Biomedical subjects

Chris Davis

Publications and source records attributed to Chris Davis.

9 recordsLinked to original sources

PubMed2005

Audio-visual speech perception off the top of the head.

The study examined whether people can extract speech related information from the talker's upper face that was presented using either normally textured videos (Experiments 1 and 3) or videos showing only the outlined of the head (Experiments 2 and 4). Experiments 1 and 2 used within- and cross-modal matching tasks. In the within-modal task, observers were presented two pairs of short silent video clips that showed the top part of a talker's head. In the cross-modal task, pairs of audio and silent video clips were presented. The task was to determine the pair in which the talker said the same sentence. Performance on both tasks was better than chance for the outline as well as textured presentation suggesting that judgments were primarily based on head movements. Experiments 3 and 4 tested if observing the talker's upper face would help identify speech in noise. The results showed the viewing the talker's moving upper head produced a small but reliable improvement in speech intelligibility, however, this effect was only secure for the expressive sentences that involved greater head movements. The results suggest that people are sensitive to speech related head movements that extend beyond the mouth area and can use these to assist in language processing.

Auditory Perception↗

PubMed2005

BK DNA viral load in plasma: evidence for an association with hemorrhagic cystitis in allogeneic hematopoietic cell transplant recipients.

We performed a case-control study to determine the association of BK plasma viremia with hemorrhagic cystitis (HC) in hematopoietic cell transplant (HCT) recipients. Thirty cases of HC (14 of which occurred after platelet engraftment with documented BK viruria [BK-HC]) were compared with matched controls. Weekly plasma samples were tested for BK virus DNA by polymerase chain reaction (PCR). BK viremia detected before or during the disease was independently associated with HC (adjusted odds ratio = 30, P < .001); BK viremia was even important before clinical symptoms of HC occurred (odds ratio = 11, P < .001). Cases of HC and BK-HC had a significantly higher peak of BK plasma viral load than controls. BK virus was detected by in situ hybridization in bladder biopsies of 2 cases with severe HC and long-lasting BK viremia. BK virus seems to play a role in the development of HC and quantitative detection of BK DNA in plasma appears to be a marker of BK virus disease in HCT recipients.

Adolescent↗

PubMed2005

Toxicity and efficacy of daily dapsone as Pneumocystis jiroveci prophylaxis after hematopoietic stem cell transplantation: a case-control study.

The toxicity and efficacy of dapsone given daily as Pneumocystis jiroveci (PCP) prophylaxis in hematopoietic stem cell transplant (HSCT) recipients who cannot take trimethoprim-sulfamethoxazole (TMP-SMX) have not been fully evaluated. We compared 155 HSCT recipients who received daily dapsone as second-line PCP prophylaxis with 310 matched control patients who received TMP-SMX throughout the posttransplantation course. Among patients who started dapsone before transplantation because of TMP-SMX allergy, there was no difference in the transfusion requirement after HSCT when compared with controls. Among patients who started dapsone after transplantation, increased red blood cell ( P<.0001) and platelet transfusion ( P=.003) requirements were noted compared with controls. This effect was, however, limited to patients who were receiving dapsone for reasons (mostly neutropenia) other than TMP-SMX allergy. Two of 155 patients developed PCP, compared with 0 of 310 controls ( P=.11); both patients survived. In conclusion, the efficacy of daily dapsone in preventing PCP was similar to that observed in patients able to remain on TMP-SMX prophylaxis. Dapsone did not seem to cause hematologic toxicity among TMP-SMX--allergic patients. The observed higher transfusion need in patients who received dapsone for reasons other than TMP-SMX allergy seems mostly due to an underlying condition of poor marrow reserve. Further studies are required to establish whether the drug has an etiologic role in these situations.

Adolescent↗

PubMed2004

The effect of script on poor readers' sensitivity to dynamic visual stimuli.

The current research examined performance of good and poor readers of Thai on two tasks that assess sensitivity to dynamic visual displays. Readers of Thai, a complex alphabetic script that nonetheless has a regular orthography, were chosen in order to contrast patterns of performance with readers of Korean Hangul (a similarly regular language but one that has a simple visual format, see ). Thai poor readers were less sensitive than good readers on the two measures of dynamic visual processing; they had higher thresholds for detecting coherent movement and required longer ISIs to report group movement in the Ternus task. These results differ from those for poor readers of Korean Hangul that found no relationship between visual processing thresholds and reading skill. This contrast suggests that the expression of visual processing problems in dyslexia is mediated by the format properties of the writing system and points to the need to consider such factors in formulating brain-behavior relationships.

Child↗

PubMed2004

Amodal processing of visual speech as revealed by priming.

This study investigated the linguistic processing of visual speech (video of a talker's utterance without audio) by determining if such has the capacity to prime subsequently presented word and nonword targets. The priming procedure is well suited for the investigation of whether speech perception is amodal since visual speech primes can be used with targets presented in different modalities. To this end, a series of priming experiments were conducted using several tasks. It was found that visually spoken words (for which overt identification was poor) acted as reliable primes for repeated target words in the naming, written and auditory lexical decision tasks. These visual speech primes did not produce associative or reliable form priming. The lack of form priming suggests that the repetition priming effect was constrained by lexical level processes. That priming found in all tasks is consistent with the view that similar processes operate in both visual and auditory speech processing.

Auditory Perception↗

PubMed2004

Audio-visual interactions with intact clearly audible speech.

