Biomedical subjects

W S Brown

Publications and source records attributed to W S Brown.

At least 37 records · Page 2Linked to original sources

PubMed1999

Estimating minimum detectable concentrations achievable while scanning building surfaces and land areas.

Scanning is performed during radiological surveys to identify elevated levels of direct radiation. The levels detected depend on the surveyor's abilities and decision processes. A method is described for anticipating levels that surveyors might reasonably be expected to detect in scanning by estimating the increment in a survey instrument's counting rate that would be necessary to support specified limits on Type I and Type II error rates, taking into account the fact that human beings typically do not operate with perfect efficiency. The result is applied to calculations of minimum detectable concentrations (MDCs) achievable while scanning structure surfaces and land areas. The approaches used for determining scan MDCs are provided, along with examples for common radionuclide contaminants and field survey instrumentation.

Efficiency↗

PubMed1998

Interhemispheric transfer in normals and acallosals: latency adjusted evoked potential averaging.

Interhemispheric transfer time (IHTT) can be estimated from visual evoked potentials (EPs). Latency adjusted averaging (LAA) produces EPs which have enhanced components. LAA also provides estimates of EP latency variance and signal-to-noise ratio (S/N). LAA was tested in analysis of EP-IHTT in normal and acallosal subjects. It was hypothesized that in normals S/N and latency variance would reveal signal degradation resulting from interhemispheric transfer. LAA in normals replicated IHTT findings for both P1 and N1 latency. Latency variance did not increase for cross-callosal measures, whereas the S/N measure showed significant EP degradation due to callosal transfer. EPs from five subjects with callosal absence (two commissurotomy; two complete and one partial callosal agenesis) showed significantly larger than normal latency variability, as well as decreased S/N ratios, for cross-hemisphere visual EPs. Results support the value of LAA in EP research on adequacy of hemispheric interactions in clinical populations.

Adolescent↗

PubMed1998

Variations in adductor spasmodic dysphonia: acoustic evidence.

Acoustic analysis was used to gain information about the normal, as well as the abnormal acoustic events associated with adductor spasmodic dysphonia (ADSD). This analysis was completed to determine whether specific acoustic events could be used to differentiate the voice of individuals with ADSD from those with normal voice. A group comparison between 14 women diagnosed with ADSD and 14 women (age-matched) with no evidence of vocal pathology or vocal dysfunction was completed. Phonatory breaks, aperiodicity, and frequency shifts, acoustic parameters previously identified in ADSD, were found throughout sustained vowel productions. The duration of the phonatory breaks and aperiodic segments was calculated and the amount of frequency shift was determined. The location of each acoustic event was marked relative to the onset of the vowel production. The subjects with ADSD presented with normal phonation and various amounts of each of the three acoustic parameters. Aperiodic segments primarily characterized the phonation of ADSD, followed by frequency shifts and phonatory breaks. The location of each of these acoustic events was within the midportion of the vowel production. The advantages of segmenting the acoustic waveform into these measures and separating the spasmodic events from normal phonation when examining laryngeal motor control of spasmodic dysphonics is discussed.

Adult↗

PubMed1998

Reliability of single sample experimental designs: comfortable effort level.

This study was designed to ascertain the intrasubject variability across multiple recording sessions-most often disregarded in reporting group mean data or unavailable because of single sample experimental designs. Intrasubject variability was assessed within and across several experimental sessions from measures of speaking fundamental frequency, vocal intensity, and reading rate. Three age groups of men and women--young, middle-aged, and elderly--repeated the vowel /a/, read a standard passage, and spoke extemporaneously during each experimental session. Statistical analyses were performed to assess each speaker's variability from his or her own mean, and that which consistently varied for any one speaking sample type, both within or across days. Results indicated that intrasubject variability was minimal, with approximately 4% of the data exhibiting significant variation across experimental sessions.

Adult↗

PubMed1997

Event-related potential correlates of linguistic information processing in schizophrenics.

Event-related potentials (ERPs) were recorded from adult schizophrenics and age- and education-matched normal controls during performance of an idiom recognition task involving judgments of the meaningfulness of idiomatic, literal, and nonsense phrases. Schizophrenics produced more errors and had prolonged reaction times while attempting to correctly differentiate meaningful from meaningless phrases. An ERP correlate of that deficit was a larger than normal N400 to idioms and literals, with no difference in N400 amplitude to nonsense phrases. This result was interpreted as evidence that the influence of the linguistic context provided by the first word of two-word idiomatic and literal phrases is reduced in schizophrenia. Schizophrenics also showed reduced amplitude P300.

