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Our ability to consciously perceive information from the visual scene relies on a myriad of intrinsic neural mechanisms. Functional neuroimaging studies have sought to identify the neural correlates of conscious visual processing and to further dissociate from those pertaining to preconscious and unconscious visual processing. However, delineating what core brain regions are involved in eliciting a conscious percept remains a challenge, particularly regarding the role of prefrontal-parietal regions. We performed a systematic search of the literature that yielded a total of 54 functional neuroimaging studies. We conducted two quantitative meta-analyses using activation likelihood estimation to identify reliable patterns of activation engaged by i. conscious (n = 45 studies, comprising 704 participants) and ii. unconscious (n = 16 studies, comprising 262 participants) visual processing during various task performances. Results of the meta-analysis specific to conscious percepts quantitatively revealed reliable activations across a constellation of regions comprising the bilateral inferior frontal junction, intraparietal sulcus, dorsal anterior cingulate, angular gyrus, temporo-occipital cortex and anterior insula. Neurosynth reverse inference revealed conscious visual processing to be intertwined with cognitive terms related to attention, cognitive control and working memory. Results of the meta-analysis on unconscious percepts revealed consistent activations in the lateral occipital complex, intraparietal sulcus and precuneus. These findings highlight the notion that conscious visual processing readily engages higher-level regions including the inferior frontal junction and unconscious processing reliably recruits posterior regions, mainly the lateral occipital complex., Competing Interests: Declaration of Competing Interest None., (Copyright © 2023. Published by Elsevier Inc.)

This paper presents a study protocol to measure the task-switching cost of using a smartphone while walking. This method involves having participants walk on a treadmill under two experimental conditions: a control condition (i.e., simply walking) and a multitasking condition (i.e., texting while walking). During these conditions, the participants must switch between the tasks related to the experimental condition and a direction determining task. This direction task is done with a point-light walker figure, seemingly walking towards the left or the right of the participant. Performance on the direction task represents the participant's task-switching costs. There were two performance measures: 1) correct identification of the direction and 2) response time. EEG data are recorded in order to measure the alpha oscillations and cognitive engagement occurring during the task switch. This method is limited in its ecological validity: pedestrian environments have many stimuli occurring simultaneously and competing for attention. Nonetheless, this method is appropriate for pinpointing task-switching costs. The EEG data allow the study of the underlying mechanisms in the brain that are related to differing task-switching costs. This design allows the comparison between task switching when doing one task at a time, as compared to task switching when multitasking, prior to the stimulus presentation. This allows understanding and pinpointing both the behavioral and neurophysiological impact of these two different task-switching conditions. Furthermore, by correlating the task-switching costs with the brain activity, we can learn more about what causes these behavioral effects. This protocol is an appropriate base for studying the switching cost of different smartphone uses. Different tasks, questionnaires, and other measures can be added to it in order to understand the different factors involved in the task-switching cost of smartphone use while walking.

Objective: Recently identified mutations of the axon guidance molecule receptor gene, DCC, present an opportunity to investigate, in living human brain, mechanisms affecting neural connectivity and the basis of mirror movements, involuntary contralateral responses that mirror voluntary unilateral actions. We hypothesized that haploinsufficient DCC +/- mutation carriers with mirror movements would exhibit decreased DCC mRNA expression, a functional ipsilateral corticospinal tract, greater "mirroring" motor representations, and reduced interhemispheric inhibition. DCC +/- mutation carriers without mirror movements might exhibit some of these features., Methods: The participants (n = 52) included 13 DCC +/- mutation carriers with mirror movements, 7 DCC +/- mutation carriers without mirror movements, 13 relatives without the mutation or mirror movements, and 19 unrelated healthy volunteers. The multimodal approach comprised quantitative real time polymerase chain reaction, transcranial magnetic stimulation (TMS), functional magnetic resonance imaging (fMRI) under resting and task conditions, and measures of white matter integrity., Results: Mirror movements were associated with reduced DCC mRNA expression, increased ipsilateral TMS-induced motor evoked potentials, increased fMRI responses in the mirroring M1 and cerebellum, and markedly reduced interhemispheric inhibition. The DCC +/- mutation, irrespective of mirror movements, was associated with reduced functional connectivity and white matter integrity., Interpretation: Diverse connectivity abnormalities were identified in mutation carriers with and without mirror movements, but corticospinal effects and decreased peripheral DCC mRNA appeared driven by the mirror movement phenotype. ANN NEUROL 2019;85:433-442., (© 2019 The Authors. Annals of Neurology published by Wiley Periodicals, Inc. on behalf of American Neurological Association.)

