title: Many neighbors are not silent. fMRI evidence for global lexical activity in visual word recognition.
abstract: Many neurocognitive studies investigated the neural correlates of visual word recognition, some of which manipulated the orthographic neighborhood density of words and nonwords believed to influence the activation of orthographically similar representations in a hypothetical mental lexicon. Previous neuroimaging research failed to find evidence for such global lexical activity associated with neighborhood density. Rather, effects were interpreted to reflect semantic or domain general processing. The present fMRI study revealed effects of lexicality, orthographic neighborhood density and a lexicality by orthographic neighborhood density interaction in a silent reading task. For the first time we found greater activity for words and nonwords with a high number of neighbors. We propose that this activity in the dorsomedial prefrontal cortex reflects activation of orthographically similar codes in verbal working memory thus providing evidence for global lexical activity as the basis of the neighborhood density effect. The interaction of lexicality by neighborhood density in the ventromedial prefrontal cortex showed lower activity in response to words with a high number compared to nonwords with a high number of neighbors. In the light of these results the facilitatory effect for words and inhibitory effect for nonwords with many neighbors observed in previous studies can be understood as being due to the operation of a fast-guess mechanism for words and a temporal deadline mechanism for nonwords as predicted by models of visual word recognition. Furthermore, we propose that the lexicality effect with higher activity for words compared to nonwords in inferior parietal and middle temporal cortex reflects the operation of an identification mechanism based on local lexico-semantic activity.
authors.affiliation: Neurocognition Lab, Centre for Cognitive Neuroscience, Universität Salzburg Salzburg, Austria ; Department of Experimental and Neurocognitive Psychology, Freie Universität Berlin Berlin, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Braun
authors.affiliation: Department of Experimental and Neurocognitive Psychology, Freie Universität Berlin Berlin, Germany ; Center for Cognitive Neuroscience Berlin Berlin, Germany ; Dahlem Institute for Neuroimaging of Emotion, Berlin Germany.
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Jacobs
authors.affiliation: Neurocognition Lab, Centre for Cognitive Neuroscience, Universität Salzburg Salzburg, Austria.
authors.forename: Fabio
authors.initials: F
authors.lastname: Richlan
authors.affiliation: Neurocognition Lab, Centre for Cognitive Neuroscience, Universität Salzburg Salzburg, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hawelka
authors.affiliation: Neurocognition Lab, Centre for Cognitive Neuroscience, Universität Salzburg Salzburg, Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Hutzler
authors.affiliation: Neurocognition Lab, Centre for Cognitive Neuroscience, Universität Salzburg Salzburg, Austria ; Christian-Doppler-Klinik, Paracelsus Medical University, Salzburg Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Kronbichler
keywords: deadline mechanism; dorso- and ventromedial cortex; fast-guess mechanism; identification mechanism; mental lexicon; neighborhood density effect; orthographic similarity; visual word recognition