Lateralization for the expression and perception of facial emotion as a function of age

Facial emotion processing hemispheric bias is weakly associated with handedness, autistic traits and biological sex, but not age

BACKGROUND

Right-hemisphere brain regions are strongly implicated in facial emotion processing (FEP), a phenomenon termed right-hemispheric bias. Variability in FEP hemispheric bias is thought to underpin differences in facial emotion recognition ability and has been associated with age, handedness, biological sex, and autistic traits. However, findings from research to date investigating factors associated with FEP hemispheric bias have been inconsistent.

OBJECTIVE

To examine if FEP hemispheric bias can be predicted by individual factors such as age, biological sex, handedness, and autistic traits.

METHODS

427 adults recruited from the general population aged 18-67 years completed the Autism-spectrum Quotient. We also assessed covariates previously linked with FEP hemispheric bias including age, handedness, and biological sex. FEP hemispheric bias was indexed using laterality quotients calculated from a Chimeric Faces Task, where participants indicated which of two identical (but mirrored) half-emotional half-neutral (no emotion) chimeric faces were more emotive.

RESULTS

Linear regression models revealed that (1) handedness predicted FEP hemispheric choice bias, (2) the attention switching Autism-spectrum Quotient subscale predicted FEP hemispheric reaction time bias, and (3) the imagination Autism-spectrum Quotient subscale predicted FEP hemispheric reaction time bias for males, but not females.

CONCLUSIONS

These findings indicate that the relationship between autistic traits and FEP hemispheric bias is nuanced. Additionally, handedness influences hemispheric bias effects during FEP. Future research should endeavour to investigate if FEP hemispheric bias is dependent on the emotion being observed and consider using more direct measures of hemispheric bias.

Distinctive types of aversiveness are represented as the same in a portion of the dorsal anterior cingulate cortex: An fMRI study with the cue paradigm

Some studies have argued that the dorsal anterior cingulate cortex (dACC) is generally activated in response to aversive information, including pain, negative affect, and cognitive conflict. Other studies have claimed that the dACC has subdivisions, and each division has a specific function. By manipulating emotionally and cognitively aversive cues, the present study determined whether the dACC is generally responsive to aversiveness or it has subdivisions for specific forms of aversiveness. Conjunction functional magnetic resonance imaging (fMRI) analysis showed that emotionally and cognitively aversive cues activated the same portion of the dACC. When these cues were contiguously presented, the region demonstrated additive activity, further supporting the overlapping representation of the two different forms of aversiveness in the dACC. Additional effective connectivity analysis showed that the dACC was co-activated with different brain regions depending on the cue type, characterizing its behavioral control mechanism. Complementary multivariate analyses showed that the reaction time was negatively correlated with the activity of the dACC and that the activity of the dACC under the emotional cue was predicted by the individual state anxiety score but not under the cognitive cue. We also found that the superior part of the dACC was uniquely activated in response to cognitively aversive cues, partially supporting the functional segregation account. Collectively, our results provide evidence that the specific locus of the dACC is generally responsive to distinctive motivational information, whereas the other loci may have segregated functions. Discussion includes recent neurocomputational theories that seem to satisfactorily account for the present results.

Validating the use of functional Near-Infrared Spectroscopy in monkeys: The case of brain activation lateralization in Papio anubis

Hemispheric asymmetries have long been seen as characterizing the human brain; yet, an increasing number of reports suggest the presence of such brain asymmetries in our closest primate relatives. However, most available data in non-human primates have so far been acquired as part of neurostructural approaches such as MRI, while comparative data in humans are often dynamically acquired as part of neurofunctional studies. In the present exploratory study in baboons (Papio anubis), we tested whether brain lateralization could be recorded non-invasively using a functional Near-Infrared Spectroscopy (fNIRS) device in two contexts: motor and auditory passive stimulations. Under light propofol anaesthesia monitoring, three adult female baboons were exposed to a series of (1) left- versus right-arm passive movement stimulations; and (2) left- versus right-ear versus stereo auditory stimulations while recording fNIRS signals in the related brain areas (i.e., motor central sulcus and superior temporal cortices respectively). For the sensorimotor condition our results show that left-arm versus right-arm stimulations induced typical contralateral difference in hemispheric activation asymmetries in the three subjects. For the auditory condition, we also revealed typical human-like patterns of hemispheric asymmetries in one subject, namely a leftward lateralization for right ear stimulations for all three channels. Overall, our findings support the use of fNIRS to investigate brain processing in non-human primates from a functional perspective, opening the way for the development of non-invasive procedures in non-human primate brain research.

Disorders of facial emotional expression and comprehension

One of the most important means of communicating emotions is by facial expressions. About 30-40 years ago, several studies examined patients with right and left hemisphere strokes for deficits in expressing and comprehending emotional facial expressions. The participants with right- or left-hemispheric strokes attempted to determine if two different actors were displaying the same or different emotions, to name the different emotions being displayed, and to select the face displaying an emotion named by the examiner. Investigators found that the right hemisphere-damaged group was impaired on all these emotional facial tests and that this deficit was not solely related to visuoperceptual processing defects. Further studies revealed that the patients who were impaired at recognizing emotional facial expressions and who had lost these visual representations of emotional faces often had damage to their right parietal lobe and their right somatosensory cortex. Injury to the cerebellum has been reported to impair emotional facial recognition, as have dementing diseases such as Alzheimer's disease and frontotemporal dementia, movement disorders such as Parkinson's disease and Huntington's disease, traumatic brain injuries, and temporal lobe epilepsy. Patients with right hemisphere injury are also more impaired than left-hemisphere-damaged patients when attempting to voluntarily produce facial emotional expressions and in their spontaneous expression of emotions in response to stimuli. This impairment does not appear to be induced by emotional conceptual deficits or an inability to experience emotions. Many of the disorders that cause impairments of comprehension of affective facial expressions also impair facial emotional expression. Treating the underlying disease may help patients with impairments of facial emotion recognition and expression, but unfortunately, there have not been many studies of rehabilitation.

