Monday, January 29, 2007

response for 1/31-reconceiving what we are looking for

In the first three chapters of Descartes’ Error, Damasio relates the cases of Phineas Gage and Elliot. Phineas Gage survived an accident in which a metal rod passed through his head and Elliot had a brain tumor removed surgically. Both survived their ordeals seemingly intact with full language and motor ability. Even cognitively neither seemed to have suffered any loss of faculties. However, according to people who knew them before their traumas, both underwent complete personality change. Phineas Gage, who had been a charming man with noted leadership abilities, became socially inappropriate, prone to fits of temper and bad language, and unable to make long-term plans for himself. Elliot underwent more subtle changes. Damasio noted how remote Elliot was. His were emotional reactions nearly completely suppressed and strangely even Elliot had noticed this change in himself. Elliot participated in experiments that showed that he had the knowledge of what a good decision would be across a variety of different situations but he was unable to make advantageous decisions for himself. Both cases suggest that the disruption of a brain system disabled social and decision-making abilities in both men. Though they both had the experience and knowledge of social norms, they were unable to make use of it. Damasio asks the questions: what was disabled in both men and, even more basic, what are the usual basic steps in decision-making for human beings whose brains are intact?

In chapter 4 of The Emotional Brain, LeDoux recounts the search to identify what process in our brains accounts for our experience of emotions and ends by reorienting it. Gall had the insight that “functions [in the brain] are localized,”(p. 76), that is that each part of the brain has specific functions. However, we now know that processes are not limited to specific areas of the brain but involve networks comprised of interacting areas. Damasio describes MacLean’s limbic system theory as having enormous influence on research up until now but explains why it is inaccurate. MacLean’s theory posited that the limbic system integrated our external and internal experience and that our emotions come out of the system. LeDoux believes that an aspect of MacLean’s theory is correct: the influence of evolution (continuity between animals and human beings that Darwin proposed) is observable in the brain. Emotions are brain functions that are beneficial to our survival. But, as he says, MacLean looked too broadly at emotions in positing that all were the result of one system. Rather, “…different emotions are involved with different survival functions…” and probably involve many specialized emotional systems in the brain. (p. 103)

The article Functional Neuroimaging Studies of Human Emotions (2004) evaluates the findings of several neuroimaging studies. Phan, Wager, Taylor and Liberzon write about the findings that observed activation of specific brain structures, anticipated to be part of the neural basis of emotion, focusing mainly on limbic structures. The authors conclude that the findings suggest that certain brain structures may be involved in specific and some in more general emotion-related tasks. In the future, the authors believe more fine-tuned imaging techniques will allow researchers to identify the interconnections of brain areas in an “emotion network.”

The last article, The Structure of Emotion, looks at the evidence so far from neuorimaging studies already conducted using fMRI and PET by comparing the findings of two meta-studies.. Barrett and Wager begin the article with the question, “What are the basic building blocks of emotional life….?” and describe two central theories. The first theory (as in Paul Ekman’s work) is that there are inheritable basic categories of emotion: anger, fear, sadness, happiness and disgust. The second theory seeks to identify in the brain signs of dimensions of emotional response. The dimensions considered are: valence (pleasure/displeasure), positive or negative activation, or approach and withdrawal. To establish evidence in support of either theory, what is needed is to be able to identify patterns of activation that are consistent and specific.
It seems from this study that previous findings do not conclusively establish or rule out either of the two theories. The authors suggest that possibly a new model should be investigated, perhaps one based on “stimulus salience. “ (I’m not sure what this is.)
They end their article by recommending issues to be considered in future studies. They point out that the technology is getting much more refined, allowing much more specific study of functional regions. This may help distinguish between emotions reflected in the activity of structures of the brain. They urge researchers to study circuits rather than specific brain areas. They also point out that in looking at brain activity researchers may be observing the brain doing more than purely responding emotionally and that researchers are getting better at identifying confounding factors. Researchers need to refine their inferential process. In brain mapping they seek to evoke a certain emotional response (fear) and look to see if a certain brain structure responds (amygdala.) But whenever the amygdala is activated, is there fear?
Their final point is a fascinating one, challenging scientists to dismantle the conceptual framework for what they are looking for. Perhaps our “emotion words” (fear, sadness, happiness, etc.) do not map out to distinct events in the brain. As I understand it, the authors suggest that researchers might look at brain responses to conceive a new understanding: observe how emotions created from psychological processes play out in neural systems, then allow this understanding to reshape how we conceive of emotions.