Epidemiological evidence suggests a strict correlation between sudden sensorineural hearing loss (SSNHL) and cerebrovascular disorders. Leukoaraiosis represents a diffuse alteration of the periventricular and subcortical white matter. The aim of our study was to verify if the presence of white matter hyperintensity (WMH) was higher in patients affected by SSNHL compared to controls and evaluate the correlation between WMH and the cardiovascular risk factors, hearing level, and the response to therapy in SSNHL patients. The study group included 36 subjects affected by unilateral SSNHL. Thirty-six age- and sex-matched normal subjects with a negative history of SSNHL were used as controls. All patients underwent magnetic resonance imaging (MRI) (1.5 Tesla GE Signa) and the extent of leukoaraiosis was assessed with the Fazekas scale. The results of the present study demonstrate a high prevalence of WMH in SSNHL patients compared to controls confirming the hypothesis of a vascular impairment in SSNHL patients. The higher recovery rate in patients with greater periventricular white matter hyperintensity (PWMH) may suggest a vascular etiology that is still responsive to medical treatment. We aim to expand both the number of patients and the controls to avoid the limitation of the still small number to warrant solid scientific conclusions.

Sounds activate occipital regions in early blind individuals. However, how different sound categories map onto specific regions of the occipital cortex remains a matter of debate. We used fMRI to characterize brain responses of early blind and sighted individuals to familiar object sounds, human voices, and their respective low-level control sounds. In addition, sighted participants were tested while viewing pictures of faces, objects, and phase-scrambled control pictures. In both early blind and sighted, a double dissociation was evidenced in bilateral auditory cortices between responses to voices and object sounds: Voices elicited categorical responses in bilateral superior temporal sulci, whereas object sounds elicited categorical responses along the lateral fissure bilaterally, including the primary auditory cortex and planum temporale. Outside the auditory regions, object sounds also elicited categorical responses in the left lateral and in the ventral occipitotemporal regions in both groups. These regions also showed response preference for images of objects in the sighted group, thus suggesting a functional specialization that is independent of sensory input and visual experience. Between-group comparisons revealed that, only in the blind group, categorical responses to object sounds extended more posteriorly into the occipital cortex. Functional connectivity analyses evidenced a selective increase in the functional coupling between these reorganized regions and regions of the ventral occipitotemporal cortex in the blind group. In contrast, vocal sounds did not elicit preferential responses in the occipital cortex in either group. Nevertheless, enhanced voice-selective connectivity between the left temporal voice area and the right fusiform gyrus were found in the blind group. Altogether, these findings suggest that, in the absence of developmental vision, separate auditory categories are not equipotent in driving selective auditory recruitment of occipitotemporal regions and highlight the presence of domain-selective constraints on the expression of cross-modal plasticity.

This study assessed whether the neonatal brain recruits different neural networks for native and non-native languages at birth. Twenty-seven one-day-old full-term infants underwent functional near-infrared spectroscopy (fNIRS) recording during linguistic and non-linguistic stimulation. Fourteen newborns listened to linguistic stimuli (native and non-native language stories) and 13 newborns were exposed to non-linguistic conditions (native and non-native stimuli played in reverse). Comparisons between left and right hemisphere oxyhemoglobin (HbO2) concentration changes over the temporal areas revealed clear left hemisphere dominance for native language, whereas non-native stimuli were associated with right hemisphere lateralization. In addition, bilateral cerebral activation was found for non-linguistic stimulus processing. Overall, our findings indicate that from the first day after birth, native language and prosodic features are processed in parallel by distinct neural networks., (Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Early blind individuals are known to exhibit structural brain reorganization. Particularly, early-onset blindness may trigger profound brain alterations that affect not only the visual system but also the remaining sensory systems. Diffusion tensor imaging (DTI) allows in-vivo visualization of brain white matter connectivity, and has been extensively used to study brain white matter structure. Among statistical approaches based on DTI, tract-based spatial statistics (TBSS) is widely used because of its ability to automatically perform whole brain white matter studies. Tract specific analysis (TSA) is a more recent method that localizes changes in specific white matter bundles. In the present study, we compare TBSS and TSA results of DTI scans from 12 early blind individuals and 13 age-matched sighted controls, with two aims: (a) to investigate white matter alterations associated with early visual deprivation; (b) to examine the relative sensitivity of TSA when compared with TBSS, for both deficit and hypertrophy of white matter microstructures. Both methods give consistent results for broad white matter regions of deficits. However, TBSS does not detect hypertrophy of white matter, whereas TSA shows a higher sensitivity in detecting subtle differences in white matter colocalized to the posterior parietal lobe.

