The invariant properties of human cortical neurons cannot be studied directly by fMRI due to its limited spatial resolution. Here, we circumvented this limitation by using fMR adaptation, namely, reduction of the fMR signal due to repeated presentation of identical images. Object-selective regions (lateral occipital complex [LOC]) showed a monotonic signal decrease as repetition frequency increased. The invariant properties of fMR adaptation were studied by presenting the same object in different viewing conditions. LOC exhibited stronger fMR adaptation to changes in size and position (more invariance) compared to illumination and viewpoint. The effect revealed two putative subdivisions within LOC: caudal-dorsal (LO), which exhibited substantial recovery from adaptation under all transformations, and posterior fusiform (PF/LOa), which displayed stronger adaptation. This study demonstrates the utility of fMR adaptation for revealing functional characteristics of neurons in fMRI studies.

The authors outline a cognitive and computational account of causal learning in children. They propose that children use specialized cognitive systems that allow them to recover an accurate "causal map" of the world: an abstract, coherent, learned representation of the causal relations among events. This kind of knowledge can be perspicuously understood in terms of the formalism of directed graphical causal models, or Bayes nets. Children's causal learning and inference may involve computations similar to those for learning causal Bayes nets and for predicting with them. Experimental results suggest that 2-to 4-year-old children construct new causal maps and that their learning is consistent with the Bayes net formalism.The input that reaches children from the world is concrete, particular, and limited. Yet, adults have abstract, coherent, and largely veridical representations of the world. The great epistemological question of cognitive development is how human beings get from one place to the other: How do children learn so much about the world so quickly and effortlessly? In the past 30 years, cognitive developmentalists have demonstrated that there are systematic changes in children's knowledge of the world. However, psychologists know much less about the representations that underlie that knowledge and the learning mechanisms that underlie changes in that knowledge.In this article, we outline one type of representation and several related types of learning mechanisms that may play a particularly important role in cognitive development. The representations are of the causal structure of the world, and the learning mechanisms involve a particularly powerful type of causal inference. Causal knowledge is important for several reasons. Knowing about causal structure permits us to make wide-ranging predictions about future events. Even more important, knowing about causal structure allows us to intervene in the world to bring about new eventsoften events that are far removed from the interventions themselves.

To investigate the relationship between perceptual awareness and brain activity, we measured both recognition performance and fMRI signal from object-related areas in human cortex while images were presented briefly using a masking protocol. Our results suggest that recognition performance is correlated with selective activation in object areas. Selective activation was correlated to object naming when exposure duration was varied from 20 to 500 milliseconds. Subjects' recognition during identical visual stimulation could be enhanced by training, which also increased the fMRI signal. Overall, the correlation between recognition performance and fMRI signal was highest in occipitotemporal object areas (the lateral occipital complex).

Functional magnetic resonance imaging was used in combined functional selectivity and retinotopic mapping tests to reveal object-related visual areas in the human occipital lobe. Subjects were tested with right, left, up, or down hemivisual field stimuli which were composed of images of natural objects (faces, animals, man-made objects) or highly scrambled (1,024 elements) versions of the same images. In a similar fashion, the horizontal and vertical meridians were mapped to define the borders of these areas. Concurrently, the same cortical sites were tested for their sensitivity to image-scrambling by varying the number of scrambled picture fragments (from 16-1,024) while controlling for the Fourier power spectrum of the pictures and their order of presentation. Our results reveal a stagewise decrease in retinotopy and an increase in sensitivity to image-scrambling. Three main distinct foci were found in the human visual object recognition pathway (Ungerleider and Haxby [1994]: Curr Opin Neurobiol 4:157-165): 1) Retinotopic primary areas V1-3 did not exhibit significant reduction in activation to scrambled images. 2) Areas V4v (Sereno et al., [1995]: Science 268:889-893) and V3A (De Yoe et al., [1996]: Proc Natl Acad Sci USA 93:2382-2386; Tootell et al., [1997]: J Neurosci 71:7060-7078) manifested both retinotopy and decreased activation to highly scrambled images. 3) The essentially nonretinotopic lateral occipital complex (LO) (Malach et al., [1995]: Proc Natl Acad Sci USA 92:8135-8139; Tootell et al., [1996]: Trends Neurosci 19:481-489) exhibited the highest sensitivity to image scrambling, and appears to be homologous to macaque the infero-temporal (IT) cortex (Tanaka [1996]: Curr Opin Neurobiol 523-529). Breaking the images into 64, 256, or 1,024 randomly scrambled blocks reduced activation in LO voxels. However, many LO voxels remained significantly activated by mildly scrambled images (16 blocks). These results suggest the existence of object-fragment representation in LO.