This last article raises the issue Elizabeth and Leah were suggesting we look at next, the role of language in understanding emotion. How specific is our language for emotion really? Are even emotions we understand as easily distinguishable from others (happiness, for example), really an experience as distinct from other emotions in our actual brains as we conceive it to be?
When LeDoux posits the existence of many emotional systems in the brain does this fit within Phan, Wager, Taylor and Liberzon’s idea that there is an “emotional network”?

Sunday, January 28, 2007

Two Opposing Theories on Emotion

This week’s readings focused primarily on the location of emotions in the human brain. In Descartes’ Error, the case studies of Phineas Gage and Elliot were discussed and compared. In The Emotional Brain, various theories of brain function and emotion were highlighted including the famous limbic system by Paul MacLean. We concluded with two research studies that used neuroimaging (PET and fMRI) to test current hypotheses regarding emotion.

In Descartes’ Error, the case of Phineas Gage was examined in depth. It is one of the most fascinating examples of brain disorder. Phineas Gage was struck by a metal rod while working on constructing a railroad in Vermont. “The iron enters Gage’s left cheek, pierces the base of the skull, traverses the front of his brain, and exits at high speed through the top of the head”(Damasio 4). Gage physically recovered from his wounds but his personality was forever changed. He was fitful, impatient, obstinate, and demanding. He no longer had the ability to hold a steady job. He seemed to have no sense of morals, ethics, or responsibility. Gage’s personality change was due to a brain lesion which impaired one area of his brain but left the other areas intact.

Gage’s incredible case started a buzz in the field of brain science. Two opposing views of brain function emerged from the frenzy. The first theory stated that psychological functions, such as language and memory were not isolated to specific regions of the brain but were part of an integrated system. The second theory opposed the first theory and stated that psychological functions were found in different regions of the brain. The debate between these two theories continues to this day.

The case of Elliot occurred many years after Phineas Gage but exhibited similar effects. Elliot had frontal lobe damage and showed signs of personality change. He was able to perform normally on various memory tests used to assess frontal lobe dysfunction. He behaved and performed ‘normally’ within society. However, Elliot’s emotional state was slightly off. He was disengaged, calm, and dispassionate when recounting horrifically tragic events. He expressed no pain over the tragedy. It was clear that damage to the frontal lobe had created a blockage in Elliot’s emotional response. Do Elliot and Pineas Gage provide evidence to support the second theory of emotion? Are emotions located in specific regions of the brain? Or do these two cases support the first theory? Is the damage blocking emotional pathways connected to various regions of the brain?

The Limbic System theory of emotion is the most accepted theory today. Previous theories on emotion helped to create it. The Limbic System theory has roots in Phrenology which was the study of brain mapping. Bumps were traced on the human head dividing the brain into various functions. The theory of localization of brain functions originated out of Phrenology. Since then, numerous neuroscientists have been trying to prove (or disprove) localization. Philip Bard “carried out a systematic series of lesion studies aimed at finding just what parts of the brain are required for the expression of rage”(Le Doux 81). Bard found that the critical lesion was on the hypothalamus. He labeled it as the centerpiece of emotion.

In opposition to localization, James Papez, a Cornell University anatomist, developed the Papez Circuit. Sensory inputs flow through the thalamus before splitting into two streams. The ‘stream of thought’ is channeled to the lateral areas of the neocortex while the ‘stream of feeling’ is channeled to the hypothalamus.

The Limbic System was developed by Paul MacLean. The hippocampus was believed to receive inputs from the external world as well as from the internal environment. The emotional experience occurred when internal and external sensations were combined together.

The Structure of Emotion paper compares two approaches to the study of emotion. Meta-analyses were conducted and the results analyzed. The basic emotion approach states that certain categories of emotion are biologically basic-inherited, reflex-like modules that cause a distinct and recognizable behavioral and physiological pattern. The dimensional approach states that these same emotional categories are part of larger biological properties such as valence, arousal, positive and negative activation, approach and withdrawal. The experimenters discovered that the right and left amygdalae were activated with the emotion fear, that the forward portions of the anterior cingulated cortex were activated by sadness, and that the basal ganglia activated the emotion disgust. The experimenters concluded from their study that in order to better understand emotion in the brain “researchers need to move from studying singular brain areas to identifying circuits, because a given brain area may be involved in more than one functional circuit” (Feldman Barrett & Wager 83). The opinions expressed in this research paper belong to the first theory that emotions are not isolated to specific regions of the brain but are a series of integrated systems.

