Effects of Unilateral Hearing Loss on Speech-Evoked Auditory Brainstem Responses and Reading: A Preliminary Study.

PURPOSE: The purpose of this study was to determine whether the speech-evoked auditory brainstem responses (sABRs) obtained by stimulating the ear with normal sensitivity in children with unilateral hearing loss (UHL) were different from that of children with normal hearing (NH), and to explore correlations between the sABR findings and measures of reading. METHOD: Eleven children with UHL and 11 children with NH were tested via the BioMARK sABR protocol using the syllable /da/; latency and amplitudes of Waves V, A, C, D, E, F, and O were measured. Participants also were tested on the Phonemic Synthesis Test (PST) and the Woodcock Reading Mastery Test-Revised (WRMT-R), particularly the Reading Readiness, Basic Skills, and Comprehension subtests. RESULTS: Multivariate analysis of variance testing showed a significantly higher amplitude for Wave A for the NH group as compared to the UHL group. Separate ANOVAs also found significantly lower scores for the UHL group compared to the NH group on Basic Skills and Comprehension subtests of the Woodcock. Significant positive Spearman rho correlations were found for the UHL group between wave amplitudes for V, A, and O and the Reading Readiness score, and between wave amplitudes for V, A, D, and O and the Reading Comprehension score. A significant correlation also was found between the Total Reading score and wave amplitudes for V and A. No such correlations were found between wave amplitude and Woodcock scores for the NH group. Further testing of the UHL data found significant relationships between the pure-tone average of the hearing loss ear and the Basic Skills, Comprehension, and Total Reading scores from the WRMT-R. There was also a significant correlation between the PST score and Wave C amplitude. CONCLUSION: There may be a connection between speech encoding and measures of reading in children with UHL.

Effects of Spectral Shaping on Speech Auditory Brainstem Responses to Stop Consonant-Vowel Syllables.

BACKGROUND: Spectral shaping is employed by hearing aids to make consonantal information, such as formant transitions, audible for listeners with hearing loss. How manipulations of the stimuli, such as spectral shaping, may alter encoding in the auditory brainstem has not been thoroughly studied. PURPOSE: The aim of this study was to determine how spectral shaping of synthetic consonant-vowel (CV) syllables, varying in their second formant (F2) onset frequency, may affect encoding of the syllables in the auditory brainstem. RESEARCH DESIGN: We employed a repeated measure design. STUDY SAMPLE: Sixteen young adults (mean = 20.94 years, 6 males) and 11 older adults (mean = 58.60 years, 4 males) participated in this study. DATA COLLECTION AND ANALYSIS: Speech-evoked auditory brainstem responses (speech-ABRs) were obtained from each participant using three CV exemplars selected from synthetic stimuli generated for a /ba-da-ga/ continuum. Brainstem responses were also recorded to corresponding three CV exemplars that were spectrally shaped to decrease low-frequency information and provide gain for middle and high frequencies according to a Desired Sensation Level function. In total, six grand average waveforms (3 phonemes [/ba/, /da/, /ga/] X 2 shaping conditions [unshaped, shaped]) were produced for each participant. Peak latencies and amplitudes, referenced to prestimulus baseline, were identified for 15 speech-ABR peaks. Peaks were marked manually using the program cursor on each individual waveform. Repeated-measures analysis of variances were used to determine the effects of shaping on the latencies and amplitudes of the speech-ABR peaks. RESULTS: Shaping effects produced changes within participants in ABR latencies and amplitudes involving onset and major peaks of the speech-ABR waveform for certain phonemes. Specifically, data from onset peaks showed that shaping decreased latency for /ga/ in older listeners, and decreased amplitude onset for /ba/ in younger listeners. Shaping also increased the amplitudes of major peaks for /ga/ stimuli in both groups. CONCLUSIONS: Encoding of speech in the ABR waveform may be more complex and multidimensional than a simple demarcation of source and filter information, and may also be influenced by cue intensity and age. These results suggest a more complex subcortical encoding of vocal tract filter information in the ABR waveform, which may also be influenced by cue intensity and age.

Three Cases of Recovery from Sensorineural Hearing Loss in the First Year of Life: Implications for Monitoring and Management.

