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Biomedical subjects

D G Jamieson

Publications and source records attributed to D G Jamieson.

At least 19 recordsLinked to original sources
PubMed1990

Studies of respiratory stridor in young children: acoustical analyses and tests of a theoretical model.

Non-invasive procedures are proposed to aid the diagnosis of childhood laryngotracheal pathology and to monitor the course of such disease. The procedures capitalize on the one-to-one relationship which exists between the acoustic phenomena (stridors) associated with respiration and the configuration of the respiratory tract. Careful analysis of these acoustic patterns can thus assist in identifying and localizing constrictions, in diagnosis, and in monitoring disease severity. Based on the acoustical analysis of the stridor generated by children with congenital stridor, subglottal laryngitis, and trachea stenosis, the present paper demonstrates that a close relationship exists between the specific pathology and the spectrum of the associated respiratory stridor.

Acoustics↗
PubMed1989

Training new, nonnative speech contrasts: a comparison of the prototype and perceptual fading techniques.

We trained unilingual adult Canadian francophone listeners to identify the English voiceless and voiced linguadental ("th") frictives, /theta/ and /delta/, using synthetic exemplars of each phoneme. Identification training with feedback improved listeners' abilities to identify both natural and synthetic tokens. These results show that training with appropriately selected prototype stimuli can produce a linguistically meaningful improvement in a listener's ability to identify new, nonnative speech sounds--both natural and synthetic. However, it is not yet clear whether such training with a single prototype can improve performance as effectively as the fading technique used by Jamieson and Morosan (1986), since prototype training produced only a moderate improvement in listeners' identifications of synthetic stimuli containing brief frication. Differences between the techniques may reflect the need for listeners to experience the appropriate types of intraphonemic and interphonemic variability during training. Such variability may help to define the category prototype by desensitizing the subjects to differences between exemplars of the same category and by sharpening sensitivity to differences between categories.

Adolescent↗
PubMed1989

Perception of voiceless fricatives by children with a functional articulation disorder.

The two studies presented here examine the relationship between speech perception and speech production errors in children who have a functional articulation disorder. In both experiments, speech perception was assessed with a word identification test, based upon a synthesized continuum of speech stimuli, contrasting the specific phonemes that were associated with production errors in our sample of articulation-disordered subjects. Experiment 1 required subjects to identify words that contrasted the phonemes /s/ and /S/. In this test, adults, normal speaking 5-year-olds, and some articulation-disordered 5-year-olds identified the words seat and sheet appropriately and reliably. However, a subgroup of articulation-disordered children were unable to identify the test stimuli appropriately. Experiment 2 required a second group of subjects to identify words that contrasted the phonemes /s/ and /theta/. Although both adults and normal speaking children responded appropriately to the words sick and thick, in this test, none of the articulation-disordered children was able to identify these words appropriately. It is concluded that, for a subgroup of children who have a functional articulation disorder, production errors may reflect speech perception errors.

Adult↗
PubMed1989

Evaluation of a technique for training new speech contrasts: generalization across voices, but not word-position or task.

We used the perceptual fading technique (Jamieson & Morosan, 1986) to teach unilingual adult Canadian francophones to identify the voiceless and voiced linguadental fricatives, /0/ and /o/. Training began with the identification of synthetic consonant-vowel (CV) exemplars that contained exaggerated amounts of frication (140 ms), with feedback given to identify errors and correct responses. Subsequently, stimuli with progressively shorter fricative durations were added to the identification set. After just 90 min of such training, francophone adults were better able to identify both the training stimuli and an untrained set of natural CVs produced by four different speakers, two men and two women. These results replicate and extend those reported by Jamieson and Morosan, and establish that such training generalizes to the identification of natural CVs produced by a variety of voices, both male and female. Thus, the effects of training are not restricted to a small range of acoustic cues. However, such learning was still strongly sensitive both to other aspects of the acoustic context and to the testing situation: Training failed to improve identifications of /0/ and /o/ phonemes when these were presented in word-medial and word-final positions, and identifications of synthetic and natural examples of /o/ vs. /d/ did not improve, even though identifications of /0/ vs. /o/ were very good.

Adolescent↗
PubMed1989

Comparison of CT, MR, and PET in Alzheimer's dementia and normal aging.

We compared the findings of computed tomography (CT), magnetic resonance (MR), and positron emission tomography (PET) scans of glucose metabolism in 30 patients with clinically diagnosed Alzheimer's Disease (DAT) to those noted in 25 age-matched normal controls. Mean ratings of cortical and ventricular atrophy on CT and of metabolic abnormality on PET were significantly different (p less than 0.001 and p less than 0.0001, respectively) between two subject groups, however, there was a considerable overlap in reading of cortical atrophy. CT hypodensities were present in 17% of DAT patients and 12% of controls. MR revealed numerous additional periventricular and deep white matter signal changes. Neither hypodensities nor hyperintensities were correlated with PET abnormalities. Although, not infrequently, hypometabolic areas on PET scans corresponded to atrophic regions on anatomic images, they also occurred without such changes. Interestingly, cortical high signal intensity seen on MRI was frequently observed to be associated with areas of hypometabolism. Our results suggest that PET may be the most sensitive modality for detecting cortical involvement in DAT.

Aged↗
PubMed1988

Atherosclerotic carotid artery disease in patients with retinal ischemic syndromes.

