RESUMEN
OBJECTIVE: To learn if people with persistent developmental stuttering and atypical anatomy of their auditory temporal cortex have, when compared to control subjects, changes in fluency induced with delayed auditory feedback (DAF). BACKGROUND: DAF improves fluency in many individuals who stutter, and induces dysfluency in some normal people. The planum temporale (PT), a portion of auditory temporal cortex, is anatomically atypical in some adults who stutter and atypical anatomy might induce aberrant function. Thus, the people who demonstrate the paradoxical response to DAF might be those who have atypical anatomy. METHODS: Experimental subjects were adults with developmental stuttering (n = 14) and control subjects (n = 14) matched for age, sex, education, and handedness. Volumetric MRI scans of all subjects were obtained and the PT was measured in the right and left hemispheres. Based on these scans, subjects were classified as typical (leftward PT asymmetry) or atypical (rightward PT asymmetry). Prose passages were read at baseline, with non-altered feedback (NAF), and with DAF, and fluency was measured in these three conditions. RESULTS: At baseline the adults with developmental stuttering were significantly more dysfluent than controls (p < 0.0005). Controls' fluency did not significantly change with DAF, but DAF improved fluency in adults with developmental stuttering (p < 0.0005). In the stutter group enhanced fluency was associated with atypical (rightward) PT asymmetry, and the presence of typical (leftward) PT asymmetry was not associated with any significant change in fluency. The individuals with atypical PT asymmetry also had more severe stuttering at baseline compared to the experimental subjects with typical PT anatomy. CONCLUSIONS: In adults with persistent developmental stuttering and atypical PT anatomy, fluency is improved with DAF. These experimental subjects who showed improvement had more severe stuttering at baseline. Anomalous PT anatomy may be a neural risk for developmental stuttering in some individuals. Although a number of explanations are tenable, it may be that atypical rightward PT asymmetry may alter speech feedback, and treatment with DAF might allow these people to compensate.
Asunto(s)
Corteza Auditiva/patología , Trastornos de la Percepción Auditiva/patología , Trastornos de la Percepción Auditiva/fisiopatología , Tartamudeo/patología , Tartamudeo/fisiopatología , Adulto , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Lectura , Tartamudeo/diagnósticoRESUMEN
A method for determining oxygen-carrying capacity of blood substitutes has been developed using the short-lived cyclotron-produced positron-emitting isotope 15O. This method measures the oxygen-carrying capacity of the blood substitutes in vivo in the presence of red blood cells and allows determination of changes in the oxygen-carrying capacity over time after exchange transfusion. This method is applied to the blood substitutes of liposome-encapsulated hemoglobin (LEH) and cell-free hemoglobin (Hb). We have used 15O (half-life of 2 min) to quantitate the lung uptake and tissue delivery of [15O2]LEH. Lung uptake studies were performed in intubated, catheterized rats after a 40% exchange transfusion of bovine LEH (LEBH; 0.68 g Hb/kg body wt), human hemolysate LEH (LEHH; 1.0 g Hb/kg body wt), or free bovine hemoglobin (SFHS; 0.56 g Hb/kg body wt). A bolus inhalation of 15O2 (3-5 mCi) was given at 15 min, 3 h, and 24 h post-transfusion. Arterial blood samples were collected, spun, and separated into LEH, red blood cell, and plasma fractions. 15O activity and hemoglobin content were determined for each fraction. Oxygen-carrying capacity was calculated as a percentage of the original red blood cell fraction removed. For LEBH, the carrying capacity was 15% at 15 min, 13% at 3 h, and 1% at 24 h. For LEHH, the carrying capacity was 30% at 15 min, 26% at 3 h, and 19% at 24 h. The marked decrease in carrying capacity at 24 h for LEBH compared with LEHH was attributable to the increased formation of methemoglobin in the circulating LEBH rather than increased removal from circulation, because total hemoglobin concentrations measured for both LEH samples decreased at a similar rate during the 24 h. The presence of methemoglobin reductase and other naturally occurring antioxidants in the LEHH may be responsible for maintaining the higher levels of oxyhemoglobin. Oxygen-carrying capacity for SFHS also decreased over time but at a much sharper rate compared with both LEH formulations. The carrying capacity for SFHS of 8% measured at 15 min decreased to 0.3% at 3 h and undetectable levels at 24 h. This sharper decrease in carrying capacity for SFHS is attributable to the rapid removal of the hemoglobin from circulation.
Asunto(s)
Sustitutos Sanguíneos , Radioisótopos de Oxígeno , Animales , Volumen Sanguíneo , Hemoglobinas , Liposomas/química , Pulmón/irrigación sanguínea , Masculino , Oxígeno/sangre , Ratas , Ratas Sprague-DawleyRESUMEN
The special magnetization characteristics of hyperpolarized noble gases have led to an interest in using these agents for new MRI applications. In this note, the magnetization effects and NMR signal dependence of two noble gases, 3He and l29Xe, are modeled across a range of gradient-echo imaging parameters. Pulse-sequence analysis shows a wide variation in optimum flip angles between imaging of gas (e.g., 3He or 129Xe) in air spaces (e.g., trachea and lung) and in blood vessels. To optimize imaging of the air spaces, it is also necessary to reduce the otherwise substantial signal losses from diffusion effects by increasing voxel size. The possibility of using hyperpolarized 129Xe for functional MRI (fMRI) is discussed in view of the results from the blood flow analysis. The short-lived nature of the hyperpolarization opens up new possibilities, as well as new technical challenges, in its potential application as a blood-flow tracer.