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PubMed1993

A physiological coma scale: grading of coma by combined use of brain-stem trigeminal and auditory evoked potentials and the Glasgow Coma Scale.

Forty-five comatose patients were prospectively studied by means of clinical examination and evoked potentials. In each patient, clinical data included Glasgow Coma Scale (GCS) score, age, pupillary response to light, corneal reflex, and eye movements. Neurophysiological evaluation was based on brain-stem trigeminal evoked potentials (BTEPs) and brain-stem auditory evoked potentials (BAEPs). For each physiological test, a progressive grading system was designed. This system was based on the evaluation of central conduction times along the trigeminal and the auditory pathways within the brain-stem. The accuracy of the clinical and the neurophysiological indicants in predicting "favorable" or "unfavorable" outcome was assessed singly and in combination. Of the clinical indicants, the GCS provided the most accurate prognosis (80%). Similar results were provided by the BAEP and the BTEP, with significant improvement in the confidence of outcome prediction. No significant difference in the accuracy of outcome predictions could be found between combined clinical data and neurophysiological data. However, the combination of clinical and neurophysiological data markedly increased both the accuracy and the confidence of outcome prediction, reaching 86% correct predictions at the over 90% confidence level with only 2% false pessimistic errors. According to these findings, a clinical-physiological coma scale, the trigeminal-auditory Glasgow (Coma Scale) score (TAG score) was designed. The TAG score demonstrated the highest accuracy at each confidence level as compared to other single indicants. We concluded that the TAG score may improve the evaluation of deep comatose patients and assist the physician in the management of such patients.

Adolescent↗
PubMed2000

Functional magnetic resonance imaging may avoid misdiagnosis of cochleovestibular nerve aplasia in congenital deafness.

OBJECTIVE: To investigate a narrow internal auditory canal (IAC) syndrome using functional magnetic resonance imaging (fMRI) of the auditory cortex. STUDY DESIGN: The study design was a case report. The follow-up period lasted 18 months. SETTING: The study was carried out in the audiology clinic of an ear, nose, and throat department and in the department of pediatric neuroradiology at a university hospital. MAIN OUTCOME MEASURES: Age-appropriate observational audiometry, objective audiovestibular tests, computed tomography (CT), magnetic resonance imaging (MRI), and (fMRI) of the auditory cortex were performed to analyze in detail the profound deafness of a young child. RESULTS: Audiovestibular examination demonstrated both measurable hearing and normal vestibulo-ocular reflex, and CT showed narrow IACs combined with normal labyrinths. Axial MR images completed by sagittal sections perpendicular to the IAC delineated a single nerve that was initially supposed to be the facial nerve. No cochleovestibular nerve was identified. However, fMRI performed with the patient under general anesthesia demonstrated activation of the primary auditory cortex during 1-kHz monaural stimulation on the left side. CONCLUSIONS: The absence of cochleovestibular nerve on MR studies cannot exclude connections between the inner ear and the central auditory pathways. This might be caused by a lack of spatial resolution of anatomical MR studies. The single nerve delineated within the IAC might also carry both facial and cochleovestibular fibers. Functional MRI can assess the cortical response to acoustic stimuli when aplasia of the cochleovestibular nerve is suspected. This case study illustrates a novel and atypical presentation of cochlear nerve dysplasia.

Acoustic Stimulation↗
PubMed2004

Longer storage of auditory than of visual information in the rabbit brain: evidence from dorsal hippocampal electrophysiology.

Whereas sensory memory in humans has been found to store auditory information for a longer time than visual information, it is unclear whether this is the case also in other species. We recorded hippocampal event-related potentials (ERPs) in awake rabbits exposed to occasional changes in a repeated 50-ms acoustic (1000 versus 2000 Hz) and visual (vertical versus horizontal orientation) stimulus. Three intervals (500, 1500, or 3000 ms) between stimulus repetitions were applied. Whereas acoustic changes significantly affected ERPs with the repetition intervals of 500 and 1500 ms, visual changes did so only with the repetition interval of 500 ms. Our finding, thus, suggests a similarity in sensory processing abilities between human and non-human mammals.

