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Response time as an index for selective auditory cognitive deficits.

The full or partial recovery of cognitive functions following brain lesions is believed to rely on the recruitment of alternative neural networks. This has been shown anatomically for selective auditory cognitive functions (Adriani et al. 2003b). We investigate here behavioral correlates that may accompany the use of alternative processing networks and in particular the resulting increase in response times. The performance of 5 patients with right or left unilateral hemispheric infarction and 6 normal control subjects in sound identification, asemantic sound recognition, sound localization, and sound motion perception was evaluated by the number of correct replies and response times for correct and wrong replies. Performance and response times were compared across patients and normal control subjects. Two patients with left lesions were deficient in sound identification and sound motion perception and normal in sound localization and asemantic sound recognition; one patient with right lesion was deficient in sound localization and sound motion perception and normal in sound identification and asemantic sound recognition; deficient performance was associated with increased response times. The remaining 2 patients (1 with left, 1 with right lesion) had normal performance in all 4 tasks but had significantly longer response times in some (but not all) tasks. Patients with normal or deficient performance tended more often than normal subjects to give faster correct than wrong replies. We propose that increased response time is an indication of processing within an alternative network.

Auditory Pathways↗

High-level psychophysical tuning curves: forward masking in normal-hearing and hearing-impaired listeners.

Forward-masked psychophysical tuning curves (PTCs) were obtained for 1000-Hz probe tones at multiple probe levels from one ear of 26 normal-hearing listeners and from 24 ears of 21 hearing-impaired listeners with cochlear hearing loss. Comparisons between normal-hearing and hearing-impaired PTCs were made at equivalent masker levels near the tips of PTCs. Comparisons were also made of PTC characteristics obtained by fitting each PTC with three straight-line segments using least-squares fitting procedures. Abnormal frequency resolution was revealed only as abnormal downward spread of masking. The low-frequency slopes of PTCs from hearing-impaired listeners were not different from those of normal-hearing listeners. That is, hearing-impaired listeners did not demonstrate abnormal upward spread of masking when equivalent masker levels were compared. Ten hearing-impaired ears demonstrated abnormally broad PTCs, due exclusively to reduced high-frequency slopes in their PTCs. This abnormal downward spread of masking was observed only in listeners with hearing losses greater than 40 dB HL. From these results, it would appear that some, but not all, cochlear hearing losses greater than 40 dB HL influence the sharp tuning capabilities usually associated with outer hair cell function.

Acoustics↗

Forms of binaural summation and the implications of individual variability for binaural hearing aids.

The advantages which a two-ear system has over a one-ear system appear to be manifold, but not all understood in detail. All probably play some role in the generally recognised advantage of binaural aids in offsetting auditory disabilities. Several possible forms of binaural summation are distinguished here and their possible role discussed. Experimental results with normally-hearing listeners and with aid users show that binaural summation is likely to lead to gain settings of about 6 dB lower than with otherwise equivalent monaural amplification. In some cases this may be a direct cause of benefit. However individuals differ systematically in the extent to which they show this effect, which may be relevant to prognosis for binaural aiding. Evidence is reported of an association between binaural summation and binaural advantage. Individuals also differ systematically in binaural summation for uncomfortable loudness level.

Auditory Perception↗

Speech sound representation in the brain.

Biologic processes underlying speech sound perception and learning have been addressed using the mismatch negativity (MMN) evoked response. First is a consideration of how the acoustic properties of the signal affect the neural mechanisms and brain regions engaged. Because the MMN differs depending on the acoustic characteristics of the stimuli used to elicit the response, it has been used to probe mechanisms underlying the neural representation of stimuli along the auditory pathway. Second is a consideration of neurophysiologic correlates of speech sound perception and learning. Detailed is a 'behavioral-neurophysiologic, acoustic-phonetic approach', used to link perception with underlying physiologic processes in humans. The focus here is on children and what has been learned about normal maturation of speech sound perception and its disruption in certain children with learning disorders. The last topic is a consideration of central nervous system changes with perceptual learning. This includes long-term experience with one's native language and short-term auditory training in the laboratory. Limitations and future challenges are discussed.

Auditory Pathways↗

M50 sensory gating predicts negative symptoms in schizophrenia.

Impaired auditory sensory gating is considered characteristic of schizophrenia and a marker of the information processing deficit inherent to that disorder. Predominance of negative symptoms also reflects the degree of deficit in schizophrenia and is associated with poorer pre-morbid functioning, lower IQ, and poorer outcomes. However, a consistent relationship between auditory sensory gating and negative symptoms in schizophrenia has yet to be demonstrated. The absence of such a finding is surprising, since both impaired auditory gating and negative symptoms have been linked with impaired fronto-temporal cortical function. The present study measured auditory gating using the P50 event related potential (ERP) in a paired-click paradigm and capitalized on the relative localization advantage of magnetoencephalography (MEG) to assess auditory sensory gating in terms of the event related field (ERF) M50 source dipoles on bilateral superior temporal gyrus (STG). The primary hypothesis was that there would be a positive correlation between lateralized M50 auditory sensory gating measures and negative symptoms in patients with schizophrenia. A standard paired-click paradigm was used during simultaneous EEG and MEG data collection to determine S2/S1 sensory gating ratios in a group of 20 patients for both neuroimaging techniques. Participants were administered the Schedule for the Assessment of Negative Symptoms (SANS), the Positive and Negative Symptom Scale (PANSS), and the Calgary Depression Scale for Schizophrenia. Consistent with previous reports, there was no relationship between ERP P50 sensory gating and negative symptoms. However, right (not left) hemisphere ERF M50 sensory gating ratio was significantly and positively correlated with negative symptoms. This finding is compatible with information processing theories of negative symptoms and with more recent findings of fronto-temporal abnormality in patients with predominantly negative symptoms.