Adult↗

PubMed1997

Bilateral field interactions, hemispheric specialization and evoked potential interhemispheric transmission time.

The interrelationship between bilateral visual field processing, hemispheric specialization and interhemispheric transmission time (IHTT) was examined in two experiments in order to test two theories regarding callosal function and lateralized visual processing. Contrary to both theoretical speculations [Braun, Neuropsychology Review, Vol. 3, pp. 321-365, 1992] and a recent report [Nowicka et al., Neuropsychologia, Vol. 34, pp. 147-151, 1996], the directional asymmetry in evoked potential measures of IHTT did not vary with task differences in indices of hemispheric specialization. IHTT was faster from right to left hemispheres regardless of visual field advantage for the task. Similarly, patterns of correlation between IHTT and bilateral field advantage did not change between verbal and spatial matching tasks, despite differences in visual field advantage. Since the latter data did not consistently support the Brown and Jeeves [Neuropsychologia, Vol. 31. pp. 1267-1281, 1993] hypothesis, an alternative hypothesis involving hemispheric asymmetries in attention rather than processing specialization was proposed.

Adult↗

PubMed1997

Speech breathing during reading in women with vocal nodules.

This study examined speech breathing patterns during reading by women with bilateral vocal fold nodules judged as mildly dysphonic and by women without vocal nodules. Although it might be predictable that the speech breathing patterns of individuals with laryngeal dysfunction will differ from those without laryngeal dysfunction, there is a lack of empirical data to support such assumptions. The results of the current study indicated that glottal airflow was greater during reading for the women with vocal nodules and that a larger volume of air was expended both per syllable and per breath group during reading. The rate of speech did not significantly differ between the two groups of women. There was no significant difference for the average duration of the breath groups and no significant difference for the number of syllables spoken per breath group. Additionally, both groups of women demonstrated a similar pattern of inspiratory pause location during the reading. The results suggest that speech breathing patterns associated with dysphonia be examined independently to distinguish specifically the nature of the interaction between the laryngeal dysfunction and the speech breathing pattern. Certainly, more information on how the severity of a voice disorder influences speech breathing is necessary.

Adolescent↗

PubMed1997

Soluble human leukocyte antigens, interleukin-6, and interferon-gamma during pregnancy.

PROBLEM: Soluble human leukocyte antigens (sHLA), interferon-gamma (IFN-gamma), and interleukin-6 (IL-6) were studied during human pregnancy to test the hypothesis that sHLA concentrations are regulated by these specific cytokines. METHOD OF STUDY: Enzyme-linked immunoadsorbent assays (ELISA) were used to measure sHLA I and II in maternal circulation, cord blood, and placenta effluents of pregnant and nonpregnant women; maternal serum cytokines were also determined. RESULTS: sHLA in maternal and cord blood were equivalent to that in the placenta. By the third trimester, sHLA I concentrations in maternal plasma were significantly reduced compared to the first or second trimesters. sHLA II was increased during the second trimester relative to that postpartum. Maternal IL-6 and IFN-gamma concentrations were not statistically different throughout gestation or postpartum. CONCLUSIONS: These data do not suggest a role for maternal plasma IL-6 or IFN-gamma in regulation of systemic sHLA class I during pregnancy, but they do not address whether such events take place in local tissues of the maternal-fetal unit.

Female↗

PubMed1996

Continuous-processing--related event-related potentials in children with attention deficit hyperactivity disorder.

Visual information processing in children with attention deficit hyperactivity disorder (ADHD) was studied using event-related potentials recorded during two versions of the Continuous Performance Task (CPT). ADHD children made more errors, and had longer reaction times than normal children on both the single- and dual-target CPT. Event-related potential waveforms were normal in the ADHD children with reference to early processing stages, i.e., contingent negative variation, P1-N1 laterality, and processing negativities, suggesting that ADHD children did not differ in their level of preparedness or their ability to mobilize resources for target identification and categorization. With respect to later processing, P3 amplitude was reduced in the ADHD group, whereas P3 latency was longer than normal. ADHD children had a diminished late frontal negative component, suggestive of reduced involvement in postdecisional processing.

