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Biomedical subjects

S C Levine

Publications and source records attributed to S C Levine.

At least 19 recordsLinked to original sources
PubMed1992

Variations in characteristic perceptual asymmetry: modality specific and modality general components.

The current study investigates sources of between-subjects variation in asymmetry scores on visual half-field and dichotic listening tasks. For each of these presentation modalities, subjects were given multiple laterality tasks. Results indicate that about 50% of the between-subjects variations in asymmetry scores in each modality is attributable to individual differences in perceptual asymmetries that are not stimulus-specific, referred to as "characteristic perceptual asymmetries" in this paper. In addition, the question of whether individual differences in characteristic perceptual asymmetries are modality specific, modality general, or both was investigated by entering subjects' asymmetry scores from visual half-field and dichotic listening tasks into a principal component analysis. The results of this analysis indicate that there are both modality specific and modality general influences on subjects' characteristic perceptual asymmetries.

Adult↗
PubMed1992

Development of calculation abilities in young children.

This study investigates the development of skills for solving verbally and nonverbally presented calculation problems in children between 4 and 6 years of age. Identical addition and subtraction calculations were presented in three problem-type formats: nonverbal problems, story problems, and number-fact problems. The nonverbal problems involved presenting sets of physical referents that were then transformed either by adding or removing elements. The child saw the initial set and the number of elements that were added or removed, but not the final set. The task was to construct an array that contained the number of elements in the final set. The story problems and number-fact problems were presented orally, without props. Results indicate that children as young as 4 years of age have some success on the nonverbal problems, showing that they can transform sets by adding or subtracting elements. In contrast, children do not achieve comparable levels of success on the story problems or number-fact problems until 5 1/2 to 6 1/2 years of age. Moreover, throughout the age range tested, children performed better on nonverbal problems than on either story problems or number-fact problems. These results suggest that children's earliest ability to add and subtract is based on experiences combining and separating sets of objects in the world and that this ability precedes the development of conventional verbal methods of calculating.

Aptitude↗
PubMed1992

Effect of ear-canal air pressure on evoked otoacoustic emissions.

The effect of ear-canal air pressure on click-evoked otoacoustic emissions was measured for pressures ranging from 200 to -200 daPa and stimulus levels ranging from 60-90 dB PeSPL. Positive and negative ear-canal pressures (relative to ambient pressure) reduced the emission amplitude by 3-6 dB. A spectral analysis of the emissions revealed that the effect of ear-canal air pressure is that of a high-pass filter with a cutoff frequency of 2600 Hz and a slope of 4 dB/oct. The spectral changes are the expected effect of an increase in stiffness of the middle ear and were independent of pressure polarity and click level. Ear-canal air pressure substantially reduced the reproducibility of the emission waveform, in many cases rendering the emission indistinguishable from background noise. The implication of these findings for hearing screening applications is that a high false alarm rate may occur in normal-hearing patients with intratympanic air pressures that are significantly different from ambient pressure.

Adult↗
PubMed1992

Tympanic electrocochleography for evaluation of endolymphatic hydrops.

There has been increased interest in electrocochleography for the diagnosis and intraoperative monitoring of patients with endolymphatic hydrops. Attention has been focused on the determination of the summating potential:action potential (SP:AP) ratio from alternating polarity clicks. Review of this technique at the University of Minnesota led to a reevaluation of the usual interpretation of these recordings. Separate examination of the rarefaction and condensation click recordings provides insight into abnormal response patterns. Cases are presented to illustrate a variety of normal and abnormal patterns including abnormal differences in the latency of condensation and rarefaction-click-generated action potentials, increased summating potential, uncanceled cochlear microphonic, and reduced action potential and summating potential amplitudes. These response categories may be useful in understanding the pathophysiology of Meniere's disease.

Acoustic Stimulation↗
PubMed1992

Tympanic electrocochleography: normal and abnormal patterns of response.

Electrocochleography has been widely used in human and animal studies of endolymphatic hydrops. A variety of response patterns have been reported in normal and hydropic ears. Recent clinical studies have focused almost exclusively on the amplitude ratio of the summating potential (SP) and action potential (AP) derived from alternating polarity click responses. In this report normal response patterns are described with a tympanic membrane electrode employing condensation, rarefaction and alternating polarity clicks and tone burst stimulation. A variety of response abnormalities are described in patients with suspected endolymphatic hydrops. The exclusive use of alternating polarity clicks is not adequate to reveal the nature of these abnormalities.

