Cross-species affective neuroscience decoding of the primal affective experiences of humans and related animals

Perspective biopsychologique systémique des émotions de base1

La perspective biopsychologique systémique des émotions de base est un modèle heuristique permettant de mieux comprendre comment l’individu apprend à s’adapter à son environnement grâce aux différentes émotions qui se sont développées progressivement en même temps que la myélinisation des circuits neurohormonaux, de la naissance jusqu’à environ vingt et un ans. Ce sont ces mêmes émotions, agissant en complémentarité, qui vont permettre à l’individu de maintenir son équilibre tout au long de sa vie.

Cinq émotions de base ont été retenues, car dans la documentation scientifique, cinq circuits neuronaux associés aux émotions sont définis, soit les cinq circuits décrits par Panksepp : celui de l’agressivité (rage-colère), celui du stress (peur-surprise), développé par LeDoux, celui de la récompense (recherche-joie), développé par Tassin, celui de l’empathie (panique-tristesse), développé par Decety, et celui de la conscience (conscience-bonheur), développé par Damasio.

The role of the cannabinoid receptor in adolescents' processing of facial expressions

The processing of emotional faces is an important prerequisite for adequate social interactions in daily life, and might thus specifically be altered in adolescence, a period marked by significant changes in social emotional processing. Previous research has shown that the cannabinoid receptor CB1R is associated with longer gaze duration and increased brain responses in the striatum to happy faces in adults, yet, for adolescents, it is not clear whether an association between CBR1 and face processing exists. In the present study we investigated genetic effects of the two CB1R polymorphisms, rs1049353 and rs806377, on the processing of emotional faces in healthy adolescents. They participated in functional magnetic resonance imaging during a Faces Task, watching blocks of video clips with angry and neutral facial expressions, and completed a Morphed Faces Task in the laboratory where they looked at different facial expressions that switched from anger to fear or sadness or from happiness to fear or sadness, and labelled them according to these four emotional expressions. A-allele versus GG-carriers in rs1049353 displayed earlier recognition of facial expressions changing from anger to sadness or fear, but not for expressions changing from happiness to sadness or fear, and higher brain responses to angry, but not neutral, faces in the amygdala and insula. For rs806377 no significant effects emerged. This suggests that rs1049353 is involved in the processing of negative facial expressions with relation to anger in adolescence. These findings add to our understanding of social emotion-related mechanisms in this life period.

Affective preclinical modeling of psychiatric disorders: taking imbalanced primal emotional feelings of animals seriously in our search for novel antidepressants

Preclinical animal models of psychiatric disorders are of critical importance for advances in development of new psychiatric medicine. Regrettably, behavior-only models have yielded no novel targeted treatments during the past half-century of vigorous deployment. This may reflect the general neglect of experiential aspects of animal emotions, since affective mental states of animals supposedly cannot be empirically monitored. This supposition is wrong-to the extent that the rewarding and punishing aspects of emotion circuit arousals reflect positive and negative affective states. During the past decade, the use of such affective neuroscience-based animal modeling has yielded three novel antidepressants (i) via the alleviation of psychic pain with low doses of buprenorphine; (ii) via the amplification of enthusiasm by direct stimulation of the medial forebrain bundle); and (iii) via the facilitation of the capacity for social joy with play facilitators such as rapastinel (GLYX13). All have progressed to successful human testing. For optimal progress, it may be useful for preclinical investigators to focus on the evolved affective foundations of psychiatrically relevant brain emotional disorders for optimal animal modeling.

A review of white matter microstructure alterations of pathways of the reward circuit in depression

BACKGROUND

Depressed mood, anhedonia, psychomotor retardation and alterations of circadian rhythm are core features of the depressive syndrome. Its neural correlates can be located within a frontal-striatal-tegmental neural network, commonly referred to as the reward circuit. It is the aim of this article to review literature on white matter microstructure alterations of the reward system in depression.

METHOD

We searched for diffusion tensor imaging (DTI)-studies that have explored neural deficits within the cingulum bundle, the uncinate fasciculus and the supero-lateral medial forebrain bundle/anterior thalamic radiation - in adolescent and adult depression (acute and remitted), melancholic depression, treatment-resistant depression and those at familial risk of depression. The relevant diffusion MRI literature was identified using PUBMED.

RESULTS

Thirty-five studies were included. In people at familial risk for depression the main finding was reduced fractional anisotropy (FA) in the cingulum bundle. Both increases and decreases of FA have been reported in the uncinate fasciculus in adolescents. Reductions of FA in the uncinate fasciculus and the anterior thalamic radiation/supero-lateral medial forebrain bundle during acute depressive episodes in adults were most consistently reported.

LIMITATIONS

Non-quantitative approach.

CONCLUSIONS

Altered cingulum bundle microstructure in unaffected relatives may either indicate resilience or vulnerability to depression. Uncinate fasciculus and supero-lateral medial forebrain bundle microstructure may be altered during depressive episodes in adult MDD. Future studies call for a careful clinical stratification of clinically meaningful subgroups.