Assessing Self-Reported Mood in Aphasia Following Stroke: Challenges, Innovations and Future Directions

Assessment of mood is critical in determining rehabilitation outcomes for stroke and other acquired brain injury, yet a common consequence of such injuries is aphasia, where language is impaired. Consequently, the use of language-based measures in this population is often not possible. Following a critical review of the neuropsychological aspects of self-reported mood, this paper evaluates the problems in reporting mood after stroke due to aphasia, and discusses implications for the design of adapted instruments. The paper then appraises the construction and psychometric properties of existing, adapted self-report measures developed to try and address these problems, and evaluates their utility and limitations. This includes a focus on the recently validated tablet-based Dynamic Visual Analog Mood Scales (D-VAMS), which uses innovative non-verbal assessment methods based on facial expression modulated via a slider control on a touchscreen interface. Currently, most studies evaluating recovery interventions simply omit individuals with aphasia because of the difficulty of assessing mood and quality of life in this population. However, adapted scales such as the D-VAMS appear to represent an important step forward in assessing mood in people with language impairments, with the use of interactive modulated imagery having wider applications for nonverbal communication as well as the quantification of subjective phenomena.

Does right hemisphere superiority sufficiently explain the left visual field advantage in face recognition?

The tendency to perceive the identity of the left half of a centrally viewed face more strongly than that of the right half is associated with visual processing of faces in the right hemisphere (RH). Here we investigate conditions under which this well-known left visual field (LVF) half-face advantage fails to occur. Our findings challenge the sufficiency of its explanation as a function of RH specialization for face processing coupled with LVF-RH correspondence. In two experiments we show that the LVF half-face advantage occurs for normal faces and chimeric faces composed of different half-face identities. In a third experiment, we show that face inversion disrupts the LVF half-face advantage. In two additional experiments we show that half-faces viewed in isolation or paired with inverted half-faces fail to show the LVF advantage. Consistent with previous explanations of the LVF half-face advantage, our findings suggest that the LVF half-face advantage reflects RH superiority for processing faces and direct transfer of LVF face information to visual cortex in the RH. Critically, however, our findings also suggest the operation of a third factor, which involves the prioritization of face-processing resources to the LVF, but only when two upright face-halves compete for these resources. We therefore conclude that RH superiority alone does not suffice to explain the LVF advantage in face recognition. We also discuss the implications of our findings for specialized visual processing of faces by the right hemisphere, and we distinguish LVF advantages for faces viewed centrally and peripherally in divided field studies.

Orienting asymmetries and physiological reactivity in dogs' response to human emotional faces

Recent scientific literature shows that emotional cues conveyed by human vocalizations and odours are processed in an asymmetrical way by the canine brain. In the present study, during feeding behaviour, dogs were suddenly presented with 2-D stimuli depicting human faces expressing the Ekman's six basic emotion (e.g. anger, fear, happiness, sadness, surprise, disgust, and neutral), simultaneously into the left and right visual hemifields. A bias to turn the head towards the left (right hemisphere) rather than the right side was observed with human faces expressing anger, fear, and happiness emotions, but an opposite bias (left hemisphere) was observed with human faces expressing surprise. Furthermore, dogs displayed higher behavioural and cardiac activity to picture of human faces expressing clear arousal emotional state. Overall, results demonstrated that dogs are sensitive to emotional cues conveyed by human faces, supporting the existence of an asymmetrical emotional modulation of the canine brain to process basic human emotions.

Emotions and the Right Hemisphere: Can New Data Clarify Old Models?

Models advanced to explain hemispheric asymmetries in representation of emotions will be discussed following their historical progression. First, the clinical observations that have suggested a general dominance of the right hemisphere for all kinds of emotions will be reviewed. Then the experimental investigations that have led to proposal of a different hemispheric specialization for positive versus negative emotions (valence hypothesis) or, alternatively, for approach versus avoidance tendencies (motivational hypothesis) will be surveyed. The discussion of these general models will be followed by a review of recent studies which have documented laterality effects within specific brain structures, known to play a critical role in different components of emotions, namely the amygdata in the computation of emotionally laden stimuli, the ventromedial prefrontal cortex in the integration between cognition and emotion and in the control of impulsive reactions and the anterior insula in the conscious experience of emotion. Results of these recent investigations support and provide an updated integrated version of early models assuming a general right hemisphere dominance for all kinds of emotions.

