Christian Bernard

Familiarity and Emotional Expression Influence an Early Stage of Face Processing: An Electrophysiological Study.

Recent data indicate that the familiarity and the emotional expression of faces occur at an early stage of information processing. The goal of the present study was to determine whether these two aspects interact at the structural encoding stage as reflected by the N170 component of event-related potentials in tasks requiring the subjects either to identify whether the faces were familiar or the nature of the emotional expression. The results indicate that the neural responses to level of familiarity and emotional expression were observable at this early processing stage but without interacting. In particular, faces of personal importance to the subjects differed from those of less personal importance. Because familiarity did not interact with emotional expression at behavioral and electrophysiologic levels, our results support the contention of parallel and independent processing of faces.

ERPs associated with familiarity and degree of familiarity during face recognition.

Event-related potentials (ERPs) triggered by three different faces (unfamiliar, famous, and the subjects 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 (NI70), 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.

The Stroop's Test Evokes A Negative Brain Potential, the N400

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.

CHRONOMETRY OF VISUAL WORD RECOGNITION DURING PASSIVE AND LEXICAL DECISION TASKS: AN ERP INVESTIGATION

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 presemantic 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 graphemephoneme conversion postulated by the DRC model (Coltheart et al., 2001) or semantic phonologically mediated pathway (Harm and Seidenberg, in press).

The effects of familiarity and emotional expression on face processing examined by ERPs in patients with schizophrenia

BACKGROUND The main objective of the study was to determine whether patients with schizophrenia are deficient relative to controls in the processing of faces at different levels of familiarity and types of emotion and the stage where such differences may occur. METHODS ERPs based on 18 patients with schizophrenia and 18 controls were compared in a face identification task at three levels of familiarity (unknown, familiar, subjects own) and for three types of emotion (disgust, smiling, neutral). RESULTS The schizophrenic group was less accurate than controls in the face processing, especially for unknown faces and those expressing negative emotions such as disgust. P1 and N170 amplitudes were lower and P1, N170, P250 amplitudes were of slower onset in patients with schizophrenia. N170 and P250 amplitudes were modulated by familiarity and face expression in a different manner in patients than controls. CONCLUSIONS Schizophrenia is associated with a genelarized defect of face processing, both in terms of familiarity and emotional expression, attributable to deficient processing at sensory (P1) and perceptual (N170) stages. These patients appear to have difficulty in encoding the structure of a face and thereby do not evaluate correctly familiarity and emotion.

Presynaptic actions of cholinergic agents upon the hair cell-afferent fiber synapse in the vestibular labyrinth of the frog

Spontaneous activity of semicircular canal afferents in the isolated labyrinth of the frog is altered by bath application of cholinergic agonists. Muscarinic agonists can produce an increase in action potential frequency of individual afferents. This increase develops slowly and is prolonged in the time course of its action. Nicotinic agonists can either increase (most cases) or decrease afferent activity. These effects occur rapidly and decay during the period of activation, suggesting desensitization. Muscarinic effects are blocked by prior administration of atropine and nicotinic effects (both increases and decreases in action potential frequency) by curare. Intracellular recordings reveal that the nicotinic effects on afferent action potential frequency are the result of alterations in the frequency of spontaneous synaptic potentials, indicating a presynaptic site of action on the hair cells for these compounds. This conclusion is supported by the fact that in the presence of high Mg2+/low Ca2+, which blocks hair cell release of transmitter, cholinergic agonists do not affect the resting membrane potential of the vestibular afferent. Electrical stimulation of the VIIIth cranial nerve can result in either an increase or a decrease in spontaneous synaptic potential and action potential frequency of an afferent. These effects are blocked by prior administration of curare or of nicotinic agonists. Repetitive or continuous stimulation of the VIIIth nerve results in a reversible reduction of the evoked response, suggesting desensitization. Transection of the VIIIth cranial nerve two weeks prior to recording eliminates these actions of electrical stimulation, but not the responses to cholinergic agonists, indicating that the effects of electrical stimulation are mediated by centrally arising efferents. These findings confirm that acetylcholine is probably the transmitter released from centrally arising vestibular efferents, and, in addition, demonstrate that efferent-mediated effects are predominantly expressed through nicotinic receptors. Studies comparing the effects of isolation of the semicircular canal alone versus the intact labyrinth suggest that the method of isolation may be an important factor in determining whether efferent activity results in a predominant increase or decrease in afferent activity.

