Jeffrey Martin

Some effects of aging on central auditory processing.

Seniors often have more difficulty understanding speech than younger adults, particularly in noisy environments. While loss in peripheral hearing sensitivity explains many of the listening problems of elderly persons, age-related declines in general cognitive skill and central auditory processing also appear to contribute. In this article, we focus primarily on the effects of age on central auditory mechanisms. To this end, we review research examining a central locus for deficits in temporal processing and summarize behavioral and event-related potential findings from our laboratorys research on the effects of aging on dichotic listening performance. Results show that age-related deficits in interhemispheric information processing may underlie some of the listening problems among seniors. We also discuss implications for clinical audiological rehabilitative efforts in this population.

Electrophysiological correlates of word comprehension: Event-related potential (ERP) and independent component analysis (ICA)

In this study we asked to what extent auditory evoked potentials can help us to understand the complex processes underlying word comprehension. Monosyllabic and bisyllabic words were presented to 34 young adults in the context of a semantic category judgment. The basic paradigm assessed the typicality effect, the tendency for classification of members of a category to be made more accurately and more rapidly for strong exemplars than for weak exemplars. Event-related potentials (ERPs) were recorded from 30 active scalp electrodes. The ERP waveform in response to the semantic categorization of a word was characterized by unique activity in four temporal intervals; (1) a negative peak at a latency of about 100 ms, (2) a positive peak at a latency of about 200 ms, (3) a broad negativity extending over the latency range from 200 to 600 ms, and (4) a broad positivity extending from 600 to 1400 ms. Independent component analysis (ICA) of the individual EEG epochs yielded four maximally independent components, interpreted as (1) exogenous detection of a change in the acoustic environment, followed by allocation of cognitive resources, especially sustained attention, to the analysis of subsequent acoustic events, (2) phonological processing, (3) semantic processing, and (4) decision processing. The morphologies of the four ICA waveforms were consistent with a parallel processing, interactive model of word recognition, and subsequent semantic categorization.

Dichotic listening tests in the assessment of auditory processing disorders

In the clinical audiological application of dichotic listening tests to assess interaural asymmetry, does mode of administration influence results and their interpretation? This paper reviews the various ways in which dichotic listening tests have been administered, considers the possible extra-auditory confounds that may influence each one, then presents data on 172 elderly persons to whom the Dichotic Sentence Identification (DSI) Test was administered in both divided and directed-attention modes. There were three outcome patterns. In 19% of the total cohort, DSI scores were within normal limits on both ears under both modes of administration (Pattern I). In 58% of participants the DSI score was abnormal on one ear (almost always the left ear) in the divided-attention mode but no abnormality on either ear in the directed attention mode (Pattern II). In 23% of the cohort there was an equivalent unilateral deficit under both modes of administration (Pattern III). Pattern II suggests a primarily cognitive problem, while pattern III suggests a central auditory structural problem. Results are discussed in relation to audiological applications of dichotic listening tests.

The North American Listening in Spatialized Noise - Sentences Test (NA LISN-S): Normative data and test-retest reliability studies for adolescents and young adults

BACKGROUND The Listening in Spatialized Noise-Sentences test (LiSN-S; Cameron and Dillon, 2009) was originally developed to assess auditory stream segregation skills in children aged 6 to 11 yr with suspected central auditory processing disorder. The LiSN-S creates a three-dimensional auditory environment under headphones. A simple repetition-response protocol is used to assess a listeners speech reception threshold (SRT) for target sentences presented in competing speech maskers. Performance is measured as the improvement in SRT in dB gained when either pitch, spatial, or both pitch and spatial cues are incorporated in the maskers. A North American-accented version of the LiSN-S (NA LiSN-S) is available for use in the United States and Canada. PURPOSE To develop normative data for adolescents and adults on the NA LiSN-S, to compare these data with those of children aged 6 to 11 yr as documented in Cameron et al (2009), and to consolidate the child, adolescent, and adult normative and retest data to allow the software to be used with a wider population. RESEARCH DESIGN In a descriptive design, normative data and test-retest reliability data were collected. STUDY SAMPLE One hundred and twenty normally hearing participants took part in the normative data study (67 adolescents aged 12 yr, 1 mo, to 17 yr, 10 mo, and 53 adults aged 19 yr, 10 mo, to 30 yr, 30 mo). Forty-nine participants returned between 1 and 4 mo after the initial assessment for retesting. Participants were recruited from sites in Cincinnati, Dallas, and Calgary. RESULTS When combined with data collected from children aged 6 to 11 yr, a trend of improved performance as a function of increasing age was found across performance measures. ANOVA (analysis of variance) revealed a significant effect of age on performance. Planned contrasts revealed that there were no significant differences between adults and children aged 13 yr and older on the low-cue SRT; 14 yr and older on talker and spatial advantage; 15 yr and older on total advantage; and 16 yr and older on the high-cue SRT. Mean test-retest differences on the various NA LiSN-S performance measures for the combined child, adult, and adolescent data ranged from 0.05 to 0.5 dB. Paired comparisons revealed test-retest differences were not significant on any measure of the NA LiSN-S except low-cue SRT. Test-retest differences across measures did not differ as a function of age. Test and retest scores were significantly correlated for all NA LiSN-S measures. CONCLUSIONS The ability to use either spatial or talker cues in isolation becomes adultlike by about 14 yr of age, whereas the ability to combine spatial and talker cues does not fully mature until closer to adulthood. By consolidating child, adolescent, and adult normative and retest data the NA LiSN-S can now been utilized to assess auditory processing skills in a wider population.