Adolescent↗

Reliability of clinician-based (GRBAS and CAPE-V) and patient-based (V-RQOL and IPVI) documentation of voice disorders.

This study examined the reliability of two methods for documenting voice quality by clinicians and compared the methods for documenting patients' perceptions of voice quality. It involved a prospective reliability study and a retrospective chart review. Reliability of two clinician-based voice assessment protocols-Grade, Roughness, Breathiness, Asthenia, Strain (GRBAS) and Consensus Auditory Perceptual Evaluation-Voice (CAPE-V)-was evaluated. These two protocols were then compared after use in voice assessments of 42 males and 61 females performed by a certified speech-language pathologist specializing in the assessment of voice disorders. In addition, two patient-based scales (Voice Related Quality of Life, or V-RQOL, and Iowa Patient's Voice Index, or IPVI) obtained from the same patients were compared with each other and with the clinician-based scales. Reliability of clinicians' ratings of overall severity of dysphonia using GRBAS and CAPE-V scales was very good (r>0.80). Agreement between V-RQOL Total scores and IPVI ratings of the patient's perceptions of impact of dysphonia was less strong (Spearman's r=-0.76). There was relatively weak agreement between patient-based and clinician-based scales. Clinician's perceptions of dysphonia appeared to be reliable and unaffected by rating tool, as indicated by the high level of agreement between the two rating systems when they were used together. The CAPE-V system appeared to be more sensitive to small differences within and among patients than the GRBAS system. The V-RQOL and IPVI approaches to documenting patient's perceptions of dysphonia agreed less well possibly due to differences in patient dependence on voice and on interpretation of the rating tool items. The differences between clinician-based and patient-based data support the conclusion that clinicians and patients experience and consider dysphonia very differently.

Adolescent↗

Perceptual time-frequency subtraction algorithm for noise reduction in hearing aids.

Sensorineural hearing disorders are a major and universal community health problem. In many cases, hearing aids offer the only solution for people suffering from such disorders. Unfortunately existing aids do not provide any improvement in intelligibility of the signal when background noise is present. A hearing aid system should ideally simulate auditory processes including those aspects of the speech signal that are perceptually important. This work presents a new integrated approach to the design of a digital hearing aid, based on a wavelet transform, as well as a formulation of the temporal and spectral psychoacoustic model of masking. Within the model, the Perceptual Time-Frequency Subtraction (PTFS) algorithm is developed to simulate the masking phenomena and reduce noise in single-input systems. Results show that the use of the PTFS yields a significant improvement in speech quality especially in unvoiced portions. Additionally, the noise component during periods of silence has been attenuated by up to 20 dB. This new noise reduction method is expected to be applicable in a variety of applications, including digital hearing aids and portable communication systems (e.g., cellular telephones).

Algorithms↗

Modality specificity of auditory and visual pattern recognition: implications for the assessment of central auditory processing disorders.

We determined the degree of overlap in required processing resources between simultaneously performed non-verbal auditory and visual pattern-recognition tasks. In experiment 1, concurrent presentation of binary auditory frequency pattern sequences interfered with recognition memory of both binary auditory sound pressure level and binary color sequences, but the amount of interference was greater with auditory-level patterns. In experiment 2, mutual interference was demonstrated between auditory level and visual color pattern sequences. We conclude that dual-task performance using auditory and visual pattern-recognition tasks is limited by modality-specific perceptual factors and by modality-independent cognitive factors not specific to a single sensory modality. It is concluded that poor performance on a single pattern-recognition task cannot be associated in a one-to-one fashion with a single perceptual ability or process.

Adult↗

Speech perception deficits in poor readers: auditory processing or phonological coding?

Poor readers are inferior to normal-reading peers in aspects of speech perception. Two hypotheses have been proposed to account for their deficits: (i) a speech-specific failure in phonological representation and (ii) a general deficit in auditory "temporal processing," such that they cannot easily perceive the rapid spectral changes of formant transitions at the onset of stop-vowel syllables. To test these hypotheses, two groups of second-grade children (20 "good readers," 20 "poor readers"), matched for age and intelligence, were selected to differ significantly on a /ba/-/da/ temporal order judgment (TOJ) task, said to be diagnostic of a temporal processing deficit. Three experiments then showed that the groups did not differ in: (i) TOJ when /ba/ and /da/ were paired with more easily discriminated syllables (/ba/-/sa/, /da/-/fa/); (ii) discriminating nonspeech sine wave analogs of the second and third formants of /ba/ and /da/; (iii) sensitivity to brief transitional cues varying along a synthetic speech continuum. Thus, poor readers' difficulties with /ba/-/da/ reflected perceptual confusion between phonetically similar, though phonologically contrastive, syllables rather than difficulty in perceiving rapid spectral changes. The results are consistent with a speech-specific, not a general auditory, deficit.