Hemiface Differences in Visual Exploration Patterns When Judging the Authenticity of Facial Expressions

Past studies have found asymmetry biases in human emotion recognition. The left side bias refers to preferential looking at the left-hemiface when actively exploring face images. However, these studies have been mainly conducted with static and frontally oriented stimuli, whereas real-life emotion recognition takes place on dynamic faces viewed from different angles. The aim of this study was to assess the judgment of genuine vs. masked expressions in dynamic movie clips of faces rotated to the right or left side. Forty-eight participants judged the expressions on faces displaying genuine or masked happy, sad, and fearful emotions. The head of the actor was either rotated to the left by a 45° angle, thus showing the left side of the face (standard orientation), or inverted, with the same face shown from the right side perspective. The eye movements were registered by the eye tracker and the data were analyzed for the inverse efficiency score (IES), the number of fixations, gaze time on the whole face and in the regions of interest. Results showed shorter IESs and gaze times for happy compared to sad and fearful emotions, but no difference was found for these variables between sad and fearful emotions. The left side preference was evident from comparisons of the number of fixations. Standard stimuli received a higher number of fixations than inverted ones. However, gaze time was long on inverted compared to standard faces. Number of fixations on exposed hemiface interacted with the emotions decreasing from happy to sad and fearful. An opposite pattern was found for the occluded hemiface. These results suggest a change in fixation patterns in the rotated faces that may be beneficial for the judgments of expressions. Furthermore, this study replicated the effects of the judgment of genuine and masked emotions using dynamic faces.

Left wings to the left: Posing and perceived political orientation

Images of individuals posing with the left cheek toward the camera are rated as more emotionally expressive than images with the right cheek toward the camera, which is theorized to be due to right hemisphere specialization for emotion processing. Liberals are stereotyped as being more emotional than conservatives. In the present study, we presented images of people displaying either leftward or rightward posing biases in an online task, and asked participants to rate people's perceived political orientation. Participants rated individuals portrayed with a leftward posing bias as significantly more liberal than those presented with a rightward bias. These findings support the idea that posing direction is related to perceived emotionality of an individual, and that liberals are stereotyped as more emotional than conservatives. Our results differ from those of a previous study, which found conservative politicians are more often portrayed with a leftward posing bias, suggesting differences between posing output for political parties and perceived political orientation. Future research should investigate this effect in other countries, and the effect of posing bias on perceptions of politicians.

Taking the Perfect Selfie: Investigating the Impact of Perspective on the Perception of Higher Cognitive Variables

Taking selfies is now becoming a standard human habit. However, as a social phenomenon, research is still in the fledgling stage and the scientific framework is sparse. Selfies allow us to share social information with others in a compact format. Furthermore, we are able to control important photographic and compositional aspects, such as perspective, which have a strong impact on the assessment of a face (e.g., demonstrated by the height-weight illusion, effects of gaze direction, faceism-index). In Study 1, we focused on the impact of perspective (left/right hemiface, above/below vs. frontal presentation) on higher cognitive variables and let 172 participants rate the perceived attractiveness, helpfulness, sympathy, dominance, distinctiveness, and intelligence, plus important information on health issues (e.g., body weight), on the basis of 14 3D faces. We could show that lateral snapshots yielded higher ratings for attractiveness compared to the classical frontal view. However, this effect was more pronounced for left hemifaces and especially female faces. Compared to the frontal condition, 30° right hemifaces were rated as more helpful, but only for female faces while faces viewed from above were perceived as significant less helpful. Direct comparison between left vs. right hemifaces revealed no effect. Relating to sympathy, we only found a significant effect for 30° right male hemifaces, but only in comparison to the frontal condition. Furthermore, female 30° right hemifaces were perceived as more intelligent. Relating to body weight, we replicated the so-called “height-weight illusion.” Other variables remained unaffected. In Study 2, we investigated the impact of a typical selfie-style condition by presenting the respective faces from a lateral (left/right) and tilted (lower/higher) vantage point. Most importantly, depending on what persons wish to express with a selfie, a systematic change of perspective can strongly optimize their message; e.g., increasing their attractiveness by shooting from above left, and in contrast, decreasing their expressed helpfulness by shooting from below. We could further extent past findings relating to the height-weight illusion and showed that an additional rotation of the camera positively affected the perception of body weight (lower body weight). We discuss potential explanations for perspective-related effects, especially gender-related ones.

Discriminative Thresholds in Facial Asymmetry: A Review of the Literature

Background

Facial symmetry is intimately correlated with attractiveness. Perfect facial symmetry is disconcerting and a degree of facial asymmetry is considered normal. There is a lack of data on the limits of normality across facial subunits.

Objectives

This systematic review aims to establish categories of facial asymmetry perception for facial aesthetic units by establishing a discriminative threshold of "deformity perception" across facial subunits and a threshold for intervention (unacceptable asymmetry).

Methods

A review of the literature was performed across Medline and Embase databases using OvidSP. All prospective studies evaluating the perception of progressive facial asymmetry in laymen or clinicians using a two- or three-dimensional model were included. Studies that did not evaluate rates of perception at varying degrees of asymmetry were excluded as these did not allow for the identification of a perceptive threshold.

Results

Each facial feature possesses a unique threshold of perception defined by an abrupt, statistically significant increase in detection. Asymmetry of the eyelid position at rest is the most sensitive facial feature (perceptive threshold, 2 mm) (P < 0.02). This is followed by deviations of the oral commissure (3 mm) (P < 0.001), brow position (3.5 mm) (P < 0.001), nasal tip deviation (4 mm) (P < 0.001), and chin deviation (6 mm) (P < 0.001). Desire for surgery for worsening deformities beyond the intervention threshold is characterized by an exponential, rather than linear, correlation.

Conclusions

Categories of facial asymmetry perception establish a framework to counsel patients with facial asymmetries, and are a valuable adjunct to clinical judgment in the management of static and dynamic facial deformities.