Light regulates multiple non-image-forming (or nonvisual) circadian, neuroendocrine, and neurobehavioral functions, via outputs from intrinsically photosensitive retinal ganglion cells (ipRGCs). Exposure to light directly enhances alertness and performance, so light is an important regulator of wakefulness and cognition. The roles of rods, cones, and ipRGCs in the impact of light on cognitive brain functions remain unclear, however. A small percentage of blind individuals retain non-image-forming photoreception and offer a unique opportunity to investigate light impacts in the absence of conscious vision, presumably through ipRGCs. Here, we show that three such patients were able to choose nonrandomly about the presence of light despite their complete lack of sight. Furthermore, 2 sec of blue light modified EEG activity when administered simultaneously to auditory stimulations. fMRI further showed that, during an auditory working memory task, less than a minute of blue light triggered the recruitment of supplemental prefrontal and thalamic brain regions involved in alertness and cognition regulation as well as key areas of the default mode network. These results, which have to be considered as a proof of concept, show that non-image-forming photoreception triggers some awareness for light and can have a more rapid impact on human cognition than previously understood, if brain processing is actively engaged. Furthermore, light stimulates higher cognitive brain activity, independently of vision, and engages supplemental brain areas to perform an ongoing cognitive process. To our knowledge, our results constitute the first indication that ipRGC signaling may rapidly affect fundamental cerebral organization, so that it could potentially participate to the regulation of numerous aspects of human brain function.

During child development, physiological changes occur in the auditory cortex, which are reflected by differences in the electrophysiological signals. This study aimed to examine the age-related changes of the Mismatch Negativity component (MMN) in response to speech and non-speech stimuli in a cross-sectional design. Results revealed distinct patterns of activation according to stimulus type and age. Age-related differences for tone discrimination occurred earlier in children's development than did the discriminative process for speech sounds. Therefore, networks involved in speech processing are still immature in late childhood and may be more vulnerable to physiological changes.