Dissociated neural effects of cortisol depending on threat escapability

Evolution has provided us with a highly flexible neuroendocrine threat system which, depending on threat imminence, switches between active escape and passive freezing. Cortisol, the "stress-hormone", is thought to play an important role in both fear behaviors, but the exact mechanisms are not understood. Using pharmacological functional magnetic resonance imaging we investigated how cortisol modulates the brain's fear systems when humans are under virtual-predator attack. We show dissociated neural effects of cortisol depending on whether escape from threat is possible. During inescapable threat cortisol reduces fear-related midbrain activity, whereas in anticipation of active escape cortisol boosts activity in the frontal salience network (insula and anterior cingulate cortex), which is involved in autonomic control, visceral perception and motivated action. Our findings suggest that cortisol adjusts the human neural threat system from passive fear to active escape, which illuminates the hormone's crucial role in the adaptive flexibility of fear behaviors.

The use of animal models in behavioural neuroscience research

Animal models are used in experiments in the behavioural neurosciences that aim to contribute to the prevention and treatment of cognitive and affective disorders in human beings, such as anxiety and depression. Ironically, those animals that are likely to be the best models for psychopathology are also likely to be considered the ones that are most morally problematic to use, if it seems probable that (and if indeed they are initially selected as models because) they have experiences that are similar to human experiences that we have strong reasons to avoid causing, and indeed aim to alleviate (such as pain, anxiety or sadness). In this paper, against the background of contemporary discussions in animal ethics and the philosophy of animal minds, we discuss the views that it is morally permissible to use animals in these kinds of experiments, and that it is better to use less cognitively complex animals (such as zebrafish) than more complex animals (such as dogs). First, we criticise some justifications for the claim that human beings and more complex animals have higher moral status. We argue that contemporary approaches that attribute equal moral status to all beings that are capable of conscious strivings strivings (e.g. avoiding pain and anxiety; aiming to eat and play) are based on more plausible assumptions. Second, we argue that it is problematic to assume that less cognitively complex animals have a lesser sensory and emotional experience than more complex beings across the board. In specific cases, there might be good reasons to assume that more complex beings would be harmed more by a specific physical or environmental intervention, but it might also be that they sometimes are harmed less because of a better ability to cope. Determining whether a specific experiment is justified is therefore a complex issue. Our aim in this chapter is to stimulate further reflection on these common assumptions behind the use of animal models for psychopathologies. In order to be able to draw more definite conclusions, more research will have to be done on the influence of cognitive complexity on the experience of (human and non-human) animals.

Non-mammalian models in behavioral neuroscience: consequences for biological psychiatry

Current models in biological psychiatry focus on a handful of model species, and the majority of work relies on data generated in rodents. However, in the same sense that a comparative approach to neuroanatomy allows for the identification of patterns of brain organization, the inclusion of other species and an adoption of comparative viewpoints in behavioral neuroscience could also lead to increases in knowledge relevant to biological psychiatry. Specifically, this approach could help to identify conserved features of brain structure and behavior, as well as to understand how variation in gene expression or developmental trajectories relates to variation in brain and behavior pertinent to psychiatric disorders. To achieve this goal, the current focus on mammalian species must be expanded to include other species, including non-mammalian taxa. In this article, we review behavioral neuroscientific experiments in non-mammalian species, including traditional "model organisms" (zebrafish and Drosophila) as well as in other species which can be used as "reference." The application of these domains in biological psychiatry and their translational relevance is considered.

The ontogenesis of narrative: from moving to meaning

Narrative, the creation of imaginative projects and experiences displayed in expressions of movement and voice, is how human cooperative understanding grows. Human understanding places the character and qualities of objects and events of interest within stories that portray intentions, feelings, and ambitions, and how one cares about them. Understanding the development of narrative is therefore essential for understanding the development of human intelligence, but its early origins are obscure. We identify the origins of narrative in the innate sensorimotor intelligence of a hypermobile human body and trace the ontogenesis of narrative form from its earliest expression in movement. Intelligent planning, with self-awareness, is evident in the gestures and motor expressions of the mid-gestation fetus. After birth, single intentions become serially organized into projects with increasingly ambitious distal goals and social meaning. The infant imitates others’ actions in shared tasks, learns conventional cultural practices, and adapts his own inventions, then names topics of interest. Through every stage, in simple intentions of fetal movement, in social imitations of the neonate, in early proto-conversations and collaborative play of infants and talk of children and adults, the narrative form of creative agency with it four-part structure of ‘introduction,’ ‘development,’ ‘climax,’ and ‘resolution’ is present. We conclude that shared rituals of culture and practical techniques develop from a fundamental psycho-motor structure with its basic, vital impulses for action and generative process of thought-in-action that express an integrated, imaginative, and sociable Self. This basic structure is evident before birth and invariant in form throughout life. Serial organization of single, non-verbal actions into complex projects of expressive and explorative sense-making become conventional meanings and explanations with propositional narrative power. Understanding the root of narrative in embodied meaning-making in this way is important for practical work in therapy and education, and for advancing philosophy and neuroscience.

