Arousal and valence have dissociable effects on responses to schematic emotional faces.

Studies examining behavioural responses to emotional stimuli usually report one of two patterns of responses to negative stimuli. Some studies find faster responses to negative material. Other studies find slower responses to negative stimuli. While the attentional mechanisms proposed to explain these findings (attentional capture in the former case, delayed disengagement in the latter) are not at odds with one another, the behavioural findings do need to be reconciled. We posit that arousal, being the primary differentiator of threatening and nonthreatening stimuli, needs to be more carefully considered. To this end, two experiments were conducted evaluating the role of stimulus arousal and valence in the processing of schematic emotional faces. In Experiment 1, stimulus arousal was manipulated via the presence or absence of eyebrows in the schematic faces in a faces flanker task. Results showed faster responses to faces with eyebrows but no differences in the faces flanker asymmetry between faces with and without eyebrows. In Experiment 2, participants rated the faces on an evaluative space grid. Results showed the presence of the eyebrows had a greater impact on negative ratings for negative faces than for the other expressions. This suggests that stimulus valence and arousal were manipulated by the eyebrows and the reaction time differences could not be attributed purely to perceptual differences. Together these results suggests that both valence and arousal impact the processing of emotional schematic faces, and that these effects are dissociable. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Dissociating affective and perceptual effects of schematic faces on attentional scope.

Attention allocation to positive and negative stimuli differs. For example, the flanker-interference asymmetry describes a pattern of results on flanker tasks using emotional stimuli, where a typical flanker-interference effect is observed for positive targets but not for negative targets. There are two dominant explanations for the flanker-interference asymmetry. According to the emotion-first explanation, negative targets are preferentially processed to facilitate the processing of potentially threatening stimuli. In contrast, feature-first explanations argue that the asymmetry results from differences in perceptual complexity between positive and negative stimuli. Three experiments used schematic emotional faces in a flanker task to directly compare these explanations. To manipulate the perceptual complexity of the stimuli, an enclosing circle was present on half of the trials. In all three experiments, reaction times showed the expected flanker-interference asymmetry, but the pattern was not influenced by the presence of the circle. However, event-related potentials showed that perceptual complexity influenced both the structural encoding and evaluative processing of the faces in the N170 and P3b time windows. These results suggest that both perceptual complexity and emotional valence play an important role in the processing of schematic emotional faces, but that emotional valence may have a stronger effect at evaluative stages of processing. Other findings show that the enclosing circle may alter the perceived emotional expression of neutral faces. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The role of selective attention in the positivity offset: Evidence from event related potentials.

Some research suggests that positive and negative valence stimuli may be processed differently. For example, negative material may capture and hold attention more readily than equally arousing positive material. This is called the negativity bias, and it has been observed as both behavioural and electroencephalographic (EEG) effects. Consequently, it has been attributed to both automatic and elaborative processes. However, at the lowest levels of arousal, faster reaction times and stronger EEG responses to positive material have been observed. This is called the positivity offset, and the underlying cognitive mechanism is less understood. To study the role of selective attention in the positivity offset, participants completed a negative affective priming (NAP) task modified to dissociate priming for positive and negative words. The task required participants to indicate the valence of a target word, while simultaneously ignoring a distractor. In experiment 1, a behavioural facilitation effect (faster response time) was observed for positive words, in stark contrast to the original NAP task. These results were congruent with a previously reported general categorization advantage for positive material. In experiment 2, participants performed the task while EEG was recorded. In additional to replicating the behavioural results from experiment 1, positive words elicited a larger Late Positive Potential (LPP) component on ignored repetition relative to control trials. Surprisingly, negative words elicited a larger LPP than positive words on control trials. These results suggest that the positivity offset may reflect a greater sensitivity to priming effects due to a more flexible attentional set.

Preserved stenography reading in a patient with pure alexia. A model for dissociated reading processes.

A proficient stenographer who had had cerebral metastases suffered from pure alexia for normal print but could still read stenography with ease. It is suggested that especially the visuospatial properties of stenography made possible "alternative" reading, most likely via the right hemisphere.

Dissociation of color from object in amnesia.

A patient with persistent amnesia after bilateral medial temporal and left inferotemporo-occipital infarction could not match colors to objects in verbal, visual, or visuoverbal tasks. A severe naming disorder for objects was present but the patient could name colors and point to colors whose name was given. The matching disorder appeared to be a deficit in the semantic classification of objects rather than a problem in identifying colors.