Vagus Nerve Stimulation Paired with Tones for the Treatment of Tinnitus: A Prospective Randomized Double-blind Controlled Pilot Study in Humans

The aim of the pilot study was to evaluate the effect of Vagus Nerve Stimulation (VNS) paired with sounds in chronic tinnitus patients. All participants were implanted and randomized to a paired VNS (n = 16) or control (n = 14) group. After 6 weeks of home therapy, all participants received paired VNS. The device was used on 96% of days with good compliance. After 6 weeks, the paired VNS group improved on the Tinnitus Handicap Inventory (THI) (p = 0.0012) compared to controls (p = 0.1561). The between-group difference was 10.3% (p = 0.3393). Fifty percent of the participants in the paired VNS group showed clinically meaningful improvements compared to 28% in controls. At one year, 50% of participants had a clinically meaningful response. The therapy had greater benefits for participants with tonal and non-blast induced tinnitus at the end of 6 (24.3% vs. 2%, p = 0.05) and 12 weeks (34% vs. 2%, p = 0.004) compared to controls with 80% and 70% responding at 6 months and 1 year, respectively. Adverse effects were mild and well-tolerated and the therapy had a similar safety profile to VNS for epilepsy. VNS paired with tones may be effective for a subgroup of tinnitus patients and provides impetus for a larger pivotal study.

Some effects of aging on event-related potentials during a linguistic monitoring task

Two groups of adults, one young and one elderly, were compared on a dichotic task in which continuous speech was monitored for grammatically and semantically anomalous words. Event-related potentials (ERPs) elicited by these anomalies were analyzed in terms of peak amplitude and peak latency of the evoked late-positive component (LPC). Results showed that while LPC peak amplitudes were overall reduced for the group of seniors, LPC peak latencies were similar between both groups of listeners. These findings are consistent with the hypothesis that elderly persons can offset declines in memory, perceptual processes, and speed of mental processing by taking advantage of contextual and prosodic cues in running speech. Additionally, an apparently asymmetric processing negativity was observed in the waveforms of young adults but not seniors. Possible mechanisms include the N400 response to semantic incongruity and a processing negativity component associated with attentional bias toward right hemispace.

Pairing sound with vagus nerve stimulation modulates cortical synchrony and phase coherence in tinnitus: An exploratory retrospective study

Recent research has shown that vagus nerve stimulation (VNS) paired with tones or with rehabilitative training can help patients to achieve reductions in tinnitus perception or to expedite motor rehabilitation after suffering an ischemic stroke. The rationale behind this treatment is that VNS paired with experience can drive neural plasticity in a controlled and therapeutic direction. Since previous studies observed that gamma activity in the auditory cortex is correlated with tinnitus loudness, we assessed resting-state source-localized EEG before and after one to three months of VNS-tone pairing in chronic tinnitus patients. VNS-tone pairing reduced gamma band activity in left auditory cortex. VNS-tone pairing also reduced the phase coherence between the auditory cortex and areas associated with tinnitus distress, including the cingulate cortex. These results support the hypothesis that VNS-tone pairing can direct therapeutic neural plasticity. Targeted plasticity therapy might also be adapted to treat other conditions characterized by hypersynchronous neural activity.

Auditory-cognitive interactions underlying interaural asymmetry in an adult listener: A case study

Abstract Objective: Abnormal interaural asymmetry on tests of dichotic listening is commonly observed in individuals suspected of auditory processing disorder (APD). Although a structural basis for the abnormality has been widely accepted, the influence of cognitive variables on the degree of observed asymmetry has gained increasing attention. To study this issue, we manipulated cognitive influences on interaural asymmetry in an adult with the auditory complaints typically associated with APD. Study sample: A 55 year-old woman with complaints of difficulty understanding speech in noisy environments despite normal audiometric levels. Design: Several experimental dichotic procedures were administered. Each procedure was characterized by the manipulation of cognitive task demands. Results: Interaural asymmetry was greatest when the demands on attention and/or memory were maximal. Electrophysiological data revealed interaural asymmetry on later stages of information processing. Conclusions: Results are discussed in relation to auditory-specific outcomes on clinical tests for APD.

Explosive offshore structure removal noise measurements

The underwater structures that support wind turbines and oil drilling rigs must eventually be removed. Explosive severing is a commonly used removal method in which charges are inserted into a pile and placed below the seafloor to sever the pile. The open-water source level of an explosive charge is readily determined from its composition and weight (Urick 1986). However, the sediment and pile absorb much of the explosion’s energy. A recent study (BSEE project M13PX00068) measured explosive removals in the Gulf of Mexico. Peak pressure, impulse and energy flux density metrics were measured with a 12-element, two-dimensional array spanning 90 ft vertically and at distances out to 200 ft. Peak amplitudes, compared with theoretical open-water predictions, were reduced from 76% (75 lb charges) to 54% (200 lb charges). Measured results were also compared to predictions from the UnderwaterCalculator (Dzwilewski and Fenton 2003) that included pile and sediment attenuation effects. It accurately predicted the pro...

The effect of context priming on the auditory potential evoked by semantic analysis (N400).

Context is an important aspect of the perception of ongoing speech. Understanding a speech message in the presence of background noise is aided by knowledge of the context of the message even though the audibility of specific phonemes may be compromised. In this experiment, we used a context priming paradigm to investigate the importance of context to word recognition. We studied the auditory ERP, specifically the N400 response, to presented words which had been previously heard in the context of a story. Results showed that words preceded by a word from the target story elicited a smaller N400 negativity than words preceded by a word from either a different story or from neither story. Thus, words that came from the same story (i.e., had congruent context) were processed with less effort than words from a different story. This “context effect” is discussed in relation to the perception of ongoing speech under difficult listening conditions.