Early-infant diagnostic predictors of the neuro-behavioral development after neonatal care

Multidimensional diagnosis plays a central role in infant developmental care, which leads to the prediction of future disabilities. Information consolidated from objective and subjective, early and late, central and peripheral data may reveal neuro-pathological mechanisms and realize earlier and more precise preventive intervention. In the current study, we retrospectively searched correlating factors to the following neurological and behavioral development of 'Head Control' and 'Roll Over' using multivariate correlation analysis of differ-ent diagnostic domains over age, subject/object information of the patients who were previously admitted in our neonatal intensive care unit (NICU) and could be developmentally followed up in our outpatient clinic. Based on the hematologic and biochemical data, MRI brain anatomy during NICU hospitalization, we characterized all the acquired data distribution from 31 infants with either 'appeared neurologically normal (ANN, n = 21)’ or 'appeared neurologically abnormal (ANA, n = 10)’ pro tempore, with a physician's clinical judgment before discharge. Besides single factor comparisons between ANN and ANA, we examined their development difference by using the multidimensional information processing, principal component analysis (PCA). The diagnostic predictors of neuro-behavioral development were selected by regression analysis with variable selection. It resulted that hematological and brain anatomical factors seemed correlated to both ‘Head Control’ and ‘Roll Over’. This report suggested certain possibility of the cross-domain translational approach between subjective and objective developmental information through multivariate analyses, with candidate markers preliminarily to be evaluated in further studies.

Reflections on a footnote: implications for the study of emotions in animals

<p>A footnote (FN) originally submitted as a comment to the article "Parsing Reward" led me to write this essay. The comment was rejected by the editor of a prestigious scientific journal in the area of behavioral neuroscience with the suggestion that it would be more appropriate for an "idle talk". I believe that the core issues involved are important to address explicitly in a debate within the broad domain of the frontiers of human and biological sciences. The protagonists involved in the didactic episode of the FN, whose articles and books I have been reading over the years, are leaders in the field of neuroscience. In this essay the episode is historically contextualized and discussed in terms of potential implications for ethology, psychology and neuroscience.</p>

Stress, trauma and PTSD: translational insights into the core synaptic circuitry and its modulation

Evidence is considered as to whether behavioral criteria for diagnosis of post-traumatic stress disorder (PTSD) are applicable to that of traumatized animals and whether the phenomena of acquisition, extinction and reactivation of fear behavior in animals are also successfully applicable to humans. This evidence suggests an affirmative answer in both cases. Furthermore, the deficits in gray matter found in PTSD, determined with magnetic resonance imaging, are also observed in traumatized animals, lending neuropsychological support to the use of animals to probe what has gone awry in PTSD. Such animal experiments indicate that the core synaptic circuitry mediating behavior following trauma consists of the amygdala, ventral-medial prefrontal cortex and hippocampus, all of which are modulated by the basal ganglia. It is not clear if this is the case in PTSD as the observations using fMRI are equivocal and open to technical objections. Nevertheless, the effects of the basal ganglia in controlling glutamatergic synaptic transmission through dopaminergic and serotonergic synaptic mechanisms in the core synaptic circuitry provides a ready explanation for why modifying these mechanisms delays extinction in animal models and predisposes towards PTSD. In addition, changes of brain-derived neurotrophic factor (BDNF) in the core synaptic circuitry have significant effects on acquisition and extinction in animal experiments with single nucleotide polymorphisms in the BDNF gene predisposing to PTSD.

Intranasal adminsitration of oxytocin in postnatal depression: implications for psychodynamic psychotherapy from a randomized double-blind pilot study

Oxytocin is a neuropeptide that is active in the central nervous system and is generally considered to be involved in prosocial behaviors and feelings. In light of its documented positive effect on maternal behavior, we designed a study to ascertain whether oxytocin exerts any therapeutic effects on depressive symptoms in women affected by maternal postnatal depression. A group of 16 mothers were recruited in a randomized double-blind study: the women agreed to take part in a brief course of psychoanalytic psychotherapy (12 sessions, once a week) while also being administered, during the 12-weeks period, a daily dose of intranasal oxytocin (or a placebo). The pre-treatment evaluation also included a personality assessment of the major primary-process emotional command systems described by Panksepp () and a semi-quantitative assessment by the therapist of the mother's depressive symptoms and of her personality. No significant effect on depressive symptomatology was found following the administration of oxytocin (as compared to a placebo) during the period of psychotherapy. Nevertheless, a personality trait evaluation of the mothers, conducted in our overall sample group, showed a decrease in the narcissistic trait only within the group who took oxytocin. The depressive (dysphoric) trait was in fact significantly affected by psychotherapy (this effect was only present in the placebo group so it may reflect a positive placebo effect enhancing the favorable influence of psychotherapy on depressive symptoms) but not in the presence of oxytocin. Therefore, the neuropeptide would appear to play some role in the modulation of cerebral functions involved in the self-centered (narcissistic) dimension of the suffering that can occur with postnatal depression. Based on these results, there was support for our hypothesis that what is generally defined as postnatal depression may include disturbances of narcissistic affective balance, and oxytocin supplementation can counteract that type of affective disturbance. The resulting improvements in well-being, reflected in better self-centering in post-partuent mothers, may in turn facilitate better interpersonal acceptance of (and interactions with) the child and thereby, improved recognition of the child's needs.