"Gourmand syndrome": eating passion associated with right anterior lesions.

We present a new benign eating disorder associated with lesions involving parts of the right anterior cerebral hemisphere. This "gourmand" syndrome describes a preoccupation with food and a preference for fine eating. Two exemplary case reports illustrate this new syndrome. Analysis of the clinical and anatomical data of 36 patients who displayed this behavior revealed, in 34, a strong association with lesion location in the right anterior part of the brain involving cortical areas, basal ganglia, or limbic structures. Our finding provides further evidence of a correlation between right hemispheric damage, eating, and other impulse control disorders. We conjecture that the serotonergic system subserves different functions in the left and right hemisphere.

Persistent cognitive impairment in climbers after repeated exposure to extreme altitude.

We performed neuropsychological testing in eight world class climbers who had reached summits higher than 8,500 meters without supplementary oxygen. Five had mildly impaired concentration, short-term memory, and ability to shift concepts and control errors. There were no defects in perception or other cognitive activities. The pattern of impairment suggests malfunctioning of bifronto-temporo-limbic structures. Repeated extreme-altitude exposure can cause mild but persistent cognitive impairment.

Dissociated hemispheric superiorities for reading stenography vs print.

In two lateralized tachistoscopic lexical decision experiments at different exposure durations, we found for high-frequency function words written in stenography a shift from a RVF advantage at long exposures to a LVF advantage at short exposures, while for the same words written in print a strong RVF effect persisted. We suggest that a reduction of exposure duration, together with the strong visuo-spatial features in stenography, activate right-hemispheric word recognition. Stenography, a non-orthographic and syllabic-ideographic writing system, could be a model to investigate different hemispheric reading processes in Western subjects.

Processing of spatial locations: hemispace effects during encoding but not recall.

Traditionally, functional differences in the visual modality between the two hemispheres are investigated by tachistoscopic procedures. In these experiments, the stimuli reach the contralateral hemisphere first, and results are commonly interpreted on the basis of neuroanatomical access models. However, numerous studies demonstrated that the hemispace where the stimulus is perceived also plays a critical role in producing laterality effects ("hemispace effects"). In the present experiment, subjects were instructed to memorize the relative spatial positions of six figures horizontally aligned on a presentation board. The presentation board was located either to the left, to the right or in front of the subjects (left, right and central learning positions). During a recall phase, each figure was presented in the center of a computer screen and subjects were required to indicate by keypress whether a figure had been located in the left or right half of the presentation board. As in the learning phase, the computer screen was located to the left, the right or in front of the subjects (left, right and central recall positions). We found that the positions of the figures initially memorized in the left hemispace were recalled faster than figures initially memorized in the right hemispace. Hemispatial position during recall had no effect on performance. These results are discussed with respect to hemispheric specialization and theories of hemispace effects.

Faces and emotions: brain electric field sources during covert emotional processing.

Covert brain activity related to task-free, spontaneous (i.e. unrequested), emotional evaluation of human face images was analysed in 27-channel averaged event-related potential (ERP) map series recorded from 18 healthy subjects while observing random sequences of face images without further instructions. After recording, subjects self-rated each face image on a scale from "liked" to "disliked". These ratings were used to dichotomize the face images into the affective evaluation categories of "liked" and "disliked" for each subject and the subjects into the affective attitudes of "philanthropists" and "misanthropists" (depending on their mean rating across images). Event-related map series were averaged for "liked" and "disliked" face images and for "philanthropists" and "misanthropists". The spatial configuration (landscape) of the electric field maps was assessed numerically by the electric gravity center, a conservative estimate of the mean location of all intracerebral, active, electric sources. Differences in electric gravity center location indicate activity of different neuronal populations. The electric gravity center locations of all event-related maps were averaged over the entire stimulus-on time (450 ms). The mean electric gravity center for disliked faces was located (significant across subjects) more to the right and somewhat more posterior than for liked faces. Similar differences were found between the mean electric gravity centers of misanthropists (more right and posterior) and philanthropists. Our neurophysiological findings are in line with neuropsychological findings, revealing visual emotional processing to depend on affective evaluation category and affective attitude, and extending the conclusions to a paradigm without directed task.

Semantic paralexia: a release of right hemispheric function from left hemispheric control.

In an unselected group of aphasics those patients who produced semantic paralexias had significantly larger lesions than those without semantic paralexias. The possible mechanisms of the release of "alternative" right hemisphere reading from left hemisphere control are discussed.

