Face processing in different brain areas,and critical band masking

Neurophysiological evidence is described showing that some neurons in the macaque inferior temporal visual cortex have responses that are invariant with respect to the position, size, view, and spatial frequency of faces and objects, and that these neurons show rapid processing and rapid learning. Critical band spatial frequency masking is shown to be a property of these face‐selective neurons and of the human visual perception of faces. Which face or object is present is encoded using a distributed representation in which each neuron conveys independent information in its firing rate, with little information evident in the relative time of firing of different neurons. This ensemble encoding has the advantages of maximizing the information in the representation useful for discrimination between stimuli using a simple weighted sum of the neuronal firing by the receiving neurons, generalization, and graceful degradation. These invariant representations are ideally suited to provide the inputs to brain regions such as the orbitofrontal cortex and amygdala that learn the reinforcement associations of an individual's face, for then the learning, and the appropriate social and emotional responses generalize to other views of the same face. A theory is described of how such invariant representations may be produced by self‐organizing learning in a hierarchically organized set of visual cortical areas with convergent connectivity. The theory utilizes either temporal or spatial continuity with an associative synaptic modification rule. Another population of neurons in the cortex in the superior temporal sulcus encodes other aspects of faces such as face expression, eye‐gaze, face view, and whether the head is moving. These neurons thus provide important additional inputs to parts of the brain such as the orbitofrontal cortex and amygdala that are involved in social communication and emotional behaviour. Outputs of these systems reach the amygdala, in which face‐selective neurons are found, and also the orbitofrontal cortex, in which some neurons are tuned to face identity and others to face expression. In humans, activation of the orbitofrontal cortex is found when a change of face expression acts as a social signal that behaviour should change; and damage to the human orbitofrontal and pregenual cingulate cortex can impair face and voice expression identification, and also the reversal of emotional behaviour that normally occurs when reinforcers are reversed.     

The functions of the orbitofrontal cortex

The orbitofrontal cortex contains the secondary taste cortex, in which the reward value of taste is represented. It also contains the secondary and tertiary olfactory cortical areas, in which information about the identity and also about the reward value of odours is represented. The orbitofrontal cortex also receives information about the sight of objects from the temporal lobe cortical visual areas, and neurons in it learn and reverse the visual stimulus to which they respond when the association of the visual stimulus with a primary reinforcing stimulus (such as taste) is reversed. This is an example of stimulus-reinforcement association learning, and is a type of stimulus-stimulus association learning. More generally, the stimulus might be a visual or olfactory stimulus, and the primary (unlearned) positive or negative reinforcer a taste or touch. A somatosensory input is revealed by neurons that respond to the texture of food in the mouth, including a population that responds to the mouth feel of fat. In complementary neuroimaging studies in humans, it is being found that areas of the orbitofrontal cortex are activated by pleasant touch, by painful touch, by taste, by smell, and by more abstract reinforcers such as winning or losing money. Damage to the orbitofrontal cortex can impair the learning and reversal of stimulus-reinforcement associations, and thus the correction of behavioural responses when there are no longer appropriate because previous reinforcement contingencies change. The information which reaches the orbitofrontal cortex for these functions includes information about faces, and damage to the orbitofrontal cortex can impair face (and voice) expression identification. This evidence thus shows that the orbitofrontal cortex is involved in decoding and representing some primary reinforcers such as taste and touch; in learning and reversing associations of visual and other stimuli to these primary reinforcers; and in controlling and correcting reward-related and punishment-related behavior, and thus in emotion. The approach described here is aimed at providing a fundamental understanding of how the orbitofrontal cortex actually functions, and thus in how it is involved in motivational behavior such as feeding and drinking, in emotional behavior, and in social behavior.     

Emotional appraisal is influenced by cardiac afferent information

Influential models highlight the central integration of bodily arousal with emotion. Some emotions, notably disgust, are more closely coupled to visceral state than others. Cardiac baroreceptors, activated at systole within each cardiac cycle, provide short-term visceral feedback. Here we explored how phasic baroreceptor activation may alter the appraisal of brief emotional stimuli and consequent cardiovascular reactions. We used functional MRI (fMRI) to measure brain responses to emotional face stimuli presented before and during cardiac systole. We observed that the processing of emotional stimuli was altered by concurrent natural baroreceptor activation. Specifically, facial expressions of disgust were judged as more intense when presented at systole, and rebound heart rate increases were attenuated after expressions of disgust and happiness. Neural activity within prefrontal cortex correlated with emotionality ratings. Activity within periaqueductal gray matter reflected both emotional ratings and their interaction with cardiac timing. Activity within regions including prefrontal and visual cortices correlated with increases in heart rate evoked by the face stimuli, while orbitofrontal activity reflected both evoked heart rate change and its interaction with cardiac timing. Our findings demonstrate that momentary physiological fluctuations in cardiovascular afferent information (1) influence specific emotional judgments, mediated through regions including the periaqueductal gray matter, and (2) shape evoked autonomic responses through engagement of orbitofrontal cortex. Together these findings highlight the close coupling of visceral and emotional processes and identify neural regions mediating bodily state influences on affective judgment.     