BACKGROUND: Three infants with different risk factors, behavioral and physiologic audiometric histories, and diagnoses were fit with amplification between 3 and 8 months of age. Two of the three met criteria for cochlear implantation. PURPOSE: This article aims to heighten awareness of the rare possibility of recovery from sensorineural hearing loss in infants with varying histories and emphasize the importance of a full diagnostic test battery in all infants diagnosed with sensorineural hearing loss every 3 months until objective and subjective thresholds are stable to ensure appropriate intervention. RESEARCH DESIGN: Case reports. RESULTS: All three infants demonstrated improvement or full recovery of hearing and cochlear function by approximately 12 months old. Their change in hearing was discovered due to frequent follow-up and/or caregiver report. One of these infants was tentatively scheduled to have cochlear implant surgery 2 months later. CONCLUSION: Appropriate early intervention for infants with hearing loss is critical to ensure maximum accessibility to speech and language cues. The Federal Drug Administration approves cochlear implantation in infants as young as 12 months. When providing audiometric management of infants with sensorineural hearing loss, it is imperative to conduct a full diagnostic test battery every 3 months (including tympanometric, acoustic reflex, and otoacoustic emission measurement) until objective and subjective thresholds are stable. There was no apparent pattern of factors to predict that the infants highlighted in these cases would recover. Discussion among pediatric audiologists and otologists and comparison of data from clinics across the U.S. is needed to identify predictive patterns and determine appropriate, consistent monitoring of infants with sensorineural hearing loss.

Click-evoked and speech-evoked auditory brainstem responses from individuals with multiple sclerosis.

PURPOSE: To determine whether speech-evoked auditory brainstem response (ABR) is more sensitive to the effects of multiple sclerosis (MS) than click-evoked ABR. MATERIALS AND METHODS: Eleven previously-confirmed MS patients (8 females, 3 males) and nine controls (7 females, 2 males), matched in age and gender, participated in a repeated-measures design. Stimuli were presented monaurally to the right ear via insert earphone. All evoked potential responses were collected by a single-channel montage where three electrodes were placed on the center of the head (Cz: non-inverting/ active), the ipsilateral earlobe (inverting/ reference) and the contralateral earlobe (ground). Rarefaction clicks of 0.1 ms duration were presented at rates of 13.30 and 91.1 clicks per second. Speech-evoked ABRs were obtained using the BioMARK software and the Bio-Logic Navigator PRO hardware. A synthesized /da/ syllable of 40-ms duration was presented via alternating polarity and at a rate of 10.9 stimuli per second. Stimuli were presented at 80 dB SPL. Speech-evoked ABR responses were obtained in quiet and in noise. RESULTS: Conventional click ABR responses were absent more often at high presentation rates in control subjects than in MS patients. Speech-evoked ABR peak amplitudes, wave E latency and VA complex slope variables separated the MS patients from controls. Group differences were also found in speech-evoked ABR response correlations in quiet versus noise conditions. CONCLUSIONS: The speech-evoked ABR is as or more sensitive to MS than conventional ABR measures without resort to simply noting missing peaks. Comparison of speech-evoked ABR responses in quiet and in noise highlight loss of neural synchrony in MS.

Effects of Aging on the Subcortical Encoding of Stop Consonants.

Purpose The main purpose of this study was to evaluate aging effects on the predominantly subcortical (brainstem) encoding of the second-formant frequency transition, an essential acoustic cue for perceiving place of articulation. Method Synthetic consonant-vowel syllables varying in second-formant onset frequency (i.e., /ba/, /da/, and /ga/ stimuli) were used to elicit speech-evoked auditory brainstem responses (speech-ABRs) in 16 young adults (M age = 21 years) and 11 older adults (M age = 59 years). Repeated-measures mixed-model analyses of variance were performed on the latencies and amplitudes of the speech-ABR peaks. Fixed factors were phoneme (repeated measures on three levels: /b/ vs. /d/ vs. /g/) and age (two levels: young vs. older). Results Speech-ABR differences were observed between the two groups (young vs. older adults). Specifically, older listeners showed generalized amplitude reductions for onset and major peaks. Significant Phoneme × Group interactions were not observed. Conclusions Results showed aging effects in speech-ABR amplitudes that may reflect diminished subcortical encoding of consonants in older listeners. These aging effects were not phoneme dependent as observed using the statistical methods of this study.

Influences of cognitive load on sensorimotor contributions to working memory: An EEG investigation of mu rhythm activity during speech discrimination.