Adolescent↗

PubMed1996

Callosal transfer of finger localization information in phonologically dyslexic adults.

Dyslexia, particularly phonological dyslexia, has been hypothesized to be associated with deficits in interhemispheric interactions mediated by the corpus callosum. Twenty-one dyslexic subjects were compared to 21 controls on the Finger Localization Test in order to observe patterns of tactile-motor integration and interhemispheric collaboration. When compared to control subjects, dyslexics showed consistent deficits in finger localization, particularly when more complex trials had to be completed. When subjects were re-grouped according to phonological processing ability (regardless of diagnostic group membership), subjects with lower phonological processing scores were found to perform poorly on complex trials of finger localization, particularly on those trials which reflect callosal transfer of finger localization information from one hemisphere (hand) to the other. These results suggest that interhemispheric transfer of information is critical to efficient phonological processing.

Adolescent↗

PubMed1996

Comfortable effort level revisited.

The purpose of this study was to measure the variability of frequency and intensity of speech, using multiple voice samples obtained over a period of time at a speaker's "comfortable effort level." Variability in vocal output within and across several experimental sessions was assessed from measures of speaking fundamental frequency (SFF) and vocal intensity for utterances repeated three times a day over a 3-day period. Three distinct age groups of men and women-young, middle-aged and elderly-repeated the vowel /a/, read a standard passage, and spoke extemporaneously during each experimental session. Results indicated that variability in SFF and intensity were present across experimental sessions, age groups, gender, and speaking samples. Generally, group means indicated that approximately +/- 1 semitone of variability for SFF and approximately 2 db sound pressure level (SPL) variation in vocal intensity from any one experimental session to the next could be expected; individual variations within any group may reach two semitones and 6 db SPL.

Adult↗

PubMed1996

Comparison of various automatic means for measuring mean fundamental frequency.

The purpose of this paper was to evaluate the reliability of, and agreement among, six speech analysis systems in the determination of fundamental frequency. Five male and five female speakers provided oral reading and sustained vowel samples for analysis. Each sample was analyzed five times by each system. The results indicated high reliability for all of the systems for both sexes and both utterance types. Agreement among the systems was high for the male sustained vowels and the female oral reading samples. In contrast, poor agreement occurred among the systems for the male oral reading samples and the female sustained vowels. The findings indicate that the output of these automatic methods tends to be consistent over repeated trials within the systems in their extraction of fundamental frequency; however, agreement among these systems varies.

Adolescent↗

PubMed1996

Respiratory and laryngeal function associated with experimental coupling of the oral and nasal cavities.

Three experimental openings (10 mm2, 20 mm2, 30 mm2) were placed one at a time in a man's palatal obturator at a location approximating the junction of the prepalate and the palatal shelves. The man's laryngeal and respiratory function were examined during his production of a series of CV syllables [pa] repeated at a comfortable and loud vocal intensity for each of the three experimental conditions. Two more conditions, in which the subject's obturator was not altered (no hole) and in which no obturator was worn, were also included for study. Laryngeal and respiratory function adjustments were most apparent during the 30 mm2 hole size and no obturator conditions. Laryngeal adjustment, as measured by fundamental frequency, was the most identifiable. A respiratory adjustment, which involved the expenditure of more lung volume as nasal airflow leakage increased, was also observed. These observations imply an active physiologic adjustment rather than a passive response to aberrant oronasal coupling.

Adaptation, Physiological↗

PubMed1995

Bimanual coordination in dyslexic adults.

Various types of dyslexia have been associated with tactile-motor coordination deficits and inefficient transfer of information between the two cerebral hemispheres. Twenty-one dyslexic adults were compared to 21 controls on the Bimanual Coordination Task, a test of tactile-motor coordination and interhemispheric collaboration. When compared to control subjects, dyslexics showed a consistent pattern of deficits in bimanual motor coordination, both with and without visual feedback. In particular, dyslexics had greater difficulty relative to normals when the left hand had to move faster than the right, and when the hands had to make opposite (mirror-image) movements, suggesting problems with interhemispheric modulation of visuomotor control. In addition, accuracy on this bimanual coordination task was significantly correlated with the Block Design subtest of the WAIS--R, but not with a rhyme fluency task, suggesting some contribution of right hemisphere controlled visuospatial skill to performance.