A comparative neurological approach to emotional expressions in primate vocalizations

Different approaches from different research domains have crystallized debate over primate emotional processing and vocalizations in recent decades. On one side, researchers disagree about whether emotional states or processes in animals truly compare to those in humans. On the other, a long-held assumption is that primate vocalizations are innate communicative signals over which nonhuman primates have limited control and a mirror of the emotional state of the individuals producing them, despite growing evidence of intentional production for some vocalizations. Our goal is to connect both sides of the discussion in deciphering how the emotional content of primate calls compares with emotional vocal signals in humans. We focus particularly on neural bases of primate emotions and vocalizations to identify cerebral structures underlying emotion, vocal production, and comprehension in primates, and discuss whether particular structures or neuronal networks solely evolved for specific functions in the human brain. Finally, we propose a model to classify emotional vocalizations in primates according to four dimensions (learning, control, emotional, meaning) to allow comparing calls across species.

The Emotion Recognition Task: A Paradigm to Measure the Perception of Facial Emotional Expressions at Different Intensities

The Emotion Recognition Task is a computer-generated paradigm for measuring the recognition of six basic facial emotional expressions: anger, disgust, fear, happiness, sadness, and surprise. Video clips of increasing length were presented, starting with a neutral face that changes into a facial expression of different intensities (20%–100%). The present study describes methodological aspects of the paradigm and its applicability in healthy participants ( N = 58; 34 men; ages between 22 and 75), specifically focusing on differences in recognition performance between the six emotion types and age-related change. The results showed that happiness was the easiest emotion to recognize, while fear was the most difficult. Moreover, older adults performed worse than young adults on anger, sadness, fear, and happiness, but not on disgust and surprise. These findings indicate that this paradigm is probably more sensitive than emotion perception tasks using static images, suggesting it is a useful tool in the assessment of subtle impairments in emotion perception.

Mu desynchronization during observation and execution of facial expressions in 30-month-old children

Simulation theories propose that observing another's facial expression activates sensorimotor representations involved in the execution of that expression, facilitating recognition processes. The mirror neuron system (MNS) is a potential mechanism underlying simulation of facial expressions, with like neural processes activated both during observation and performance. Research with monkeys and adult humans supports this proposal, but so far there have been no investigations of facial MNS activity early in human development. The current study used electroencephalography (EEG) to explore mu rhythm desynchronization, an index of MNS activity, in 30-month-old children as they observed videos of dynamic emotional and non-emotional facial expressions, as well as scrambled versions of the same videos. We found significant mu desynchronization in central regions during observation and execution of both emotional and non-emotional facial expressions, which was right-lateralized for emotional and bilateral for non-emotional expressions during observation. These findings support previous research suggesting movement simulation during observation of facial expressions, and are the first to provide evidence for sensorimotor activation during observation of facial expressions, consistent with a functioning facial MNS at an early stage of human development.

Read My Lips

It is well known that the right side of the mouth moves more than the left during speech, but little is known about how this asymmetry affects lipreading. We investigated asymmetries in the visual expression and perception of speech using the McGurk effect—an illusion in which incongruent lip movements cause listeners to misreport sounds. Thirty right-handed participants watched film clips in which the left, the right, or neither side of the mouth was covered. The McGurk effect was attenuated when the right side of the mouth was covered, demonstrating that this side is more important to lipreading than is the left side of the mouth. Mirror-reversed images tested whether the asymmetry was the result of an observer bias toward the left hemispace. The McGurk effect was stronger in the normal than in the mirror orientation when the mouth was fully visible. Thus, observers attend more to what they think is the right side of the speaker's mouth. Asymmetries in mouth movements may reflect the gestural origins of language, which are also right lateralized.

Perceptual bias, more than age, impacts on eye movements during face processing

Consistent with the right hemispheric dominance for face processing, a left perceptual bias (LPB) is typically demonstrated by younger adults viewing faces and a left eye movement bias has also been revealed. Hemispheric asymmetry is predicted to reduce with age and older adults have demonstrated a weaker LPB, particularly when viewing time is restricted. What is currently unclear is whether age also weakens the left eye movement bias. Additionally, a right perceptual bias (RPB) for facial judgments has less frequently been demonstrated, but whether this is accompanied by a right eye movement bias has not been investigated. To address these issues older and younger adults' eye movements and gender judgments of chimeric faces were recorded in two time conditions. Age did not significantly weaken the LPB or eye movement bias; both groups looked initially to the left side of the face and made more fixations when the gender judgment was based on the left side. A positive association was found between LPB and initial saccades in the freeview condition and with all eye movements (initial saccades, number and duration of fixations) when time was restricted. The accompanying eye movement bias revealed by LPB participants contrasted with RPB participants who demonstrated no eye movement bias in either time condition. Consequently, increased age is not clearly associated with weakened perceptual and eye movement biases. Instead an eye movement bias accompanies an LPB (particularly under restricted viewing time conditions) but not an RPB.

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.

Lateralized hybrid faces: evidence of a valence-specific bias in the processing of implicit emotions

It is well known that hemispheric asymmetries exist for both the analyses of low-level visual information (such as spatial frequency) and high-level visual information (such as emotional expressions). In this study, we assessed which of the above factors underlies perceptual laterality effects with "hybrid faces": a type of stimulus that allows testing for unaware processing of emotional expressions, when the emotion is displayed in the low-frequency information while an image of the same face with a neutral expression is superimposed to it. Despite hybrid faces being perceived as neutral, the emotional information modulates observers' social judgements. In the present study, participants were asked to assess friendliness of hybrid faces displayed tachistoscopically, either centrally or laterally to fixation. We found a clear influence of the hidden emotions also with lateral presentations. Happy faces were rated as more friendly and angry faces as less friendly with respect to neutral faces. In general, hybrid faces were evaluated as less friendly when they were presented in the left visual field/right hemisphere than in the right visual field/left hemisphere. The results extend the validity of the valence hypothesis in the specific domain of unaware (subcortical) emotion processing.

