Level dependence of contextual modulation in auditory cortex

from the Journal of Neurosphysiology

Responses of cortical neurons to sensory stimuli within their receptive fields can be profoundly altered by the stimulus context. In visual and somatosensory cortex, contextual interactions have been shown to change sign from facilitation to suppression depending on stimulus strength. Contextual modulation of high contrast stimuli tends to be suppressive, but for low contrast stimuli tends to be facilitative. This trade-off may optimize contextual integration by cortical cells, and has been suggested to be a general feature of cortical processing, but it remains unknown whether a similar phenomenon occurs in auditory cortex. Here we used whole cell and single unit recordings to investigate how contextual interactions in auditory cortical neurons depend on the relative intensity of masker and probe stimuli in a two-tone stimulus paradigm. We tested the hypothesis that relatively low level probes should show facilitation, whereas relatively high level probes should show suppression. We found that contextual interactions were primarily suppressive across all probe levels, and that relatively low level probes were subject to stronger suppression than high level probes. These results were virtually identical for spiking and subthreshold responses. This suggests that, unlike visual cortical neurons, auditory cortical neurons show maximal suppression rather than facilitation for relatively weak stimuli.

Aphasic speech with and without SentenceShaper® : Two methods for assessing informativeness

from Aphasiology

Background: SentenceShaper® (SSR) is a computer program that is for speech what a word-processing program is for written text; it allows the user to record words and phrases, play them back, and manipulate them on-screen to build sentences and narratives. A recent study demonstrated that when listeners rated the informativeness of functional narratives produced by chronic aphasic speakers with and without the program they gave higher informativeness ratings to the language produced with the aid of the program (Bartlett, Fink, Schwartz, & Linebarger, 2007). Bartlett et al. (2007) also compared unaided (spontaneous) narratives produced before and after the aided version of the narrative was obtained. In a subset of comparisons, the sample created after was judged to be more informative; they called this “topic-specific carryover”.

Aims: (1) To determine whether differences in informativeness that Bartlett et al.’s listeners perceived are also revealed by Correct Information Unit (CIU) analysis (Nicholas & Brookshire, 1993) – a well studied, objective method for measuring informativeness – and (2) to demonstrate the usefulness of CIU analysis for samples of this type.

Methods & Procedures: A modified version of the CIU analysis was applied to the speech samples obtained by Bartlett et al. (2007). They had asked five individuals with chronic aphasia to create functional narratives on two topics, under three conditions: Unaided (“U”), Aided (“SSR”), & Post-SSR Unaided (“Post-U”). Here, these samples were analysed for differences in % CIUs across conditions. Linear associations between listener judgements and CIU measures were evaluated with bivariate correlations and multiple regression analysis.

Outcomes & Results: (1) The aided effect was confirmed: samples produced with SentenceShaper had higher % CIUs, in most cases exceeding 90%. (2) There was little evidence of topic-specific carryover. (3) CIU measures and listener ratings correlated strongly.

Conclusions: That the percentage of CIUs was higher in SSR-aided samples than in unaided samples confirms the central finding in Bartlett et al. (2007), based on subjective judgements, and thus extends the evidence that aided effects from SentenceShaper are demonstrable across a range of measures, stimuli and participants (cf. Linebarger, Schwartz, Romania, Kohn, & Stephens, 2000). The data also attest to the effectiveness of the CIU analysis for quantifying differences in the informativeness of aphasic speech with and without SentenceShaper; and they support prior studies that have shown that CIU measures correlate with the informativeness ratings of unfamiliar listeners.

Hemispheric dissociation and dyslexia in a computational model of reading

from Brain and Language

There are several causal explanations for dyslexia, drawing on distinctions between dyslexics and control groups at genetic, biological, or cognitive levels of description. However, few theories explicitly bridge these different levels of description. In this paper, we review a long-standing theory that some dyslexics’ reading impairments are due to impairments in hemispheric transfer. We test this theory in a computational model of reading, implementing anatomical features of the visual system. We demonstrate that, when callosal transfer is impaired, the model reads nonwords as well as an unimpaired model, but reads exception words poorly: a pattern of behaviour similar to surface dyslexia. This computational modelling provides a causal link between brain-based theories of dyslexia to cognitive-level theories that refer specifically to phonological impairments within the reading system.

