Neurophysiological differentiation between preattentive and attentive processing of emotional expressions on French vowels.

The present electrophysiological study investigated the processing of emotional prosody by minimizing as much as possible the effect of emotional information conveyed by the lexical-semantic context. Emotionally colored French vowels (i.e., happiness, sadness, fear, and neutral) were presented in a mismatch negativity (MMN) oddball paradigm. Both the MMN, i.e., an event-related potential (ERP) component thought to reflect preattentive change detection, and the P3a, i.e., an ERP marker of involuntary orientation of attention toward deviant stimuli, were significantly modulated by the emotional deviants compared to the neutral ones. Critically, the largest amplitude (MMN, P3a) and the shortest peak latency (MMN) were observed for fear deviants, all other things being equal. Taken together, the present findings lend support to a sequential neurocognitive model of emotion processing (Scherer, 2001) which postulates, among other checks, a first stage of automatic emotion detection (MMN) followed by a second stage of subjective evaluation of the stimulus or event (P3a). Consistently with previous studies, our data suggest that among the six universal emotions, fear could have a special status probably because of its adaptive role in the evolution of the human species.

Functional significance of the semantic P600: evidence from the event-related brain potential source localization.

Previous event-related potentials studies of sentence comprehension have usually associated syntactic repair/reanalysis processes with the P600 component. However, the functional significance of the P600 was recently questioned on the basis of the observation of P600 effects in response to the processing of semantically anomalous sentences. In the present study, we investigated the functional significance of the 'semantic P600' using a semantic violation paradigm with a focus-on-syntax instruction. Using a source localization analysis, we tested three alternative hypotheses on the function of the P600: (i) a syntactic function, (ii) an executive function, and (iii) a semantic/integrational function. We assumed that distinct neuronal generators should reflect each of these functions. Although the syntactic generators are expected to be mainly located in the left inferior frontal gyrus, the semantic generators should be observed in the left superior temporal gyrus as well as in the right anterior prefrontal cortex (semantic retrieval); moreover, the generator of executive function (conflict monitoring) should be found in the anterior cingulate cortex. Critically, we defined a dipole model using 17 dipoles, 14 of which were placed in the three regions of interest corresponding to our hypotheses, namely, syntactic, executive, and semantic regions. Our data showed that the P600 effect was significant in the anterior cingulate cortex and marginally significant in the right anterior prefrontal cortex. This finding suggests that the P600 might reflect more general mechanisms of conflict monitoring and semantic reinterpretation leading to a retrieval of world knowledge from long-term memory rather purely syntactic processes.

Perceptual and gaze biases during face processing: related or not?

Previous studies have demonstrated a left perceptual bias while looking at faces, due to the fact that observers mainly use information from the left side of a face (from the observer's point of view) to perform a judgment task. Such a bias is consistent with the right hemisphere dominance for face processing and has sometimes been linked to a left gaze bias, i.e. more and/or longer fixations on the left side of the face. Here, we recorded eye-movements, in two different experiments during a gender judgment task, using normal and chimeric faces which were presented above, below, right or left to the central fixation point or on it (central position). Participants performed the judgment task by remaining fixated on the fixation point or after executing several saccades (up to three). A left perceptual bias was not systematically found as it depended on the number of allowed saccades and face position. Moreover, the gaze bias clearly depended on the face position as the initial fixation was guided by face position and landed on the closest half-face, toward the center of gravity of the face. The analysis of the subsequent fixations revealed that observers move their eyes from one side to the other. More importantly, no apparent link between gaze and perceptual biases was found here. This implies that we do not look necessarily toward the side of the face that we use to make a gender judgment task. Despite the fact that these results may be limited by the absence of perceptual and gaze biases in some conditions, we emphasized the inter-individual differences observed in terms of perceptual bias, hinting at the importance of performing individual analysis and drawing attention to the influence of the method used to study this bias.