Acute pharmacologically induced shifts in serotonin availability abolish emotion-selective responses to negative face emotions in distinct brain networks

Pharmacological manipulation of serotonin availability can alter the processing of facial expressions of emotion. Using a within-subject design, we measured the effect of serotonin on the brain's response to aversive face emotions with functional MRI while 20 participants judged the gender of neutral, fearful and angry faces. In three separate and counterbalanced sessions, participants received citalopram (CIT) to raise serotonin levels, underwent acute tryptophan depletion (ATD) to lower serotonin, or were studied without pharmacological challenge (Control). An analysis designed to identify distributed brain responses identified two brain networks with modulations of activity related to face emotion and serotonin level. The first network included the left amygdala, bilateral striatum, and fusiform gyri. During the Control session this network responded only to fearful faces; increasing serotonin decreased this response to fear, whereas reducing serotonin enhanced the response of this network to angry faces. The second network involved bilateral amygdala and ventrolateral prefrontal cortex, and these regions also showed increased activity to fear during the Control session. Both drug challenges enhanced the neural response of this set of regions to angry faces, relative to Control, and CIT also enhanced activity for neutral faces. The net effect of these changes in both networks was to abolish the selective response to fearful expressions. These results suggest that a normal level of serotonin is critical for maintaining a differentiated brain response to threatening face emotions. Lower serotonin leads to a broadening of a normally fear-specific response to anger, and higher levels reduce the differentiated brain response to aversive face emotions.

Behavioral neuroscience of emotion in aging

Recent research on emotion and aging has revealed a stability of emotional experience from adulthood to older age, despite aging-related decrements in the perception and categorization of emotionally relevant stimuli. Research also shows that emotional expression remains intact with aging. In contrast, other studies provide evidence for an age-related decrease in autonomic nervous system physiological arousal, particularly in response to emotionally negative stimuli, and for shifts in central nervous system physiologic response to emotional stimuli, with increased prefrontal cortex activation and decreased amygdala activation in aging. Research on attention and memory for emotional information supports a decreased processing of negative emotional stimuli (i.e., a decrease in the negativity effect seen in younger adults), and a relative increase in the processing of emotionally positive stimuli (positivity effect). These physiological response and attentional/memory preference differences across increasingly older groups have been interpreted, within socioemotional selectivity theory, as reflecting greater motivation for emotion regulation with aging. According to this theory, as persons age, their perceived future time horizon shrinks, and a greater value is placed upon cultivating close, familiar, and meaningful relationships and other situations that give rise to positive emotional experience, and avoiding, or shifting attention from, those people and situations that are likely to elicit negative emotion. Even though there are central nervous system structural changes in emotion-relevant brain regions with aging, this shift in socioemotional selectivity, and perhaps the decreased autonomic nervous system physiological arousal of emotion with aging, facilitate enhanced emotion regulation with aging.

Processing emotion from the eyes: a divided visual field and ERP study

The right cerebral hemisphere is preferentially involved in recognising at least some facial expressions of emotion. We investigated whether there is a laterality effect in judging emotions from the eyes. In one task a pair of emotionally expressive eyes presented in central vision had to be physically matched to a subsequently presented set of eyes in one or other visual hemifield (eyes condition). In the second task a word was presented centrally followed by a set of eyes to left or right hemifield and the participant had to decide whether the word correctly described the emotion portrayed by the laterally presented set of eyes (word condition). Participants were a group of undergraduate students and a group of older volunteers (> 50). There was no visual hemifield difference in accuracy or raw response times in either task for either group, but log-transformed times showed an overall left hemifield advantage. Contrary to the right hemisphere ageing hypothesis, older participants showed no evidence of a relative right hemisphere decline in performance on the tasks. In the younger group mean peak amplitude of the N170 component of the EEG at lateral posterior electrode sites was significantly greater over the right hemisphere (T6/PO2) than the left (T5/PO1) in both the perceptual recognition task and the emotional judgement task. It was significantly greater for the task of judging emotion than in the eyes-matching task. In future it would be useful to combine electrophysiological techniques with lateralised visual input in studying lateralisation of emotion with older as well as younger participants.

Individual Differences in Cognitive Performance Due to Right Hemisphere Arousal

The purpose of this study was to investigate the relationship between individual differences in cognition and asymmetric patterns of cortical arousal in normal right-handed adults. Leftward asymmetry on a chimeric faces task was correlated with the ability to recognise faces and facial expression, and certain aspects of social skill. The correlation with face and emotional expression recognition was significant only for subjects who reported using a non-verbal strategy. These results further support the role of the right hemisphere in various aspects of social cognition, but also point to the need to consider individual differences in strategies employed during task performance.

The right-hemisphere and valence hypotheses: could they both be right (and sometimes left)?