The preparatory set: a novel approach to understanding stress, trauma, and the bodymind therapies

Basic to all motile life is a differential approach/avoid response to perceived features of environment. The stages of response are initial reflexive noticing and orienting to the stimulus, preparation, and execution of response. Preparation involves a coordination of many aspects of the organism: muscle tone, posture, breathing, autonomic functions, motivational/emotional state, attentional orientation, and expectations. The organism organizes itself in relation to the challenge. We propose to call this the "preparatory set" (PS). We suggest that the concept of the PS can offer a more nuanced and flexible perspective on the stress response than do current theories. We also hypothesize that the mechanisms of body-mind therapeutic and educational systems (BTES) can be understood through the PS framework. We suggest that the BTES, including meditative movement, meditation, somatic education, and the body-oriented psychotherapies, are approaches that use interventions on the PS to remedy stress and trauma. We discuss how the PS can be adaptive or maladaptive, how BTES interventions may restore adaptive PS, and how these concepts offer a broader and more flexible view of the phenomena of stress and trauma. We offer supportive evidence for our hypotheses, and suggest directions for future research. We believe that the PS framework will point to ways of improving the management of stress and trauma, and that it will suggest directions of research into the mechanisms of action of BTES.

Survival implications of the development of behavioural responsiveness and awareness in different groups of mammalian young

This paper focuses on the development of behaviours that are critical for the survival of newborn and juvenile mammals of veterinary and wider biological interest. It provides an updated, integrated and comparative analysis of how postnatal maturation of sensory, motor and perceptual capacities support and constrain behavioural interactions between mammalian young and the mother, any littermates and the environment. Young that are neurologically exceptionally immature, moderately immature and mature at birth are compared, and include, for example, marsupial joeys, rodent pups and ruminant offspring. Mothers in these three groups exhibit distinctive patterns of birthing and postnatal care behaviours. To secure survival of the young, maternal care must compensate for behavioural inadequacies imposed by the limited sensory capacities the young possess at each stage. These sensory capacities develop in a predictable sequence in most mammals such that before birth the sequence progresses to an extent that parallels the degree of neurological maturity reached at birth. The extent of neurological maturity is likewise reflected in how long it takes after birth for the necessary brain circuit connectivity to develop sufficiently to support cortically based cognitive modulation of behaviour. This takes several months, days-to-weeks or minutes-to-hours in young that are, respectively, neurologically exceptionally immature, moderately immature, or mature at birth. Once achieved, cognitive awareness confers a high degree of behavioural flexibility that allows the young to respond more effectively to the unpredictability of their postnatal environments. It is shown that the onset of this cognitively based flexibility in the young of each group coincides with their first exposure to a variable environment that requires such behavioural flexibility.

Evolutionary aspects of self- and world consciousness in vertebrates

Although most aspects of world and self-consciousness are inherently subjective, neuroscience studies in humans and non-human animals provide correlational and causative indices of specific links between brain activity and representation of the self and the world. In this article we review neuroanatomic, neurophysiological and neuropsychological data supporting the hypothesis that different levels of self and world representation in vertebrates rely upon (i) a “basal” subcortical system that includes brainstem, hypothalamus and central thalamic nuclei and that may underpin the primary (or anoetic) consciousness likely present in all vertebrates; and (ii) a forebrain system that include the medial and lateral structures of the cerebral hemispheres and may sustain the most sophisticated forms of consciousness [e.g., noetic (knowledge based) and autonoetic, reflective knowledge]. We posit a mutual, bidirectional functional influence between these two major brain circuits. We conclude that basic aspects of consciousness like primary self and core self (based on anoetic and noetic consciousness) are present in many species of vertebrates and that, even self-consciousness (autonoetic consciousness) does not seem to be a prerogative of humans and of some non-human primates but may, to a certain extent, be present in some other mammals and birds

Ventromedial hypothalamic neurons control a defensive emotion state

Defensive behaviors reflect underlying emotion states, such as fear. The hypothalamus plays a role in such behaviors, but prevailing textbook views depict it as an effector of upstream emotion centers, such as the amygdala, rather than as an emotion center itself. We used optogenetic manipulations to probe the function of a specific hypothalamic cell type that mediates innate defensive responses. These neurons are sufficient to drive multiple defensive actions, and required for defensive behaviors in diverse contexts. The behavioral consequences of activating these neurons, moreover, exhibit properties characteristic of emotion states in general, including scalability, (negative) valence, generalization and persistence. Importantly, these neurons can also condition learned defensive behavior, further refuting long-standing claims that the hypothalamus is unable to support emotional learning and therefore is not an emotion center. These data indicate that the hypothalamus plays an integral role to instantiate emotion states, and is not simply a passive effector of upstream emotion centers.