Functional inhibition and release: unilateral tachistoscopic performance and stereoelectroencephalographic activity in a case with left limbic status epilepticus.

During prolonged nonconvulsive unilateral left limbic status epilepticus, a natural model of functional hemispheric inhibition, we performed two tachistoscopic experiments, a lexical decision task associated with a RVF (left hemisphere) superiority and a facial matching task associated with a LVF (right hemisphere) superiority. We found that epileptic activity in the left hemisphere, especially rhythmic high-frequency "tonic" discharges, inhibited performance on the lexical task but not on the facial matching task. This suggests that only cognitive activity in the discharging hemisphere is inhibited. Strikingly, the best performance of the right hemisphere was obtained while the left hemisphere was most inhibited, suggesting a functional balance of inhibition and release.

Sensitivity to eye gaze in prosopagnosic patients and monkeys with superior temporal sulcus ablation.

Accuracy at perceiving frontal eye gaze was studied in monkeys and human subjects using a forced-choice detection task on paired photographs of a single human face. Monkeys learned the task readily, but after bilateral removal of the banks and floor of the superior temporal sulcus (STS) they failed to perform the task efficiently. This result is consistent with the conclusion, based on recordings from single cells in awake, behaving monkeys [Perret et al., Physiological Aspects of Clinical Neuro-ophthalmology, Chapman & Hall, London, 1988] that this region of the temporal lobe is important for coding information about eye-gaze of a confronting animal. Human subjects were given identical stimuli in a task where they were asked to detect "the face that is looking straight at you". Human performance is sensitive to the degree of angular deviation from the frontal gaze position, being poorest at small angular deviations from 0 degrees. This was also true of monkeys viewing these stimuli, pre- and post-operatively. Compared with normal controls, two humans prosopagnosics were impaired at this task. However the extent of impairment was different in the two patients. These findings are related to earlier reports (including those for patients with right-hemisphere damage without prosopagnosia), to normal performance with upright and inverted face photographs, and to notions of independent subsystems in face processing.

Shift of functional cerebral asymmetry during the menstrual cycle.

This study investigated whether for females, who are said to be less strongly lateralized for cognitive functions than men, hemispheric superiority might depend on the phase of the menstrual cycle. The results show that while asymmetry in lexical decisions did not change throughout the menstrual cycle, asymmetry in face perception decreased linearly from a large right hemisphere superiority during menstruation to a small left hemisphere superiority during the premenstrual phase. This is seen as being relevant not only for the discussion of sex differences in cerebral asymmetry but also for the concept of cerebral organization in general.

Neuropsychological studies of auditory-visual fusion illusions. Four case studies and their implications.

A heard speech sound which is not the same as the synchronized speech sound can sometimes give rise to an illusory phonological percept. Typically, a heard /ba/ combines with a seen /ga/ to give the impression that /da/ has been heard (McGurk, H. and MacDonald, J. Nature Lond. 264, 746-748, 1976). We report the susceptibility to this illusion of four individuals with localized brain lesions affecting perceptual function. We compare their performance to that of ten control subjects and relate these findings to the efficiency of processing seen and heard speech in separate and combined modalities. The pattern of performance strongly suggests LH specialization for the phonological integration of seen and heard speech. The putative site of such integration can be effectively isolated from unilateral and from bilateral inputs and may be driven by either modality.

Affective attitudes to face images associated with intracerebral EEG source location before face viewing.

We investigated whether different, personality-related affective attitudes are associated with different brain electric field (EEG) sources before any emotional challenge (stimulus exposure). A 27-channel EEG was recorded in 15 subjects during eyes-closed resting. After recording, subjects rated 32 images of human faces for affective appeal. The subjects in the first (i.e., most negative) and fourth (i.e., most positive) quartile of general affective attitude were further analyzed. The EEG data (mean=25+/-4. 8 s/subject) were subjected to frequency-domain model dipole source analysis (FFT-Dipole-Approximation), resulting in 3-dimensional intracerebral source locations and strengths for the delta-theta, alpha, and beta EEG frequency band, and for the full range (1.5-30 Hz) band. Subjects with negative attitude (compared to those with positive attitude) showed the following source locations: more inferior for all frequency bands, more anterior for the delta-theta band, more posterior and more right for the alpha, beta and 1.5-30 Hz bands. One year later, the subjects were asked to rate the face images again. The rating scores for the same face images were highly correlated for all subjects, and original and retest affective mean attitude was highly correlated across subjects. The present results show that subjects with different affective attitudes to face images had different active, cerebral, neural populations in a task-free condition prior to viewing the images. We conclude that the brain functional state which implements affective attitude towards face images as a personality feature exists without elicitors, as a continuously present, dynamic feature of brain functioning.

