EQUIVALENT RESPONSES TO LEXICAL AND NONLEXICAL VISUAL-STIMULI IN OCCIPITAL CORTEX - A FUNCTIONAL MAGNETIC-RESONANCE-IMAGING STUDY

Stimulus-related changes in cerebral blood oxygenation were measured u sing high-resolution functional magnetic resonance imaging sequentiall y covering visual occipital areas in contiguous sections. During dynam ic imaging, healthy subjects silently viewed pseudowords, single false fonts, or length-matched strings of the same false fonts. The paradig m consisted of a sixfold alternation of an activation and a control ta sk. With pseudowords as activation vs single false fonts as control, r esponses were seen mainly in medial occipital cortex. These responses disappeared when pseudowords were alternated with false font strings a s the control and reappeared when false font strings instead of pseudo words served as activation and were alternated with single false fonts . The string-length contrast alone, therefore, is sufficient to accoun t for the activation pattern observed in medial visual cortex when wor d-like stimuli are contrasted with single characters. (C) 1997 Academi c Press.