DOI:http://dx.doi.org/10.7554/eLife.06633.001

Animals have evolved a large number of ‘defensive behaviors’ to deal with the threat of predators. Examples include reptiles camouflaging themselves to avoid discovery, fish and birds swarming to confuse predators, insects releasing toxic chemicals, and humans readying themselves to fight or flee.

In mammals, defensive behaviors are thought to be mediated by a region of the brain called the amygdala. This structure, which is known as the brain's ‘emotion center’, receives and processes information from the senses about impending threats. It then sends instructions on how to deal with these threats to other regions of the brain including the hypothalamus, which pass them on to the brain regions that control the behavioral, endocrine and involuntary responses of the mammal.

For many years it has been thought that the role of the hypothalamus is to serve simply as a relay for emotion states encoded in the amygdala, rather than as an emotion center itself. However, Kunwar et al. have now challenged this assumption with the aid of a technique called optogenetics, in which light is used to activate specific populations of genetically labeled neurons. When light was used to directly activate neurons within the ventromedial hypothalamus in awake mice, the animals instantly froze and/or fled, just as they would when faced with a predator. Given that the optical stimulation had completely bypassed the amygdala, this suggested that the hypothalamus must be capable of generating this defensive response without any input from the amygdala.

The freezing and fleeing responses resembled the responses to a predator in a number of key ways. Mice chose to avoid areas of their cage in which they had received the stimulation, suggesting that—like a predator—these areas induced an unpleasant emotional state, perhaps akin to anxiety or fear. Freezing and fleeing persisted for several seconds after the stimulation had stopped, just as freezing and fleeing responses to predators do not immediately cease after the threat has gone. And finally, destroying the neurons targeted by the stimulation made mice less likely to avoid one of their main predators, the rat. It also made the animals less anxious.

Overall the results suggest that the hypothalamus may be more than simply a relay for the amygdala, and that ‘amygdala-centric’ views of emotion processing may need to be re-visited.

DOI:http://dx.doi.org/10.7554/eLife.06633.002

Embodied intersubjective engagement in mother-infant tactile communication: a cross-cultural study of Japanese and Scottish mother-infant behaviors during infant pick-up

This study examines the early development of cultural differences in a simple, embodied, and intersubjective engagement between mothers putting down, picking up, and carrying their infants between Japan and Scotland. Eleven Japanese and ten Scottish mothers with their 6- and then 9-month-old infants participated. Video and motion analyses were employed to measure motor patterns of the mothers’ approach to their infants, as well as their infants’ collaborative responses during put-down, pick-up, and carry phases. Japanese and Scottish mothers approached their infants with different styles and their infants responded differently to the short duration of separation during the trial. A greeting-like behavior of the arms and hands was prevalent in the Scottish mothers’ approach, but not in the Japanese mothers’ approach. Japanese mothers typically kneeled before making the final reach to pick-up their children, giving a closer, apparently gentler final approach of the torso than Scottish mothers, who bent at the waist with larger movements of the torso. Measures of the gap closure between the mothers’ hands to their infants’ heads revealed variably longer duration and distance gap closures with greater velocity by the Scottish mothers than by the Japanese mothers. Further, the sequence of Japanese mothers’ body actions on approach, contact, pick-up, and hold was more coordinated at 6 months than at 9 months. Scottish mothers were generally more variable on approach. Measures of infant participation and expressivity indicate more active participation in the negotiation during the separation and pick-up phases by Scottish infants. Thus, this paper demonstrates a culturally different onset of development of joint attention in pick-up. These differences reflect cultures of everyday interaction.

State-dependent μ-opioid modulation of social motivation

Social mammals engage in affiliative interactions both when seeking relief from negative affect and when searching for pleasure and joy. These two motivational states are both modulated by μ-opioid transmission. The μ-opioid receptor (MOR) system in the brain mediates pain relief and reward behaviors, and is implicated in social reward processing and affiliative bonding across mammalian species. However, pharmacological manipulation of the μ-opioid system has yielded opposite effects on rodents and primates: in rodents, social motivation is generally increased by MOR agonists and reduced by antagonists, whereas the opposite pattern has been shown in primates. Here, we address this paradox by taking into account differences in motivational state. We first review evidence for μ-opioid mediation of reward processing, emotion regulation, and affiliation in humans, non-human primates, rodents and other species. Based on the consistent cross-species similarities in opioid functioning, we propose a unified, state-dependent model for μ-opioid modulation of affiliation across the mammalian species. Finally, we show that this state-dependent model is supported by evidence from both rodent and primate studies, when species and age differences in social separation response are taken into account.