Rapid emotional face processing in the human right and left brain hemispheres: an ERP study.

Imaging work has begun to elucidate the spatial organization of emotions; the temporal organization, however, remains unclear. Adaptive behavior relies on rapid monitoring of potentially salient cues (typically with high emotional value) in the environment. To clarify the timing and speed of emotional processing in the two human brain hemispheres, event-related potentials (ERPs) were recorded during hemifield presentation of face images. ERPs were separately computed for disliked and liked faces, as individually assessed by postrecording affective ratings. After stimulation of either hemisphere, personal affective judgements of face images significantly modulated ERP responses at early stages, 80-116 ms after right hemisphere and 104-160 ms after left hemisphere stimulation. This is the first electrophysiological evidence for valence-dependent, automatic, i.e. pre-attentive emotional processing in humans.

Intermanual transfer of training: blood flow correlates in the human brain.

In a previous study, we found that relearning of a task with one hand might negatively be influenced by previous, opposite hand training of the analogue task, Thut G., et al., Exp. Brain Res., 108 (1996) 321-327. Drawing of a figure with the right hand, following left hand training, was slower than right hand drawing of an unknown figure. These conditions were termed right hand transfer learning (rTL) and right hand original learning (rOL). The present study aimed to identify the cerebral areas associated with these influences by measuring regional cerebral blood flow (rCBF) in 16 right-handed, healthy subjects during rTL and rOL. Positron emission tomography and statistical parametric mapping were used. Compared with rOL, rTL was associated with increased rCBF in the left medial prefrontal cortex and the right prefrontal convexity. Individual rCBF changes in the area homotopic to the right prefrontal convexity furthermore correlated with individual changes in rTL performance. While the smallest rCBF increases were found in subjects with weakest slowing of rTL relative to rOL, highest rCBF increases were present when rTL slowing dominated. Comparisons between rTL and rOL, however, revealed on average no performance differences. Our data suggest that relearning after previous opposite hand training activates neural mechanisms within the prefrontal convexity which might have an inhibitory function but that inhibition does not have to be the net final behavioral result.

Face-elicited ERPs and affective attitude: brain electric microstate and tomography analyses.

OBJECTIVES: Although behavioral studies have demonstrated that normative affective traits modulate the processing of facial and emotionally charged stimuli, direct electrophysiological evidence for this modulation is still lacking. METHODS: Event-related potential (ERP) data associated with personal, traitlike approach- or withdrawal-related attitude (assessed post-recording and 14 months later) were investigated in 18 subjects during task-free (i.e. unrequested, spontaneous) emotional evaluation of faces. Temporal and spatial aspects of 27 channel ERP were analyzed with microstate analysis and low resolution electromagnetic tomography (LORETA), a new method to compute 3 dimensional cortical current density implemented in the Talairach brain atlas. RESULTS: Microstate analysis showed group differences 132-196 and 196-272 ms poststimulus, with right-shifted electric gravity centers for subjects with negative affective attitude. During these (over subjects reliably identifiable) personality-modulated, face-elicited microstates, LORETA revealed activation of bilateral occipito-temporal regions, reportedly associated with facial configuration extraction processes. Negative compared to positive affective attitude showed higher activity right temporal; positive compared to negative attitude showed higher activity left temporo-parieto-occipital. CONCLUSIONS: These temporal and spatial aspects suggest that the subject groups differed in brain activity at early, automatic, stimulus-related face processing steps when structural face encoding (configuration extraction) occurs. In sum, the brain functional microstates associated with affect-related personality features modulate brain mechanisms during face processing already at early information processing stages.

Experimentally induced semantic paralexias in normals: a property of the right hemisphere.

The recently proposed association between semantic paralexias and right hemispheric reading processes was investigated in normals with a tachistoscopic half-field reading experiment. With extremely brief lateralized exposure of nouns, permitting only 25% of correct reading, semantic paralexias were induced. These semantic substitutions occurred three times more often to LVF (right hemisphere) than to RVF (left hemisphere) presentations, whereas other errors were observed with similar frequency to both visual fields. We concluded that semantic paralexias, as they are observed in patients, occur in normals induced by reduced reading time and are the product of right hemispheric reading processes.