on this index. The extent of visual competition was better conveyed when examined on a case-by-case basis, in which was revealed a subgroup of the sample that was negatively affected by visual competition. There was no interaction between competition and click stimulus level. CONCLUSIONS: Although competition stimuli can negatively affect the amplitude of the N1-P2, consideration should be given to subjects on a case-by-case basis to warrant if removal of this stimulus is necessary.