Using perfusion fMRI to measure continuous changes in neural activity with learning

In this study, we examine the suitability of a relatively new imaging technique, arterial spin labeled perfusion imaging, for the study of continuous, gradual changes in neural activity. Unlike BOLD imaging, the perfusion signal is stable over long time-scales, allowing for accurate assessment of continuous performance. In addition, perfusion fMRI provides an absolute measure of blood flow so signal changes can be interpreted without reference to a baseline. The task we used was the serial response time task, a sequence learning task. Our results show reliable correlations between performance improvements and decreases in blood flow in premotor cortex and the inferior parietal lobe, supporting the model that learning procedures that increase efficiency of processing will be reflected in lower metabolic needs in tissues that support such processes. More generally, our results show that perfusion fMRI may be applied to the study of mental operations that produce gradual changes in neural activity.     

Does aging influence people's metacomprehension? Effects of processing ease on judgments of text learning

In 2 experiments, the authors investigated whether age-related differences exist in metacomprehension by evaluating predictions based on the ease-of-processing (EOP) hypothesis. According to this hypothesis, judgments of how well a text has been learned are based on how easily each text was processed; easier processing results in higher judgments. Participants read either sentence pairs or longer texts and judged their learning of each immediately afterward. Although an age-related difference in the use of processing ease in judgments was observed with sentence pairs, for longer texts older and younger adults' judgments were similarly related to processing ease. In both experiments, age equivalence was also evident in the accuracy of the judgments at predicting performance on the criterion test. The overall pattern of results suggests that judging text learning remains largely intact with aging.     

Neural circuits mediating latent learning and conditioning for salt in the rat

Male Long-Evans rats alternately drank a salt solution in one distinctive compartment of a conditioned cue preference (CCP) apparatus and water in a different compartment over 8 days (training trials) and were then given a choice between the two compartments with no solutions present (test trial). Rats that were water deprived during training, then salt+water deprived during testing, spent more time in their salt-paired compartments, a salt latent cue preference (LCP). Rats that were water-only deprived during training and testing spent more time in their water-paired compartments, a water CCP. Rats that were salt+water deprived during both training and testing spent more time in their salt-paired compartments, a salt CCP. Bilateral, pre-training lesions of the lateral amygdala impaired the water and salt CCPs but not the salt LCP, reflecting the role of the amygdala in Pavlovian conditioning. Lesions of the dorsal or ventral hippocampus impaired the salt LCP and the water and salt CCPs, possibly reflecting the role of the hippocampus in contextual learning. Lesions of the fimbria-fornix impaired the water and salt CCPs but not the salt LCP, while lesions of the entorhinal cortex impaired the salt LCP but not the CCPs. This suggests that the LCP depends on a circuit that includes dorsal and ventral hippocampus and entorhinal cortex, a major conduit of sensory information from the cortex. In contrast, the CCPs depend on the amygdala and a circuit that includes the hippocampus and fimbria-fornix, possibly as a conduit of motivational information from subcortical structures.     

The regional genetic and newborn screening service collaboratives: the first two years

Newborn screening and genetic technologies are expanding and changing rapidly, increasing the demand for genetic specialty services. Because of the scarcity and geographic maldistribution of genetic specialty services, access to these services is a critical issue. This article discusses some of the efforts initiated by the Maternal and Child Health Bureau of the Health Resources and Services Administration, particularly the establishment of regional genetic and newborn screening collaboratives to improve access to these services and expertise.     

Race, family interactions, and patient stabilization in schizophrenia

This study examined family interactions associated with a failure to stabilize in schizophrenia. Fifty-eight patient and parent dyads completed a problem-solving task soon after an acute episode. Stabilization was assessed over the following 6 months. African American patients' self-initiated discussions of substance use and increased anxiety during the interaction were associated with a failure to stabilize. Nonstabilization in White patients was associated with high levels of both the patients' odd thinking and the parents' criticism. White patients who were depressed during the interaction were also less likely to stabilize. Findings suggest that family relationships may play in important role in determining whether patients stabilize after an acute episode. Results also point to the importance of cultural factors in predicting patient stabilization.     

The visual and haptic perception of natural object shape

In this study, we evaluated observers' ability to compare naturally shaped three-dimensional (3-D) objects, using their senses of vision and touch. In one experiment, the observers haptically manipulated 1 object and then indicated which of 12 visible objects possessed the same shape. In the second experiment, pairs of objects were presented, and the observers indicated whether their 3-D shape was the same or different. The 2 objects were presented either unimodally (vision-vision or haptic-haptic) or cross-modally (vision-haptic or haptic-vision). In both experiments, the observers were able to compare 3-D shape across modalities with reasonably high levels of accuracy. In Experiment 1, for example, the observers' matching performance rose to 72% correct (chance performance was 8.3%) after five experimental sessions. In Experiment 2, small (but significant) differences in performance were obtained between the unimodal vision-vision condition and the two cross-modal conditions. Taken together, the results suggest that vision and touch have functionally overlapping, but not necessarily equivalent, representations of 3-D shape.     

Effects of preshift small magnitude of reward received during goalbox placements on the negative contrast effect

During preshift, one experimental group of rats was given a large magnitude of food reward following a traversal of a straight alley and during a goalbox placement, while the other experimental group was given a small reward during goalbox placement and a large reward following a run. During postshift, all experimental groups were given a small reward of food following a traversal down the runway and during a goalbox placement. A control group was maintained on small reward during placements and following a traversal throughout the study. Only the group who received preshift large reward during placement and following a runway response ran slower to small reward during postshift than the control group maintained on small reward (negative contrast effect).