Learning depends on surprise and is not engendered by predictable occurrences. In this functional magnetic resonance imaging (fMRI) study of causal associative learning, we show that dorsolateral prefrontal cortex (DLPFC) is associated specifically with the adjustment of inferential learning on the basis of unpredictability. At the outset, when all associations were unpredictable, DLPFC activation was maximal. This response attenuated with learning but, subsequently, activation here was evoked by surprise violations of the learned association. Furthermore, the magnitude of DLPFC response to a surprise event was sensitive to the relationship that had been learned and was predictive of subsequent behavioral change. In short, the physiological response properties of right DLPFC satisfied specific predictions made by associative learning theory.

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Hyperventilation increases the volume of severely hypoperfused tissue within the injured brain, despite improvements in cerebral perfusion pressure and intracranial pressure. Significant hyperperfusion is uncommon, even at a time when conventional clinical management includes a role for modest hyperventilation. These reductions in regional cerebral perfusion are not associated with ischemia, as defined by global monitors of oxygenation, but may represent regions of potentially ischemic brain tissue.

Double reading of chest x-rays is often used to ensure that fewer abnormalities are missed, but very little is known about how the search behavior of others affects observer performance. A series of experiments investigated whether radiographers benefit from knowing where another person looked for pulmonary nodules, and whether the expertise of the model providing the search behavior was a contributing factor. Experiment 1 compared the diagnostic performance of novice and experienced radiographers examining chest x-rays and found that both groups performed better when shown the search behavior of either a novice radiographer or an expert radiologist. Experiment 2 established that benefits in performance only arose when the eye movements shown were related to the search for nodules; however, only the novices' diagnostic performance consistently improved when shown the expert's search behavior. Experiment 3 reexamined the contribution of task, image, and the expertise of the model underlying this benefit. Consistent with Experiment 1, novice radiographers were better at identifying nodules when shown either a naı ¨ve's search behavior or an expert radiologist's search behavior, but they demonstrated no improvement when shown a naı ¨ve model not searching for nodules. Our results suggest that although the benefits of this form of attentional guidance may be short-lived, novices can scaffold their decisions based on the search behavior of others.

Summary:Regional cerebral blood flow (CBF) was studied with O 15-water positron emission tomography and anatomic region-of-interest analysis on coregistered magnetic resonance in patients with idiopathic (n ‫ס‬ 12) and secondary (n ‫ס‬ 5) normal pressure hydrocephalus (NPH). Mean CBF was compared with values obtained from healthy volunteers (n ‫ס‬ 12) and with clinical parameters. Mean CBF was significantly decreased in the cerebrum and cerebellum of patients with NPH.The regional analysis demonstrated that CBF was reduced in the basal ganglia and the thalamus but not in white matter regions. The results suggest that the role of the basal ganglia and thalamus in NPH may be more prominent than currently appreciated. The implications for theories regarding the pathogenesis of NPH are discussed.

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Since publication, three errors have been highlighted:(1) Two fetal recordings were excluded from the final sample due to technical issues resulting in corruption of the scan at the source. The final sample and analysis remains unchanged. (2) A typographical error in the reported equation from Del Giudice ( 2011) was incorporated into the ''Method Details'' section.The actual calculation utilized in the original paper was the correct equation from Del Giudice (2011). (3) A statement related to normal distribution of the data has been removed from the ''Quantification and Statistical Analysis'' section. The original paper used non-parametric analyses, which are unaffected.