Sensorimotor activity during speech perception is highly variable and is thought to be related to the underlying cognitive processes recruited to meet task demands. The purpose of the current study was to evaluate the impact of cognitive load on sensorimotor-based attention and working memory processes during speech perception. Manipulations of set size and signal clarity were employed to alter cognitive load. Raw EEG data recorded from 42 subjects during accurate discrimination of CV syllable pairs were decomposed by Independent component analysis; identifying sensorimotor mu components from 37 subjects. Time-frequency analyses revealed event related desynchronization (ERD) across alpha and beta frequency bands during and following stimulus presentation in all conditions, reflecting working memory maintenance through covert articulatory rehearsal. No early attentional activity was observed, suggesting adaptation to tasks. However, modulation of late working memory activity was observed between degraded and non-degraded conditions. Weak and delayed alpha and beta ERD in degraded conditions were interpreted as evidence of delayed implementation of covert rehearsal due to the prolonged time necessary to extract a phonological representation from the auditory signal. Findings are interpreted within Analysis by Synthesis to characterize the multi-faceted and temporally distinct contributions of anterior sensorimotor regions to working memory in support of speech discrimination.

Sex differences in early sensorimotor processing for speech discrimination.

Sensorimotor activity in speech perception tasks varies as a function of context, cognitive load, and cognitive ability. This study investigated listener sex as an additional variable. Raw EEG data were collected as 21 males and 21 females discriminated /ba/ and /da/ in quiet and noisy backgrounds. Independent component analyses of data from accurately discriminated trials identified sensorimotor mu components with characteristic alpha and beta peaks from 16 members of each sex. Time-frequency decompositions showed that in quiet discrimination, females displayed stronger early mu-alpha synchronization, whereas males showed stronger mu-beta desynchronization. Findings indicate that early attentional mechanisms for speech discrimination were characterized by sensorimotor inhibition in females and predictive sensorimotor activation in males. Both sexes showed stronger early sensorimotor inhibition in noisy discrimination conditions versus in quiet, suggesting sensory gating of the noise. However, the difference in neural activation between quiet and noisy conditions was greater in males than females. Though sex differences appear unrelated to behavioral accuracy, they suggest that males and females exhibit early sensorimotor processing for speech discrimination that is fundamentally different, yet similarly adaptable to adverse conditions. Findings have implications for understanding variability in neuroimaging data and the male prevalence in various neurodevelopmental disorders with inhibitory dysfunction.

Power and phase coherence in sensorimotor mu and temporal lobe alpha components during covert and overt syllable production.

The sensorimotor dorsal stream is known to activate in both overt and covert speech production. However, overt production produces sensory consequences that are absent during covert production. Thus, the purpose of the current study is to investigate differences in dorsal stream activity between these two production conditions across the time course of utterances. Electroencephalography (EEG) was recorded from 68 channels while 23 participants overtly (Op) and covertly (Cp) produced orthographically cued bisyllabic targets. Sensorimotor mu and auditory alpha components (from anterior and posterior aspects of the dorsal stream) were identified using independent component analysis (ICA). Event-related spectral perturbation (ERSP) analyses identified changes in mu and alpha oscillatory power over time, while intercomponent phase coherence (IPC) measured anterior-posterior connectivity in the two conditions. Results showed greater beta (15-25 Hz) suppression during speech planning across left and right hemisphere sensorimotor and temporal ICs for Op relative to Cp. By contrast, greater intrahemispheric beta coherence was observed for Cp compared to Op during speech planning. During execution, greater beta suppression was observed along with greater low frequency (< 10 Hz) power enhancement and intrahemispheric phase coherence in Op compared to Cp. The findings implicate low frequency sensorimotor and posterior temporal phase coherence in the integration of somatosensory and acoustic feedback in overt relative to covert execution. Findings are consistent with early frontal-temporal forward models involved in planning and execution with modulations depending on whether the task goal is internal or overt syllable production.

Trait related sensorimotor deficits in people who stutter: An EEG investigation of µ rhythm dynamics during spontaneous fluency.

Stuttering is associated with compromised sensorimotor control (i.e., internal modeling) across the dorsal stream and oscillations of EEG mu (µ) rhythms have been proposed as reliable indices of anterior dorsal stream processing. The purpose of this study was to compare µ rhythm oscillatory activity between (PWS) and matched typically fluent speakers (TFS) during spontaneously fluent overt and covert speech production tasks. Independent component analysis identified bilateral µ components from 24/27 PWS and matched TFS that localized over premotor cortex. Time-frequency analysis of the left hemisphere µ clusters demonstrated significantly reduced µ-α and µ-ß ERD (pCLUSTER < 0.05) in PWS across the time course of overt and covert speech production, while no group differences were found in the right hemisphere in any condition. Results were interpreted through the framework of State Feedback Control. They suggest that weak forward modeling and evaluation of sensory feedback across the time course of speech production characterizes the trait related sensorimotor impairment in PWS. This weakness is proposed to represent an underlying sensorimotor instability that may predispose the speech of PWS to breakdown.