Subliminal versus supraliminal stimuli activate neural responses in anterior cingulate cortex, fusiform gyrus and insula: a meta-analysis of fMRI studies

Background

Non-conscious neural activation may underlie various psychological functions in health and disorder. However, the neural substrates of non-conscious processing have not been entirely elucidated. Examining the differential effects of arousing stimuli that are consciously, versus unconsciously perceived will improve our knowledge of neural circuitry involved in non-conscious perception. Here we conduct preliminary analyses of neural activation in studies that have used both subliminal and supraliminal presentation of the same stimulus.

Methods

We use Activation Likelihood Estimation (ALE) to examine functional Magnetic Resonance Imaging (fMRI) studies that uniquely present the same stimuli subliminally and supraliminally to healthy participants during functional magnetic resonance imaging (fMRI). We included a total of 193 foci from 9 studies representing subliminal stimulation and 315 foci from 10 studies representing supraliminal stimulation.

Results

The anterior cingulate cortex is significantly activated during both subliminal and supraliminal stimulus presentation. Subliminal stimuli are linked to significantly increased activation in the right fusiform gyrus and right insula. Supraliminal stimuli show significantly increased activation in the left rostral anterior cingulate.

Conclusions

Non-conscious processing of arousing stimuli may involve primary visual areas and may also recruit the insula, a brain area involved in eventual interoceptive awareness. The anterior cingulate is perhaps a key brain region for the integration of conscious and non-conscious processing. These preliminary data provide candidate brain regions for further study in to the neural correlates of conscious experience.

Electronic supplementary material

The online version of this article (doi:10.1186/s40359-014-0052-1) contains supplementary material, which is available to authorized users.

Toward the Constitution of Emotional Feelings: Synergistic Lessons From Izard’s Differential Emotions Theory and Affective Neuroscience

Cal Izard has provided psychology a robust vision of human emotional feelings. He has addressed the full spectrum of emotional-developmental-cognitive complexities entailed in clarifying seemingly impenetrable mysteries: How do we experience emotions and how do they guide cognitive development? Izard’s developmental studies of infant minds integrate the primal evolutionary affective foundations of our nature with the diverse paths of nurture, and are framed in ways that can promote human thriving. His multilayered vision of our emotional nature resonates well with modern cross-species affective neuroscience perspectives.

Central amygdala PKC-δ(+) neurons mediate the influence of multiple anorexigenic signals

Feeding can be inhibited by multiple cues, including those associated with satiety, sickness or unpalatable food. How such anorexigenic signals inhibit feeding at the neural circuit level is not completely understood. Although some inhibitory circuits have been identified, it is not yet clear whether distinct anorexigenic influences are processed in a convergent or parallel manner. The amygdala central nucleus (CEA) has been implicated in feeding control, but its role is controversial. The lateral subdivision of CEA (CEl) contains a subpopulation of GABAergic neurons that are marked by protein kinase C-δ (PKC-δ). We found that CEl PKC-δ(+) neurons in mice were activated by diverse anorexigenic signals in vivo, were required for the inhibition of feeding by such signals and strongly suppressed food intake when activated. They received presynaptic inputs from anatomically distributed neurons activated by different anorexigenic agents. Our data suggest that CEl PKC-δ(+) neurons constitute an important node that mediates the influence of multiple anorexigenic signals.

A cross-species socio-emotional behaviour development revealed by a multivariate analysis

Recent progress in affective neuroscience and social neurobiology has been propelled by neuro-imaging technology and epigenetic approach in neurobiology of animal behaviour. However, quantitative measurements of socio-emotional development remains lacking, though sensory-motor development has been extensively studied in terms of digitised imaging analysis. Here, we developed a method for socio-emotional behaviour measurement that is based on the video recordings under well-defined social context using animal models with variously social sensory interaction during development. The behaviour features digitized from the video recordings were visualised in a multivariate statistic space using principal component analysis. The clustering of the behaviour parameters suggested the existence of species- and stage-specific as well as cross-species behaviour modules. These modules were used to characterise the behaviour of children with or without autism spectrum disorders (ASDs). We found that socio-emotional behaviour is highly dependent on social context and the cross-species behaviour modules may predict neurobiological basis of ASDs.

The Brain Derived Neurotrophic Factor and Personality

The study of the biological basis of personality is a timely research endeavor, with the aim of deepening our understanding of human nature. In recent years, a growing body of research has investigated the role of the brain derived neurotrophic factor (BDNF) in the context of individual differences across human beings, with a focus on personality traits. A large number of different approaches have been chosen to illuminate the role of BDNF for personality, ranging from the measurement of BDNF in the serum/plasma to molecular genetics to (genetic) brain imaging. The present review provides the reader with an overview of the current state of affairs in the context of BDNF and personality.

Unconscious influences on decision making: neuroimaging and neuroevolutionary perspectives

Newell and Shanks provide a useful critique on unconscious decision making. However, they do not consider an important set of functional brain imaging studies of unconscious processes. Here we review briefly the relevant brain imaging and psychobiological literature and its implications for understanding unconscious decision making.

