& What happens in the brain when you conjure up a mental image in your mind’s eye? We tested whether the particular regions of extrastriate cortex activated during mental imagery depend on the content of the image. Using functional magnetic resonance imaging (fMRI), we demonstrated selective activation within a region of cortex specialized for face perception during mental imagery of faces, and selective activation within a place-selective cortical region during imagery of places. In a further study, we compared the activation for imagery and perception in these regions, and found greater response magnitudes for perception than for imagery of the same items. Finally, we found that it is possible to determine the content of single cognitive events from an inspection of the fMRI data from individual imagery trials. These findings strengthen evidence that imagery and perception share common processing mechanisms, and demonstrate that the specific brain regions activated during mental imagery depend on the content of the visual image. &

& Several functional neuroimaging studies have compared words and pseudowords to test different cognitive models of reading. There are difficulties with this approach, however, because cognitive models do not make clear-cut predictions at the neural level. Therefore, results can only be interpreted on the basis of prior knowledge of cognitive anatomy. Furthermore, studies comparing words and pseudowords have produced inconsistent results. The inconsistencies could reflect false-positive results due to the low statistical thresholds applied or confounds from nonlexical aspects of the stimuli. Alternatively, they may reflect true effects that are inconsistent across subjects; dependent on experimental parameters such as stimulus rate or duration; or not replicated across studies because of insufficient statistical power. In this fMRI study, we investigate consistent and inconsistent differences between word and pseudoword reading in 20 subjects, and distinguish between effects associated with increases and decreases in activity relative to fixation. In addition, the interaction of word type with stimulus duration is explored. We find that words and pseudowords activate the same set of regions relative to fixation, and within this system, there is greater activation for pseudowords than words in the left frontal operculum, left posterior inferior temporal gyrus, and the right cerebellum. The only effects of words relative to pseudowords consistent over subjects are due to decreases in activity for pseudowords relative to fixation; and there are no significant interactions between word type and stimulus duration. Finally, we observe inconsistent but highly significant effects of word type at the individual subject level. These results (i) illustrate that pseudowords place increased demands on areas that have previously been linked to lexical retrieval, and (ii) highlight the importance of including one or more baselines to qualify word type effects. Furthermore, (iii) they suggest that inconsistencies observed in the previous literature may result from effects arising from a small number of subjects only. &

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A prevailing neurobiological theory of semantic memory proposes that part of our knowledge about concrete, highly imageable concepts is stored in the form of sensory–motor representations. While this theory predicts differential activation of the semantic system by concrete and abstract words, previous functional imaging studies employing this contrast have provided relatively little supporting evidence. We acquired event-related functional magnetic resonance imaging (fMRI) data while participants performed a semantic similarity judgment task on a large number of concrete and abstract noun triads. Task difficulty was manipulated by varying the degree to which the words in the triad were similar in meaning. Concrete nouns, relative to abstract nouns, produced greater activation in a bilateral network of multimodal and heteromodal association areas, including ventral and medial temporal, posterior–inferior parietal, dorsal prefrontal, and posterior cingulate cortex. In contrast, abstract nouns produced greater activation almost

this paper, we demonstrated the possibility performing structural morphometry using automatic image analysis tools to extract the cortical folds (Mangin et al., 1995a,b). The fold labeling according to the sulcus nomenclature, however, was performed manually by a neurosurgeon. We have recently developed a system to perform this labeling automatically, using a set of 500 neural networks trained on a manually labeled database (Riviere et al., 2002). Each neural network is in charge of a local anatomical feature. This opens the door to automatic "Structural Based Morphometry" (SBM), that is to say a large-scale morphometric study similar to those performed with a voxel-based approach. We have also reported the advent of new visualization tools dedicated to the 3D shape of the folding that can be used to improve the current understanding of the folding patterns. These tools can be used to study the variability of the buried gyri (pli de passage) which often interrupt the usual sulci. Future work consists of the validation and automatic recognition of the foetal sulcal root patterns, which would improve the reliability of the morphometric attributes used for the automatic studies. This work will rely on longitudinal studies of the folding process and new mathematical methods to infer the buried gyri localization for the curvature of the cortical surface (Cachia et al., 2001)

It is proposed that the human brain is proactive in that it continuously generates predictions that anticipate the relevant future. In this proposal, analogies are derived from elementary information that is extracted rapidly from the input, to link that input with the representations that exist in memory. Finding an analogical link results in the generation of focused predictions via associative activation of representations that are relevant to this analogy, in the given context. Predictions in complex circumstances, such as social interactions, combine multiple analogies. Such predictions need not be created afresh in new situations, but rather rely on existing scripts in memory, which are the result of real as well as of previously imagined experiences. This cognitive neuroscience framework provides a new hypothesis with which to consider the purpose of memory, and can help explain a variety of phenomena, ranging from recognition to first impressions, and from the brain’s ‘default mode ’ to a host of mental disorders.

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Advancing age is associated with a decline in physical and cognitive abilities. Multiple theories have been proposed to account for the psychological impairments seen in older age. These include changes in sensory acuity, general slowing of the nervous system, declines in working memory capacity, and a loss of inhibitory control. Although not inherently incompatible, each of the theories provides a unique interpretation of the observed pattern of psychological and neuronal data. To test the veracity of the inhibitory theory a series of experiments was performed. The first experiment used functional magnetic resonance imaging (fMRI) to assess a classical Sternberg paradigm with five increasing levels of cognitive demand ranging from a set size of two letters up to six letters. Comparisons of mean levels of recruitment and inhibition were done between younger and older adults revealing that older adults greatly over recruit but under inhibit areas of the brain compared to their younger counterparts. A region of interest analysis revealed that older adults recruit tissue in a linear fashion from almost all areas in the task evoked visual and attentional networks while younger adults modulate the activity in only a subset of regions.