The Effects of Fluency Enhancing Conditions on Sensorimotor Control of Speech in Typically Fluent Speakers: An EEG Mu Rhythm Study.

Objective: To determine whether changes in sensorimotor control resulting from speaking conditions that induce fluency in people who stutter (PWS) can be measured using electroencephalographic (EEG) mu rhythms in neurotypical speakers. Methods: Non-stuttering (NS) adults spoke in one control condition (solo speaking) and four experimental conditions (choral speech, delayed auditory feedback (DAF), prolonged speech and pseudostuttering). Independent component analysis (ICA) was used to identify sensorimotor µ components from EEG recordings. Time-frequency analyses measured µ-alpha (8-13 Hz) and µ-beta (15-25 Hz) event-related synchronization (ERS) and desynchronization (ERD) during each speech condition. Results: 19/24 participants contributed µ components. Relative to the control condition, the choral and DAF conditions elicited increases in µ-alpha ERD in the right hemisphere. In the pseudostuttering condition, increases in µ-beta ERD were observed in the left hemisphere. No differences were present between the prolonged speech and control conditions. Conclusions: Differences observed in the experimental conditions are thought to reflect sensorimotor control changes. Increases in right hemisphere µ-alpha ERD likely reflect increased reliance on auditory information, including auditory feedback, during the choral and DAF conditions. In the left hemisphere, increases in µ-beta ERD during pseudostuttering may have resulted from the different movement characteristics of this task compared with the solo speaking task. Relationships to findings in stuttering are discussed. Significance: Changes in sensorimotor control related feedforward and feedback control in fluency-enhancing speech manipulations can be measured using time-frequency decompositions of EEG µ rhythms in neurotypical speakers. This quiet, non-invasive, and temporally sensitive technique may be applied to learn more about normal sensorimotor control and fluency enhancement in PWS.

Sensorimotor activity measured via oscillations of EEG mu rhythms in speech and non-speech discrimination tasks with and without segmentation demands.

Better understanding of the role of sensorimotor processing in speech and non-speech segmentation can be achieved with more temporally precise measures. Twenty adults made same/different discriminations of speech and non-speech stimuli pairs, with and without segmentation demands. Independent component analysis of 64-channel EEG data revealed clear sensorimotor mu components, with characteristic alpha and beta peaks, localized to premotor regions in 70% of participants.Time-frequency analyses of mu components from accurate trials showed that (1) segmentation tasks elicited greater event-related synchronization immediately following offset of the first stimulus, suggestive of inhibitory activity; (2) strong late event-related desynchronization in all conditions, suggesting that working memory/covert replay contributed substantially to sensorimotor activity in all conditions; (3) stronger beta desynchronization in speech versus non-speech stimuli during stimulus presentation, suggesting stronger auditory-motor transforms for speech versus non-speech stimuli. Findings support the continued use of oscillatory approaches for helping understand segmentation and other cognitive tasks.

Detection of Deafness in Puppies Using a Hand-Held Otoacoustic Emission Screener.

The purpose of this study was to evaluate the use of a hand-held otoacoustic emissions screener to detect deafness in puppies. Specifically, distortion product otoacoustic emissions were recorded from 34 puppies (both sexes) of a variety of breeds, from 6-10 wk of age, and the results were compared to brainstem auditory evoked responses (BAER) recorded from the same puppies. Recordings were obtained from both ears in awake or lightly anesthetized puppies, and the results from each ear were compared. In all 62 ears that had normal BAERs, the distortion product otoacoustic emissions screener gave a response of "Pass." The three puppies that had flat BAER recordings in one or both ears provided a screener result of "Refer." In two ears with unusual BAERs (waveforms with reduced amplitudes and prolonged latencies) and a "Refer" response from the screener, there was compacted debris in one external ear canal, and the other ear canal was normal. The screener technology has proven application in human infants and is an attractive alternative to BAER testing in puppies because of expense and ease of use.

EEG Mu (µ) rhythm spectra and oscillatory activity differentiate stuttering from non-stuttering adults.