Functional magnetic resonance imaging (fMRI) combined with electroencephalography (fMRI-EEG) is a neuroimaging technique based on the blood oxygenation level dependent (BOLD) signal which has been shown to be useful in the study of epilepsy for the localization of the epileptogenic focus. Functional near-infrared spectroscopy (fNIRS) combined with EEG (fNIRS-EEG) is another imaging technique based on the measurement of oxygenated and deoxygenated hemoglobin with complementary clinical potential in epilepsy, for continuous patient monitoring, language lateralization, and focus localization. In this work fMRI-EEG and fNIRS-EEG are used to quantify nonlinear hemodynamic responses in three cases of human refractory focal epilepsy, by using the Volterra kernel expansion up to second order. Prior to analyzing real data, extensive simulations are carried out to show that nonlinearities are estimable. The Volterra methodology is then applied to multimodal data recorded from 3 epileptic patients selected for their frequent spiking activity. Care is taken to account for variability of hemodynamic responses due to other causes than Volterra nonlinearities. Statistically significant nonlinearities are observed for all patients and all modalities. Good concordance between fNIRS and fMRI is found for both the amplitude of the Volterra responses, and, with limitations, in the localization of the epileptic focus and regions of inverted responses (negative BOLD signals). In one patient, Volterra nonlinearities allowed epileptic focus identification with fMRI, while analyses without nonlinearities failed to see it. In simulations when nonlinearities were included, analysis without Volterra nonlinearities performed poorly. These two observations suggest routinely checking for nonlinearities in functional imaging of patients presenting with frequent spikes., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Background: CREB1 has previously been implicated in mood disorders, suicide, and antidepressant response. There is some evidence that the T allele in rs4675690, a single-nucleotide polymorphism near the CREB1 gene, is involved in the modulation of neural responses to negative stimuli. It is not known whether differential brain activity during negative mood state appears early in life in T allele carriers., Methods: Functional magnetic resonance imaging (fMRI) was used to measure brain activity, during a transient state of sadness, in children homozygous for the T allele or the C allele. This primary emotion was selected given that it is the prevailing mood in major depressive disorder (MDD). Blood-oxygen-level dependent (BOLD) signal changes were measured while subjects viewed blocks of neutral film excerpts and blocks of sad film excerpts., Results: There was significantly greater BOLD activation in the TT group, compared to the CC group, in the right dorsal anterior cingulate cortex (Brodmann area [BA 24]), right putamen, right caudate nucleus and left anterior temporal pole (BA 21), when the brain activity associated with the viewing of the emotionally neutral film excerpts was subtracted from that associated with the viewing of the sad film excerpts., Limitations: A replication study using larger samples may be required for more definitive conclusions., Conclusions: The different pattern of regional brain activation found here during transient sadness - in children carrying the T allele, compared to those carrying the C allele - might increase later in life susceptibility to emotional dysregulation and depressive symptoms., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The purpose of this review is to consider new sensory rehabilitation avenues in the context of the brain's remarkable ability to reorganize itself following sensory deprivation. Here, deafness and blindness are taken as two illustrative models. Mainly, two promising rehabilitative strategies based on opposing theoretical principles will be considered: sensory substitution and neuroprostheses. Sensory substitution makes use of the remaining intact senses to provide blind or deaf individuals with coded information of the lost sensory system. This technique thus benefits from added neural resources in the processing of the remaining senses resulting from crossmodal plasticity, which is thought to be coupled with behavioral enhancements in the intact senses. On the other hand, neuroprostheses represent an invasive approach aimed at stimulating the deprived sensory system directly in order to restore, at least partially, its functioning. This technique therefore relies on the neuronal integrity of the brain areas normally dedicated to the deprived sense and is rather hindered by the compensatory reorganization observed in the deprived cortex. Here, we stress that our understanding of the neuroplastic changes that occur in sensory-deprived individuals may help guide the design and the implementation of such rehabilitative methods., (Copyright © 2011 Elsevier B.V. All rights reserved.)

In the prelingual and congenital deaf, functional reorganization is known to occur throughout brain regions normally associated with hearing. However, the anatomical correlates of these changes are not yet well understood. Here, we perform the first tensor-based morphometric analysis of voxel-wise volumetric differences in native signing prelingual and congenitally deaf subjects when compared with hearing controls. We obtained T1-weighted scans for 14 native signing prelingual and congenitally deaf subjects and 16 age- and gender-matched controls. We used linear and fluid registration to align each image to a common template. Using the voxel-wise determinant of the Jacobian of the fluid deformation, significant volume increases, of up to 20%, were found in frontal lobe white matter regions including Broca's area, and adjacent regions involved in motor control and language production. A similar analysis was performed on hand-traced corpora callosa. A strong trend for group differences was found in the area of the splenium considered to carry fibers connecting the temporal (and occipital) lobes. These anatomical differences may reflect experience-mediated developmental differences in myelination and cortical maturation associated with prolonged monomodal sensory deprivation., ((c) 2009 Wiley-Liss, Inc.)

We examined 3D patterns of volume differences in the brain associated with blindness, in subjects grouped according to early and late onset. Using tensor-based morphometry, we mapped volume reductions and gains in 16 early-onset (EB) and 16 late-onset (LB) blind adults (onset <5 and >14 years old, respectively) relative to 16 matched sighted controls. Each subject's structural MRI was fluidly registered to a common template. Anatomical differences between groups were mapped based on statistical analysis of the resulting deformation fields revealing profound deficits in primary and secondary visual cortices for both blind groups. Regions outside the occipital lobe showed significant hypertrophy, suggesting widespread compensatory adaptations. EBs but not LBs showed deficits in the splenium and the isthmus. Gains in the non-occipital white matter were more widespread in the EBs. These differences may reflect regional alterations in late neurodevelopmental processes, such as myelination, that continue into adulthood.

