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Biomedical subjects

C Drake

Publications and source records attributed to C Drake.

At least 19 recordsLinked to original sources
PubMed2000

Skill acquisition in music performance: relations between planning and temporal control.

We investigated the acquisition of music performance skills in novice and expert pianists. Temporal disruptions in novice performances coincided with constraints in planning capacities. Child and adult pianists ranging in age (9-26 years), training (3-15 years) and sight-reading ability learned to perform a novel musical piece in eleven practice trials. Computer-detected pitch and timing errors revealed: (1) gradual improvements in performance tempo and pitch accuracy with skill level and practice, generally fitting a power function; (2) a relative-timing/pitch accuracy trade-off and high incidence of simultaneous pitch/time errors; (3) improvements in relative timing (temporal continuity, underlying beat, metrical structure) with skill and practice; and (4) increased anticipatory behavior and a greater range of planning with skill and practice. A strong positive relationship between the mastery of temporal constraints and planning abilities within performance suggests that these two cognitive indicators are closely related and may arise from segmentation processes during performance. Examination of sequence timing may explicate planning abilities that underlie many complex skills.

Adolescent↗
PubMed1999

Mortality among recent purchasers of handguns.

BACKGROUND: There continues to be considerable controversy over whether ownership of a handgun increases or decreases the risk of violent death. METHODS: We conducted a population-based cohort study to compare mortality among 238,292 persons who purchased a handgun in California in 1991 with that in the general adult population of the state. The observation period began with the date of handgun purchase (15 days after the purchase application) and ended on December 31, 1996. The standardized mortality ratio (the ratio of the number of deaths among handgun purchasers to the number expected on the basis of age- and sex-specific rates among adults in California) was the principal outcome measure. RESULTS: In the first year after the purchase of a handgun, suicide was the leading cause of death among handgun purchasers, accounting for 24.5 percent of all deaths and 51.9 percent of deaths among women 21 to 44 years old. The increased risk of suicide by any method among handgun purchasers (standardized mortality ratio, 4.31) was attributable entirely to an excess risk of suicide with a firearm (standardized mortality ratio, 7.12). In the first week after the purchase of a handgun, the rate of suicide by means of firearms among purchasers (644 per 100,000 person-years) was 57 times as high as the adjusted rate in the general population. Mortality from all causes during the first year after the purchase of a handgun was greater than expected for women (standardized mortality ratio, 1.09), and the entire increase was attributable to the excess number of suicides by means of a firearm. As compared with the general population, handgun purchasers remained at increased risk for suicide by firearm over the study period of up to six years, and the excess risk among women in this cohort (standardized mortality ratio, 15.50) remained greater than that among men (standardized mortality ratio, 3.23). The risk of death by homicide with a firearm was elevated among women (standardized mortality ratio at one year, 2.20; at six years, 2.01) but low among men (standardized mortality ratio at one year, 0.84; at six years, 0.79). CONCLUSIONS: The purchase of a handgun is associated with a substantial increase in the risk of suicide by firearm and by any method; the increase in the risk of suicide by firearm is apparent within a week after the purchase of a handgun. The magnitude of the increase and the relation between handgun purchase and the risk of death by homicide differ between men and women.

Adult↗
PubMed1999

Possible interaction of genotypes at cystathionine beta-synthase and methylenetetrahydrofolate reductase (MTHFR) in neural tube defects. NTD Collaborative Group.

Neural tube defects are a common, complex disorder with genetic and environmental components to risk. We investigated the previously reported interaction between homozygosity for the thermolabile variant at the methylenetetrahydrofolate reductase and heterozygosity for the 844ins68 allele at the cystathionine beta-synthase loci in cases with lumbosacral myelomeningocele and their parents. Using control allele frequencies from our sample pooled with those published in the literature, we confirm a marginally significant interaction at these two loci. This finding suggests that additional, larger studies are warranted to investigate this possible interaction in more detail.

Alleles↗
PubMed1999

The auditory continuity phenomenon: role of temporal sequence structure.

The auditory continuity phenomenon occurs when listening to a series of alternating high- and low-level tones: instead of perceiving this intermittence, listeners often report hearing a continuous tone upon which is superimposed a series of intermittent tones. The temporal limits to the perception of this phenomenon are investigated, as well as effects of task instructions on it. A loudness-matching paradigm developed previously [McAdams et al., J. Acoust. Soc. Am. 130, 1580-1591 (1998)] provided both an objective indication of this phenomenon and an indication of its strength. In the studies reported here, the phenomenon was observed reliably when the low-level tones were at least half the duration of the high-level tones: the greater the duration ratio between low-level and high-level tones, the stronger the phenomenon. Duty-cycle duration did not affect the strength of this phenomenon. It proved to be particularly robust as its strength was unaffected by task instructions, level of expertise, and repetition. A model is proposed in which adjusted levels depend on the relative levels of the high- and low-level tones weighted by relative duration and attentional focusing.

