Both low and high spatial frequencies drive the early posterior negativity in response to snake stimuli.

Previous event-related potential (ERP) studies have shown that snake pictures elicit greater early posterior negativity (EPN) compared to other animal pictures. The EPN reflects early selective visual processing of emotionally significant stimuli. Evidence for the role that high and low spatial frequencies play in the early detection of snakes is still inconsistent. The current study aims to clarify this by studying the effect of high and low spatial frequencies on the elevated EPN for snakes separately. Using a rapid serial visual presentation paradigm, participants viewed images of snakes, spiders and birds in three different conditions of filtered spatial frequencies: high spatial frequency, low spatial frequency, and full spatial frequency (the original image). P1 and mean EPN activity in a time window of 225-300 ms after stimulus onset were measured at the occipital cluster (O1, O2, Oz). The results show smaller P1 amplitudes and shorter P1 latencies in response to full-spectrum snake pictures compared to full-spectrum spider and bird pictures, and an increased EPN in response to snake pictures compared to spider and bird pictures in all three filtering conditions. The EPN in response to full-spectrum snake pictures was larger than the EPN in response to filtered snake images. No difference in EPN was found between the snake pictures in the high and low spatial frequency conditions. The results suggest that the roles of high and low spatial frequencies in early automatic attention to snakes are equally important.

The effect of mouth opening in emotional faces on subjective experience and the early posterior negativity amplitude.

Previous studies have examined the role of the eye region in emotional expressions, but the mouth region is understudied. The main goal of this study was to examine how mouth opening in emotional faces affects subjective experience and early automatic attentional capture, as measured by the early posterior negativity (EPN) amplitude. Participants in two studies viewed angry, happy, and neutral faces with mouths open and closed while their electroencephalogram was recorded. Afterwards, participants indicated how unpleasant-pleasant (i.e., valence) and calming-arousing (i.e., arousal) each face made them feel. Angry and happy faces (and neutral faces to a lesser extent) with an open vs. closed mouth made observers feel more extreme valence and arousal. In addition, there generally was an EPN for angry and happy faces (and neutral faces to a lesser extent) with open vs. closed mouths, which suggests that emotional expressions with an open mouth capture early automatic attention more than expressions with a closed mouth. Finally, the effects of mouth opening were somewhat modulated by face gender, but not by observer gender. The current findings contribute to our knowledge of facial expressions and social interaction, but also have relevance for the growing fields of social robotics and digital animation.

Incidental picture exposure affects later reading: evidence from the N400.

Language comprehenders form a mental representation of the implied shape of objects mentioned in the text. In the present study, the influence of prior visual experience on subsequent reading was assessed. In two separate phases, participants saw a picture of an object and read a text about the object, suggesting the same or a different shape. When the shapes in the two phases mismatched, ERPs during reading showed a larger N400 amplitude than when the shapes matched, suggesting that a picture presented incidentally 15 min earlier affected reading. These results further strengthen the case for the interaction of language and visual experience during language comprehension.

Effects of attention on dichotic listening in elderly and patients with dementia of the Alzheimer type.

This article presents an overview of our studies in elderly and Alzheimer patients employing Kimura's dichotic digits paradigm as a measure for left hemispheric predominance for processing language stimuli. In addition to structural brain mechanisms, we demonstrated that attention modulates the direction and degree of ear asymmetry in dichotic listening. Elderly showed increasingly more difficulties focusing attention on the left ear (LE) with advancing age. Alzheimer patients showed severe deficits to allocate attention to the LE, which could result in a right ear advantage. These results may be attributed to a breakdown of the cortical attentional network which is mediated by frontal (inhibitory control of attention) and parietal regions (spatial attention and 'disengagement processes'). Both interhemispheric disconnectivity (callosal atrophy) and intrahemispheric disconnectivity (subcortical white matter lesions) appear to be important factors contributing to these findings.

Effects of recent word exposure on emotion-word Stroop interference: an ERP study.

Attentional bias towards emotional linguistic material has been examined extensively with the emotion-word Stroop task. Although findings in clinical groups show an interference effect of emotional words that relate to the specific concern of the group, findings concerning healthy groups are less clear. In the present study, we investigated whether emotional Stroop interference in healthy individuals is affected by exposure of the words prior to the task. We used event-related potentials (ERPs) to examine the temporal aspects of Stroop interference. Participants took longer to indicate the colour of negative than of neutral words. Exposure of words prior to the Stroop task increased response latencies, but this effect was equal for neutral and negative words. At the neurophysiological level, we found more positive-going ERPs at later latencies (P290, N400 and LPP) in response to negative than in response to neutral Stroop words. The N400 was less negative for exposed than for new words, but this effect did not interact with the emotional valence of the words. For new (i.e., unexposed) words, the behavioural Stroop interference correlated with the P290, N400 and LPP emotion effects (negative minus neutral words). The successive ERP components suggest better prelexical, semantic, and sustained attentional processing of emotion words, even when the emotional content of the words is task-irrelevant.

Automatic processing of emotional words during an emotional Stroop task.

There is evidence that early event-related potential components, such as the early posterior negativity (EPN; 200-300 ms), are modulated by emotional words. This study addressed the automaticity of this early response in an emotional Stroop task. The results show that the EPN was modulated by emotional connotation. In addition, an enhanced frontal P3 and an enhanced, more broadly distributed, late positive potential emerged as response to emotional words. The present results suggest that this early event-related potential activity represents the fast and automatic processing of emotional words. Furthermore, as the EPN originates from the posterior visual association cortex, the present results suggest a role of these areas in the automatic processing of emotional connotation.

