C1 and P1 visual responses to words are enhanced by attention to orthographic vs. lexical properties.

Attention to word orthographic properties has been shown to enhance the activity of VWFA. The temporal resolution of this effect remains still uncertain. In this study the attentive processing of orthographic vs. semantic features was compared by presenting the same set of words in two different conditions: letter detection vs. lexical decision. ERPs to targets were recorded in thirty-two right-handed students from 128 scalp sites. RTs, ERPs and swLORETA source reconstruction showed the prioritized processing of word orthographic features, able to enhance the activity of left fusiform gyrus (BA19/37) and cerebellar structures as early as 70-90 ms from stimulus-onset, as reflected by the increased amplitude of mesial C1 and lateral-occipital P1 components. On the other hand, attention to word lexical properties strongly enhanced the amplitude of left occipito/temporal N170, whose neural generators seemed to include regions devoted to lexical processing (VWFA), semantic processing (left BA39), and the effortful retrieval of semantic information (left and right BA10).