NAD Works With PepsiCo On Super Bowl Ad In American Sign Language

from Medical News Today.com

The National Association of the Deaf (NAD) was asked by PepsiCo to provide advice, feedback, and comments on a 60-second commercial filmed entirely in American Sign Language (ASL), with open captions for hearing viewers. The PepsiCo ad, featuring PepsiCo employees, will be aired on February 3, 2008 during the Super Bowl pre-game program.

Focal white matter changes in spasmodic dysphonia: a combined diffusion tensor imaging and neuropathological study

from Brain

Spasmodic dysphonia is a neurological disorder characterized by involuntary spasms in the laryngeal muscles during speech production. Although the clinical symptoms are well characterized, the pathophysiology of this voice disorder is unknown. We describe here, for the first time to our knowledge, disorder-specific brain abnormalities in these patients as determined by a combined approach of diffusion tensor imaging (DTI) and postmortem histopathology. We used DTI to identify brain changes and to target those brain regions for neuropathological examination. DTI showed right-sided decrease of fractional anisotropy in the genu of the internal capsule and bilateral increase of overall water diffusivity in the white matter along the corticobulbar/corticospinal tract in 20 spasmodic dysphonia patients compared to 20 healthy subjects. In addition, water diffusivity was bilaterally increased in the lentiform nucleus, ventral thalamus and cerebellar white and grey matter in the patients. These brain changes were substantiated with focal histopathological abnormalities presented as a loss of axonal density and myelin content in the right genu of the internal capsule and clusters of mineral depositions, containing calcium, phosphorus and iron, in the parenchyma and vessel walls of the posterior limb of the internal capsule, putamen, globus pallidus and cerebellum in the postmortem brain tissue from one patient compared to three controls. The specificity of these brain abnormalities is confirmed by their localization, limited only to the corticobulbar/corticospinal tract and its main input/output structures. We also found positive correlation between the diffusivity changes and clinical symptoms of spasmodic dysphonia (r = 0.509, P = 0.037). These brain abnormalities may alter the central control of voluntary voice production and, therefore, may underlie the pathophysiology of this disorder.

Loss of Saccular Function after Cochlear Implantation: The Diagnostic Impact of Intracochlear Electrically Elicited Vestibular Evoked Myogenic Potentials

from Audiology & Neuro-Otology

Cochlear implant surgery has become a successful procedure for deaf patients to restore their hearing again. Some of the patients, however, complain of persisting dizziness after the surgery which can have a major impact on their quality of life. Neurotological tests of the vestibular system were applied in a total of 18 cochlear implantees pre- and postoperatively. In addition, vestibular evoked myogenic potentials were evoked intraoperatively to investigate possible interferences of the electrically stimulated cochlear implant electrode (eVEMP) with vestibular receptor cells of the saccule in more detail. After cochlear implantation, the saccular function was impaired in the majority of the patients. However, eVEMPs could be recorded intraoperatively in all patients by intracochlear, high-level electrical stimulation via the cochlear implant electrode. In essence, acute, short-term dizziness after cochlear implantation seems to result primarily from a transient vestibular deficit of various origins. In contrast to this, chronic, persisting dizziness after cochlear implant surgery is largely based on a dysfunction of the saccular macula which is an integral component of the otolith system. This saccular impairment is induced most likely by the insertion trauma of the cochlear implant electrode when advancing it into the inner ear. A possible coactivation of the inferior vestibular nerve by the electrical stimulation might play an additional role in the pathogenesis of the persisting postsurgical dizziness.

Otologic Manifestations of Hunter Syndrome and Their Relationship with Speech Development

from Audiology & Neuro-Otology

The excessive storage of mucopolysaccharide in Hunter syndrome leads to various otologic manifestations. We interviewed 19 patients with Hunter syndrome to assess their otologic problems, and conducted audiologic tests and temporal bone CT. Patients with the intermediate or severe form exhibited severe speech delay by more than 2 years (12/14 patients). However, in patients with the mild form (5/5), speech development was not much disturbed (2/5), although otoscopic findings were similar. The hearing threshold determined by the auditory brainstem response differed significantly between the mild and intermediate/severe forms (p < 0.05). Therefore, patients with the mild form may benefit from active otologic intervention such as VT insertion, amplification, and speech therapy.