Child↗

Chronic tinnitus: association with psychiatric diagnoses.

Twenty-one consecutive patients with severe tinnitus were interviewed using a structured psychiatric interview (the National Institute of Mental Health Diagnostic Interview Schedule) and were asked to complete the Hopkins Symptom Checklist (SCL-90) and the Chronic Illness Problem Inventory. They were compared to a control group of 14 patients attending an otolaryngological clinic with a complaint of hearing loss. The tinnitus patients had a significantly greater lifetime prevalence of major depression (62% vs 21%) than controls and a significantly higher prevalence of current major depression (48% vs 7%). The currently depressed tinnitus patients had significantly higher scores on all subscales of the SCL-90, except the phobia and paranoid subscales, compared to the non-depressed tinnitus group and on all scales compared to the controls. The number of psychosocial problems and thus the resulting disability experienced was significantly greater in the tinnitus group compared to controls and in the currently depressed tinnitus patients when compared to non-depressed tinnitus patients. In view of our results treatment should aim at not only alleviation of tinnitus, but also the frequently co-existing major depression.

Auditory Threshold↗

Visual processing, lateralization and syndromes of schizotypy.

There is an association between positive features of schizotypy and dyslexia, largely involving distortions of visual and auditory perception and associated cognitive anomalies. In dyslexia, there is strong evidence for a disorder of subcortical magnocellular pathways, which may underlie these perceptual aberrations. Here we investigated visual processing in relation to three syndromes of schizotypy-Active, Withdrawn and Unreality-in normal adults, using a "dot localization" test of visual direction sense on which dyslexics perform poorly, and which should be sensitive to magnocellular dysfunction. Results showed that increased error scores were associated with both the positive syndromes, Active and Unreality, which in this study were highly correlated. There were also interactions between each syndrome and the direction of errors, such that high scorers on the Unreality and Active syndromes made more errors on leftward trials, while high Withdrawn subjects made fewer left and more right errors. Mixed handers also showed poorer performance than consistent handers. The evidence of poor visual direction sense in relation to positive syndromes of schizotypy and mixed handedness is consistent with the previous results for dyslexics, who also show these features. The opposite lateralization of errors in the positive v negative syndromes of schizotypy is in keeping with the model of hemisphere imbalance and patterns of cognitive asymmetry which distinguish Active from Withdrawn syndromes. These results are considered in relation to the proposal that a disorder of magnocellular function may underlie the perceptual distortions which are common to dyslexia and positive syndromes of schizotypy.

Adolescent↗

Processing of auditory stimuli during visual attention in patients with schizophrenia.

BACKGROUND: The aim of this study was to evaluate attentional functioning in patients with schizophrenia with an emphasis on automatic processes using the mismatch negativity (MMN) component of the event-related brain potential. METHODS: Participants were asked to perform a challenging visual discrimination task and simultaneously ignore auditory stimuli presented in the background. In different blocks of trials, the background was either a sequence of tones that included rare deviant tones differing in pitch or a sequence of tones that alternated regularly in pitch with occasional deviant repetitions. In a second experiment, participants were asked to actively respond to auditory deviant stimuli. RESULTS: Visual targets generated smaller N1, N2, and P3b deflections in patients than in control subjects, suggesting deficits in controlled attentional processes. Auditory deviant stimuli elicited an MMN that varied in scalp distribution as a function of the deviant-type (pitch vs. pattern). In patients with schizophrenia, impaired auditory discrimination was associated with altered MMN topography and reduced MMN amplitude. CONCLUSIONS: These findings are consistent with impaired automatic processes in patients with schizophrenia, which may contribute to their difficulties in processing complex auditory sequences. The timing and scalp topography are consistent with impaired auditory pattern analysis in posterior association cortices.

Adult↗

Reduction of left visual field lexical decision accuracy as a result of concurrent nonverbal auditory stimulation.

To investigate whether concurrent nonverbal sound sequences would affect visual-hemifield lexical processing, lexical-decision performance of 24 strongly right-handed students (12 men, 12 women) was measured in three conditions: baseline, concurrent neutral sound sequence, and concurrent emotional sound sequence. With the neutral sequence, Naveteru, Roy, Ovelac, and Steinling (1992) had observed a right greater than left cerebral blood flow, and an opposite pattern with the emotional sequence. In the present study, the neutral sound sequence induced a significant accuracy reduction for lexical decisions to stimuli presented in the left visual field. It is hypothesized that RH activation in response to neutral sounds interferes with the limited lexical processing resources of that hemisphere.

Adult↗