SCIENTISTS UNRAVEL BRAIN CIRCUITS INVOLVED IN JOY AND SADNESS
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SCIENTISTS UNRAVEL BRAIN CIRCUITS INVOLVED IN JOY AND SADNESS.
ORLANDO, Tuesday, Nov. 5 - In new studies, scientists are unraveling the complex circuits and structures important for understanding emotions such as sadness and joy and even how individuals read emotions in a face.
Several reports reveal that young and mature women use the same circuit to feel emotions, which helps scientists understand how emotions are generated. Researchers also have found that as humans age, their physiological response to an emotional event lessens but the intensity of a felt emotion increases in response to certain stimuli. In addition, scientists have begun to sort out the separate brain structures responsible for bringing special attention to faces and for reading facial expressions. The new studies were reported today during the 32nd annual meeting of the Society for Neuroscience.
In a powerful example of how mood can influence behavior, researchers at Bowling Green State University in Ohio found that women were able to feel joy and sorrow simply from imagining the physical act of laughing and crying. "Furthermore, imagined laughter was effective at reducing sadness, and, imagined crying reduced happiness," says study author Nakia Gordon, MA. The study sheds light on how emotions are generated internally from within ourselves
In the study, 20 women were trained in performing the laughing and crying imaging tasks for three days prior to brain scanning with functional magnetic resonance imaging (fMRI). They imagined the physical movements associated with laughter and crying and rated their emotions on a scale of 1 to 9 before and after the imagery. These emotions were also induced externally by using personally meaningful musical selections.
Brain activity during these tasks showed involvement of brain areas typically associated with the generation of emotions and areas that control motor behavior. Listening to self-selected happy and sad musical selections also produced brain activity associated with emotions and music processing.
"These results are interesting because they demonstrate the connection between motor behavior and emotion," says Gordon. "Specifically, imagining the motor act of laughter and crying produced patterns of brain activity associated with emotion, but also with motor areas that were not activated when subjects imagined the motor act of walking. This might suggest that emotions are intimately linked to basic motor behavior.
Since it is believed that emotions are important for survival, this connection would support the idea that our emotional responses are not superfluous feelings but related to innate bodily processes. They also highlight the ability of mental imagery to simulate actual behavior."
Gordon says that an internally generated emotional state might emotional state might replicate more closely the various fleeting emotional states humans have throughout the course of a day, rather than those generated from processing external stimuli. Additionally, it is of considerable interest to compare and contrast how distinct emotions are represented by differential activation of brain systems. This type of localization work can help resolve where certain internal, subjectively experienced states occur within the brain.
In another new study, scientists found that the neural substrate associated with sadness is comparable in healthy girls and adults women. This substrate encompassed brain regions that we commonly refer to as the 'emotional brain.' "These findings reinforce the view - commonly held by many neuroscientists and psychologists - that primary emotions are innate and hard wired in the brain," says study author Johanne Levesque of the University of Montreal.
From a clinical point of view, these findings are very important because knowledge about the neurobiological underpinnings of emotional processing in young and healthy children is of paramount importance with respect to our understanding of affective disorders in childhood and adolescence, Levesque says. From a basic neuroscience perspective, the results support the view that the neural circuitry underlying sadness is comparable in childhood and adulthood.
In the study, ten healthy right-handed girls aged eight to ten, and twenty healthy right-handed women aged 20 to 30 were scanned using fMRI after they were instructed to react normally to a series of sad film excerpts. They had to allow themselves to become sad in response to viewing the sad film excerpts. In both girls and women, significant loci of activation were noted in brain regions having been shown, in previous functional neuroimaging studies, to be associated with sadness in healthy adults - the midbrain, ventrolateral prefrontal cortex, anterior temporal pole.
The next step of this research is to look at the neural underpinnings of other primary emotions in healthy children, to determine whether there is a specific neural circuitry associated with each primary emotion. Another goal is to identify and compare, in healthy children and adults, the brain regions correlated with the various dimensions of emotion, including experiential, cognitive, behavioral and physiological.