Orbitofrontal cortex and dynamic filtering of emotional stimuli

Event-related potentials (ER) were recorded in response to mildly aversive somatosensory and auditory stimuli. Patients with orbitofrontal lesions exhited enhanced ERPs (i.e., P3 amplitudes), as compared with control subjects. Moreover, these patients did not habituate to somatoensory stimuli across blocks of trials. The results were specific to orbitofrontal damage, since patients with damage to the dorsolateral prefontal cortex did not exhibit enhanced P3 amplitudes. These findings suggest damage to the orbitofrontal cortex impairs the ability to modulate or inhibit neural responses to aversive stimuli. The findings are couched in terms of dynamic filtering theory, which suggests that the orbitofrontal cortex is involved in the selection and active inhibition of neural circuits associated with emotional responses.     

Neurobiologische Grundlagen psychotherapeutischer Verfahren

In the last few years the investigation of the neurobiological basis of psychotherapeutic treatments has gained importance. Therapy-associated functional changes have been studied in a number of different psychiatric diseases. It has been shown that diseases with a central role of emotions (e.g. depression, anxiety disorders, borderline personality disorder) often demonstrate dysfunctions in brain areas that are linked to emotional regulation. Psychotherapeutic interventions can lead to a kind of normalization of brain responses in these areas (e.g. amygdala, ventromedial prefrontal cortex, anterior cingulate cortex, orbitofrontal cortex). In addition, therapy-associated transformations were also demonstrated in areas which are related to attention processes and visual perception. Other studies have aimed at finding neurobiological parameters that can be used to predict a therapeutic outcome or to choose between various therapeutic strategies. For instance, in depression, the amygdala and the anterior cingulate cortex are assumed to play a major role. Altogether, knowledge on the neurobiological basis of psychotherapeutic procedures is limited. A comparatively small number of studies and several methodological problems (e.g. small sample sizes, insufficient control groups, variability of methods used) make it difficult to propose reliable statements.     

Novel visual stimuli activate a population of neurons in the primate orbitofrontal cortex

Neurons were found in the rhesus macaque anterior orbitofrontal cortex that respond to novel but not to familiar visual stimuli. Some of these neurons responded to all novel stimuli, and others to only a subset (e.g., to novel faces). The neurons have no responses to familiar reward- or punishment-associated visual stimuli, nor to taste, olfactory or somatosensory inputs. The responses of the neurons typically habituated with repeated presentations of a novel stimulus, and five presentations each 1s was the median number for the response to reach half-maximal. The neurons did not respond to stimuli which had been novel and shown a few times on the previous day, indicating that the neurons were involved in long-term memory. The median latency of the neuronal responses was 120 ms. The median spontaneous firing rate was 1.3 spikes/s, and the median response to novel visual stimuli was 6.0 spikes/s. These findings indicate that the long-term memory for visual stimuli is information that is represented in a region of the primate anterior orbitofrontal cortex.     

Controlling the integration of emotion and cognition: the role of frontal cortex in distinguishing helpful from hurtful emotional information

Emotion has been both lauded and vilified for its role in decision making. How are people able to ensure that helpful emotions guide decision making and irrelevant emotions are kept out of decision making? The orbitofrontal cortex has been identified as a neural area involved in incorporating emotion into decision making. Is this area's function specific to the integration of emotion and cognition, or does it more broadly govern whether emotional information should be integrated into cognition? The present research examined the role of orbitofrontal cortex when it was appropriate to control (i.e., prevent) the influence of emotion in decision making (Experiment 1) and to incorporate the influence of emotion in decision making (Experiment 2). Together, the two studies suggest that activity in lateral orbitofrontal cortex is associated with evaluating the contextual relevance of emotional information for decision making.     

