The electrophysiological effects of a brain injury on auditory memory functioning. The QEEG correlates of impaired memory.
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The effect of a brain injury on the quantitative EEG (QEEG) variables during an auditory memory activation condition was examined with 56 normal subjects and 85 mild traumatic brain-injured (MTBI) subjects. An analysis was conducted on the different response patterns of the two groups, the variables which were correlated with memory performance in the brain-injured group, and the variables which predicted the memory score for the combined two groups (normal and brain injured). The three conditions included the input task, the immediate recall, and the delayed recall task. The consistent effect of a brain injury was a lowering of the connectivity patterns in the beta1 and beta2 frequencies (phase and coherences) and increases predominantly in the relative power of beta1 (13-32Hz), which were correlated with the differences in recall. There is a subtle shift to right hemisphere/right temporal functioning and employment of the higher beta1 and beta2 frequencies (phase and coherence) in the response pattern of the MTBI subject. Memory functioning is predominantly positively correlated with connection activity (phase and coherence) and negatively correlated with beta activation at specific locations. (+info)
Auditory hypersensitivity in children and teenagers with autistic spectrum disorder.
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OBJECTIVE: To verify if the clinical behavior of auditory hypersensitivity, reported in interviews with parents/caregivers and therapists/teachers of 46 children and teenagers suffering from autistic spectrum disorder, correspond to audiological findings. METHOD: The clinical diagnosis for auditory hypersensitivity was investigated by means of an interview. Subsequently, a test of the acoustic stapedial reflex was conducted, and responses to intense acoustic stimulus in open field were observed. RESULTS: Of the 46 subjects, 11 (23.9%) were clinically diagnosed as oversensitive to sound and only 2 showed discomfort when exposed to intense acoustic stimulus in open field. There was no statistically significant difference for the test of the ipsilateral acoustic stapedial reflex between the groups. CONCLUSION: Behavioral manifestations to sounds are not associated to hypersensitivity of the auditory pathways, but instead these are associated to difficulties in the upper processing, involving systems that usually are impaired in autistic spectrum patients, such as the limbic system. (+info)
Perceptual consequences of disrupted auditory nerve activity.
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Perceptual consequences of disrupted auditory nerve activity were systematically studied in 21 subjects who had been clinically diagnosed with auditory neuropathy (AN), a recently defined disorder characterized by normal outer hair cell function but disrupted auditory nerve function. Neurological and electrophysical evidence suggests that disrupted auditory nerve activity is due to desynchronized or reduced neural activity or both. Psychophysical measures showed that the disrupted neural activity has minimal effects on intensity-related perception, such as loudness discrimination, pitch discrimination at high frequencies, and sound localization using interaural level differences. In contrast, the disrupted neural activity significantly impairs timing related perception, such as pitch discrimination at low frequencies, temporal integration, gap detection, temporal modulation detection, backward and forward masking, signal detection in noise, binaural beats, and sound localization using interaural time differences. These perceptual consequences are the opposite of what is typically observed in cochlear-impaired subjects who have impaired intensity perception but relatively normal temporal processing after taking their impaired intensity perception into account. These differences in perceptual consequences between auditory neuropathy and cochlear damage suggest the use of different neural codes in auditory perception: a suboptimal spike count code for intensity processing, a synchronized spike code for temporal processing, and a duplex code for frequency processing. We also proposed two underlying physiological models based on desynchronized and reduced discharge in the auditory nerve to successfully account for the observed neurological and behavioral data. These methods and measures cannot differentiate between these two AN models, but future studies using electric stimulation of the auditory nerve via a cochlear implant might. These results not only show the unique contribution of neural synchrony to sensory perception but also provide guidance for translational research in terms of better diagnosis and management of human communication disorders. (+info)
Postural hallucinations? An unusual presentation of anaemia.
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The case of a 14 year old girl is reported, referred to Child Psychiatry with tearfulness and possible auditory hallucinations. Closer questioning revealed a history of low energy, sleeping excessively without refreshment, exertional dyspnoea, and poor growth. Psychologically, there was no evidence of low mood or negative cognitions despite the inexplicable tearfulness. Detailed enquiry revealed the "hallucinations" to be "whooshing" noises in her ears precipitated by standing. She was found to have a haemoglobin level of 55 g/l, attributed to a combination of poor diet and menorrhagia.Periodic, anaemic, cerebral hypoxia could be proposed to be the root of most, if not all, of the symptoms, illustrating the importance of marrying physical and psychological history taking with suitable investigations for an eminently treatable condition. (+info)
Brainstem timing: implications for cortical processing and literacy.
