Argument structure and morphological factors in noun and verb processing: an fMRI study.

In a functional MRI (fMRI) study, we have investigated the grammatical categories of object noun, event noun and verb in order to assess the cortical regions of activation supporting their processing. Twelve Italian healthy participants performed a lexical decision task. They had to decide whether a string was an Italian word or not. Words could be objects like medaglia (medal), or events like the noun pianto (cry); or the verb dormire (to sleep). Noun and verb comparison shows differences in regions of activation in the left Inferior Frontal cortex and in the extent of the same areas. We have found specific areas of activation for object noun, and similarities in the pattern of activation for event noun and verb. The activations induced by pseudowords highly resembled the areas activated by the corresponding word category. The implications of the results are discussed in light of the recent debate on the role of grammatical category in the brain.

Frontostriatal response to set switching is moderated by reward sensitivity.

The reinforcement sensitivity theory (RST) relates individual differences in reward sensitivity to the activation of the behavioral approach system (BAS). Dopamine-related brain structures have been repeatedly associated with reward processing, but also with cognitive processes such as task switching. In the present study, we examined the association between reward sensitivity and the event-related fMRI BOLD response with set switching in 31 males. As expected, the right inferior frontal cortex (rIFG) and the striatum (i.e. the left putamen) were involved in set-switching activity for the overall sample. Interindividual differences in Gray's reward sensitivity were related to stronger activity in the rIFG and the ventral striatum. Thus, trait reward sensitivity contributed to the modulation of brain responsiveness in set-switching tasks. Having considered previous research, we propose that higher BAS activity is associated with a stronger reward to process a better implementation of goal-directed tasks and the diminished processing of secondary cues.

Dependence of the fractional anisotropy in cervical spine from the number of diffusion gradients, repeated acquisition and voxel size.

The aim of this study is to investigate the consequences of using different gradient schemes, number of repeated measurements and voxel size on the fractional anisotropy (FA) value in a diffusion tensor imaging (DTI) sequence on the cervical tract of the spinal cord. Twenty healthy volunteers underwent a total of 86 DTI axial acquisitions performed by using different voxel size and number of diffusion gradient directions (NDGDs). Three different diffusion gradient schemes were applied, named 6, 15 and 32 according to the NDGD. Furthermore, some acquisitions were repeated to investigate the effects of image averaging on FA value. Our results indicate that the FA value in the cervical spinal cord decreases when increasing the NDGD for a fixed spatial resolution, or when identical acquisitions are repeated, thus, increasing the acquisition time. This effect is observed in all subjects without exceptions, and the differences result statistically significant: the average FA obtained from 6, 15 and 32 NDGD is 0.84 (range, 0.82-0.87), 0.75 (range, 0.68-0.80) and 0.70 (range, 0.65-0.77), respectively, for isotropic 8 mm(3) voxel size. When varying the spatial resolution in a volume range of 2 to 8 mm(3) for a fixed NDGD (6 or 15), the differences in FA values are smaller albeit still statistically significant: the smaller the voxel, the larger the FA. No significant dependence of the FA value from the spatial resolution is observed in the 32 NDGD acquisitions in the studied volume range. In conclusion, our results indicate that the value of the FA in the cervical tract of the spinal cord vary with regularity in intrasubject acquisitions when modifying the NDGD and when repeated acquisitions are used; these observations confirm that the signal-to-noise ratio introduces a systematic error in FA measurements that does not allow simple comparison of quantitative results obtained from separated studies.