The extent to which primary visual cues such as motion or luminance are segregated in different cortical areas is a subject of controversy. To address this issue, we examined cortical activation in the human occipital lobe using functional magnetic resonance imaging (fMRI) while subjects performed a fixed visual task, object recognition, using three different primary visual cues: motion, texture, or luminance contrast. In the first experiment, a region located on the lateral aspect of the occipital lobe (LO complex) was preferentially activated in all 11 subjects both by luminance and motion-defined object silhouettes compared to full-field moving and stationary noise (ratios, 2.00+/-0.19 and 1.86+/-0.65, respectively). In the second experiment, all subjects showed enhanced activation in the LO complex to objects defined both by luminance and texture contrast compared to full-field texture patterns (ratios, 1.43+/-0.08 and 1.32+/-0.08, respectively). An additional smaller dorsal focus that exhibited convergence of object-related cues appeared to correspond to area V3a or a region slightly anterior to it. These results show convergence of visual cues in LO and provide strong evidence for its role in object processing.

Psychological scientists use statistical information to determine the workings of fellow humans. We argue so do young children. In a few years, children progress from viewing human actions as intentional and goal-directed to reasoning about the psychological causes underlying such actions. Here we show that preschoolers and 20-month-old infants can use statistical information – namely, a violation of random sampling – to infer that an agent is expressing a preference for one object over another. Children saw a person remove 5 items of one type from a container of objects. Preschoolers and infants only inferred a preference for that type of object when there was a mismatch between the sample and population. Mere outcome consistency, time spent with and positive attention toward the objects did not lead children to infer a preference. The findings provide an important demonstration of how statistical learning could underpin the rapid acquisition of early psychological knowledge.

Children's causal learning has been characterized as a rational process, in which children appropriately evaluate evidence from their observations and actions in light of their existing conceptual knowledge. We propose a similar framework for children's selective social learning, concentrating on information learned from others' testimony. We examine how children use their existing conceptual knowledge of the physical and social world to determine the reliability of testimony. We describe existing studies that offer both direct and indirect support for selective trust as rational inference and discuss how this framework may resolve some of the conflicting evidence surrounding cases of indiscriminate trust. Importantly, this framework emphasizes that children are active in selecting evidence (both social and experiential), rather than being passive recipients of knowledge, and motivates further studies that more systematically examine the process of learning from social information.

Background/aims Erythropoiesis in long‐term hemodialyzed (LTH) patients is supported by erythropoietin (rHuEpo) and intravenous (IV) iron. This treatment may end up in iron overload (IO) in major organs. We studied such patients for the parameters of IO in the serum and in major organs. Methods Patients were treated with rHuEpo (6–8 x 103 units × 1–3/wk) and IV 100 mg ferric saccharate. Results Of 115 patients, 21 had serum ferritin (SF) > 1000 ng/mL. This group was further analyzed. Their SF and transferrin saturation (TSAT) were 2688 ± 1489 ng/mL and 54.2 ± 32.7%, respectively (vs. 125–360 ng/mL and 20–50% in normal controls). Serum hepcidin was 60.1 ± 29.5 nm (vs. 10.61 ± 6.44 nm in controls) (P < 0.001). Nineteen patients had increased malonyldialdehyde, a product of lipid peroxidation, indicating oxidative stress. T2* MRI disclosed in 19 of 21 patients moderate to severe IO in the liver and spleen, in three of eight patients in the pancreas, but in no patient in the heart. After stopping IV iron for a mean of 12 months, while continuing rHuEpo, the mean SF decreased in 11 patients to 1682 ng/mL and the mean TSAT decreased to 28%, whereas hemoglobin did not change indicating that tissue iron was utilized. Conclusion High SF correlates with IO in the liver and spleen, but not in the heart.