Search results for "evoked potential"
showing 10 items of 604 documents
Enhancement of Gamma Oscillations Indicates Preferential Processing of Native over Foreign Phonemic Contrasts in Infants
2013
Young infants discriminate phonetically relevant speech contrasts in a universal manner, that is, similarly across languages. This ability fades by 12 months of age as the brain builds language-specific phonemic maps and increasingly responds preferentially to the infant's native language. However, the neural mechanisms that underlie the development of infant preference for native over non-native phonemes remain unclear. Since gamma-band power is known to signal infants' preference for native language rhythm, we hypothesized that it might also indicate preference for native phonemes. Using high-density electroencephalogram/event-related potential (EEG/ERP) recordings and source-localization…
A muscarinic receptor different from the M1, M2, M3 and M4 subtypes mediates the contraction of the rabbit iris sphincter
1992
In order to analyse the subtype of muscarinic receptors involved in the methacholine-induced contraction of the rabbit iris sphincter we have determined equilibrium dissociation constants (KB) of various antagonists in the sphincter muscle. The values were compared with those observed at M1 (rabbit vas deferens), M2 (heteroreceptors in rat iris) and M3 receptors (guinea-pig ileum), or at the muscarinic receptors in the guinea-pig uterus. The methacholine-induced contraction of the uterus from immature guinea-pigs was competitively antagonized by pirenzepine (6.64, -log KB), 4-DAMP (8.39), hexahydrodifenidol (HHD; 7.00 for the (R)- and 5.40 for the (S)-enantiomer), p-fluoro-hexahydrosiladife…
Electrical responses of pineal cells to melatonin and putative transmitters
1981
The effects of microelectrophoretically applied melatonin (N-acetyl-5-methoxy-tryptamine), noradrenaline (NOR) or acetylcholine (ACH) on the electrical activity of pineal cells during both the day- and night-time were studied in urethane anesthetised guinea-pigs. A total of 288 cells were tested with melatonin, and in addition with either NOR (120 cells) or ACH (138 cells). Of the 206 cells responding to melatonin application, 139 were excited and 67 inhibited. A total of 85 cells responded to the application of NOR, 45 being excited and 40 inhibited. Responses to ACH application were observed in 75 pineal cells, 49 units being inhibited and 26 excited. It was possible to observe excitation…
Gentamicin increases nitric oxide production and induces hearing loss in guinea pigs.
2008
Objectives/Hypothesis: Gentamicin application is an important therapeutic option for Meniere's disease. However, even if given at intervals, a destruction of the cochlea was often observed in various animal models together with an increased content of nitric oxide (NO) and reactive oxygen species. The present study was undertaken to identify the correlation between hearing threshold alteration and the NO production in the lateral wall and organ of Corti of the guinea pig in response to gentamicin application. Study Design: Prospective animal study in guinea pigs. Methods: A single dose of gentamicin (10 mg/kg body weight) was injected intratympanally into male guinea pigs and the auditory b…
Auditory Neuropathy in Children
2001
Auditory neuropathy is a sensorineural disorder characterized by absent or abnormal auditory brainstem evoked potentials and normal cochlear outer hair cell function. A variety of processes is thought to be involved in its pathophysiology and their influence on hearing may be different. We present here the diagnostic sequence and management of two new cases of auditory neuropathy in breastfeeding children.
An experimental comparative study of dexamethasone, melatonin and tacrolimus in noise-induced hearing loss.
2008
The calcineurin inhibitor tacrolimus (TCR) and the pineal gland hormone and antioxidant melatonin (MLT) have been shown to possess otoprotective properties against noise-induced hearing loss (NIHL). In contrast, dexamethasone (DXM) was not effective as an otoprotective agent against NIHL. Further studies are needed to understand the exact molecular mechanisms involved.Exposure to noise pollution and use of audio devices for long periods of time at high volume is known to cause hearing loss or NIHL. Our goal was to evaluate the effectiveness of various known compounds such as the anti-inflammatory DXM, the antioxidant MLT and the immunosuppressant TCR against NIHL.Thirty-two Wistar rats were…
Estimating brain load from the EEG.
2009
Modern work requires cognitively demanding multitasking and the need for sustained vigilance, which may result in work-related stress and may increase the possibility of human error. Objective methods for estimating cognitive overload and mental fatigue of the brain on-line, during work performance, are needed. We present a two-channel electroencephalography (EEG)–based index, theta Fz/alpha Pz ratio, potentially implementable into a compact wearable device. The index reacts to both acute external and cumulative internal load. The index increased with the number of tasks to be performed concurrently (p= 0.004) and with increased time awake, both after normal sleep (p= 0.002) and sleep restr…
Doxycycline reduces nitric oxide production in guinea pig inner ears.
2011
Abstract Objective Gentamicin application is an important therapeutic option to control vertigo spells in Meniere's disease. However, even in the case of low-dose intratympanic application, gentamicin might contribute to a pathological NO-increase leading to cochlear damage and hearing impairment. The study was performed to evaluate the nitric oxide (NO) reducing capacity of doxycycline in the inner ear after NO-induction by gentamicin. Methods In a prospective animal study, a single dose of gentamicin (10 mg/kg body weight) was injected intratympanically into male guinea pigs (n = 48). The auditory brainstem responses (ABRs) were recorded prior to application and 3, 5 and 7 days afterwards…
Diagnostic subgroups of developmental dyslexia have different deficits in neural processing of tones and phonemes.
2004
The present study addressed auditory processing in 8-11-year-old children with developmental dyslexia by means of event-related brain potentials (ERP). Cortical sound reception was evaluated by recording N250 responses to syllables and tones and cortical sound discrimination by analyzing the mismatch negativity (MMN) to syllable and tone changes. We found that both cortical sound reception and sound discrimination were impaired in dyslexic children. The analysis of the data obtained from two dyslexic subgroups, Dyslexics-1 being impaired in non-word reading (or both non-word and frequent word reading) and Dyslexics-2 in frequent word reading but not in non-word reading, revealed that the MM…
Maturational effects on newborn ERPs measured in the mismatch negativity paradigm.
2003
Abstract The mismatch negativity (MMN) component of event-related potentials (ERPs), a measure of passive change detection, is suggested to develop early in comparison to other ERP components, and an MMN-like response has been measured even from preterm infants. The MMN response in adults is negative in polarity at about 150–200 ms. However, the response measured in a typical MMN paradigm can also be markedly different in newborns, even opposite in polarity. This has been suggested to be related to maturational factors. To verify that suggestion, we measured ERPs of 21 newborns during quiet sleep to rarely occurring deviant tones of 1100 Hz (probability 12%) embedded among repeated standard…