The two halves of the brain are believed to play different roles in emotional processing, but the specific contribution of each hemisphere continues to be debated. The right-hemisphere hypothesis suggests that the right cerebrum is dominant for processing all emotions regardless of affective valence, whereas the valence specific hypothesis posits that the left hemisphere is specialized for processing positive affect while the right hemisphere is specialized for negative affect. Here, healthy participants viewed two split visual-field facial affect perception tasks during functional magnetic resonance imaging, one presenting chimeric happy faces (i.e. half happy/half neutral) and the other presenting identical sad chimera (i.e. half sad/half neutral), each masked immediately by a neutral face. Results suggest that the posterior right hemisphere is generically activated during non-conscious emotional face perception regardless of affective valence, although greater activation is produced by negative facial cues. The posterior left hemisphere was generally less activated by emotional faces, but also appeared to recruit bilateral anterior brain regions in a valence-specific manner. Findings suggest simultaneous operation of aspects of both hypotheses, suggesting that these two rival theories may not actually be in opposition, but may instead reflect different facets of a complex distributed emotion processing system.

Abnormal spatiotemporal processing of emotional facial expressions in childhood autism: dipole source analysis of event-related potentials

Previous studies of face processing in autism suggest abnormalities in anatomical development, functioning and connectivity/coordination of distributed brain systems involved in social cognition, but the spatial sequence and time course of rapid (sub-second) neural responses to emotional facial expressions have not been examined in detail. Source analysis of high-density event-related potentials (ERPs) is an optimal means to examine both the precise temporal profile and spatial location of early electrical brain activity in response to emotionally salient stimuli. Therefore, we recorded 128-channel ERPs from high-functioning males with autism (aged 6-10 years), and age-, sex- and IQ-matched typically developing controls during explicit and implicit processing of emotion from pictures showing happy, angry, fearful, sad and neutral facial expressions. Children with autism showed normal patterns of behavioural and ERP (P1, N170 and P2) responses. However, dipole source analysis revealed that ERP responses relating to face detection (visual cortex) and configural processing of faces (fusiform gyrus), as well as mental state decoding (medial prefrontal lobe), were significantly weaker and/or slower in autism compared with controls during both explicit and implicit emotion-processing tasks. Slower- and larger-amplitude ERP source activity in the parietal somatosensory cortices possibly reflected more effortful compensatory analytical strategies used by the autism group to process facial gender and emotion. Such aberrant neurophysiological processing of facial emotion observed in children with autism within the first 300 ms of stimulus presentation suggests abnormal cortical specialization within social brain networks, which would likely disrupt the development of normal social-cognitive skills.

Spatial-attention and emotional evocation: line bisection performance and visual art emotional evocation

Lesion studies demonstrate that the right temporal-parietal region (RTP) is important for mediating spatial attention. The RTP is also involved in emotional experiences that can be evoked by art. Normal people vary in their ability to allocate spatial attention, thus, people who can better allocate attention might also be more influenced by the emotional messages of the paintings (evocative impact). Seventeen healthy participants bisected an unlabeled 100mm line and their performance on this task was used to create two groups, individuals who were more (mALB) and less accurate (lALB). These participants also judged 10 paintings on five qualities, Evocative Impact, Aesthetics, Novelty, Technique, and Closure by marking a 100mm line from 1 (low degree) to 10 (high degree). An ANOVA indicated differences in accuracy on the line bisection (LB) between the two groups. Additional ANOVAs, using the quality ratings as the dependent measure, revealed that the mALB group scored the Evocative Impact greater than the lALB group. These results suggest that the differences in attentional bias between the two groups, as indicated by their LB performance, might influence their evocative impact or reactions and also be a 'barometer' of other RTP functions, including emotional processing.

Emotional Experience and Facial Expression in Alzheimer's Disease

Emotional experiences and facial muscle activity of individuals with Alzheimer's Disease (AD) (n = 13) and healthy elderly control subjects (n = 21) were measured while viewing emotion-eliciting images. Alzheimer's disease and control groups rated their emotional experiences similarly and in the expected directions on dimensions of valence and arousal. Change in corrugator activity while viewing images, compared to baseline, was comparable across groups and was greatest while viewing negative images. Change in zygomatic activity, however, was significantly different between AD and control groups, with AD subjects demonstrating an inverted pattern of activity compared to controls. These findings are discussed as possible consequences of frontal cortical system involvement accompanying the disease process.

Is the P300 deficit in alcoholism associated with early visual impairments (P100, N170)? An oddball paradigm

OBJECTIVE

Studies exploring chronic alcoholism with event-related potentials (ERPs) have shown delayed latency and reduced amplitude of the P300, a long-lasting positive potential reflecting decisional processing. This P300 deficit in alcoholism is generally interpreted as a disturbance in central nervous system inhibition or in memory/attention. The present study aimed at identifying if this electrophysiological deficit is already present on earlier components, and advances a new hypothesis concerning the interpretation of the P300 alteration.

METHODS

Patients suffering from alcoholism and matched healthy controls had to detect, in an oddball paradigm, emotional faces among a succession of neutral faces. Behavioral performance and ERP data (recorded from 32 electrodes) were analyzed.

RESULTS

In line with previous studies, data showed that alcoholism led to a P300 deficit. Moreover, we observed for the first time that this deficit begins at earlier visual (P100) and face-processing (N170) stages, and we found high positive correlations between P100, N170 and P300 for amplitude and latency values, suggesting cumulative deficits on the cognitive continuum.

CONCLUSIONS

We suggest that the P300 deficit observed in chronic alcoholism could be linked to earlier visuo-spatial deficits rather than being an impairment of the specific processes linked to the P300.

SIGNIFICANCE

These results call for reconsidering the interpretation of P300 impairments at a fundamental and clinical level, and shows that earlier ERP components must be taken into account in future studies.

