PubMed · 5653414
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J L Bradshaw. 1968. Pupil size and problem solving.. https://doi.org/10.1080/14640746808400139
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Behavioral states are stable structures of behaviors that become more definable and coordinated with increasing age. With ultrasound we can see the fetus move, breathe, and react to changes in its environment. Ultrasound used in conjunction with Doppler fetal heart rate recording provides behavioral and neurophysiologic data useful in state determination. The Fetal Neurobehavioral Profile (FNP) was developed by our group as an assessment of fetal behaviors reflecting CNS integrity in the drug-exposed fetus. The FNP was designed to parallel methods of examining the newborn infant, especially in state-related behaviors. The FNP measures: fetal responsiveness and arousal after environmental perturbation with vibroacoustic stimulation (VAS); habituation to VAS; state recovery; and self-regulation post-VAS. From the behavioral and physiologic recordings, the constructs of state differentiation, organization, and regulation as well as fetal arousal and regulation competency can be measured. Previous work using the FNP showed that those fetuses with abnormal or suspect fetal state regulation demonstrated impaired performance on the NBAS (Am. J. Obstet. Gynecol. 161: 685, 1989). To expand these observations, three populations are currently being studied: prenatal nicotine-exposed, prenatal cocaine-exposed, and controls. Data are from 97 women/fetus dyads and a total of 236 FNP at ages 28-30 weeks gestational age, 31-34 weeks gestational age, and > 36 weeks gestational age. Although there are no group differences in the ability to achieve state by 36 weeks, interesting trends emerge: fetuses prenatally cocaine-exposed spend less time in 1F, more time in 4F and have fewer transitions. At FNP, fewer cocaine-exposed fetuses had an initial reaction to VAS, whereas fewer nicotine-exposed fetuses habituated. Although the ability to habituate to VAS did not discriminate the cocaine group from the control or nicotine groups, the number of stimuli required for habituation differed between groups: 7 for the cocaine-exposed, 3 for the nicotine, and 5 for the control groups. Thus latency, a measure of arousal, differs among the groups Preliminary data also suggest a correlation of prenatal data with postnatal outcome.
A new functional imaging method has been developed and used to measure T2*- and initial intensity (I0)-parameter maps of multiple slices during activation of the cortex with high temporal resolution. Multiple echo-planar images (EPIs) are read out after a single excitation of the spin system, leading to several images with increasing effective echo times. Changes induced by primary visual stimulation in T2* and I0 were measured in eight subjects. Although stimulation-induced increases in I0 only occurred at short repetition times, T2* increased from 57.3 to 60.9 ms on average. The method combines the high stability of a single shot EPI experiment with the high information content of a multiecho acquisition. In addition, stimulation-induced changes in inflow can be easily separated from true blood oxygenation level dependent (BOLD) signal changes.
Recently, several implementations of arterial spin labeling (ASL) techniques have been developed for producing MRI images sensitive to local tissue perfusion. For quantitation of perfusion, both pulsed and continuous labeling methods potentially suffer from a number of systematic errors. In this study, a general kinetic model for the ASL signal is described that can be used to assess these errors. With appropriate assumptions, the general model reduces to models that have been used previously to analyze ASL data, but the general model also provides a way to analyze the errors that result if these assumptions are not accurate. The model was used for an initial assessment of systematic errors due to the effects of variable transit delays from the tagging band to the imaging voxel, the effects of capillary/tissue exchange of water on the relaxation of the tag, and the effects of incomplete water extraction. In preliminary experiments with a human subject, the model provided a good description of pulsed ASL data during a simple sensorimotor activation task.