The Functional Neuroimaging Studies of Human Emotion uses PET and fMRI to test various hypotheses about emotion. They found that the amygdala was critical to fear-related processing; the medial prefrontal cortex is involved in emotion-related decision making and emotional self-regulation, the insula is the brain’s alarm center that combines internal somatic cues with emotional experience. The experimenters concluded that some regions of the brain are involved in specific emotional tasks while others are involved in more general emotional tasks. The opinions expressed in this research paper belong to the second theory that emotions are found in different regions of the brain.

This week’s readings highlighted and discussed the two basic theories on emotion and provided research to back up both sides of the debate. However, the debate does not seem to be resolved and we do not seem to be any closer to knowing how emotions function in the brain.

Damasio, A. (1994). Descartes’ Error: Emotion, Reason, and the Human Brain. New York: Penguin Books.

Le Doux, J. (1996). The Emotional Brain: The Mysterious Underpinnings of Emotional Life. New York: Simon & Schuster.

Feldman Barrett, L. & Wager, T.D. (2006). The Structure Of Emotion: Evidence From Neuroimaging Studies. Current Directions in Psychological Science, Vol. 15, pp.79-83. http://www.columbia.edu/cu/psychology/tor/

Response to 1/31 readings

This weeks reading is composed of detailed literature that illustrate how scientist have been trying to map the brain. There has been much focus on trying to match specific elements of the human mind, such as memory and emotions, to specific regions of the brain. This has been accomplished by studying individuals who have had brain trauma or by inducing trauma with brain lesions and trying to match up the mental defect with the location of the brain damage.

More recent advances in neuroimaging have provided scientist with fMRI and PET scans to monitor brain activity in the presence of stimuli. An fMRI measures increases in cerebral blood flow in specific regions, which may not be caused by metabolic demands as it initially appears to be, but instead driven by the presence of neurotransmitters such as glutamate. PET scans on the other hand use a radioactive isotope that decays over time and releases positrons that are detected through out the body.

In the review article “Functional Neuroimaging Studies of Human Emotions” they use these methods to determine if there are patterns of brain activation when they elicit different emotions with a range of emotional tasks. Though out the article they summarize how specific regions are active when specific emotions are induced. The amygdala for instance is shown to be involved in “fear-related responding” where it is the most active when participants have been shown fearful faces, even if they are unconscious of the fact that they are seeing fearful faces. I wonder though how the researchers can be so certain that just by having the participants classify the faces by gender rather than emotion that they are assuring unconscious perception of the facial expressions. Yet from their technique they deduced that perhaps the amygdala might be responsible for signaling a threat instead of evoking fear. The description of their results brings to mind how only certain areas of the brain, and even certain areas of the amygdala are activated when stimulus is conscious or unconscious in the subject. There seems to be conflicting evidence around whether if the amygdala is under a “top down control” where activity in this region is dependent on the amount of attention the participant pays to the stimuli and hence would help define its precise role in the emotion fear.

My problem with reading this article is that it brings to light the difficulty with identifying a specific region as being responsible for a particular mental faculty. As stated in the conclusion of “The Emotion of Fear”, researchers need to put less energy in identifying a specific region with a specific function, and more with identifying circuits in the brain as they run through specific brain regions. As it was seen with Phineas Gage and later Damasio’s patient Elliot, it was almost impossible to locate the specific problem that Elliot had when it came to decision-making. That might be why doctors thought that the problem was not physical but instead psychological. It was obvious that the tumor had caused brain damage in a general location, but his actual mental defect was difficult to locate as it seemed that somewhere along the decision making process Elliot lacked a tool needed to make a decision that was in his best interest. As the third chapter of Damasio’s story illustrates, it was a frustrating task to pinpoint Elliot’s problem with the use of tests commonly used by psychologists. It seemed that the tests were unable to properly identify the problem he was having with real life scenarios, hence making his case hard to prove as they attempt to show it is a physical disability.

What Damasio did conclude was that Elliot had a “reduction in emotional reactivity and feelings”(p.51) that effected his reasoning and decision making processes. This very concept goes against some basics in western philosophy such as the difference between reason and emotions. What I need to understand now is how emotions help us make proper decisions when all this time I thought it would inhibit my ability to make decisions.