Neural Correlates of Emotional Reactivity in Sensation Seeking

ABSTRACT— High sensation seeking has been linked to increased risk for drug abuse and other negative behavioral outcomes. This study explored the neurobiological basis of this personality trait using functional magnetic resonance imaging (fMRI). High sensation seekers (HSSs) and low sensation seekers (LSSs) viewed high- and low-arousal pictures. Comparison of the groups revealed that HSSs showed stronger fMRI responses to high-arousal stimuli in brain regions associated with arousal and reinforcement (right insula, posterior medial orbitofrontal cortex), whereas LSSs showed greater activation and earlier onset of fMRI responses to high-arousal stimuli in regions involved in emotional regulation (anterior medial orbitofrontal cortex, anterior cingulate). Furthermore, fMRI response in anterior medial orbitofrontal cortex and anterior cingulate was negatively correlated with urgency. Finally, LSSs showed greater sensitivity to the valence of the stimuli than did HSSs. These distinct neurobiological profiles suggest that HSSs exhibit neural responses consistent with an overactive approach system, whereas LSSs exhibit responses consistent with a stronger inhibitory system.     

Social and emotional functioning following bilateral and unilateral neurosurgical prefrontal cortex lesions

Alterations in emotional and social functioning such as impaired ability to recognize emotions in others, a lack of empathy and poor insight have commonly been reported following prefrontal cortex damage. This study sought to investigate the subtleties of such difficulties in 34 individuals with discrete unilateral and bilateral neurosurgical lesions encroaching on the orbitofrontal, medial, and dorsolateral regions of the prefrontal cortex. A specifically devised self‐ and informant report measure, the social‐emotional questionnaire was used to examine five factors of functioning: emotion recognition; empathy; social conformity; antisocial behaviour; and sociability. There were some specific significant differences between the clinical and control groups' informant‐ratings in certain domains of social and emotional functioning. Individuals with damage involving the orbitofrontal region were reported to display elevated levels of antisocial behaviour. Individuals with bilateral orbitofrontal lesions were rated as showing significantly reduced social and emotional functioning in comparison with individuals with unilateral lesions and controls. In addition, individuals with bilateral lesions had significantly less insight overall regarding their social‐emotional abilities. The right unilateral lesion group showed significantly less insight into their abilities to recognize emotion in others in comparison with the left unilateral group. In conclusion, these results suggest that specific social‐emotional and insight deficits may form separate constellations of impairment. The findings also indicate that marked changes in social and emotional functioning are more likely following bilateral damage, and unilateral lesions do not inevitably lead to impairments.     

Emotions: From neuropsychology to functional imaging

Recent developments in functional imaging techniques, such as Positron Emission Tomography (PET) and functional Magnetic Resonance Imaging (fMRI), allow us to characterize more precisely the functional neuroanatomy mediating emotional responding. This corpus of studies has led to the development of affective neuroscience. First, we present a summary of the studies aimed at understanding the underlying mechanisms of the emotional response, which were conducted prior to the use of the brain imaging techniques. Then, this paper reviews the studies investigating the neural substrates implicated in the processing of facial expressions and those implicated in the production of experimentally induced emotional responses. This review of the literature includes a meta‐analysis of eight studies using PET and one fMRI study reporting the neural correlates of experimentally induced emotions in healthy individuals. The methods and results of these studies are described through figures drawn from the reported Talairach's coordinates depicting the cerebral regions activated in relation to different experimental conditions. The implications of the results and the role of the cerebral structures that have been identified are discussed. As regards the studies on the neural bases of the processing of facial expressions of emotion, there are separable neural circuits that are involved in mediating responding to differing categories of facial expressions of emotion. Fearful expressions have relatively consistently been found to activate the amygdala, as, occasionally, have sad and happy expressions. The anterior insula and the putamen seem to be particularly involved in disgust expression recognition, whereas the facial expression of anger seems to be predominantly associated with anterior cingular and orbitofrontal cortex activity. Among the cerebral structures that have appeared to be activated by experimentally induced emotions, the anterior cingulate cortex seems to play a specific role in representing subjective emotional responses.     

The impact of orbital prefrontal cortex damage on emotional activation to unanticipated and anticipated acoustic startle stimuli

Damage to the orbital prefrontal cortex has been implicated in selectively diminishing electrodermal autonomic nervous system responses to anticipated punishing stimuli (e.g., losing money; Bechara, Damasio, & Damasio, 2000), but not to unanticipated punishing stimuli (e.g., loud noises; Damasio, Tranel, & Damasio, 1990). We extended this research by examining the effects of orbitofrontal damage on emotional responses to unanticipated and anticipated acoustic startles and collecting a more extensive set of physiological measures, emotional facial behavior, and self-reported emotional experience. Consistent with previous research, patients showed intact physiology to an unanticipated startle but failed to show appropriate anticipatory cardiovascular responses (patients’ heart rates decreased, controls’ increased). In addition, patients displayed more surprise facial behavior and reported marginally more fear than did controls in response to the unanticipated startle. Thus, orbitofrontal damage may compromise the ability to anticipate physiologically the onset of aversive stimuli, despite intact or enhanced emotional responses when such stimuli occur unexpectedly.     

