Distinct brain systems for processing concrete and abstract concepts.

Behavioral and neurophysiological effects of word imageability and concreteness remain a topic of central interest in cognitive neuroscience and could provide essential clues for understanding how the brain processes conceptual knowledge. We examined these effects using event-related functional magnetic resonance imaging while participants identified concrete and abstract words. Relative to nonwords, concrete and abstract words both activated a left-lateralized network of multimodal association areas previously linked with verbal semantic processing. Areas in the left lateral temporal lobe were equally activated by both word types, whereas bilateral regions including the angular gyrus and the dorsal prefrontal cortex were more strongly engaged by concrete words. Relative to concrete words, abstract words activated left inferior frontal regions previously linked with phonological and verbal working memory processes. The results show overlapping but partly distinct neural systems for processing concrete and abstract concepts, with greater involvement of bilateral association areas during concrete word processing, and processing of abstract concepts almost exclusively by the left hemisphere.

Neural correlates of lexical access during visual word recognition.

People can discriminate real words from nonwords even when the latter are orthographically and phonologically word-like, presumably because words activate specific lexical and/or semantic information. We investigated the neural correlates of this identification process using event-related functional magnetic resonance imaging (fMRI). Participants performed a visual lexical decision task under conditions that encouraged specific word identification: Nonwords were matched to words on orthographic and phonologic characteristics, and accuracy was emphasized over speed. To identify neural responses associated with activation of nonsemantic lexical information, processing of words and nonwords with many lexical neighbors was contrasted with processing of items with no neighbors. The fMRI data showed robust differences in activation by words and word-like nonwords, with stronger word activation occurring in a distributed, left hemisphere network previously associated with semantic processing, and stronger nonword activation occurring in a posterior inferior frontal area previously associated with grapheme-to-phoneme mapping. Contrary to lexicon-based models of word recognition, there were no brain areas in which activation increased with neighborhood size. For words, activation in the left prefrontal, angular gyrus, and ventrolateral temporal areas was stronger for items without neighbors, probably because accurate responses to these items were more dependent on activation of semantic information. The results show neural correlates of access to specific word information. The absence of facilitatory lexical neighborhood effects on activation in these brain regions argues for an interpretation in terms of semantic access. Because subjects performed the same task throughout, the results are unlikely to be due to task-specific attentional, strategic, or expectancy effects.

Quantifying variability in the planum temporale: a probability map.

The acquisition of definitive evidence for systematic hemispheric asymmetries in the size of the planum temporale (PT) has been restricted by difficulties in identifying, standardizing and measuring the region of interest. In this paper an operational definition for identifying the problematic posterior border of the PT on magnetic resonance imaging (MRI) scans is proposed. An interactive voxel-painting program was used to identify and label the PT simultaneously in horizontal, sagittal and coronal planes in MRI scans, transformed into the standardized Talairach-Tournoux stereo-taxic space, from 50 normal right-handed volunteers. Both grey matter volume and cortical surface area of the PT were measured, while controlling for individual variation in overall brain shape and volume. The labeled tissue was averaged together to produce a probability map in standardized space of the region of interest. The PT region is highly variable, with no single voxel being labeled with a probability of >65%. In this study there were no significant hemispheric differences in volume or area of the PT. An asymmetry in area and volume was introduced by using an alternative method - the 'knife-cut' method - for identifying the posterior border. Implications for functional neuroimaging of the PT are discussed.

Functional anatomy of musical processing in listeners with absolute pitch and relative pitch.

We used both structural and functional brain imaging techniques to investigate the neural basis of absolute pitch (AP), a specialized skill present in some musicians. By using positron emission tomography, we measured cerebral blood flow during the presentation of musical tones to AP possessors and to control musicians without AP. Listening to musical tones resulted in similar patterns of increased cerebral blood flow in auditory cortical areas in both groups, as expected. The AP group also demonstrated activation of the left posterior dorsolateral frontal cortex, an area thought to be related to learning conditional associations. However, a similar pattern of left dorsolateral frontal activity was also observed in non-AP subjects when they made relative pitch judgments of intervals, such as minor or major. Conversely, activity within the right inferior frontal cortex was observed in control but not in AP subjects during the interval-judgment task, suggesting that AP possessors need not access working memory mechanisms in this task. MRI measures of cortical volume indicated a larger left planum temporale in the AP group, which correlated with performance on an pitch-naming task. Our findings suggest that AP may not be associated with a unique pattern of cerebral activity but rather may depend on the recruitment of a specialized network involved in the retrieval and manipulation of verbal-tonal associations.

Interaction with a 'sex-expert' system enhances attitudes towards computerized sex therapy.

The present experiment investigated whether a new rule-based expert system, Sexpert, designed to assess and treat sexual dysfunction would be positively evaluated by näive users. In a between groups design, four groups of eight students were randomly assigned to one of two experimental groups or one of two control groups. Ss in the experimental groups interacted with one of two versions of Sexpert. Ss in one control group filled out a questionnaire concerning their sexual functioning while Ss in the other interacted with a non-sex related computer program. Perceived dissimilarity to other established treatments for sexual dysfunction and semantic differential attitudes measures taken both before and after the experimental manipulations showed a significant positive shift in favor of computerized sex therapy for those Ss who interacted with either version of Sexpert but not for Ss in either of the control conditions.