Acoustic Stimulation↗
PubMed1991

Sources of between-subjects variability in perceptual asymmetries: a meta-analytic review.

A number of studies have reported correlations between subjects' asymmetry scores on left and right hemisphere specialized tasks. In this paper we report the results of meta-analyses performed on these correlations. Results showed positive correlations between subjects' asymmetry scores on left and right hemisphere specialized tasks in both modalities (asymmetry scores were computed as R-L for both left and right hemisphere specialized tasks). Thus, in both modalities, some of the between-subjects variability in asymmetry scores appears to reflect non-stimulus specific individual differences in perceptual asymmetry. For the visual asymmetry tasks, results also showed that the subjects' asymmetry scores on left and right hemisphere specialized tasks were more highly correlated under conditions of bilateral than unilateral input. This finding suggests that bilateral tasks may be more sensitive to "characteristic perceptual asymmetry" than unilateral tasks.

Dichotic Listening Tests↗
PubMed1991

Inferring patterns of hemispheric specialization for individual subjects from laterality data: a two-task criterion.

Sixty-three subjects (31 dextrals and 32 sinistrals) were given two visual half-field laterality tasks (recognition of words and faces). Subjects were classified as having typical or atypical hemispheric specialization on the basis of the relative magnitude of their asymmetry scores on the two laterality tasks. Those subjects whose word asymmetry scores were larger than their face asymmetry scores (asymmetry scores computed as RVF-LVF for both tasks) were classified into Group Typical and those subjects whose word asymmetry scores were smaller than their face asymmetry scores were classified into Group Atypical. For both dextrals and sinistrals, the proportion of subjects classified into Groups Typical and Atypical was consistent with estimates of the incidence of typical and atypical hemispheric asymmetry patterns based on sodium amytal testing. These results support the hypothesis that the relative magnitude of asymmetry scores on left and right hemisphere specialized tasks index individual differences in patterns of hemispheric specialization.

Adolescent↗
PubMed1991

Relative value of diagnostic tests for small acoustic neuromas.

Auditory brainstem response is now widely employed as a screening test for acoustic neuromas because it is equally sensitive when standardized against computed tomography. We have detected eight small (less than 10 mm) acoustic neuromas using gadolinium enhanced magnetic resonance imaging. In three of these cases, the auditory brainstem response was falsely negative. In contrast, 19 patients with larger tumors (greater than or equal to 10 mm) were found to have no false negative auditory brainstem responses. Auditory brainstem response appears to be less sensitive for detecting small, symptomatic acoustic neuromas.

Adult↗
PubMed1991

Acoustic reflex measures in audiologic evaluation.

Measurement of the acoustic-stapedius reflex is useful in the diagnosis of certain otologic diseases. The anatomy and physiology of the middle ear muscles and the acoustic reflex arc are reviewed for normal and pathologic ears. The application of acoustic reflex measures to clinical diagnosis is illustrated by a series of case studies.

Auditory Threshold↗
PubMed1990

The effects of developmental factors on IQ in hemiplegic children.

The effects of early unilateral brain lesions on subsequent intellectual functioning were explored in hemiplegic children with congenital or acquired lesions. For congenital hemiplegics who sustained damage pre- or perinatally, lower intellectual functioning (IQ) was most highly associated with longer elapsed time since lesion. Moreover, including lesion size as an additional predictor of IQ did not account for significantly more variance than elapsed time since lesion alone. In contrast, for acquired hemiplegics who sustained damage after birth, lower intellectual functioning was highly associated with larger lesion size. In this group neither elapsed time since lesion nor age at testing accounted for significantly more IQ variance than lesion size alone. Possible effects of maturational factors and functional plasticity are considered in interpreting this pattern of results.

Adolescent↗
PubMed1990

Are variations among subjects in lateral asymmetry real individual differences or random error in measurement? Putting variability in its place.

The current research investigates sources of variability in subjects' asymmetry scores on commonly used laterality tasks. In particular, subjects' asymmetry scores on four bilateral tachistoscopic tasks and one free-vision task were entered into a principal component analysis (PCA) in order to investigate components that explain the maximum variance of the sample. The results indicate that about half of the variation (45.2%) in asymmetry scores on both tachistoscopic and free-vision tasks is attributable to individual differences in characteristic perceptual asymmetry. The amount of variance explained by this characteristic perceptual asymmetry component is similar in a sample of dextrals and a sample of sinistrals. No significant relation was revealed between individual differences in characteristic perceptual asymmetry and performance on various verbal and spatial cognitive tasks.