The functional neuroanatomy of emotion and affective style

Recently, there has been a convergence in lesion and neuroimaging data in the identification of circuits underlying positive and negative emotion in the human brain. Emphasis is placed on the prefrontal cortex (PFC) and the amygdala as two key components of this circuitry. Emotion guides action and organizes behavior towards salient goals. To accomplish this, it is essential that the organism have a means of representing affect in the absence of immediate elicitors. It is proposed that the PFC plays a crucial role in affective working memory. The ventromedial sector of the PFC is most directly involved in the representation of elementary positive and negative emotional states while the dorsolateral PFC may be involved in the representation of the goal states towards which these elementary positive and negative states are directed. The amygdala has been consistently identified as playing a crucial role in both the perception of emotional cues and the production of emotional responses, with some evidence suggesting that it is particularly involved with fear-related negative affect. Individual differences in amygdala activation are implicated in dispositional affective styles and increased reactivity to negative incentives. The ventral striatum, anterior cingulate and insular cortex also provide unique contributions to emotional processing.     

情绪加工中杏仁核的效价特异性

杏仁核是情绪信息加工的关键脑区。近年来心理学和神经科学领域发现了杏仁核情绪加工的效价特异性现象,并且整体存在左侧杏仁核对正性情绪、右侧杏仁核对负性情绪以及双侧杏仁核负性偏好的特异性趋势,且受到材料突出特征、个体差异、任务条件的调节。未来可进一步探索注意对杏仁核情绪效价特异性的调节作用,探究动态情绪刺激加工时杏仁核的活动特点,考察心理障碍患者加工负性情绪时的杏仁核激活模式,并确定杏仁核的效价特异性在思维、计划、决策等高级认知过程中的表现。     

Slow wave changes in amygdala to visual, auditory, and social stimuli following lesions of the inferior temporal cortex in squirrel monkey (Saimiri sciureus)

Radiotelemetry of slow wave activity of the amygdala was recorded under a variety of conditions. Power, and the percentage of power in the delta band, increased in response to stimulation. Recordings of monkey vocalizations and slides of ethologically relevant, natural objects produced a greater increase in power than did control stimuli. The responses to auditory stimuli increased when these stimuli were presented in an unrestrained, group setting, yet the responses to the vocalizations remained greater than those following control stimuli. Both the natural auditory and visual stimuli produced a reliable hierarchy with regard to the magnitude of response. Following lesions of inferior temporal cortex, these two hierarchies are disrupted, especially in the auditory domain. Further, these same stimuli, when presented after the lesion, produced a decrease, rather than an increase, in power. Nevertheless, the power recorded from the natural stimuli was still greater than that recorded from control stimuli in that the former produced less of a decrease in power, following the lesion, than did the latter. These data, in conjunction with a parallel report on evoked potentials in the amygdala, before and after cortical lesions, lead us to conclude that sensory information, particularly auditory, available to the amygdala, following the lesion, is substantially the same, and that it is the interpretation of this information, by the amygdala, which is altered by the cortical lesion.     

A Role for the Human Amygdala in Recognizing Emotional Arousal From Unpleasant Stimuli

Functional neuroimaging and lesion-based neuropsychological experiments have demonstrated the human amygdala's role in recognition of certain emotions signaled by sensory stimuli, notably, fear and anger in facial expressions. We examined recognition of two emotional dimensions, arousal and valence, in a rare subject with complete, bilateral damage restricted to the amygdala. Recognition of emotional arousal was impaired for facial expressions, words, and sentences that depicted unpleasant emotions, especially in regard to fear and anger. However, recognition of emotional valence was normal. The findings suggest that the amygdala plays a critical role in knowledge concerning the arousal of negative emotions, a function that may explain the impaired recognition of fear and anger in patients with bilateral amygdala damage, and one that is consistent with the amygdala's role in processing stimuli related to threat and danger.     

