No abstract

Event-related potentials (ERPs) triggered by three different faces (unfamiliar, famous, and the subject's own) were analyzed during passive viewing. A familiarity effect was defined as a significant difference between the two familiar faces as opposed to the unfamiliar face. A degree of familiarity effect was defined as a significant difference between all three conditions. The results show a familiarity effect 170 ms after stimulus onset (N170), with larger amplitudes seen for both familiar faces. Conversely, a degree of familiarity effect arose approximately 250 ms after stimulus onset (P2) in the form of progressively smaller amplitudes as a function of familiarity (subject's face < famous face < unfamiliar). These results demonstrate that the structural encoding of faces, as reflected by N170 activities, can be modulated by familiarity and that facial representations acquire specific properties as a result of experience. Moreover, these results confirm the hypothesis that N170 is sensitive to face versus, object discriminations and to the discrimination among faces.

No abstract

The Event Related Potential (ERP) of 8 french right handed subjects were recorded with 5 active electrodes located in frontal (Fz), central (Cz), occipital (Oz) and right/left parietal (RH, LH) sites while they were performing a modified version of the test of Stroop. They had either to read the names of basic colors (yellow, green, blue, red) written in the same colors (red written in red: concordant stimuli) or in a different color (red written in blue: discordant stimuli) or to name mentally the color in which was written the name of a color, both colors being concordant or discordant. The ERPs for reading were similar for concordant and discordant stimuli and showed no sign of a N400 wave, this was also the case for the mental naming of a color associated to the written name of the same color. A N400 wave with a Cz location was evident for the mental naming of a color when it was associated to the written name of another color. In this last case, the automatic reading of the name of a color would correspond to a priming which interferes with the access to the target word: the name of another color that the subject is required to evoke mentally.

No abstract

In order to investigate the neuroanatomical chronometry of word processing, two experiments using: Event-Related Potentials (ERPs) have been performed. The first one was designed to test the effects of orthographic, phonologic, and lexical properties of linguistic items on the pre-semantic components of ERPs during a passive reading task and massive repetition used to reduce familiarity effect between words and nonwords. In a second study, the level of familiarity was investigated by varying stimulus repetition and frequency in a lexical decision task. Overall results suggest a functional discrimination between orthographic and nonorthographic stimuli begun as early as 170 ms (N170 component) whereas the next components (N230 and N320) were sensitive to the orthographic nature of the stimuli, but also to their lexical/phonologic proprieties. The N320 associated to phonological processing (Bentin et al., 1999) was modulated by word frequency and massive repetition caused its disappearance. This suggests that this component may reflect a nonobligatory phonologic stage of grapheme-phoneme conversion postulated by the DRC model (Coltheart et al., 2001) or semantic phonologically mediated pathway (Harm & Seidenberg, in press).

No abstract

No abstract