Emotion experience and expression across the adult life span: insights from a multimodal assessment study

This investigation represents a multimodal study of age-related differences in experienced and expressed affect and in emotion regulatory skills in a sample of young, middle-aged, and older adults (N=96), testing formulations derived from differential emotions theory. The experimental session consisted of a 10-min anger induction and a 10-min sadness induction using a relived emotion task; participants were also randomly assigned to an inhibition or noninhibition condition. In addition to subjective ratings of emotional experience provided by participants, their facial behavior was coded using an objective facial affect coding system; a content analysis also was applied to the emotion narratives. Separate repeated measures analyses of variance applied to each emotion domain indicated age differences in the co-occurrence of negative emotions and co-occurrence of positive and negative emotions across domains, thus extending the finding of emotion heterogeneity or complexity in emotion experience to facial behavior and verbal narratives. The authors also found that the inhibition condition resulted in a different pattern of results in the older versus middle-aged and younger adults. The intensity and frequency of discrete emotions were similar across age groups, with a few exceptions. Overall, the findings were generally consistent with differential emotions theory.

Is emotion processing affected by advancing age? An event-related brain potential study

The recognition of emotions is presumably affected by advancing age, which is known from subjective reports and recognition tasks. To differentiate perception from executive function more clearly, the discrimination of emotions was investigated with event-related brain potentials (ERPs) from 21 electrodes in 14 elderly (ages 59-74) and 13 younger participants (ages 30-40) triggered by a rapid (3 Hz) serial visual presentation (RSVP) of high and low arousing pictures. Additionally, affective ratings of valence and arousal of a representative sample of 54 pictures were obtained. An early posterior negativity (EPN) as an index of early emotion discrimination was analyzed in an early (168-232 ms) and a late (232-296 ms) time window. Both groups showed an EPN associated with pictures of high emotional arousal. However, the EPN was slightly delayed in elderly participants. Thus, the affective modulation of the EPN was reduced in elderly subjects in the early time window, but not in the late time window. Ratings of valence or arousal did not differ between groups. In sum, these results point towards an age-related delay of early visual emotion discrimination. However, this delay seems not to influence further evaluative processing of emotional stimuli.

When advertising turns “cheeky”!

Portraits typically exhibit leftward posing biases, with people showing more of their left cheek than their right. The current study investigated posing biases in print advertising to determine whether the product advertised affects the posing bias. As the posing bias may be decreasing over time, we also investigated changes in posing biases over a span of more than 100 years. The current investigation coded 2664 advertisements from two time periods; advertisements were coded for target group of advertisement (men, women, both) and posing bias (rightward, leftward, or central). Unlike other studies that typically observe a leftward posing bias, print advertisements exhibit a rightward posing bias, regardless of time-frame. Thus, print advertisements differ greatly from portraits, which may relate to the purpose of advertisements and the role of attractiveness in advertising.

Changes in posed facial expression of emotion across the adult life span

The purpose of this study was to examine changes in the facial expression of emotion across the adult life span. Two positive and two negative emotional expressions were posed by 30 young (21 to 39 years), 30 middle-aged (40 to 59 years), and 30 older (60 to 81 years) healthy, right-handed women. Photographs of the four emotional expressions were rated by independent judges for intensity, accuracy, and confidence. Special features of this study were the use of a neutral face as a nonemotional control, as well as careful cognitive and affective screening procedures for posers and judges. Overall, the expressions of older posers were rated as significantly less accurate and with significantly less confidence than those of younger posers. Although the neutral faces of older posers were rated as significantly more intense than those of younger posers, there were no significant age-related intensity differences for positive and negative emotions. The results are discussed in terms of theoretical models of aging.

Detecting hemifacial asymmetries in emotional expression with three-dimensional computerized image analysis

Emotions are expressed more clearly on the left side of the face than the right: an asymmetry that probably stems from right hemisphere dominance for emotional expression (right hemisphere model). More controversially, it has been suggested that the left hemiface bias is stronger for negative emotions and weaker or reversed for positive emotions (valence model). We examined the veracity of the right hemisphere and valence models by measuring asymmetries in: (i) movement of the face; and (ii) observer's rating of emotionality. The study uses a precise three-dimensional (3D) imaging technique to measure facial movement and to provide images that simultaneously capture the left or right hemifaces. Models (n = 16) with happy, sad and neutral expressions were digitally captured and manipulated. Comparison of the neutral and happy or sad images revealed greater movement of the left hemiface, regardless of the valence of the emotion, supporting the right hemisphere model. There was a trend, however, for left-sided movement to be more pronounced for negative than positive emotions. Participants (n = 357) reported that portraits rotated so that the left hemiface was featured, were more expressive of negative emotions whereas right hemiface portraits were more expressive for positive emotions, supporting the valence model. The effect of valence was moderated when the images were mirror-reversed. The data demonstrate that relatively small rotations of the head have a dramatic effect on the expression of positive and negative emotions. The fact that the effect of valence was not captured by the movement analysis demonstrates that subtle movements can have a strong effect on the expression of emotion.

Age-related impairments in comprehending affective prosody with comparison to brain-damaged subjects

This study evaluated the ability to produce and comprehend affective prosody across age groups and compared patterns of impaired performance to deficits observed after focal brain damage. Sixty-nine healthy subjects, ages 22 to 83 years, were given the Aprosodia Battery, a test that distinguishes between affective prosodic processing deficits following right- versus left-brain damage through the use of stimuli with progressively reduced verbal articulatory content. Production of affective prosody, measured by variation in fundamental frequency, was unimpaired in older subjects, whereas comprehension of affective prosody was impaired, particularly for tasks with reduced verbal articulatory content. The pattern of performance across affective comprehension tasks in the older subjects resembled the pattern found after right-brain damage. The results demonstrate age-related loss in comprehension of affective prosody that is most likely due to a processing deficit involving the right hemisphere.