Stuttering is linked to sensorimotor deficits related to internal modeling mechanisms. This study compared spectral power and oscillatory activity of EEG mu (µ) rhythms between persons who stutter (PWS) and controls in listening and auditory discrimination tasks. EEG data were analyzed from passive listening in noise and accurate (same/different) discrimination of tones or syllables in quiet and noisy backgrounds. Independent component analysis identified left and/or right µ rhythms with characteristic alpha (α) and beta (ß) peaks localized to premotor/motor regions in 23 of 27 people who stutter (PWS) and 24 of 27 controls. PWS produced µ spectra with reduced ß amplitudes across conditions, suggesting reduced forward modeling capacity. Group time-frequency differences were associated with noisy conditions only. PWS showed increased µ-ß desynchronization when listening to noise and early in discrimination events, suggesting evidence of heightened motor activity that might be related to forward modeling deficits. PWS also showed reduced µ-α synchronization in discrimination conditions, indicating reduced sensory gating. Together these findings indicate spectral and oscillatory analyses of µ rhythms are sensitive to stuttering. More specifically, they can reveal stuttering-related sensorimotor processing differences in listening and auditory discrimination that also may be influenced by basal ganglia deficits.

Auditory cortical deactivation during speech production and following speech perception: an EEG investigation of the temporal dynamics of the auditory alpha rhythm.

Sensorimotor integration (SMI) across the dorsal stream enables online monitoring of speech. Jenson et al. (2014) used independent component analysis (ICA) and event related spectral perturbation (ERSP) analysis of electroencephalography (EEG) data to describe anterior sensorimotor (e.g., premotor cortex, PMC) activity during speech perception and production. The purpose of the current study was to identify and temporally map neural activity from posterior (i.e., auditory) regions of the dorsal stream in the same tasks. Perception tasks required "active" discrimination of syllable pairs (/ba/ and /da/) in quiet and noisy conditions. Production conditions required overt production of syllable pairs and nouns. ICA performed on concatenated raw 68 channel EEG data from all tasks identified bilateral "auditory" alpha (α) components in 15 of 29 participants localized to pSTG (left) and pMTG (right). ERSP analyses were performed to reveal fluctuations in the spectral power of the α rhythm clusters across time. Production conditions were characterized by significant α event related synchronization (ERS; pFDR < 0.05) concurrent with EMG activity from speech production, consistent with speech-induced auditory inhibition. Discrimination conditions were also characterized by α ERS following stimulus offset. Auditory α ERS in all conditions temporally aligned with PMC activity reported in Jenson et al. (2014). These findings are indicative of speech-induced suppression of auditory regions, possibly via efference copy. The presence of the same pattern following stimulus offset in discrimination conditions suggests that sensorimotor contributions following speech perception reflect covert replay, and that covert replay provides one source of the motor activity previously observed in some speech perception tasks. To our knowledge, this is the first time that inhibition of auditory regions by speech has been observed in real-time with the ICA/ERSP technique.

Effect of Repetitive, Subconcussive Impacts on Electrophysiological Measures of Attention.

OBJECTIVES: In this preliminary study, the auditory P3b response, when measured during a visually distracting task, was investigated as an index of change in cognitive function resulting from exposure to subconcussive impacts (SCIs) in collision sports over time. METHODS: Both pre- and postseason P3b responses were examined in seven first-year collegiate-level American football players. Comparisons were made between a group of seven third- and fourth-year players and a control group of seven noncontact athletes. RESULTS: No difference in P3b amplitude was revealed in pre- versus postseason data of the first-year players. Furthermore, no P3b amplitude differences were found when comparing first-year players with controls. P3b amplitudes of third- and fourth-year players versus first-year players were smaller along the midline electrode sites. CONCLUSIONS: Preliminary results suggest exposure to SCIs during the course of a season does not affect brain function negatively, as measured by the P3b response; however, differences between first-year players and the group of third- and fourth-year players suggest that exposure to hundreds of SCIs in multiple seasons leads to changes in brain activation patterns. Subtle effects such as difficulty with attentional resource allocation may develop. Longitudinal studies are necessary before definitive conclusions can be drawn.

Temporal dynamics of sensorimotor integration in speech perception and production: independent component analysis of EEG data.