Beyond arousal and valence: The importance of the biological versus social relevance of emotional stimuli

The present study addressed the hypothesis that emotional stimuli relevant to survival or reproduction (biologically emotional stimuli) automatically affect cognitive processing (e.g., attention, memory), while those relevant to social life (socially emotional stimuli) require elaborative processing to modulate attention and memory. Results of our behavioral studies showed that (1) biologically emotional images hold attention more strongly than do socially emotional images, (2) memory for biologically emotional images was enhanced even with limited cognitive resources, but (3) memory for socially emotional images was enhanced only when people had sufficient cognitive resources at encoding. Neither images’ subjective arousal nor their valence modulated these patterns. A subsequent functional magnetic resonance imaging study revealed that biologically emotional images induced stronger activity in the visual cortex and greater functional connectivity between the amygdala and visual cortex than did socially emotional images. These results suggest that the interconnection between the amygdala and visual cortex supports enhanced attention allocation to biological stimuli. In contrast, socially emotional images evoked greater activity in the medial prefrontal cortex (MPFC) and yielded stronger functional connectivity between the amygdala and MPFC than did biological images. Thus, it appears that emotional processing of social stimuli involves elaborative processing requiring frontal lobe activity.     

Ecstasy and agony: activation of the human amygdala in positive and negative emotion

Considerable evidence indicates that the amygdala plays a critical role in negative, aversive human emotions. Although researchers have speculated that the amygdala plays a role in positive emotion, little relevant evidence exists. We examined the neural correlates of positive and negative emotion using positron emission tomography (PET), focusing on the amygdala. Participants viewed positive and negative photographs, as well as interesting and uninteresting neutral photographs, during PET scanning. The left amygdala and ventromedial prefrontal cortex were activated during positive emotion, and bilateral amygdala activation occurred during negative emotion. High-interest, unusual photographs also elicited left-amygdala activation, a finding consistent with suggestions that the amygdala is involved in vigilance reactions to associatively ambiguous stimuli. The current results constitute the first neuroimaging evidence for a role of the amygdala in positive emotional reactions elicited by visual stimuli. Although the amygdala appears to play a more extensive role in negative emotion, it is involved in positive emotion as well.     

The amygdala and ventromedial prefrontal cortex in morality and psychopathy

Recent work has implicated the amygdala and ventromedial prefrontal cortex in morality and, when dysfunctional, psychopathy. This model proposes that the amygdala, through stimulus-reinforcement learning, enables the association of actions that harm others with the aversive reinforcement of the victims' distress. Consequent information on reinforcement expectancy, fed forward to the ventromedial prefrontal cortex, can guide the healthy individual away from moral transgressions. In psychopathy, dysfunction in these structures means that care-based moral reasoning is compromised and the risk that antisocial behavior is used instrumentally to achieve goals is increased.     

Neuroticism and psychopathy predict brain activation during moral and nonmoral emotion regulation

Functional neuroimaging has identified brain regions associated with voluntary regulation of emotion, including the prefrontal cortex and amygdala. The neural mechanisms underlying individual differences in emotion regulation have not been extensively studied. We investigated the neural correlates of neuroticism and psychopathic personality traits in the context of an emotion regulation task. Results showed that amygdala activity elicited by unpleasant pictures was positively correlated with neuroticism and negatively correlated with a specific psychopathic trait related to emotional underreactivity. During active attempts to decrease emotional responses to unpleasant pictures, superior and ventrolateral prefrontal activity was positively correlated with psychopathy, but not with neuroticism. In contrast, dorsolateral prefrontal activity was positively correlated with neuroticism, but not with psychopathy. Psychopathy was also negatively correlated with medial prefrontal activity in response to pictures depicting moral violations, suggesting reduced emotional responses to moral stimuli in individuals with high levels of psychopathic traits. These results demonstrate dissociable influences of different personality traits on neural activity associated with responses to emotional stimuli and on the recruitment of regulation-related brain activity during the active down-regulation of responses to negative emotional stimuli. These results have implications for the etiology of trait-based psychopathology involving emotional dysregulation.     

Amygdala circuitry in attentional and representational processes

The amygdala has long been implicated in the display of emotional behavior and emotional information processing, especially in the context of aversive events. In this review, we discuss recent evidence that links the amygdala to several aspects of food-motivated associative learning, including functions often characterized as attention, reinforcement and representation. Each of these functions depends on the operation of separate amygdalar subsystems, through their connections with other brain systems. Notably, very different processing systems seem to be mediated by the central nucleus and basolateral amygdala, subregions of the amygdala that differ in their anatomy and in their connectivity. The basolateral amygdala is involved in the acquisition and representation of reinforcement value, apparently through its connections with ventral striatal dopamine systems and with the orbitofrontal cortex. The dentral nucleus, however, contributes heavily to attentional function in conditioning, by way of its influence on basal forebrain cholinergic systems and on the dorsolateral striatum.