Acoustic Stimulation↗
PubMed1982

Rapid learning of visual and auditory spatial task in binocularly deprived cats.

Visually deprived and non-deprived cats were trained in a task involving a directional alimentary response spatially contiguous with a visual or an auditory cue. Both visual and auditory tasks were learned much faster by deprived cats. In these cats targeting reflexes evoked by the cues were stronger. When the modality of the cue was changed (from visual into auditory or vice versa), the learning was rapid in both non-deprived and deprived cats.

Animals↗
PubMed1993

[Presbycusis].

Hearing loss in the elderly is the most common type of hearing impairment. The term presbyacusis has been used to describe this category of hearing loss when there are no other etiological factors. However, the term is not precise, because any of several locations along the auditory pathway may be involved to produce the symptoms. The diagnosis is based more on the course of the hearing loss and the associated biological signs of aging than on specific criteria. The loss of speech-understanding ability is one of the most important indicators for a therapeutic intervention, which generally aims at amplification using a personal hearing aid. An improvement in speech-understanding ability with a hearing aid depends on several complex factors, and there is a large amount of intersubject variability in the benefit derived from amplification, even when the magnitude of the hearing loss is comparable. The aim of research on presbyacusis over the next several years--keeping in mind the demographic development in the industrialized countries--will be to further the differential analysis of the factors contributing to auditory communication disorders in the aging population.

Aged↗
PubMed1991

Increment of brain temporal perfusion during auditory stimulation. Preliminary study with technetium-99m HMPAO SPET.

A study on the dynamic exploration of the auditory pathway is presented, in which technetium-99m hexamethylpropylene amine oxime single-photon emission computed tomography (SPET) was used in volunteers with normal hearing. Changes in 99mTc-HMPAO distribution were calculated using a region of interest/whole-brain count ratio. The results showed a temporal perfusion increment of 17% (right) and 19% (left) during tonal supraliminar stimulation, which was significantly different from the control ROI. Sensitivity tests for the method were requested before any clinical application.

Acoustic Stimulation↗
PubMed1987

The sequence of myelination in the brainstem of the rat monitored by myelin basic protein immunohistochemistry.

The temporal order which is observed by nervous pathways in their myelination was investigated in the brainstem of neonatal to 16-day-old albino rats. The immunohistochemical detection of myelin basic protein in newly forming myelin sheaths provided a highly sensitive and specific criterion to judge the time of onset and the progress of myelination in its initial stages. Immunohistochemistry was performed on paraffin-embedded tissue according to the unlabeled peroxidase-antiperoxidase method. A small number of immunoreactive fibers was already present in neonate rats in the ventral funiculus of the cervical spinal cord and in the medial longitudinal fascicle of the medulla oblongata. By the 4th postnatal day myelination had commenced in many sensory tracts and in the trigeminal root, in the tectospinal tract, in the inferior cerebellar peduncle and in the roots of most cranial motor nerves. The auditory pathway up to the inferior colliculus, the gracile, spinocerebellar and rubrospinal tracts and the superior cerebellar peduncle had acquired some myelin on the 7th day. Phylogenetic late fiber systems also appeared to myelinate comparatively late: the transverse pontine fibers and the medial cerebellar peduncle started on the 10th day, and in the corticospinal tract a conspicuously synchronized myelination appeared on the 13th day. All pathways of the brainstem possessed myelinated fibers on the 16th day and some tracts had approached their relative maturity.

Aging↗
PubMed2005

Tapping in synchrony to auditory rhythms: effect of temporal structure on behavior and neural activity.

This study examines how synchronizing movements to auditory rhythms affects behavioral performance and neural activity as assessed using fMRI. Subjects perform worse as they tap along with increasingly complex musical rhythms, with responses becoming progressively asynchronous. This behavioral change also correlates with increasing neural activity in several motor-related brain regions, such as the cerebellum and premotor cortex (medial and lateral), highlighting the role of these areas in auditory-motor interactions during temporal processing.

Acoustic Stimulation↗
PubMed1986

Brain maturity in regard to the auditory brainstem response in small-for-date neonates.