In another fMRI study from the same research group, scientists found that the neural circuit recruited to voluntarily self-regulate (suppress) sadness is comparable in healthy girls and adults women. This neural circuit comprises several regions of the prefrontal cortex, including the orbitofrontal cortex, anterior cingulate cortex and dorsolateral prefrontal cortex.
Girls judged that the suppression of sadness was more difficult than women did. In keeping with this, voluntary suppression of sadness was associated, in girls, with significant activation of the hypothalamus - a pivotal brain structure involved in the visceral dimension of emotion - whereas no such hypothalamic activation was noted in women. "These findings suggest that the less efficient emotion regulatory capacity seen in children may be ascribable to the fact that, in humans, the development of the prefrontal cortex is not complete until early adulthood," notes Mario Beauregard, PhD.
This study represents the first experimental attempt at delineating the neural circuitry underlying conscious and voluntary self-regulation of emotion in healthy children. First, from a phylogenetic perspective, such a circuit may implement one of the most remarkable human faculties that have emerged in the course of human evolution. At both an individual and a collective level, a defect of this neural circuitry may have disastrous psychological and social consequences, says Beauregard.
Second, from a philosophical perspective, Beauregard says that these findings suggest that humans have the capacity to influence the electrochemical dynamics of our brains by voluntarily changing the nature of our mind processes. "This discovery contradicts the materialistic-mechanistic-reductionist view that humans are biological machines completely determined by our genes, our neurons, and our environment.
These findings are clinically important because the ability to consciously and voluntarily self-regulate negative emotions is essential to a healthy psyche. Indeed, in children as well as in adults, psychological disorders, like depression and anxiety, are characterized by a chronic inability to suppress negative emotions, such as sadness and fear. Furthermore, it has been postulated that impulsive aggression and violence arise as a consequence of defective regulation of emotional response, particularly anger.
"Given that the ability to modulate emotions is at the heart of the human experience, and that a defect in this function may have disastrous socio-emotional consequences, it is essential to learn as much as possible about the neural underpinnings of this psychological function," Beauregard says. "The findings also clearly demonstrate that, as human beings, we have the capacity to consciously and voluntarily modulate the electrical and chemical functioning of our brains."
Later in life, physical declines have led to the general belief that emotional experience also slows with age, resulting in less emotional feeling. A new study finds that as humans age there is a lessening of physiological response to emotional stimuli but there is an increase in felt emotion to certain stimuli.
In the study, 30 young, middle, and old age subjects were shown pictures with varying emotional content. The middle and old age subjects exhibited smaller heart rate, skin conductance and facial muscle changes in response to the pictures compared to the young subjects. However, when subjects rated their felt emotion in response to the pictures, older subjects rated their felt emotion - happy or sad, excited or calm - as more intense than younger subjects. When comparing males and females of all age groups, the researchers found that females, as a group, tend to feel more happiness or sadness in response to the pictures than males.
"Our findings challenge the belief that people become less emotional as they age, depending on the measures used," says Donald Powell, PhD, of the Dorn Department of
Veterans Affairs Medical Center in Columbia, SC. "When looking only at physiological measures, there is a definite decline in response to emotional stimuli as one ages. However, when measuring what one perceives as their emotional response, an increase in felt emotion occurs as one ages." Powell performed the work with Luisa Prescott, PhD, also of the VA Medical Center.
He notes that classical theories of emotion have characterized emotional experience as having both a physiological and a cognitive component. Early theorists proposed that when an emotional stimulus is presented, physiological responses that are specific to specific emotions occur that are then interpreted by the brain as the feeling of happiness, sadness, fear, delight, etc. Later theorists proposed that a general physiological response occurs to a stimulus and a cognitive assessment of the stimulus then determines what emotional label is given to the response. A third theory proposes that the cognitive assessment of the stimulus occurs, which then induces the appropriate physiological response.
"Our findings suggest that these theories may not be in conflict, but may actually represent a continuum of emotional responding that one moves through as one ages," Powell says. "Young people show strong physiological responses to stimuli but a less intense sense of the labeled or felt emotion, whereas older people show less physiological responding but a more intense sense of the labeled or felt emotion perhaps resulting from a more in-depth cognitive appraisal. This may indicate that as one accumulates more life experience, and more associations with various stimuli, that this depth of cognitive memory allows a shift to be made from a dominant physiological response to a primary cognitive response. Hence, one may appear to be less emotionally responsive as aging occurs but actually experience a deeper, more intense response colored with the richness and depth of a lifetime of experience."