Pain is associated with the activation of many brain areas involved in the multiple dimensions of the experience. Several of those brain areas may also contribute to the monitoring and regulation of autonomic activity but this aspect of pain responses has been largely overlooked in human imaging studies. This functional magnetic resonance imaging (fMRI) study relied on blood-oxygen level dependent (BOLD) signal to investigate subject-related differences in brain activity associated with the individual differences in electrodermal responses evoked by 30 s noxious (pain) and innocuous (warm) thermal stimuli. Pain-related activity (pain-warm) was found in the thalamus, somatosensory cortices (leg area of SI/MI, SII, and insula), the anterior cingulate cortex (ACC), and the amygdala. Brain activation related to stimulus-evoked electrodermal activity was identified by modeling the predicted BOLD responses with the magnitude of each subject's skin conductance reactivity. Subjects showing larger skin conductance reactivity to the innocuous and/or noxious stimuli displayed larger stimulus-evoked brain responses in the somato-motor cortices (SI/MI, SII, and insula), the perigenual and supracallosal ACC, the orbitofrontal cortex and the medulla. Further analyses revealed brain activation more specifically associated with the pain-related skin conductance reactivity in the supracallosal ACC, amygdala, thalamus, and hypothalamus. These findings demonstrate that individual differences in electrodermal reactivity partly reflect differences in pain-evoked brain responses, consistent with a role of these structures in the monitoring/regulation of pain-related autonomic processes.

Regardless of the fact that emotions are usually recognized by combining facial and vocal expressions, the multisensory nature of affect perception has scarcely been investigated. In the present study, we show results of three experiments on multisensory perception of emotions using newly validated sets of dynamic visual and non-linguistic vocal clips of affect expressions. In Experiment 1, participants were required to categorize fear and disgust expressions displayed auditorily, visually, or using congruent or incongruent audio-visual stimuli. Results showed faster and more accurate categorisation in the bimodal congruent situation than in the unimodal conditions. In the incongruent situation, participant preferentially categorized the affective expression based on the visual modality, demonstrating a visual dominance in emotional processing. However, when the reliability of the visual stimuli was diminished, participants categorized incongruent bimodal stimuli preferentially via the auditory modality. These results demonstrate that visual dominance in affect perception does not occur in a rigid manner, but follows flexible situation-dependent rules. In Experiment 2, we requested the participants to pay attention to only one sensory modality at a time in order to test the putative mandatory nature of multisensory affective interactions. We observed that even if they were asked to ignore concurrent sensory information, the irrelevant information significantly affected the processing of the target. This observation was especially true when the target modality was less reliable. Altogether, these findings indicate that the perception of emotion expressions is a robust multisensory situation which follows rules that have been previously observed in other perceptual domains.

It is without a doubt that humans are first and foremost visual beings. Even though the other sensory modalities provide us with valuable information, it is vision that generally offers the most reliable and detailed information concerning our immediate surroundings. It is therefore not surprising that nearly a third of the human brain processes, in one way or another, visual information. But what happens when the visual information no longer reaches these brain regions responsible for processing it? Indeed numerous medical conditions such as congenital glaucoma, retinis pigmentosa and retinal detachment, to name a few, can disrupt the visual system and lead to blindness. So, do the brain areas responsible for processing visual stimuli simply shut down and become non-functional? Do they become dead weight and simply stop contributing to cognitive and sensory processes? Current data suggests that this is not the case. Quite the contrary, it would seem that congenitally blind individuals benefit from the recruitment of these areas by other sensory modalities to carry out non-visual tasks. In fact, our laboratory has been studying blindness and its consequences on both the brain and behaviour for many years now. We have shown that blind individuals demonstrate exceptional hearing abilities. This finding holds true for stimuli originating from both near and far space. It also holds true, under certain circumstances, for those who lost their sight later in life, beyond a period generally believed to limit the brain changes following the loss of sight. In the case of the early blind, we have shown their ability to localize sounds is strongly correlated with activity in the occipital cortex (the location of the visual processing), demonstrating that these areas are functionally engaged by the task. Therefore it would seem that the plastic nature of the human brain allows them to make new use of the cerebral areas normally dedicated to visual processing.

