LEXICAL DECISION AFTER LEFT, RIGHT AND BILATERAL PRESENTATION OF FUNCTION WORDS, CONTENT WORDS AND NON-WORDS - EVIDENCE FOR INTERHEMISPHERIC INTERACTION

Function words, content words and pronounceable non-words (pseudowords ) were presented tachistoscopically either in the left or the right vi sual field or with identical copies flashed simultaneously to both vis ual half-fields. Consistent with earlier studies [10], function words were found to show a right visual field advantage, whereas for content words the right visual field advantage was absent. Compared to either of the unilateral modes of presentation bilateral presentation of ide ntical word stimuli improved accuracy and latency significantly. The b ilateral (Bi) advantage was largest for content words, and was also hi ghly significant for function words in both latency and accuracy. The Bi gain was absent for non-words (significant interaction of Wordness x Visual Field), These results indicate that the lexicons of the left and right hemisphere can ''collaborate'' rather than inhibit each othe r or act independently when processing the same linguistic stimuli. Ou r findings are consistent with tl;e view that the neuronal counterpart s of words are Hebbian cell assemblies consisting of strongly connecte d excitatory neurons of both hemispheres. Since function words show a right visual field advantage in addition to their Bi gain, their assem blies are likely to have most of their neurons located in the left hem isphere. Neuronal assemblies corresponding to content words may be les s strongly lateralized.