These findings point out the need for clinicians to consider the intensified, not diminished, emotional quality of life in older people. "Isolation, depression, loss, grief, fear and sadness may be intensely felt in the elderly, but so then are joy, delight, happiness, intimacy and dignity," Powell says "Those factors need to be given due regard when considering quality of life and what support, treatment, and care an elderly person receives and how they receive it."
The study provides insight into the experience of emotion and point out a need to further explore the changes that occur with aging, Powell says. For instance, what changes occur in the brain that allow an emotion to be more intensely felt with less physiological response? Which factors in emotional responding are conducive to positive healthy aging and which contribute to disease states, such as coronary artery disease or emotional disorders such as depression, post traumatic stress disorder, or anxiety disorders?
Finally, a new study in monkeys helps to clarify the areas of the brain that are important for reading the emotions in a face. Researchers found that the amygdala, a structure buried deep within each half of the temporal lobe, and the orbital frontal cortex, a cortical area just above the eyes, are two brain areas that are important for facial processing. They also demonstrate the different functions of these two brain areas in our abilities to read emotions in other people's faces.
Jocelyne Bachevalier, PhD, and Eugena Pixley, BA, at the University of Texas at Houston Health Science Center found that the amygdala is important for bringing special attention to faces so that they can be analyzed further. They found that the orbital frontal cortex is critical to read some facial expressions.
In many human disorders - autism, Alzheimer's disease and schizophrenia - something has gone wrong in the brain that impairs the ability to relate normally to other people. Interestingly, in each of these disorders, patients perform poorly on tasks that require them to tell the difference between faces showing different emotions. "It seems probable that this impairment in seeing emotion in faces may contribute to the general problems they demonstrate with social interactions. Thus, if we can gain a better understanding of how the brain processes emotion in faces, we may be further along in knowing what goes wrong in the brains of patients with these illnesses, and how we might develop preventions, treatments, and cures," Bachevalier, says.
In the study, the research team surgically damaged specific brain areas that have been shown to be important in other aspects of emotion, and tested monkeys for their ability to read facial expressions in other monkeys. These facial expressions included grins (signifying fear or submission), open mouths (signifying aggression), and lip smacks (repetitive kissing motions, signifying affiliation).
Normal monkeys usually look for a longer amount of time at faces and at faces showing an emotion than objects other than faces, such as a tree or a chair. For these animals, it appears that faces are more interesting to look at than objects. Monkeys with damage to the orbital frontal cortex showed the same pattern as normal animals: they look longer at faces than at objects. However, monkeys with damage to the amygdala look for the same amount of time at faces and objects. This lack of interest in faces in animals without the amygdala suggests that in monkeys, and perhaps also in humans, the amygdala is important for bringing special attention to faces so that they can be analyzed further.
The next step in this research will be to establish whether the brain areas examined are equally important for the discrimination of all facial emotions or whether the reading of some emotions will be more difficult than others after damage to these brain structures, says Bachevalier. This stems from previous work suggesting that the amygdala may be specifically important for processing fear. Also, by restricting the lesion to specific components of the amygdala and orbital frontal cortex or, better, by using infusion of drugs that can deactivate small portions of these two brain areas while the animal is performing the task, we could learn whether specific nuclei within the amygdala or specific areas within the orbital frontal cortex are more critical to our ability to read facial emotions than others, or whether the structures in the left hemisphere are more important than those in the right for this ability.
Finally, she notes, it will be essential to determine the specific mechanism which is impaired after damage to these brain areas. For example, by tracking the animal's eye movements while it is examining a picture, it would be possible to determine how the animals study the pictures. Animals with damage to the amygdala or orbital frontal cortex may have different patterns when inspecting faces. It has already been shown that people with autism, for example, show an abnormal pattern of looking at faces. Whereas normal children focus on the eyes, autistic children focus elsewhere, such as at the mouth.
