Visual word recognition is a key element of language comprehension. The vast majority of current models assume that the recognition of a printed word is based on the activation of abstract letter identity representations. The hierarchical neural accounts of letter/word recognition of Dehaene, Cohen, Sigman, and Vinckier (2005) and Grainger, Rey, and Dufau (2008) posit that, early in the process of lexical access, there are neuronal assemblies that respond to the word's case-specific letters (e.g., they respond to 'e' but not to 'E'). Later in processing, there are neuronal assemblies that respond to the abstract representation of the letter identity (e.g., they respond to the same degree to 'e' and to 'E').
Behavioral evidence using masked priming
To our knowledge, only a previous experiment
investigated the temporal processing of
lettercase using event-related potentials in an
unmasked paradigm
The main aim of this study is to examine the time
course of letter-case on lexical access. The ERPs
may help to disentangle whether letter case is an
attribute that is only relevant in early perceptual
processing or whether it is also relevant in the
retrieval of lexical representations. To attain this
goal, we examined whether the effects of
lettercase (lowercase vs. UPPERCASE) are
modulated by word-frequency
Method Twenty-two healthy, right-handed, native Spanish-speaking Valencia University students, naïve to the manipulation of the stimuli, participated in the study in exchange for a small gift.
We selected a set of 160 words from the
Webaccessible EsPal database
Participants were instructed to decide as accurately and rapidly as possible whether or not the stimulus was a Spanish word. They pressed one of two response buttons (YES/NO). The electroencephalogram (EEG) was recorded from 29 electrodes, averaged separately for each of the experimental conditions, each of the subjects and each of the electrode sites. For each time window, we conducted ANOVAs with wordfrequency (high, low), case (lowercase, UPPERCASE), and AP (anterior, central-anterior, central, central-posterior and posterior) as factors in the design.
Results and Conclusions The behavioral data revealed significantly faster responses for high-frequency than for lowfrequency words (656 vs. 702 ms) and significantly faster responses for lowercase than for uppercase words (675 vs. 683 ms). There were no signs of an interaction between the two factors. The error data revealed the same pattern as the response time data.
In the N/P150, larger negative values were observed for lowercase than for uppercase words, with a central scalp distribution, whereas the effect of word-frequency was not significant. In the P200, and only for low-frequency words, larger positive values were observed for the lowercase than for uppercase words in frontal/central scalp areas. With respect to the N400, the ERP waves revealed a dissociation of the letter-case effect for low- and high-frequency words. Highfrequency words showed an effect of letter-case in an early stage of the N400, whereas lowfrequency words showed an effect of letter-case (in the opposite direction; see Figure 1) in a later stage of the N400.
As expected, there was an early pre-lexical effect
of letter-case that did not interact with
wordfrequency. Importantly, we found an interaction
between letter-case and word-frequency not only
in the N400 time window –which is commonly
associated to lexical-semantic processing, but
also the P200 time window, thus supporting the
hypothesis that letter-case may affect the
mapping of visual-orthographic information onto
word representations. Taken together, the present
ERP data provide empirical support to the
hypothesis that letter-case information may be
stored in the abstract word representations