In order to evaluate the callosal involvement in sound localization, the present study examined the response accuracy of acallosal and early callosotomized subjects to monaural and binaural auditory targets presented in three-dimensional space. In these subjects, bilateral localization cues, such as interaural time and level differences, are integrated at the cortical and subcortical levels without the additional support of the callosal commissure. Because acallosal and early-callosotomized subjects have developed with this reduced source of binaural activation of cortical cells, they might have perfected their ability to use monaural sound localization cues. This hypothesis was tested by assessing localization performance under both binaural and monaural listening conditions. Five subjects with callosal agenesis, one callosotomized subject operated early in life and 19 control subjects were asked to localize broad-band noise bursts (BBNBs) of fixed intensity in the horizontal plane in an anechoic chamber. BBNBs were delivered through randomly selected loudspeakers. Two conditions were tested: (i) localization of a stationary sound source; and (ii) localization of a moving sound source. Listeners had to report the apparent stimulus location by pointing to its perceived position on a graduated perimeter. The results indicated that the acallosal subjects were less accurate than controls, but only in the binaural moving sound condition. More interestingly, in the monaural testing conditions, some of the acallosal subjects and the early-callosotomized subject performed significantly better than control subjects. This suggests that, because of the absence of the corpus callosum, these subjects compensate for their reduced access to cortically determined binaural cues by making more efficient use of monaural cues.

We have used event-related potentials (ERP) to assess cerebral activity following mild traumatic brain injuries in 20 college athletes practising contact sports. Concussion victims showed a striking decrease in P300 amplitude, an effect presumed to reflect alterations in attentional-cognitive processes. Moreover, the degree of impairment was strongly related to the severity of post-concussion symptoms. Our data suggest that concussions cause objectively measurable changes in the electrophysiological markers of brain activity and hence in the functions of the structures from which they originate. ERPs may thus constitute a reliable method to accurately monitor the clinical course and recovery of head injuries in athletes.

Visually challenged individuals often compensate for their handicap by developing supra-normal abilities in their remaining sensory systems. Here, we examined the scalp distribution of components N1 and P3 of auditory evoked potentials during a sound localization task in four totally blind subjects who had previously shown better performance than sighted subjects. Both N1 and P3 waves peaked at their usual positions while blind and sighted individuals performed the task. However, in blind subjects these two components were also found to be robust over occipital regions while in sighted individuals this pattern was not seen. We conclude that deafferented posterior visual areas in blind individuals are recruited to carry out auditory functions, enabling these individuals to compensate for their lack of vision.

A 26-year-old man developed transient bilateral internuclear ophthalmoplegia with exotropia after cranial irradiation and intrathecal administration of methotrexate for lymphoma. Resolution of the ophthalmoplegia and the decrease in abnormally high levels of cerebrospinal fluid myelin basic protein after discontinuation of intrathecal medication suggested demyelination from chemotherapy and irradiation.

In this study the role of serotonin in pain sensitivity was investigated. Brain serotonin was elevated via low and high doses of precursor tryptophan and lowered via parachlorophenylalanine or lesions placed in the dorsal raphe nucleus. The effects on pain sensitivity were then assessed using two psychophysical pain testing procedures: (1) minimum shock intensity (threshold) which produced a conditioned escape response; and (2) total activity elicited by highly aversive inescapable shock. The results showed that only a large elevation of serotonin produced a change in escape thresholds in the direction of hypoalgesia. When total activity to a painful inescapable stimulus was evaluated only lowering of serotonin produced an effect, and this change was in the direction of hyperalgesia. The conclusion was made that serotonin does contribute to the mechanism of pain.

Abstract: The mechanisms responsible for the perception of illusory modal figures are usually studied by presenting entire Kanizsa figures at stimulus onset. However, with this mode of presentation, the brain activity generated by the inducers (the ‘pacmen’) is difficult to differentiate from the activity underlying the perception of the illusory figure. Therefore, in addition to this usual presentation mode, we used an alternative presentation mode. Inducer disks remained permanently on the screen and the illusory figure was induced by just removing the notches from the disks. The results support the heuristic value of this alternative mode of presentation. The P1 deflection of the visual evoked potentials (VEPs) was found to be greater for the illusory modal figure than for its control and for an amodal figure. This modulation is one of the earliest direct evidences for a low-level processing of illusory forms in the human brain. Meanwhile, larger N1s were obtained for the control figures than for the illusory figures in the notch mode of presentation. While this new type of N1 modulation could shed some light on the stage of processing indexed by this deflection, several propositions are put forward to account for the P1 and N1 variations found. [Copyright &y& Elsevier]