The auditory brainstem response has been used in neonates at risk of hearing impairment or as a functional measurement of brain maturity. The goal of the present study was to evaluate the auditory brainstem response in small-for-date newborns, in relation to changes observed with fetal maturity in a control group. Compared to controls with similar maturity, a significant delay for the appearance of waves III and V, and between waves I-V was observed in the small-for-date newborns, suggesting an alteration of the auditory pathway within the brainstem rather than an impairment of the peripheral auditive apparatus. Indeed, small-for-date newborns reacted to the test in a similar manner as premature babies in whom such a delay was also observed. Our data would suggest a functional brain immaturity in small-for-date newborns, during the first days of life, in regard to the auditive evoked potential, which may be related to some alterations in brain development reported with fetal malnutrition.

Birth Weight↗
PubMed1985

The anatomical consequences of acoustic injury: A review and tutorial.

The anatomic consequences of acoustic overstimulation are explored in this presentation, and attention is directed toward issues where improvements in technology and empirical observation are needed before further advances in our understanding can be achieved. Gains have been made in the last decade in appreciating sound-induced cochlear injury, but there is now a need to evaluate not only cochlear pathology but also the functional state of the surviving structures. There is a wealth of information about the susceptibility of inner or outer hair cells to acoustic injury; however, the etiology of this injury is not yet fully understood. In addition, current ideas concerning the effects of noise on hair-cell stereocilia, hair-cell synapses, the cochlear vascular supply, and the central auditory pathways are in a state of flux and are either undergoing revision or emerging. Other issues, such as the basis of temporary or permanent threshold shift at the cellular level, and the individual differences in susceptibility to injury are in need of a fresh approach. It would seem that the time is now ripe to review our knowledge, recognize its gaps, and develop testable hypotheses concerning the mechanisms of acoustic injury to the ear.

Animals↗
PubMed1994

Laterality effects in normal subjects: evidence for interhemispheric interactions.

In this review we describe three methods of research that have been used to study relationships between the cerebral hemispheres in normal human subjects. We briefly mention reaction-time studies, which have been used to measure interhemispheric transmission time; more pertinent to laterality effects, however, are lateralized visual field studies, in which stimuli can be presented either unilaterally or to both visual fields simultaneously, and dichotic listening studies, wherein different stimuli are presented to the two ears simultaneously. Recent examples from the literature of experiments employing these techniques are discussed as they pertain to an understanding of interhemispheric interaction. Some suggestions are offered concerning appropriate procedures for studying interhemispheric interactions in normal human subjects.

Attention↗
PubMed2003

Auditory thalamic nuclei projections to the temporal cortex in the rat.

Thalamocortical projections from the auditory thalamic nuclei were examined systematically in the rat, including those from the dorsal division (MGD) of the medial geniculate body (MG), which were less clearly determined in previous studies. Injections of biocytin confined in each thalamic nucleus revealed characteristic features of projections in terms of cortical areas and layers of termination. In contrast to exclusively selective projections to cortical area Te1 from the ventral division (MGV) of the MG, diffuse and selective terminations were observed in the projections from the dorsal (MGD) and medial divisions (MGM) of the MG and the suprageniculate nucleus (SG). Diffuse termination was continuous in layer I or VI of the temporal cortex, while selective termination was in layers III and IV of discrete cortical areas. In addition to diffuse termination in the upper half of layer I of cortical areas Te1, Te2d and Te3v, the MGD and SG projections formed plexuses of axons selectively in lower layer III and layer IV of Te2d and Te3v. The SG projections targeted further the dorsal bank of the perirhinal cortex (PRh), while the MGD projections targeted in part the ventral fringe of Te1. The MGM projections terminated diffusely in layer VI of Te1 and Te3v, and selectively in lower layer III and layer IV of the rostral part of Te3v. Diffuse projections to layers I and VI from the SG and MGM extended in cortical regions over the dorsal fringe of Te1. Selective dense projections to middle cortical layers of Te2d and Te3v (especially its rostral part) indicate the existence of auditory areas, which could be involved in cross-modal interaction with visual and somatosensory system, respectively. Diffuse projections are supposed to bind information processings in these areas and the primary auditory area (Te1).

