The cerebral organization of word identification processes in reading was examined using functional magnetic resonance imaging (fMRI). Changes in fMRI signal intensities were measured in 38 subjects (19 males and 19 females) during visual (line judgement), orthographic (letter case judgement), phonological (nonword rhyme judgement) and semantic (semantic category judgement) tasks. A strategy of multiple subtractions was employed in order to validate relationships between structure and function. Orthographic processing made maximum demands on extrastriate sites, phonological processing on a number of frontal and temporal sites, and lexical-semantic processing was most strongly associated with middle and superior temporal sites. Significant sex differences in the cerebral organization of reading-related processes were also observed.

The fusiform face area (FFA) is a region of human cortex that responds selectively to faces, but whether it supports a more general function relevant for perceptual expertise is debated. Although both faces and objects of expertise engage many brain areas, the FFA remains the focus of the strongest modular claims and the clearest predictions about expertise. Functional MRI studies at standard-resolution (SR-fMRI) have found responses in the FFA for nonface objects of expertise, but high-resolution fMRI (HR-fMRI) in the FFA [Grill-Spector K, et al. (2006) Nat Neurosci 9:1177-1185] and neurophysiology in face patches in the monkey brain [Tsao DY, et al. (2006) Science 311:670-674] reveal no reliable selectivity for objects. It is thus possible that FFA responses to objects with SR-fMRI are a result of spatial blurring of responses from nonfaceselective areas, potentially driven by attention to objects of expertise. Using HR-fMRI in two experiments, we provide evidence of reliable responses to cars in the FFA that correlate with behavioral car expertise. Effects of expertise in the FFA for nonface objects cannot be attributed to spatial blurring beyond the scale at which modular claims have been made, and within the lateral fusiform gyrus, they are restricted to a small area (200 mm 2 on the right and 50 mm 2 on the left) centered on the peak of face selectivity. Experience with a category may be sufficient to explain the spatially clustered face selectivity observed in this region.neural selectivity | object recognition | individual differences | response reliability | ventral temporal cortex

An NMR method is applied for separating blood volume and magnetic susceptibility effects in response to neuronal stimulation in a rat model. The method uses high susceptibility contrast agents to enhance blood volume induced signal changes. In the absence of exogenous agent, the dominant source of signal change on neuronal activation is associated with the signal increase from the blood oxygen level dependent (BOLD) effect. The relative negative contribution of blood volume changes to BOLD changes is maximally estimated to be 34%. The blood volume changes associated with median nerve stimulation (7 Hz) in the motor cortex are 26+/-7% and the corresponding blood susceptibility changes are 0.021+/-0.006 ppm. These methods can be applied to enhance the sensitivity of fMRI signal response and provide accurate quantitative measures of blood volume response to stimulation.

Purpose Cell size is a fundamental characteristic of all tissues, and changes in cell size in cancer reflect tumor status and response to treatments, such as apoptosis and cell‐cycle arrest. Unfortunately, cell size can currently be obtained only by pathological evaluation of tumor tissue samples obtained invasively. Previous imaging approaches are limited to preclinical MRI scanners or require relatively long acquisition times that are impractical for clinical imaging. There is a need to develop cell‐size imaging for clinical applications. Methods We propose a clinically feasible IMPULSED (imaging microstructural parameters using limited spectrally edited diffusion) approach that can characterize mean cell sizes in solid tumors. We report the use of a combination of pulse sequences, using different gradient waveforms implemented on clinical MRI scanners and analytical equations based on these waveforms to analyze diffusion‐weighted MRI signals and derive specific microstructural parameters such as cell size. We also describe comprehensive validations of this approach using computer simulations, cell experiments in vitro, and animal experiments in vivo and demonstrate applications in preoperative breast cancer patients. Results With fast acquisitions (~7 minutes), IMPULSED can provide high‐resolution (1.3 mm in‐plane) mapping of mean cell size of human tumors in vivo on clinical 3T MRI scanners. All validations suggest that IMPULSED provides accurate and reliable measurements of mean cell size. Conclusion The proposed IMPULSED method can assess cell‐size variations in tumors of breast cancer patients, which may have the potential to assess early response to neoadjuvant therapy.