Auditory Perception↗
PubMed1999

Clinical and financial benefits of rapid bacterial identification and antimicrobial susceptibility testing.

To assess the expected clinical and financial benefits of rapid reporting of microbiology results, we compared patients whose cultured samples were processed in the normal manner to patients whose samples were processed more rapidly due to a minor change in work flow. For the samples tested in the rapid-reporting time period, the vast majority of bacterial identification and antimicrobial susceptibility testing (AST) results were verified with the Vitek system on the same day that they were available. This time period was called rapid AST (RAST). For RAST, a technologist on the evening shift verified the data that became available during that shift. For the control time period, cultures were processed in the normal manner (normal AST [NAST]), which did not include evening-shift verification. For NAST, the results for approximately half of the cultures were verified on the first day that the result was available. The average turnaround time for the reporting of AST results was 39.2 h for RAST and 44.4 h for NAST (5.2 h faster for RAST [P = 0.001]). Subsequently, physicians were able to initiate appropriate antimicrobial therapy sooner for patients whose samples were tested as part of RAST (P = 0.006). The mortality rates were 7. 9 and 9.6% for patients whose samples were tested as part of RAST and NAST, respectively (P = 0.45). The average length of stay was 10. 7 days per patient for RAST and 12.6 days for NAST, a difference of 2.0 days less for RAST (P = 0.006). The average variable cost was $4, 927 per patient for RAST and $6,677 for NAST, a difference of $1,750 less per patient for RAST (P = 0.001). This results in over $4 million in savings in variable costs per year in our hospital.

Bacteria↗
PubMed1998

The effect of autonomic nervous system activity on gastric myoelectrical activity: does the spectral reserve hypothesis hold for the stomach?

Previous studies have associated changes in gastric myoelectrical activity during motion sickness, as indexed using the electrogastrogram (EGG), with changes in autonomic nervous system (ANS) activity. Subjects who did not report nausea in a rotating optokinetic drum were characterized by normal 3 cycles per minute (cpm) gastric myoelectrical activity, strong parasympathetic nervous system (PNS) activity, and low sympathetic nervous system (SNS) activity. The goals of this study were: (1) to determine whether tasks previously shown to alter ANS activity as indexed by changes in cardiac inter-beat intervals (IBIs) would result in systematic changes in gastric myoelectrical activity in accord with the findings from motion sickness studies; and (2) to determine whether the 'spectral reserve hypothesis' applies to gastric myoelectrical activity. EGGs and IBIs were collected from 24 healthy subjects during resting/baseline, reaction time/shock-avoidance (RT) and cold face stress (CF) tasks. Tachyarrhythmia was found to be significantly greater during the RT task than during the baseline and CF tasks. It was concluded that: (1) tasks that alter ANS activity do systematically alter gastric myoelectrical activity; and (2) gastric myoelectrical activity does not follow the cardiac model of health being associated with increased spectral complexity.

Adult↗
PubMed1998

Auditory continuity and loudness computation.

Sequences composed of alternating bursts of different levels with no silences separating them can give rise to a perception of a continuous sound upon which is superimposed an intermittent stream. These experiments sought to determine how the perceived loudness of the intermittent stream depends on the level difference between higher-level and lower-level bursts in the sequence in cases in which continuity is either heard or not heard. In the main experiment, listeners were asked to adjust the level of continuous or intermittent comparison sequences to match the loudness of components that appeared to be either continuous or intermittent in an alternating-level reference sequence, thus urging them to focus on the two-stream percept. Loudness matches of continuous comparison stimulus were close to physical levels of the lower-level bursts, whereas matches of the intermittent comparison stimulus were well below the physical levels of higher-level bursts. These results are discussed in terms of Bregman's [Auditory Scene Analysis (MIT, Cambridge, MA, 1990)] "old-plus-new" hypothesis: The loudness of the intermittent stream should result from the subtraction of the lower level from the higher level under the assumption that the higher-level burst represents a simultaneous mixture of sounds including the continuation of the lower-level burst. Additional experiments verified that, in the absence of the continuity phenomenon, matched levels were very close to the physical levels and that matches to fixed-level continuous and intermittent sequences were precise. The matching results from the main experiment support predictions of neither classical loudness models that do not take auditory organization processes into account nor schema-based models that presume a selection of information from the higher-level burst that does not affect the perceptual content of this burst. The matched levels fell between predictions of models based on subtraction of acoustic pressure and acoustic power, but were very different from subtraction of loudness measured in sones, suggesting that loudness is computed subsequent to auditory organization processes.

Acoustic Stimulation↗
PubMed1998

Effect of maternal hydration on mild fetal pyelectasis.