Adolescent↗
PubMed1990

Discrimination of normal and at-risk preschool children on the basis of neurological tests.

A set of neurological tasks was administered to normal three- and five-year-old preschool children as well as to equal-age children identified as being at-risk for learning disabilities. 12 neurological test items were identified that differentiated normal from at-risk children at one or both ages. Follow-up of the five-year-olds at age seven showed a significant linear relation between scores on neurological tasks and the Wechsler Intelligence Test for Children. The neurological examination at age five also had predictive value regarding class placement at age seven. The findings suggest that a simple neurological test may be helpful for the early identification of preschool children who are at risk for learning difficulties.

Brain Damage, Chronic↗
PubMed1990

Diagnosis and treatment of arachnoid cysts of the posterior fossa.

Arachnoid cysts of the posterior fossa are rare. When arachnoid cysts are encountered, the presenting symptoms are frequently otologic, with hearing loss and imbalance occurring commonly. Three cases are presented with a previously unreported otologic symptom, that of bilateral hearing loss, which in one case was fluctuant. None of the patients had the common symptoms of unilateral hearing loss and headache. With the advent of computed tomography and magnetic resonance imaging, these cysts may be readily identified, usually with diagnostic imaging alone. Unfortunately there is often a delay in diagnosis because of the vague and fleeting nature of the symptoms. Because no single diagnostic symptom pattern is able to characterize all cases, it is believed computed tomography or magnetic resonance imaging or both are indicated in patients with long-standing otologic complaints--even in the absence of unilateral symptoms. Treatment of posterior fossa arachnoid cysts primarily consists of surgical procedures designed to decompress the cyst. In this series, treatment with diuretics alone resulted in improvement of symptoms during several years of followup, with no evidence of enlargement of the cysts.

Adult↗
PubMed1990

Long-term results of labyrinthectomy.

Ten years after labyrinthectomy, 38 patients responded to a questionnaire. There was a slight decline in relief of vertigo from 93% to 76%. Symptoms following the procedure are discussed. It is believed that the reason for the decline is secondary to the age of the patients, the occasional bilateral nature of Meniere's disease, and possibly postsurgical neuroma formation. The ramifications of this study are discussed with respect to hearing-conservation procedures.

Ear, Inner↗
PubMed1990

Recurrent hemangioma of the external auditory canal.

Hemangiomas of the external auditory canal rarely occur. These lesions have been reported to involve men in their sixth decade. This case report represents the fourth such lesion reported in the literature and the first to be seen in a woman. The clinical presentation, surgical therapy, and pathology are discussed. This tumor represents an unusual cause of hearing loss.

Ear Canal↗
PubMed1989

A complex case of cochlear implant electrode placement.

Cochlear implantation is becoming an increasingly accepted rehabilitative procedure for post lingually deafened adults. The testing, evaluation, and surgery have become standardized procedures. In this case results of two different promontory tests were contradictory. A constant voltage stimulation test was negative, while a later constant current stimulation test indicated good residual function. The CT scan accurately predicted the location of the round window remanent. In order to gain access to the cochlea, a partial labyrinthectomy was performed. Successful implantation was ultimately achieved. This implies that a previous labyrinthectomy may not be an absolute contraindication to cochlear implantation.

Adult↗
PubMed1988

Face recognition: a general or specific right hemisphere capacity?

Face-recognition ability has been claimed to be qualitatively different from other pattern-recognition abilities. One argument for this claim is the finding of a significant right hemisphere advantage for the recognition of upright but not inverted faces. However, this argument is justified only if this orientation-sensitive pattern is unique to faces. In the present study, comparable patterns of orientation-sensitive involvement of the right hemisphere are found for the recognition of faces and houses. This finding is interpreted as evidence for a right hemisphere schema formation capacity that is applied not only to upright faces but also to other familiar classes of stimuli in their canonical upright orientation. It is suggested that any greater right hemisphere involvement in the recognition of upright faces is due to our greater expertise at recognizing faces than other stimulus types. We also find evidence that only a subset of right-handed adults show orientation-sensitive right hemisphere involvement in the recognition of faces and houses: in particular, those dextrals with a characteristic hemispheric arousal asymmetry in favor of the right hemisphere. In contrast, dextrals with a characteristic arousal asymmetry in favor of the left hemisphere do not show significant visual field asymmetries for faces or houses in either upright or inverted orientations.

Adolescent↗