Valence interacts with the early ERP old/new effect and arousal with the sustained ERP old/new effect for affective pictures.

To examine whether valence and arousal influence recognition memory during early automatic or during more sustained processes, event-related brain potentials (ERPs) of 21 women were recorded while they made old/new judgments in a continuous recognition task with pictures from the International Affective Picture System. The pictures were presented twice and differed in emotional valence and arousal. The P1 peak and four time windows were investigated: 200-300 ms, 300-400 ms, 400-600 ms, and 750-1000 ms after stimulus onset. There was a robust old/new effect starting in the 200-300 ms epoch and lasting all time windows. The valence effect was mainly present in the P1 peak and the 200-400 ms epoch, whereas the arousal effect was found in the 300-1000 ms epoch. Exploratory sLORETA analyses dissociated valence-dependent ventromedial prefrontal activity and arousal-dependent occipital activity in the 350-380 ms time window. Valence interacted with the 200-400 ms old/new effect at central and frontal sites. Arousal interacted with the 750-1000 ms old/new effect at posterior sites. It is concluded that valence influences fast recognition memory, while arousal may influence sustained encoding.

Sex differences in the latency of the late event-related potential mental rotation effect.

Sex differences in event-related potentials were examined in 23 women and 24 men during a mental rotation task. We found an early (130-400 ms) and a late (400-700 ms) ERP mental rotation effect. The late rotation effect, which is thought to indicate the onset of the cognitive process of mental rotation, emerged about 100 ms earlier in men than in women. Moreover, men showed about 100 ms shorter response latencies to the task than women. These findings suggest that the faster response in men can be explained as a result of actual mental rotation taking place earlier. Furthermore, we found increased involvement of the right hemisphere specifically in men, probably pointing at a holistic strategy in men during mental rotation.

Subcortical white matter pathology as a mediating factor for age-related decreased performance in dichotic listening.

Cortical 'disconnection', involving disruption of white matter tracts in the brain, has been hypothesized as a mechanism of age-related cognitive decline. Diffuse hyperintensities in the white matter (so called white matter hyperintensities, WMH) on T2-weighted MRI scans are regarded to represent ischemic damage of the subcortical fiber system and are found to be increased with advanced age. In the present study, we examined whether WMH might be a mediating factor for age-effects in dichotic listening. For that purpose, we examined the association between age, deep or subcortical white matter hyperintensities (DWMH), periventricular hyperintensities (PVH) and dichotic listening performance in healthy older adults with ages ranging from 50 to 81 years. We found decreased dichotic listening performance with increasing age, specifically for the left ear (LE) but not the right ear (RE) in a standard unbiased-attention condition, and for the unattended ears but not the attended ears in conditions in which attention was controlled. Interestingly, hierarchical regression analyses revealed that the age-effect is partially mediated by DWMH specifically in the hemisphere contralateral to the attended ear. Moreover, we found indications that RE performance is specifically affected by DWMH in the right and left frontal and temporal areas, and that LE performance is mostly affected by DWMH selectively in the left hemisphere, including the left temporal area. The present study underlines the idea that disconnectivity is involved in age-related cognitive decline.

Attention modulates hemispheric differences in functional connectivity: evidence from MEG recordings.

The present study examined intrahemispheric functional connectivity during rest and dichotic listening in 8 male and 9 female healthy young adults measured with magnetoencephalography (MEG). Generalized synchronization within the separate hemispheres was estimated by means of the synchronization likelihood that is sensitive to linear as well as non-linear coupling of MEG signals. We found higher functional intrahemispheric connectivity of frontal and temporal areas within the right as compared to the left hemisphere in the lower and higher theta band during rest and in the lower theta band during dichotic listening. In addition, higher synchronization in the lower theta band correlated with better task performance. In the upper alpha band, hemispheric differences in intrahemispheric connectivity of the frontal regions were found to be modulated by focused attention instructions. That is, attention to the right ear exaggerates the pattern of higher synchronization likelihood for the right frontal region, while attention to the left ear has an opposite effect. We found higher intrahemispheric connectivity in males compared to females as shown by higher synchronization in the lower alpha band. Taken together, our results reflect a physiological basis for functional hemispheric laterality and support the general assumption of sex differences in brain organization. Furthermore, in addition to studies that show that controlled attention processes modulate activation of the frontal areas, our study indicates that attention modulates ipsilateral functional connectivity in the frontal areas. This supports the idea of a supervisory role for the frontal cortex in attention processes.

Age effects in identifying and localising dichotic stimuli: a corpus callosum deficit?

In the present study, dichotic listening performance of 31 older adults was compared with performance of 25 younger adults under free and focused attention conditions. In addition to an age-related general decrease in performance, we observed in the focused attention condition increased asymmetry in the elderly group: the decrease of recall performance was stronger for the left ear (LE) then for the right ear (RE), while the increase of localisation errors were greater for the RE than for LE. Identifying and localising digits appear to be different process mediated predominantly by the left and right hemisphere, respectively. Since age-related reduced performance is strongest for the ear ipsilateral to the hemisphere dominant to that particular function, these finding may be ascribed to decline of corpus callosum functioning resulting in decrease interhemispheric interaction rather than to a selective decline of right hemisphere functions.