Dynamic Coding of Events within the Inferior Frontal Gyrus in a Probabilistic Selective Attention Task

摘要

Besides the fact that RTs in cognitive tasks are affected by thenspecific demands of a trial, the context in which this trial occursncodetermines the speed of the response. For instance, invalid spatialncues generally prolong RTs to targets in the location-cueingnparadigm, whereas the magnitude of these RT costs additionallynvaries as a function of the preceding trial types so that RTs for invalidntrials may be increased when preceded by valid rather thanninvalid trials. In the present fMRI study, we investigated trial sequenceneffects in a combined oddball and location-cueing paradigm.nIn particular, we tested whether RTs and neural activity toninfrequent invalid or deviant targets varied as a function of thennumber of preceding valid standard trials. As expected, RTs in invalidnand deviant trials were significantly slower when more validnstandard trials had been presented beforehand. This behavioral effectnwas reflected in the neural activity of the right inferior/middlenfrontal gyrus where the amplitude of the hemodynamic responsenin invalid and deviant trials was positively related to the number ofnpreceding valid standard trials. In contrast, decreased activity (i.e.,na negative parametric modulation effect) was observed whennmore valid standard trials were successively presented. Furthernpositive parametric effects for the number of preceding valid standardntrials were observed in the left caudate nucleus and lingualngyrus. The data suggest that inferior frontal cortex extracts bothnevent regularities and irregularities in event streams