Speech Recognition Materials and Ceiling Effects: Considerations for Cochlear Implant Programs

from Audiology & Neuro-Otology

Cochlear implant recipients have demonstrated remarkable increases in speech perception since US FDA approval was granted in 1984. Improved performance is due to a number of factors including improved cochlear implant technology, evolving speech coding strategies, and individuals with increasingly more residual hearing receiving implants. Despite this evolution, the same recommendations for pre- and postimplant speech recognition testing have been in place for over 10 years in the United States. To determine whether new recommendations are warranted, speech perception performance was assessed for 156 adult, postlingually deafened implant recipients as well as 50 hearing aid users on monosyllabic word recognition (CNC) and sentence recognition in quiet (HINT and AzBio sentences) and in noise (BKB-SIN). Results demonstrated that for HINT sentences in quiet, 28% of the subjects tested achieved maximum performance of 100% correct and that scores did not agree well with monosyllables (CNC) or sentence recognition in noise (BKB-SIN). For a more difficult sentence recognition material (AzBio), only 0.7% of the subjects achieved 100% performance and scores were in much better agreement with monosyllables and sentence recognition in noise. These results suggest that more difficult materials are needed to assess speech perception performance of postimplant patients – and perhaps also for determining implant candidacy.

Children at Familial Risk of Dyslexia: Practical Implications from an At-Risk Study

from the Child and Adolescent Mental Health

A longitudinal study was conducted of 50 at-risk poor readers who were seen at four assessment points between the ages of three years and nine months and 12–13 years. This provided a wealth of data about the incidence of reading problems, the course of developmental relationships among language and literacy skills and the factors that influence outcome (including risk and protective factors and co-morbid difficulties). The practical implications of this study are considered for the management of poor readers; including identifying children at-risk of dyslexia, assessing and teaching poor readers, addressing co-occurring difficulties, capitalising on compensatory or protective factors and providing emotional support.

• The link between early language and phonology and later reading ability suggests that it is possible to screen for dyslexia in children as young as five

• Assessment of the poor reader needs to reflect the multidimensional nature of literacy skills and its underlying phonological basis

• Assessing language, maths, attention and visuo-spatial difficulties is essential for detecting co-occurring difficulties common in children with dyslexia

• Additional literacy support needs to address the core phonological and decoding problems experienced by children with dyslexia

• Recognising and promoting the development of compensatory strategies may help to improve the outcome for many children with dyslexia

Delivering Audiology Services for the Future

from the National Library for Health

For further information contact:

Tel: 0845 056 8299 Fax: 020 7728 5299
Email: HSJconferences@emap.com

Where:London When:30 Jan 2008 09:30 – 16:30

Wertigkeit der farbkodierten Duplexsonografie bei neuro-otologischen Krankheitsbildern

from Ultraschall in der Medizin – European Journal of Ultrasound

Article is in German, English abstract is from PubMed.

PURPOSE: The successful introduction of Doppler and Color-Coded Doppler Sonography (CCDS) in the field of Otorhinolaryngology has improved the diagnostic sonographic value for several diseases of the head and neck region, e. g. in hemangiomas and vascular malformations. The diagnostic value of CCDS for examination of the extracranial brain supplying vessels in combination with neuro-otologic disorders is still under controversial discussion. MATERIALS AND METHODS: We investigated the diagnostic CCDS findings for 215 patients suffering from different neuro-otologic disorders. All patients were classified into 4 groups according to the different disorder entity (sudden deafness, tinnitus, vestibular neuropathy, combined diagnosis). The frequency of pathologic CCDS findings was correlated with the different groups using sonographic parameters such as atherosclerosis, stenosis and intima-media thickness. RESULTS: Classification of the disorder entities led to the following distribution: Sudden deafness group (85 patients; 40 %), Tinnitus group (44 patients; 20 %), Vestibular neuropathy group (41 patients; 19 %), Combined diagnosis group (45 patients; 21 %). Sonographic evaluation of atherosclerosis was possible in 76 cases (35 %), changes of the intima-media thickness were observed in 43 cases (20 %) while proof of stenoses was identified in 15 cases (7 %). The evaluation of plaque formation (atherosclerosis) in the sudden deafness group was significantly higher (p < 0.01) than in all other groups although the combined diagnosis group demonstrated certain tendencies (p < 0.08) without significant correlation. CONCLUSION: Our results reinforce the hypothesis of a vascular genesis of sudden deafness and seem to offer the possibility of sonographic differentiation between neuro-otologic disorder entities by use of CCDS. In contrast, it seems that the role of CCDS is negligible for individual diagnostic purposes.