Adolescent↗

PubMed1995

Patterns of fundamental frequency for three types of voice samples.

The purpose of this study was to determine the variability in speaking fundamental frequency (Fo) associated with sample type in two age groups of normal male and female speakers and a group with vocal-fold paralysis. Young and elderly normal control men and women produced a sustained vowel, read a passage, and spoke extemporaneously in the morning, early afternoon, and late afternoon on three different days. The vocal-fold-paralysis group produced two voice samples at different times on the same day. Two patterns of variability emerged in the normal groups. Young men produced sustained phonation at a significantly lower Fo than their reading or extemporaneous samples. Young and older women and older men produced sustained phonation with a higher Fo than their reading or extemporaneous samples. The eight subjects with unilateral vocal-fold paralysis (seven women, one man) produced samples with a pattern similar to that of the older normal groups but with greater differences between the sustained vowel and speech samples. The use of different sample types resulted in variations in mean speaking Fo in the normal subjects as well as in the vocal-fold-paralysis group. Within-day sampling of all normal subjects resulted in approximately the same variability as across-day sampling. In the vocal-fold-paralysis group, within-day sampling resulted in greater variability of mean Fo for vowels than for connected speech, following a pattern similar to the older normal control subjects and various speech materials for voice.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Phonational profiles of male trained singers and nonsingers.

The purpose of this study was to compare the mean speaking fundamental frequency (SFF), speaking frequency range, and mean speaking intensity for a group of trained male singers and a group of age-matched non-singers in three age ranges: 20 to 35 years old; 40 to 55 years old; and older than 65 years. Each subject was recorded as he read "The Rainbow Passage" and produced the vowel /a/ to the limits of his phonational frequency range. The data indicated that the mean SFF of the nonsingers was significantly lower among the middle-aged speakers than with the young or elderly. In contrast, the tenors exhibited no age-related SFF trends, and the young bass/baritones exhibited lower SFF levels than the middle-aged or elderly. The elderly nonsingers produced frequency ranges that were smaller than any other group. Finally, the young nonsingers used greater speech intensity than did the other groups.

Adult↗

PubMed1994

Continuous-processing related ERPS in schizophrenic and normal children.

The continuous performance task (CPT) has proven to be sensitive to schizophrenic impairments. Multichannel event-related potential (ERP) data were recorded from schizophrenic and normal children during performance of easy and hard versions of the CPT. Schizophrenics produced fewer hits, more false alarms, and prolonged reaction times. Poor performance in schizophrenics was associated with four ERP abnormalities: (1) Schizophrenics did not exhibit the normal increase in amplitude of an early-onset, processing-related negativity from nontarget to target stimuli, suggesting a failure to appropriately allocate attentional resources to discriminative processing. (2) Although P3 amplitude to targets was not significantly smaller in schizophrenic children, the distribution of P3 amplitude between target and nontarget responses in the easy and hard versions of the CPT was abnormal, suggesting that schizophrenics differed in the strategic allocation of resources in later stages of CPT processing. (3) In all task conditions schizophrenics showed a parietal negative component with a latency of 400 msec seen in younger, but not older normal children, suggestive of maturational lag. (4) ERP data demonstrated absence of right-lateralized P1/N1 amplitude in schizophrenic children. Taken together these data indicate that at several stages of information processing, schizophrenics are deficient in the control and strategic allocation of processing resources.

Attention↗

PubMed1994

Primary central nervous system recurrence after paclitaxel therapy for epithelial ovarian malignancy.

Paclitaxel is currently being utilized to treat neoplasms which have a significant incidence of central nervous system metastases. It is, however, unclear as to whether paclitaxel crosses the blood-brain barrier. In this report, the authors describe a patient with refractory epithelial ovarian cancer treated with paclitaxel at 135 mg/m2/24 hr every 21 days. The patient achieved a complete clinical response of all abdominal and pelvic disease, but simultaneously developed central nervous system metastases. Paclitaxel was effective against the patient's abdominal and pelvic disease but was not protective against central nervous system metastasis.

Central Nervous System Neoplasms↗