The aim of our study was to determine whether maternal hydration status prior to prenatal sonography affects fetal renal pelvic diameter. The renal pelvic diameters of fetuses from two different institutions were compared prospectively. At one institution 74 women were asked to drink 32 to 48 ounces of water prior to undergoing sonography (hydration group), whereas at the second institution, no specific hydration regimen was requested of 176 subjects. The inclusion criteria were as follows: greater than 15 weeks' gestation, otherwise normal obstetrical sonogram, normal amniotic fluid volume, and negative family history for renal disease. Renal pelvic diameter, degree of maternal bladder fullness, and gestational age were compared between the two groups using logistic regression analysis and log-linear analysis. A P value < 0.01 was considered significant. Bladder fullness in the two groups differed significantly (P < 0.001). Logistic regression analysis showed a very strong effect of maternal bladder fullness on fetal renal pelvic diameter (P < 0.001). The log-linear analysis model showed a highly significant association between maternal bladder fullness and fetal renal pelvic diameter (P < 0.001). We conclude that maternal hydration influences fetal renal pelvic diameter. The larger fetal renal diameters seen in the hydrated group support physiologic theories that the effects of maternal hydration on amniotic fluid volume are partially mediated via fetal urine production.

Dilatation, Pathologic↗
PubMed1998

Morphologic changes and xanthine oxidase activity in the equine jejunum during low flow ischemia and reperfusion.

OBJECTIVE: To determine whether xanthine oxidase and dehydrogenase activities are altered during low flow ischemia and reperfusion of the small intestine of horses. ANIMALS: 5 clinically normal horses without histories of abdominal problems. PROCEDURE: With the horse under general anesthesia, a laparotomy was performed and blood flow to a segment of the distal jejunum was reduced to 20% of baseline for 120 minutes and was then reperfused for 120 minutes. Biopsy specimens were obtained before, during, and after ischemia for determination of xanthine oxidase and dehydrogenase activities, and for histologic and morphometric analyses. RESULTS: Percentage of xanthine oxidase activity (as a percentage of xanthine oxidase and dehydrogenase activity) was not altered during ischemia and reperfusion. An inflammatory response developed and progressed during ischemia and reperfusion. Mucosal lesions increased in severity after ischemia and reperfusion. Mucosal surface area and volume decreased during ischemia and continued to decrease during reperfusion. Submucosal volume increased slightly during ischemia, and continued to increase during reperfusion. CONCLUSIONS AND CLINICAL RELEVANCE: Evidence for conversion of xanthine dehydrogenase to xanthine oxidase during ischemia was not found. Factors other than production of reactive oxygen metabolites may be responsible for progressive epithelial loss, decrease in mucosal surface area and volume, and increase in submucosal volume observed in this study. Other methods of determining xanthine oxidase activity that detect the enzyme in sloughed epithelial cells should be used to better define the importance of this pathway in jejunal reperfusion injury in horses.

Animals↗
PubMed1997

Monitoring and planning capacities in the acquisition of music performance skills.

We investigate changes in cognitive capacities that occur as musicians acquire performance skills. Previous studies suggest that skilled behaviour is characterized by advanced abilities to monitor one's own performance or to plan upcoming events. We first report a study of child pianists (aged 6-14 years old) of beginning and intermediate skill levels who performed well-learned musical pieces. Computer-detected pitch errors in the performances provided evidence for skill-related increases in both monitoring and planning: Children with more musical training showed quicker detection and correction of errors, more anticipatory and less perseveratory behavior, and larger range of planning than children with less training. Next we report a study of adult musicians' advanced performances, which showed heightened sensitivity to melody and repeated pitch structures. Planning and monitoring capacities increased most during initial stages of musical skill acquisition, whereas sensitivity to musical structure increased across all skill levels.

Adolescent↗
PubMed1997

Perceptual attenuation of nonfocused auditory streams.

The aim of this study was to measure the perceptual attenuation, measured in decibels, resulting from the focusing of attention on one stream within a multistream auditory sequence. The intensity of a nonfocused stream was increased until the accuracy of detecting a temporal irregularity in this stream was the same as in a focused stream. Eight subjects were required to detect a temporal irregularity created by delaying or advancing one tone which could be situated in one of three temporally regular streams played simultaneously to create a multistream sequence. The three streams differed in tempo and frequency. Subjects' attention was focused on one of the streams by preceding the multistream sequence with one of the single streams (a cue). We first established the size of temporal irregularity detected at a 90% level in cued streams, confirming that subjects were able to focus on one particular stream. Second, an irregularity of this size was not detected above chance level in noncued streams, demonstrating that listeners focus only on the cued stream. Third, for 5 subjects, a 15-dB increase in the level of one of the noncued streams was necessary to bring detection up to that found in the cued streams. This gain provides an equivalent measure of the perceptual attenuation of nonfocused streams. For 3 other subjects, detection in the noncued stream remained at chance performance whatever the level. For all subjects, detection in the cued stream decreased slightly as the level of the noncued stream increased. We conclude that the attenuation of nonfocused auditory streams can attain as much as 15 dB, at least for some subjects.

Attention↗