The extracranial carotid systems of 105 patients with retinal ischemia were examined using B-mode ultrasonography with integrated pulsed Doppler. Sixty-four patients had amaurosis fugax (AF), 17 central retinal artery occlusions (CRAO), and 21 branch retinal artery occlusions (BRAO). The prevalence of carotid stenosis (greater than or equal to 60%) ipsilateral to the symptomatic eye was low (16%). Eighty-six percent of AF patients had either no plaque causing less than a 60% stenosis. A significant proportion of subjects with normal duplex scans had alternative explanations for their retinal ischemia (eg, migraine, cardiac embolus). Patients with Hollenhorst plaques were more likely to have stenotic or ulcerated plaque (p = 0.04). The degree of carotid stenosis correlated significantly with the number of vascular risk factors identified in individual patients (p = 0.02). The presence of risk factors was more common in CRAO and BRAO patients compared with the AF group. Combined ultrasound-Doppler investigations of the carotid bifurcation are valuable noninvasive tools for the screening of patients with retinal ischemia.

Arteriosclerosis↗
PubMed1986

Oligoclonal immunoglobulin bands in cerebrospinal fluid of a patient with lymphocytic choriomeningitis.

We describe a patient with meningitis caused by lymphocytic choriomeningitis virus. Oligoclonal IgG bands were found in the patient's cerebrospinal fluid during acute and convalescent stages of the illness, and results of liver function tests were abnormal. Acute attacks of lymphocytic choriomeningitis virus infection in humans can be added to the list of diseases associated with cerebrospinal fluid oligoclonal IgG.

Adult↗
PubMed1986

Programs to produce high quality dichotic tapes for central auditory testing.

Dichotic stimulation, the simultaneous presentation of two different acoustic signals to the right and left ears, respectively, is used routinely in the clinical assessment of speech lateralization as well as in other central auditory testing procedures in the clinic and laboratory. At present, most researchers and clinicians depend on a few commercial sources for dichotic tapes, because there are a limited number of facilities which are able to produce such tapes. Moreover, some of the commercial tapes currently offered for sale contain important stimulus errors. In the present paper, we describe a general set of programs for the PDP 11 series of computers, which permits sequences of dichotic stimuli to be generated and output with a high degree of precision. These programs therefore allow researchers to generate any desired sequence of dichotic stimulation, for recording and taping, for use in their research. The programs operate in two stages to generate the required dichotic sequences. In the first stage, the constrained random ordering of the stimuli is generated as specified by the user. In the second stage, after the preliminary stimulus preparation has been completed (for example, using a waveform editing package; cf., D.G. Jamieson and D. A. Naugler, Comput. Biomed. Res., 1985, 18, 480), an audio tape is generated with stimuli presented dichotically, with timing and sequencing precisely as specified.

Auditory Cortex↗
PubMed1986

Locus of selective adaptation in speech perception.

Voiced (/ba/ or /da/) and voiceless (/pa/ or /ta/) consonants seem to affect different auditory system loci. On a voice-onset-time continuum (/ba/ to /pa/ or /da/ to /ta/) the selective adaptation effects produced by voiceless consonants are largely ear-independent and endure over delays of at least 1 min. However, voiced adapters produce selective adaptation effects that are highly ear-specific and relatively short-lived (less than 15 s). These differences suggest that specific cues to voiced and voiceless consonant sounds are processed by distinct auditory mechanisms and that these processes occur at different levels of the auditory system. One mechanism, which processes cues to voiced consonants, is peripheral and ear-specific. The second mechanism, which processes cues to voiceless consonants, is central and ear-independent.

Adaptation, Physiological↗
PubMed1986

Epidural haemangiomas during pregnancy.

Two cases of vertebral haemangiomas are reported which presented as spinal cord syndromes during pregnancy. Eleven additional cases of epidural haemangiomas in the literature which became symptomatic during pregnancy are reviewed. In 11 out of 13 cases symptoms presented during the third trimester of pregnancy and in all but two cases the epidural lesions were in the upper six thoracic vertebrae. These features can be explained by the effect of the gravid uterus on the relatively sparse vascular supply of the upper thoracic spinal cord.

Adult↗
PubMed1985

A digital sound editor.

A series of digital computer programs which facilitate the production and control of acoustic stimuli for hearing assessment and research are described. The package, which is available for PDP 11 computers under RT-11, allows sounds to be digitized, adjusted for amplitude and/or dc offset, edited while in digital form, and output to file or tape. The waveform editor package includes facilities to edit sounds in time--with some sections removed or added with temporal precision of 0.1 msec or better. Two or more sounds may also be combined for stereo or monaural (sound-on-sound) output, or two may be concatenated. Together, the programs permit a wide range of manipulations useful in preparing sound stimuli for use in hearing experiments or in clinical audiometry.

Computers↗
PubMed1984

Integration of spectral and temporal cues separated in time and frequency.

Subjects discriminated a "standard" pair of tone bursts (T1, T2) from a "comparison" pair (T1 + delta t, T2 + delta f), containing increments in the duration delta t of the first burst and/or the frequency delta f of the second burst. The threshold (d' = 2.0) for delta t was measured as a function of delta f, and the threshold for delta f as a function of delta t. The integration of increments in duration and frequency was studied as a function of the spectral and temporal separation between T1 and T2. A trade-off between the values of delta t and delta f required for d' = 2.0 performance was observed. This integration takes place when delta t, delta f occur simultaneously in the same spectral region, and when they occur separated by up to 120 ms, or by up to a full octave. The efficiency of integration was similar for all conditions of temporal and spectral separation studied, because the discriminability of delta t and of delta f is also nearly uniform across experimental conditions. The results from all experimental conditions are adequately described by a vector summation model derived from TSD. In a subsidiary experiment, subjects categorized pure tones varying in duration and frequency as "high" or "low" in pitch and "long" or "short" in duration. It was found that combined variations in duration and frequency result in essentially independent perceptual processes, although pitch has a small effect upon the perceived duration. It is concluded that spectral-temporal integration is a general ability operating in a variety of stimulus conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