Preclinical modeling of primal emotional affects (Seeking, Panic and Play): gateways to the development of new treatments for depression

Mammalian brains contain at least 7 primal emotional systems--Seeking, Rage, Fear, Lust, Care, Panic and Play (capitalization reflects a proposed primary-process terminology, to minimize semantic confusions and mereological fallacies). These systems help organisms feel affectively balanced (e.g. euthymic) and unbalanced (e.g. depressive, irritable, manic), providing novel insights for understanding human psychopathologies. Three systems are especially important for understanding depression: The separation distress (Panic) system mediates the psychic pain of separation distress (i.e. excessive sadness and grief), which can be counteracted by minimizing Panic arousals (as with low-dose opioids). Depressive dysphoria also arises from reduced brain reward-seeking and related play urges (namely diminished enthusiasm (Seeking) and joyful exuberance (Play) which promote sustained amotivational states). We describe how an understanding of these fundamental emotional circuits can promote the development of novel antidepressive therapeutics--(i) low-dose buprenorphine to counteract depression and suicidal ideation emanating from too much psychic pain (Panic overarousal), (ii) direct stimulation of the Seeking system to counteract amotivational dysphoria, and (iii) the discovery and initial clinical testing of social-joy-promoting molecules derived from the analysis of the Play system.

Cross-Species Neuroaffective Parsing of Primal Emotional Desires and Aversions in Mammals

The primal motivational systems of all mammals are constituted of the evolved affective brain networks that gauge key survival issues. However, since progress in functional neuroscience has historically lagged behind conceptual developments in psychological science, motivational processes have traditionally been anchored to behavioral rather than neural and affective issues. Attempts to retrofit neuroaffective issues onto established psychological-conceptual structures are problematic, especially when fundamental evidence for primal affective circuits, and their neural nature, comes largely from animal research. This article provides a synopsis of our growing understanding of primary-process emotional systems of mammalian brains and minds, which provides a new empirically based infrastructure for higher levels of human theorizing.

Evolution of consciousness: phylogeny, ontogeny, and emergence from general anesthesia

Are animals conscious? If so, when did consciousness evolve? We address these long-standing and essential questions using a modern neuroscientific approach that draws on diverse fields such as consciousness studies, evolutionary neurobiology, animal psychology, and anesthesiology. We propose that the stepwise emergence from general anesthesia can serve as a reproducible model to study the evolution of consciousness across various species and use current data from anesthesiology to shed light on the phylogeny of consciousness. Ultimately, we conclude that the neurobiological structure of the vertebrate central nervous system is evolutionarily ancient and highly conserved across species and that the basic neurophysiologic mechanisms supporting consciousness in humans are found at the earliest points of vertebrate brain evolution. Thus, in agreement with Darwin's insight and the recent "Cambridge Declaration on Consciousness in Non-Human Animals," a review of modern scientific data suggests that the differences between species in terms of the ability to experience the world is one of degree and not kind.

Toward a cross-species understanding of empathy

Although signs of empathy have now been well documented in non-human primates, only during the past few years have systematic observations suggested that a primal form of empathy exists in rodents. Thus, the study of empathy in animals has started in earnest. Here we review recent studies indicating that rodents are able to share states of fear, and highlight how affective neuroscience approaches to the study of primary-process emotional systems can help to delineate how primal empathy is constituted in mammalian brains. Cross-species evolutionary approaches to understanding the neural circuitry of emotional 'contagion' or 'resonance' between nearby animals, together with the underlying neurochemistries, may help to clarify the origins of human empathy.

A flexion period for attachment formation in isolated chicks to unfamiliar peers visualized in a developmental trajectory space through behavioral multivariate correlation analysis

Attachment formation is crucial for social animals to survive in natural environments. Predisposition and imprinting mechanisms have been well documented as a process of con-specific affiliation development. However, it is unclear how neonatal stage attachment formation leads to juvenile peer sociality. Here we have developed an animal model (Gallus gallus domesticus) and a method of quantitative behavioral analysis, to study the developmental trajectory from postnatal day (P) 3 through to P21. Domestic chicks were raised in either group or isolated conditions and we focused on social behavior during a two-minute meeting context with unfamiliar group peers at P3, 7, 13, 16, and 21. Results showed that relative to isolated chicks, group reared chicks were more active behaviorally, when facing peers at P3 and that this activity declined slightly over development, up to P13. Isolated chicks that had not met any animals except humans, exhibited a major change in social behavior around P7, in particular, with increasing activity (head moving velocity and rotation velocity) and distress calls. This modulation disappeared after P13, suggesting the existence of a sensitive window for behavior toward peers around P7. These findings in isolated chicks suggest the maturation of new neuronal substrates for peer-social emotion and cognition, resulting in a new combination of behavioral modules.