The effects of viewing the face of the talker (visual speech) on the processing of clearly presented intact auditory stimuli were investigated using two measures likely to be sensitive to the articulatory motor actions produced in speaking. The aim of these experiments was to highlight the need for accounts of the effects of audio-visual (AV) speech that explicitly consider the properties of articulated action. The first experiment employed a syllable-monitoring task in which participants were required to monitor for target syllables within foreign carrier phrases. An AV effect was found in that seeing a talker's moving face (moving face condition) assisted in more accurate recognition (hits and correct rejections) of spoken syllables than of auditory-only still face (still face condition) presentations. The second experiment examined processing of spoken phrases by investigating whether an AV effect would be found for estimates of phrase duration. Two effects of seeing the moving face of the talker were found. First, the moving face condition had significantly longer duration estimates than the still face auditory-only condition. Second, estimates of auditory duration made in the moving face condition reliably correlated with the actual durations whereas those made in the still face auditory condition did not. The third experiment was carried out to determine whether the stronger correlation between estimated and actual duration in the moving face condition might have been due to generic properties of AV presentation. Experiment 3 employed the procedures of the second experiment but used stimuli that were not perceived as speech although they possessed the same timing cues as those of the speech stimuli of Experiment 2. It was found that simply presenting both auditory and visual timing information did not result in more reliable duration estimates. Further, when released from the speech context (used in Experiment 2), duration estimates for the auditory-only stimuli were significantly correlated with actual durations. In all, these results demonstrate that visual speech can assist in the analysis of clearly presented auditory stimuli in tasks concerned with information provided by viewing the production of an utterance. We suggest that these findings are consistent with there being a processing link between perception and action such that viewing a talker speaking will activate speech motor schemas in the perceiver.

Adult↗

PubMed2003

Adenovirus infection in hematopoietic stem cell transplantation: effect of ganciclovir and impact on survival.

Adenoviruses (ADV) are emerging as important causes of morbidity and mortality in patients undergoing hematopoietic stem cell transplantation (HSCT). In mainly non-T-cell depleted HSCT recipients, we analyzed the incidence of ADV infection, risk factors for infection, the effect of ganciclovir administered for prevention of cytomegalovirus (CMV), and the impact of ADV infection on survival. The overall incidence of ADV, irrespective of the method of detection, was 8.5% (450/5233) and 12.3% (43/348) after the first or second allogeneic HSCT, and 6.3% (78/1219) and 6.5% (5/77) after the first or second autologous HSCT, respectively. The most frequent sites of infection and disease were stool and gastrointestinal tract, respectively. Statistically significant risk factors associated with ADV infections among allogeneic recipients included younger age, grade II to IV graft-versus-host disease, year of transplantation, and a second allogeneic HSCT. Furthermore, allogeneic patients seronegative for CMV at transplantation and seropositive allogeneic patients who did not receive ganciclovir, either at engraftment or as pre-emptive therapy on CMV reactivation, were at higher risk of developing ADV infections compared with seropositive patients who received ganciclovir (odds ratio=1.8, 95% confidence interval (CI) 1.2 to 2.8, P=.005 and odds ratio=3.4, 95% CI 2.1 to 5.55, P<.0001, respectively). The hazard of overall mortality was higher in patients who contracted ADV compared with those who did not (hazard ratio 1.5, 95% CI 1.3 to 1.7, P<.0001). This study shows that ADV infections are associated with poor transplantation outcome in T-cell repleted HSCT recipients. Ganciclovir, given for CMV prevention, may have a protective effect. Controlled treatment and prevention studies are warranted.

Adenoviridae Infections↗

PubMed2003

Hearing foreign voices: does knowing what is said affect visual-masked-speech detection?

We investigated audio-visual (AV) perceptual integration by examining the effect of seeing the speaker's synchronised moving face on masked-speech detection ability. Signal amplification and higher-level cognitive accounts of an AV advantage were contrasted, the latter by varying whether participants knew the language of the speaker. An AV advantage was shown for sentences whose mid-to-high-frequency acoustic envelope was highly correlated with articulator movement, regardless of knowledge of the language. For low-correlation sentences, knowledge of the language had a large impact; for participants with no knowledge of the language an AV inhibitory effect was found (providing support for reports of a compelling AV illusion). The results indicate a role for both sensory enhancement and higher-level cognitive factors in AV speech detection.

Adult↗

PubMed2002

High risk of death due to bacterial and fungal infection among cytomegalovirus (CMV)-seronegative recipients of stem cell transplants from seropositive donors: evidence for indirect effects of primary CMV infection.

The impact of cytomegalovirus (CMV) serostatus (seropositive [(+)] or seronegative [(-)]) of the donor (D) and recipient (R) on mortality after allogeneic non-T cell-depleted stem cell transplantation (SCT) in the era of preemptive therapy was assessed among 1750 patients by means of multivariable Cox regression models. In an analysis that included only pre-SCT variables, D(+)/R(+) and D(+)/R(-) patients had the highest risk for mortality. After neutropenia or the occurrence of CMV disease was controlled for, only D(+)/R(-) patients remained at a significantly higher risk for mortality. Mortality due to bacteremia or invasive fungal infection was higher among D(+)/R(-) (18.3%) than D(-)/R(-) (9.7%) patients (P <.001). Thus, CMV serostatus remains associated with mortality; neutropenia due to ganciclovir administration and CMV disease explain the association with mortality among seropositive recipients. However, in D(+)/R(-) subjects, mortality appears to be associated with bacterial and fungal infection, indicating a possible immunomodulatory effect of primary CMV infection that was undetected despite intensive monitoring.

Adolescent↗