Event-related potentials for category-specific information during passive viewing of faces and objects.

Normal subjects passively viewed an upright or inverted face or objects during recording of event-related potentials. Face inversion augmented N170 amplitude and latency in the temporal region, but on ly the latency in the parietal region. The same manipulation slowed down the on set of the P220 and caused disappearance of the N300, whereas none of these effects was seen after object inversion. Item-specific processing of objects was observed, namely disappearance of the N190 and the appearance of a P170 wave in the left posterior hemisphere to on e object but not the other. These results are concordant with the hypothesis of category-specific processing during the recognition of faces and objects.

Orthographic transparency and grapheme–phoneme conversion: An ERP study in Arabic and French readers

Numerous behavioral studies have suggested that orthographic transparency of a language is liable to influence the use of grapheme-phoneme conversion during reading. In order to test this hypothesis, the effect of orthographic transparency on event-related potentials was assessed by comparing French to Arab readers. Indeed, French language, contrary to Arabic one, was expected to favor the use of grapheme-phoneme rules during reading. Our results demonstrated that the N320, a component implicated in phonologic transcription, was modulated by orthographic transparency. Indeed, during reading in their mother tongue, only French subjects clearly elicited a N320. Moreover, the comparisons between activations elicited by Arabic words in Arab subjects and French monolingual people also confirm that the N170 component represents an important orthographic stage. The implications of these results on bilinguism and visual word recognition models are discussed.

Other-race and inversion effects during the structural encoding stage of face processing in a race categorization task: An event-related brain potential study

To investigate the mechanisms underlying the other-race effect, in particular at what stage of face processing differences between same-race (SR) and other-race (OR) stimuli occur, electrophysiological and behavioral data were obtained on Caucasian participants viewing photographs of Caucasian, Asian, and African faces in upright and inverted orientations. During a race categorization task, reaction times were faster for African than Asian faces, and both of them faster than Caucasian ones, independent of their orientation. The face-sensitive N170 component was low in amplitude for Caucasian, intermediate for Asian, and maximal for African faces. The face inversion effect was observed for all ethnic groups on N170 amplitudes, but was more evident for Caucasian faces. According to the perceptual expertise hypothesis, our results indicate that SR faces involve more configural/holistic processing OR faces.

Early holistic face-like processing of Arcimboldo paintings in the right occipito-temporal cortex: evidence from the N170 ERP component.

The properties of the face-sensitive N170 component of the event-related brain potential (ERP) were explored through an orientation discrimination task using natural faces, objects, and Arcimboldo paintings presented upright or inverted. Because Arcimboldo paintings are composed of non-face objects but have a global face configuration, they provide great control to disentangle high-level face-like or object-like visual processes at the level of the N170, and may help to examine the implication of each hemisphere in the global/holistic processing of face formats. For upright position, N170 amplitudes in the right occipito-temporal region did not differ between natural faces and Arcimboldo paintings but were larger for both of these categories than for objects, supporting the view that as early as the N170 time-window, the right hemisphere is involved in holistic perceptual processing of face-like configurations irrespective of their features. Conversely, in the left hemisphere, N170 amplitudes differed between Arcimboldo portraits and natural faces, suggesting that this hemisphere processes local facial features. For upside-down orientation in both hemispheres, N170 amplitudes did not differ between Arcimboldo paintings and objects, but were reduced for both categories compared to natural faces, indicating that the disruption of holistic processing with inversion leads to an object-like processing of Arcimboldo paintings due to the lack of local facial features. Overall, these results provide evidence that global/holistic perceptual processing of faces and face-like formats involves the right hemisphere as early as the N170 time-window, and that the local processing of face features is rather implemented in the left hemisphere.