from Neuropsychologia 38 (2000), pp. 325-335
Abstract: To explore brain areas involved in basic numerical computation, functional magnetic imaging (fMRI) scanning was performed on college students during performance of three tasks; simple arithmetic, numerical magnitude judgment, and a perceptual- motor control task. For the arithmetic relative to the other tasks, results for all eight subjects revealed bilateral activation in Brodmann's area 44, in dorsolateral prefrontal cortex (areas 9 and 10), in inferior and superior parietal areas, and in lingual and fusiform gyri. Activation was stronger on the left for all subjects, but only at Brodmann's area 44 and the parietal cortices. No activation was observed in the arithmetic task in several other areas previously implicated for arithmetic, including the angular and supramarginal gyri and the basal ganglia. In fact, angular and supramarginal gyri were significantly deactivated by the verification task relative to both the magnitude judgment and control tasks for every subject. Areas activated by the magnitude task relative to the control were more variable, but in five subjects included bilateral inferior parietal cortex. These results confirm some existing hypotheses regarding the neural basis of numerical processes, invite revision of others, and suggest productive lines for future investigation. Published by Elsevier Science Ltd.
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from Brain 124 (2001), pp. 1681-1682
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from Neurocase (2002) Vol. 8, pp. 355–368
Abstract: We summarize two case studies as a context for discussing the use of neuroimaging as a convergent methodology in the study of neuroplasticity in single subjects. Throughout this paper we argue for a different approach for including neuroimaging in these types of study. Previous case studies of neuroplasticity in patients (ours as well as others reported elsewhere) have added neuroimaging to the traditional neuropsychological framework of comparing patient results with matched control groups, and synthesized results through descriptions of anatomical and behavioral dissociations. This type of approach is referred to as the comparison approach. We advocate a different approach that builds on findings from previous behavioral skill learning research. Specifically, we propose adding neuroimaging throughout learning or recovery of the ability of interest and making inferences from systematic changes in activation topography and intensity that occur within the context of predicted behavioral changes. We dub this approach the online approach. This approach should allow future investigators to circumvent many of the interpretation pitfalls that are common in comparison studies.
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from Journal of Cognitive Neuroscience (2003) 15:2, pp. 236–248
Abstract: Complex social behavior and the relatively large size of the prefrontal cortex are arguably two of the characteristics that distinguish humans from other animals. Grafman presented a framework concerning how the prefrontal cortex (PFC) controls complex behavior using stored structured event complexes (SECs). We report behavioral and imaging data from a modified go/no-go paradigm in which subjects had to classify words (semantic) and phrases (SEC) according to category. In experimental trials, subjects classified items according to social or nonsocial activity; in control trials, they classified items according to font. Subjects were faster to classify social than nonsocial semantic items, with the reverse pattern evident for the social and nonsocial SEC items. In addition, the conditions were associated with different patterns of PFC activation. These results suggest that there are different psychological and neural substrates for social and nonsocial semantic and SEC representations.
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from Neuropsychologia 43 (2005), pp. 249–259
Abstract: It has been proposed that behavior is influenced by representations of different types of knowledge: action representations, event knowledge, attitudes and stereotypes. Attitudes (representations of a concept or object and its emotional evaluation) allow us to respond quickly to a given stimulus. In this study, we explored the representation and inhibition of attitudes. We show that right dorsolateral prefrontal cortex mediates negative attitudes whereas left ventrolateral prefrontal cortex mediates positive attitudes. Parahippocampal regions and amygdala mediate evaluative processing. Furthermore, anxiety modulates right dorsolateral prefrontal activation during negative attitude processing. Inhibition of negative attitudes activates left orbitofrontal cortex: a region that when damaged is associated with socially inappropriate behavior in patients. Inhibition of positive attitudes activates a brain system involving right inferior frontal gyrus and bilateral anterior cingulate. Thus, we show that there are dissociable networks for the representation and inhibition of attitudes. Published by Elsevier Ltd.
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