Maggie Fenwood
The Feeling Brain
1/31/08
I found this week’s readings interesting if not purely for the fact of the diverse body of theories that are still influencing current neuroscience. I also want to say that I found it interesting that Wager and Barrett also quote Shakespeare in their article. I found it to be a nice connection to
I felt like LeDoux gave a good account of how emotion came to be considered an important part of what goes on in the brain. He does this by starting with concepts of phrenology and then moving on the theories of the limbic system. We get a sense of the origins of neuroscience of emotion and how these theories can be adapted and cited in a contemporary setting. LeDoux emphasizes the importance of these origins but also explains their inadequacy. In this chapter her focuses on the Limbic system and where he feels it goes wrong in terms of localizing brain function. Now that we have access to neuroimaging technology we can see that the limbic system theory does not account for all of the emotion functions in the brain. So instead of localizing brain function so exclusively, LeDoux suggests that brain regions pertaining to emotion also have functions which interact with a larger system. This seems to make the most sense to me because of the interconnections and overlapping in brain activation that have been shown by MRI and fMRI. Given these assumptions LeDoux makes the conclusion that there might be more than one emotional system in the brain. He goes on to give examples of when parts of the brain are removed certain functions remain intact such as in the case of ‘psychic blindness’ where the removal of the temporal lobe leaves sight intact but inhibits the sense of fear toward psychologically significant stimuli. It seems to be a more practical way to look at a phenomenon such as this; in terms of subsystems that contribute to overall brain function. For example, vision is not solely localized in the visual cortex it is a necessary part of the system that makes seeing possible, so there can be other contributing systems to sight that is not solely located in the portion of the brain that is directly connected to the eyes.
I felt LeDoux’s chapter related to the Barret and Wager meta-analysis of neuroimaging studies in that they were also emphasizing the evidence of a more integrative system in which emotion is not just localized in one particular area. In their section on ‘specificity’ they cite a study by Wager et. al (2003) in which they found that “many of the same regions showing emotion-category effects also showed specialization for the broader category of withdrawal related affects” (p.82). The example they give is that fear-related stimuli may activate the dorsal region of the amygdala because they are part of a broader class of aversive stimuli that engage in that region. So, as well as being an important area for memory consolidation and emotion processing the amygdala is visually responsive so it can compute the significance of stimuli.
If I haven’t totally misinterpreted this information, then my question is: does this mean that emotion could be registered in a number of different regions of the brain depending on the stimulus? Wager and Barrett cite studies where very specific brain regions are activated for specific emotions, however the Phan et al. (2002) and the Murphy et al. (2003) studies do not show the all the same findings. This leads me to back to the more integrative approach LeDoux talks about. It also reminds me of the discussion we had last class in which it was brought up that it is difficult to put emotion and subsequent events caused by it into a linear order. It seems like going back and forth between stages of appraisal, cognition, reaction, etc., should be taken into account instead of a strictly linear view. So, the interaction of different brain subsystems should be taken into account as well, when trying to localize brain function. Perhaps, just as it is not so simple to pin point the order of emotion stages, it also not so clear cut where these functions occur in the brain and whether maybe different stimuli activate different regions even if the emotional reaction is the same.
2 comments:
Suzanne Ardaowski
Feeling Brain 2-4-08
I was also really intrigued by LeDoux and the Barrett and Wager article which made me question the physical parts of the brain’s connection to emotion. I have always assumed from what I have learned about the brain in the past that different parts of your brain are responsible for different actions. I never really specifically thought about that in relation to emotions, but my first gut reaction would say the same is true, that certain parts are the brain are stimulated by, create, or respond to different emotions. But as Maggie points out, from these readings it seems that science has not really proved this. Is this correct? It seems that it may be partially true, that some areas of the brain can be associated with a specific emotion, but the research is not scientifically conclusive? This surprised me. A question stemming from this is how then do people suggest to change behavior and emotion by changing your “brain circuits”? Barrret and Wagner talk about the “brain mapping” approach, is their any scientific truth to this. I was also curious about the next paragraph that states, “If emotions are psychological events like memories, then they are best thought of as products if distinct but interacting psychological processes with accompanying neural systems, and scientists might begin to design experiments to systematically map how instances of emotion are synthesized from component psychological processes that we know to be implemented in the human brain” (p.83). Without making complete sense to me, this makes perfect sense to me! But what specifically do the authors mean and has anyone done this kind of research? Lastly can we go over the limbic system and why LeDoux does not embrace this concept while other people in the field do.
It seems the vital point to be taken away from the Damasio reading is indeed this notion of the procedural character of emotion / reasoning. Cases such as those of Gage, Elliot, and patient A have in common a broken line of communication between different regions of the brain. The common failure concerns late stage decision making; in short, although other areas of the brain are highly functional, the neurological conversation, as it were, has broken down, presumably due to damage to the ventromedial prefrontal cortices and the amygdale—something confirmed by the Davidson-Irwin article. In addition, we see a similar argument put by Barrett and Wager, namely that component psychological processes conspire to engender emotions.
Of perhaps greater importance to Damasio’s argument is the way in which these cases reveal that decision making and emotional life intersect at the very least in these regions and are thus mutually effected by injury/cancer. With this in mind, localization can be reconceived as a means of identifying constituent actors in the emotional drama as opposed to a single seat of emotional life.
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