Animals↗
PubMed2002

Auditory activation of "visual" cortical areas in the blind mole rat (Spalax ehrenbergi).

The mole rat (Spalax ehrenbergi) is a subterranean rodent whose adaptations to its fossorial life include an extremely reduced peripheral visual system and an auditory system suited for the perception of vibratory stimuli. We have previously shown that in this blind rodent the dorsal lateral geniculate nucleus, the primary visual thalamic nucleus of sighted mammals, is activated by auditory stimuli. In this report we focus on the manifestation of this cross-modal compensation at the cortical level. Cyto- and myeloarchitectural analyses of the occipital area showed that despite the almost total blindness of the mole rat this area has retained the organization of a typical mammalian primary visual cortex. Application of the metabolic marker 2-deoxyglucose and electrophysiological recording of evoked field potentials and single-unit activity disclosed that a considerable part of this area is activated by auditory stimuli. Previous neuronal tracing studies had revealed the origin of the bulk of this auditory input to be the dorsal lateral geniculate nucleus which itself receives auditory input from the inferior colliculus.

Acoustic Stimulation↗
PubMed2003

Dynamics of audio-visual interactions in the guinea pig brain: an electrophysiological study.

Audio-visual interactions and their specifications, evaluated by bioelectrical activities, in guinea pigs are presented in this study. The difference potential, as the evidence of an interaction, was calculated by subtracting the sum of averaged potentials recorded in visual and auditory events from the averaged potential recorded in an event where two stimuli combined in the same sweep. Dynamic investigations have shown an interaction when auditory stimulus is applied 24 ms before and 201 ms after visual stimulation. Latency between the difference potential and auditory stimulus was stable. Directional investigations have shown that the interaction is not observed when auditory and/or visual stimulation is used ipsilaterally, according to the recording side.

Acoustic Stimulation↗
PubMed2006

Early experience determines how the senses will interact.

Multisensory integration refers to the process by which the brain synthesizes information from different senses to enhance sensitivity to external events. In the present experiments, animals were reared in an altered sensory environment in which visual and auditory stimuli were temporally coupled but originated from different locations. Neurons in the superior colliculus developed a seemingly anomalous form of multisensory integration in which spatially disparate visual-auditory stimuli were integrated in the same way that neurons in normally reared animals integrated visual-auditory stimuli from the same location. The data suggest that the principles governing multisensory integration are highly plastic and that there is no a priori spatial relationship between stimuli from different senses that is required for their integration. Rather, these principles appear to be established early in life based on the specific features of an animal's environment to best adapt it to deal with that environment later in life.

Adaptation, Physiological↗
PubMed1989

[Brainstem auditory evoked potentials in head injury patients].

This study was designed to evaluate the alterations in brainstem auditory evoked potentials (BAEPs) in patients with head injuries. BAEPs were recorded of twenty-five normal subjects to serve as control group. Fifty-four patients with head injuries were evaluate prospectively by neurological check-ups, the Glasgow coma rating scale, brain CT scans, as well as BAEPs. Among them, twenty-two patients accepted a follow-up evaluation one month after the first study. In the acute stage, though the significant prolongation of peak latency occurred only in the right peak III as compared with the control group, the rate of presence decreased significantly in most of the peak waves. There were three main types of abnormality: isoelectric BAEP (13.0%), alterations in peak I (29.6%) and in interpeak latencies (13.0%). The incidence of abnormal BAEPs was 48.2% of 54 patients. Patients were divided into two groups according to whether their coma scale was above/equal to or below 9. No significant difference was shown in the rate of appearance of wave peaks and the average latency of each peak wave. This suggests BAEPs displayed a function of the auditory pathway only rather than a reticular formation in the brainstem. Concerning the group with brain stem abnormality as shown in CT scan, there was significant prolongation in most peak and interpeak latencies, and the rate of presence of each peak was significantly lower compared with the non-brainstem-abnormality group. Therefore, the alteration in BAEPs in head injuries coincide with the presence of abnormal brainstem signs in the CT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