Activity in anterior sensorimotor regions is found in speech production and some perception tasks. Yet, how sensorimotor integration supports these functions is unclear due to a lack of data examining the timing of activity from these regions. Beta (~20 Hz) and alpha (~10 Hz) spectral power within the EEG µ rhythm are considered indices of motor and somatosensory activity, respectively. In the current study, perception conditions required discrimination (same/different) of syllables pairs (/ba/ and /da/) in quiet and noisy conditions. Production conditions required covert and overt syllable productions and overt word production. Independent component analysis was performed on EEG data obtained during these conditions to (1) identify clusters of µ components common to all conditions and (2) examine real-time event-related spectral perturbations (ERSP) within alpha and beta bands. 17 and 15 out of 20 participants produced left and right µ-components, respectively, localized to precentral gyri. Discrimination conditions were characterized by significant (pFDR < 0.05) early alpha event-related synchronization (ERS) prior to and during stimulus presentation and later alpha event-related desynchronization (ERD) following stimulus offset. Beta ERD began early and gained strength across time. Differences were found between quiet and noisy discrimination conditions. Both overt syllable and word productions yielded similar alpha/beta ERD that began prior to production and was strongest during muscle activity. Findings during covert production were weaker than during overt production. One explanation for these findings is that µ-beta ERD indexes early predictive coding (e.g., internal modeling) and/or overt and covert attentional/motor processes. µ-alpha ERS may index inhibitory input to the premotor cortex from sensory regions prior to and during discrimination, while µ-alpha ERD may index sensory feedback during speech rehearsal and production.

Dynamic modulation of shared sensory and motor cortical rhythms mediates speech and non-speech discrimination performance.

Oscillatory models of speech processing have proposed that rhythmic cortical oscillations in sensory and motor regions modulate speech sound processing from the bottom-up via phase reset at low frequencies (3-10 Hz) and from the top-down via the disinhibition of alpha/beta rhythms (8-30 Hz). To investigate how the proposed rhythms mediate perceptual performance, electroencephalographic (EEG) was recorded while participants passively listened to or actively identified speech and tone-sweeps in a two-force choice in noise discrimination task presented at high and low signal-to-noise ratios. EEG data were decomposed using independent component analysis and clustered across participants using principle component methods in EEGLAB. Left and right hemisphere sensorimotor and posterior temporal lobe clusters were identified. Alpha and beta suppression was associated with active tasks only in sensorimotor and temporal clusters. In posterior temporal clusters, increases in phase reset at low frequencies were driven by the quality of bottom-up acoustic information for speech and non-speech stimuli, whereas phase reset in sensorimotor clusters was associated with top-down active task demands. A comparison of correct discrimination trials to those identified at chance showed an earlier performance related effect for the left sensorimotor cluster relative to the left-temporal lobe cluster during the syllable discrimination task only. The right sensorimotor cluster was associated with performance related differences for tone-sweep stimuli only. Findings are consistent with internal model accounts suggesting that early efferent sensorimotor models transmitted along alpha and beta channels reflect a release from inhibition related to active attention to auditory discrimination. Results are discussed in the broader context of dynamic, oscillatory models of cognition proposing that top-down internally generated states interact with bottom-up sensory processing to enhance task performance.

Effects of sentence context on phonemic categorization of natural and synthetic consonant-vowel tokens.

The purpose was to assess if phonemic categorization in sentential context is best explained by autonomous feedforward processing or by top-down feedback processing that affects phonemic representation. 11 listeners with normal hearing, ages 20-50 years, were asked to label consonants in /pi/-/ti/ consonant-vowel (CV) stimuli in 9-step continua. One continuum was derived from natural tokens and the other was synthetically generated. The CV stimuli were presented in isolation and in three sentential contexts: a neutral context, a context favoring /p/, and a context favoring /t/. For both natural and synthetic stimuli, the isolated and neutral context sentences yielded significantly more /t/ responses than sentence contexts primed for either /p/ or /t/. No other conditions were significantly different. Results did not show easily explainable semantic context effects. Instead, data clustering was more readily explained by top-down feedback processing affecting phonemic representation.

The effects of visual distracter complexity on auditory evoked p3b in contact sports athletes.

"Classic" P3b auditory oddball paradigms are insensitive to subtle deficits. An auditory oddball paradigm paired with visual distracters was used to compare football players with history of concussion, football players without history of concussion, and non-contact sport athletes. As hypothesized, increasing complexity of, and attention to, visual distracters reduced P3b amplitude. P3b amplitudes from non-contact athletes were larger than those from football players; however, players with and without a history of concussion were not significantly different. An auditory oddball paradigm with simple visual distracter improves sensitivity to cognitive deficits. Subconcussive impacts may contribute to brain damage frequently attributed to concussions.