Influence of Phonological, Semantic and Orthographic tasks on the early linguistic components N150 and N350.

With the present investigation, which comprised two ERP experiments, we aimed to compare the earliest linguistic waves, namely the N150 and the N350, evoked by single words during three explicit tasks, Phonological, Semantic and Orthographic. With respect to past studies using different samples of stimuli for different tasks, in the present research we used the same sample of words and varied only the tasks. Results were consistent across experiments and showed in the Phonological and Semantic tasks a comparable N150 peaking over left posterior regions, but for the N350 a maximum at left frontal sites in the Phonological, and a bilateral frontal component in the Semantic task. Furthermore, compared with these tasks, the Orthographic task involved a cortical network confined to left posterior sites both in the early and late latencies, a network which was probably relevant for the discrimination of the visual features requested by the task rather than for the irrelevant linguistic features of the stimuli.