Hemispheric asymmetry and aging: right hemisphere decline or asymmetry reduction

We review evidence for two models of hemispheric asymmetry and aging: the right hemi-aging model, which proposes that the right hemisphere shows greater age-related decline than the left hemisphere, and the hemispheric asymmetry reduction in old adults (HAROLD) model, which proposes that frontal activity during cognitive performance tends to be less lateralized in older than in younger adults. The right hemi-aging model is supported by behavioral studies in the domains of cognitive, affective, and sensorimotor processing, but the evidence has been mixed. In contrast, available evidence is generally consistent with the HAROLD model, which is supported primarily by functional neuroimaging evidence in the domains of episodic memory encoding and retrieval, semantic memory retrieval, working memory, perception, and inhibitory control. Age-related asymmetry reductions may reflect functional compensation or dedifferentiation, and the evidence, although scarce, tends to support the compensation hypothesis. The right hemi-aging and the HAROLD models are not incompatible. For example, the latter may apply to prefrontal regions and the former to other brain regions.

The effect of left and right poses on the expression of facial emotion

Research, using composite facial photographs has demonstrated that left-left composites are more emotionally expressive than are right-right composites. The present study investigated whether hemifacial asymmetries in expression are apparent in photographs, that feature one side of the face more than the other. Photographs were taken of the models who turned their heads: (a) 15 degrees to the left, (b) 15 degrees to the right or (c) faced directly towards the camera. It was predicted that left hemiface and midline photographs would be judged as more emotionally expressive than right hemiface photographs, where the left hemiface is less prominent. Three hundred and eighty-four participants viewed photographs of the three posing conditions, and rated each photograph along an emotional expressivity scale. Midline and left hemiface portraits were rated as more emotionally expressive than were right hemiface portraits. To investigate whether this effect was caused by observer's aesthetic/perceptual biases, mirror-reversed versions of the three posing conditions were included. Left hemiface and midline portraits were rated as more emotionally expressive, irrespective of whether they were mirror-reversed. It was concluded that head turns of just 15 degrees can bring about significant changes in the perceived emotionality. The relevance of these findings to painted portraits, which feature the left hemiface more than the right, is discussed.

Asymmetry in facial expression of emotions by chimpanzees

Asymmetries in human facial expressions have long been documented and traditionally interpreted as evidence of brain laterality in emotional behavior. Recent findings in nonhuman primates suggest that this hemispheric specialization for emotional behavior may have precursors in primate evolution. In this study, we present the first data collected on our closest living relative, the chimpanzee. Objective measures (hemimouth length and area) and subjective measures (human judgements of chimeric stimuli) indicate that chimpanzees' facial expressions are asymmetric, with a greater involvement of the left side of the face in the production of emotional responses. No effect of expression type (positive versus negative) on facial asymmetry was found. Thus, chimpanzees, like humans and some other nonhuman primates, show a right hemisphere specialization for facial expression of emotions.

Can free-viewing perceptual asymmetries be explained by scanning, pre-motor or attentional biases?

Judgments of relative magnitude between the left and right sides of a stimulus are generally weighted toward the features contained on the left side. This leftward perceptual bias could be the result of, (a) left-to-right scanning biases, (b) pre-motor activation of the right hemisphere, or (c) a left hemispatial attentional bias. The relative merits of these explanations of perceptual asymmetry were investigated. In Experiment 1, English and Hebrew readers made luminance judgements for two left/right mirror-reversed luminance gradients (greyscales task). Despite different reading/scanning habits, both groups exhibited a leftward perceptual bias. English and Hebrew readers also performed a line bisection task. Scanning biases were controlled by asking participants to follow a marker as it moved left-to-right or right-to-left and then stop it as it reached the midpoint of the line. Despite controlling scanning, a leftward bias was observed in both groups. In Experiment 2, peripheral spatial cues were presented prior to the greyscales stimuli. English readers showed a reduction in the leftward bias for right-sided cues as compared to left-sided and neutral cues. Right-side cues presumably overcame a pre-existing leftward attentional bias. In both experiments, pre-motor activation was controlled using bimanual responses. Despite this control, a leftward bias was observed throughout the study. The data support the attentional bias account of leftward perceptual biases over the scanning and pre-motor activation accounts. Whether or not unilateral hemispheric activation provides an adequate account of this attentional bias is discussed.

Development of perceptual asymmetry for free viewing of chimeric stimuli

Free-viewing chimeric stimuli tasks have been used in a number of studies to assess perceptual asymmetries and draw inferences about hemispheric lateralization in children and adults. In order to determine whether perceptual asymmetries for nonverbal information are present in children, a free-viewing chimeric stimuli task was used in 63 normally developing 6- through 16-year-old children. Stimuli included affect (happy faces), gender, quantity, and shape. An overall left hemispace (LHS) advantage was present by 6 years of age. This LHS preference was more prominent by age 10 and then plateaued. No preference for shape was detected at any of the age ranges studied. These results suggest that perceptual asymmetries for visual stimuli develop during childhood and appear to reach a plateau by age 10. The observed specificity for certain types of nonverbal stimuli should be taken into account in future studies of perceptual asymmetry in both normal and neurologically impaired children.