Differential pattern of functional brain plasticity after compassion and empathy training

Although empathy is crucial for successful social interactions, excessive sharing of others' negative emotions may be maladaptive and constitute a source of burnout. To investigate functional neural plasticity underlying the augmentation of empathy and to test the counteracting potential of compassion, one group of participants was first trained in empathic resonance and subsequently in compassion. In response to videos depicting human suffering, empathy training, but not memory training (control group), increased negative affect and brain activations in anterior insula and anterior midcingulate cortex-brain regions previously associated with empathy for pain. In contrast, subsequent compassion training could reverse the increase in negative effect and, in contrast, augment self-reports of positive affect. In addition, compassion training increased activations in a non-overlapping brain network spanning ventral striatum, pregenual anterior cingulate cortex and medial orbitofrontal cortex. We conclude that training compassion may reflect a new coping strategy to overcome empathic distress and strengthen resilience.

Familiarity perception call elicited under restricted sensory cues in peer-social interactions of the domestic chick

Social cognitive mechanisms are central to understanding developmental abnormalities, such as autistic spectrum disorder. Peer relations besides parent-infant or pair-bonding interactions are pivotal social relationships that are especially well developed in humans. Cognition of familiarity forms the basis of peer socialization. Domestic chick (Gallus gallus) studies have contributed to our understanding of the developmental process in sensory-motor cognition but many processes remain unknown. In this report, we used chicks, as they are precocial birds, and we could therefore focus on peer interaction without having to consider parenting. The subject chick behavior towards familiar and unfamiliar reference peers was video-recorded, where the subject and the reference were separated by either an opaque or transparent wall. Spectrogram and behavior correlation analyses based on principal component analysis, revealed that chicks elicited an intermediate contact call and a morphologically different distress call, more frequently towards familiar versus unfamiliar chicks in acoustic only conditions. When both visual and acoustic cues were present, subject chicks exhibited approaching and floor pecking behavior, while eliciting joyful (pleasant) calls, irrespective of whether reference peers were familiar or unfamiliar. Our result showed that chicks recognized familiarity using acoustic cues and expressed cognition through modified distress calls. These finding suggests that peer affiliation may be established by acoustic recognition, independent of visual face recognition, and that eventually, both forms of recognition are integrated, with modulation of acoustic recognition.

Genetic identification of C fibres that detect massage-like stroking of hairy skin in vivo

Stroking of the skin produces pleasant sensations that can occur during social interactions with conspecifics, such as grooming. Despite numerous physiological studies (reviewed in ref. 2), molecularly defined sensory neurons that detect pleasant stroking of hairy skin in vivo have not been reported. Previously, we identified a rare population of unmyelinated sensory neurons in mice that express the G-protein-coupled receptor MRGPRB4 (refs 5, 6). These neurons exclusively innervate hairy skin with large terminal arborizations that resemble the receptive fields of C-tactile (CT) afferents in humans. Unlike other molecularly defined mechanosensory C-fibre subtypes, MRGPRB4(+) neurons could not be detectably activated by sensory stimulation of the skin ex vivo. Therefore, we developed a preparation for calcium imaging in the spinal projections of these neurons during stimulation of the periphery in intact mice. Here we show that MRGPRB4(+) neurons are activated by massage-like stroking of hairy skin, but not by noxious punctate mechanical stimulation. By contrast, a different population of C fibres expressing MRGPRD was activated by pinching but not by stroking, consistent with previous physiological and behavioural data. Pharmacogenetic activation of Mrgprb4-expressing neurons in freely behaving mice promoted conditioned place preference, indicating that such activation is positively reinforcing and/or anxiolytic. These data open the way to understanding the function of MRGPRB4 neurons during natural behaviours, and provide a general approach to the functional characterization of genetically identified subsets of somatosensory neurons in vivo.

The mysterious motivational functions of mesolimbic dopamine

Nucleus accumbens dopamine is known to play a role in motivational processes, and dysfunctions of mesolimbic dopamine may contribute to motivational symptoms of depression and other disorders, as well as features of substance abuse. Although it has become traditional to label dopamine neurons as "reward" neurons, this is an overgeneralization, and it is important to distinguish between aspects of motivation that are differentially affected by dopaminergic manipulations. For example, accumbens dopamine does not mediate primary food motivation or appetite, but is involved in appetitive and aversive motivational processes including behavioral activation, exertion of effort, approach behavior, sustained task engagement, Pavlovian processes, and instrumental learning. In this review, we discuss the complex roles of dopamine in behavioral functions related to motivation.

Peer attachment formation by systemic redox regulation with social training after a sensitive period

Attachment formation is the most pivotal factor for humans and animals in the growth and development of social relationships. However, the developmental processes of attachment formation mediated by sensory-motor, emotional, and cognitive integration remain obscure. Here we developed an animal model to understand the types of social interactions that lead to peer-social attachment formation. We found that the social interaction in a sensitive period was essential to stabilise or overwrite the initially imprinted peer affiliation state and that synchronised behaviour with others based on common motivations could be a driver of peer social attachment formation. Furthermore, feeding experience with supplementation of ubiquinol conferred peer social attachment formation even after the sensitive period. Surprisingly, the experience of feeding beyond the cage window was also effective to reduce the required amount ubiquinol, suggesting that peri-personal space modulation may affect socio-emotional cognition and there by lead to attachment formation.