Attentional systems and the allocation of cerebral resources in reading and grammatical tasks

To evaluate the possible role of attentional centers as modulators of neural networks that mediate visual tasks involving reading and grammatical manipulations of verbs, we measured cerebral blood flow (CBF) using positron emission tomography (PET), and reaction times as subjects read verbs, "nonce verbs" such as jelt or brep, and formed past tenses of regular, irregular and nonce verbs after viewing their stems. Statistical parametric maps (SPMs) showed significant activation of the pulvinar in the read verb irregular, and generate nonce past tense tasks, compared to rest. This was confirmed by a post hoc ANOVA of CBF values from a discrete locus in the pulvinar (p = .0000417). Functional links between the pulvinar and other brain regions were shown by high correlations of CBF in the pulvinar with CBF in brain regions known to have anatomical connections to the pulvinar, particularly those mediating vision. There was also a significant relationship between task-specific reaction times and rest minus task CBF differences in a multiple regression analysis that included CBF values from the pulvinar, superior colliculus plus reticular formation, and the anterior cingulate, known attentional centers (p = .021, r2 = 0.99). Regression analyses relating reaction time to the amount of brain activated (pixels in the SPMs) and the degree of activation of the pixels (mean Z score) yielded p values of .078 and .074, respectively. Our data provide direct experimental evidence to support the hypothesis that attentional centers are activated in proportion to the complexity of visually mediated language tasks and that the centers that mediate attention modulate the activity of task-specific neural networks.