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The search for a unique biological marker of language-based learning disabilities has so far yielded inconclusive findings. Previous studies have shown a plethora of auditory processing deficits in learning disabilities at both the perceptual and physiological levels. In this study, we investigated the association among brainstem timing, cortical processing of stimulus differences, and literacy skills. To that end, brainstem timing and cortical sensitivity to acoustic change [mismatch negativity (MMN)] were measured in a group of children with learning disabilities and normal-learning children. The learning-disabled (LD) group was further divided into two subgroups with normal and abnormal brainstem timing. MMNs, literacy, and cognitive abilities were compared among the three groups. LD individuals with abnormal brainstem timing were more likely to show reduced processing of acoustic change at the cortical level compared with both normal-learning individuals and LD individuals with normal brainstem timing. This group was also characterized by a more severe form of learning disability manifested by poorer reading, listening comprehension, and general cognitive ability. We conclude that abnormal brainstem timing in learning disabilities is related to higher incidence of reduced cortical sensitivity to acoustic change and to deficient literacy skills. These findings suggest that abnormal brainstem timing may serve as a reliable marker of a subgroup of individuals with learning disabilities. They also suggest that faulty mechanisms of neural timing at the brainstem may be the biological basis of malfunction in this group. (+info)
Auditory processing deficits in dyslexia: task or stimulus related?
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The nature of the fundamental deficit underlying reading disability is the subject of a long-standing debate. We previously found that dyslexics with additional learning difficulties (D-LDs) perform poorly in simple auditory tasks. We now tried to determine whether these deficits relate to stimulus or task complexity. We found that the degree of impairment was dependent on task rather than stimulus complexity. D-LDs could adequately detect and identify mild frequency changes in simple pure tones and minimal phonemic changes in complex speech sounds when task required only simple same-different discriminations. However, when task required the identification of the direction of frequency change or the ordinal position of a repeated tonal or speech stimulus, D-LDs' performance substantially deteriorated. This behavioral pattern suggests that D-LDs suffer from a similar type of deficits when processing speech and nonspeech sounds. In both cases, the extent of difficulties is determined by the structure of the task rather than by stimulus composition or complexity. (+info)
Auditory event-related responses in children with semi-lobar holoprosencephaly.
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The purpose of this study was to evaluate auditory sensory and discrimination responses in children with semi-lobar holoprosencephaly (HPE). Event-related potential (ERP) signals were recorded to tone pair stimuli at 62 electrode sites from the scalp using an oddball paradigm (a two-block design, inter-stimulus interval=70 or 300 ms; frequency of tone pair=100 vs. 100 Hz for the frequent and 100 vs. 300 Hz for the infrequent). Latencies and amplitudes of P150, N250, and mismatch negativity (MMN)-like components were compared between children with HPE and controls. Our results revealed less organized ERP waveforms to both stimuli in children with HPE, with diminished P150 and N250 components across brain area. Robust and delayed MMN-like responses were elicited from the children with HPE, with decreased MMN amplitudes in the central, parietal, occipital, and posterior temporal areas. Our results suggest that while brain sensory responses to auditory tones may be impaired in children with semi-lobar HPE, subcomponents of auditory discrimination processes remain functional. (+info)
Music and the brain: disorders of musical listening.
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The study of the brain bases for normal musical listening has advanced greatly in the last 30 years. The evidence from basic and clinical neuroscience suggests that listening to music involves many cognitive components with distinct brain substrates. Using patient cases reported in the literature, we develop an approach for understanding disordered musical listening that is based on the systematic assessment of the perceptual and cognitive analysis of music and its emotional effect. This approach can be applied both to acquired and congenital deficits of musical listening, and to aberrant listening in patients with musical hallucinations. Both the bases for normal musical listening and the clinical assessment of disorders now have a solid grounding in systems neuroscience. (+info)