What is the Angular Gyrus?

April 4, 2011 at 3:53 PM

What is the Angular Gyrus?

Paulina Kulesza QC ’11 and Jim Stellar

Paulina is a Communication Disorders Student who participates in a small ongoing seminar with me and some folks that tries to look at what are some of the brain structures that might underlie learning from experience.  We see this effort as being like the new field of Neuroeconomics where value and choice are considered.  But it is more preliminary, less focused about the monetary price of something, and more focused on what one makes out of experiences such as undergraduate research and how those experiences might affect the choice of major or deepen one’s commitment to an academic discipline. 

One of the recent discussions concerned this brain area and its role in thinking about experience.  So, I asked Paulina to first introduce us to the area and some of the thinking about it.

 

The angular gyrus is located in the parietal lobe of the brain. It is situated by the posterior (back) and superior (or top) side of the temporal lobe.  It is next to the famous Wernicke’s area, which is thought to be the place where auditory input gets represented as the words we recognize.  Brain damage in the Wernicke’s picture1

area, particularly on the left side of the brain in a right-handed patient deprives the patient of the power of understanding spoken language. It also deprives the patient of the power of understanding written language as visual input through the angular gyrus brings those written forms into the Wernicke’s area.  All of this contrasts with brain damage to the Broca’s area which results primarily in a loss of the ability to speak (or write), leaving understanding relatively intact.

When describing the angular gyrus in relation to language and understanding, the name that comes to mind is that of Dr. V. S. Ramachandran. who is the director of the Center for Brain and Cognition at the University of California, San Diego.  He has indicated that the angular gyrus is partially responsible for metaphor comprehension. He has conducted experiments on right handed patients who had damage to their right angular gyrus and whose speaking and comprehending English skills were largely unaffected. In these patients Dr Ramachandran found that they had trouble understanding double meaning of metaphors, while not having any issues grasping their literal significance.  What was interesting about that finding was the fact that if pressed, they could contrive wilde interpretations of metaphors, that would not be accurate.  An example is the concept of qualia, which are the sensations you are conscious of, like being poked with a needle and being conscious of that pain.

 

Fascinating, but how does this relate to experiential education?

 

According to Ramachandran, you cannot have the concept of self without qualia and you can not have qualia without self.  You can not understand one without the other. He believes that to fully explain these concepts you must tackle them one at a time and first answer the question of how do neurons instantiate meaning, which is the “holy grail” of neuroscience. Ramachandran also argues that the angular gyrus, the wernicke’s area and the supramarginal gyrus, which are all unique to humans  and other structures of the brain act conjointly to generate your sense of self. You also need the sense of self to develop metacognition, which is knowing about what you have learned. This brings us to experiential education.  Thanks to metacognition, you can take these experiences you have learned during various internships, service learning events or any other experiential learning events you have attended and talk about your experiences. You can share what you have gained from working at a law firm over the summer, from building a house for Habitat for Humanity or for example shadowing a Speech Language Pathologist. You can take this knowledge you have gained and apply it to your life and future career and academic life.

 

Very cool, but let’s take one more step and talk about synesthesia, the experience of seeing colors when you hear music or experiencing numbers that are written in black type but are seen in colors.

 

The angular gyrus aside from being linked to abstract numerical cognition is also concerned with cross-modal association.  As we said before, patients with lesions in the AG have problems with non-literal meaning or words, more specifically metaphors. Although at first it might seem a bit unlikely, metaphors are not arbitrary. Ramachandran has suggested that they are event linked to synesthesia, which is cross-wiring of senses. For example, synesthetic metaphors like “ loud shirt” are directional like synesthesia itself. What I mean by that is that they are usually more one direction than the other.  It was suggested that the reason for that is that these rules result from strong anatomical constraints, which permit certain types of cross-activation and not others.

 

What we took from this exercise is that the very brain area that ties words to ideas, the angular gyrus, may well be the place where we use words to reflect on experience.  For example, if we were to build a service-learning program of experiential education, research has shown that without reflection the service experience is less likely to be seen as a part of the student’s major and career interests and maybe just something nice to have done while going through college.  But if knowledge gained from experience is at least partially implicit, as some have argued, then reflection helps to bring that implicit knowledge to a high level of consciousness where it can be integrated with other forms of academic knowledge.  So perhaps a student majoring in economics engages in service to homeless people.  After enough reflection and other discussion (e.g. presentations on the causes of homeless by experts), that student may begin to see the economic factors at work and implications for society.  Thus the economics major is no longer separated from the act of service and comes to nuance and maybe deepen the passion for the study of economics.  Maybe that reflection involves the angular gyrus even if the passion involves another brain area.  Someone should look.

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Brain Networks: Blog 1 – The Default Mode Network
1 Comment

One Response to “What is the Angular Gyrus?”

  1. Pamela Rigg says:

    The fact that the angular gyrus is proportionately much larger in hominids than other primates, and its strategic location at the crossroads of areas specialized for processing touch, hearing and vision, leads Ramachandran to believe that it is critical both to conceptual metaphors and to cross-modal abstractions more generally. However, recent research challenges this theory

    Research by Krish Sathian (Emory University) using functional magnetic resonance imaging (fMRI) suggests that the angular gyrus does not play a role in creating conceptual metaphors. Sathian theorizes that conceptual metaphors activate the texture-selective somatosensory cortex in the parietal operculum.[2] Sathian stated that “I don’t think that there’s only one area for metaphor processing…several recent lines of research indicate that engagement with abstract concepts is distributed around the brain.”[3] Vilayanur Ramachandran commented that“the authors have paved the way” to study how different brain regions communicate. “This is a very ingenious and elegant approach to the problem.”[4]

    In Montessori education for the child 3 – 6 years old (a lot of experiential learning there!) the AG is seen as coming to play in the interconnection of touch, hearing and vision as found in the “sandpaper letters” as the child feel, says the sound of the letter, and sees the letter simultaneously! The sandpaper letters, a century before fMRI, functioned to maximize the AG processing center of the brain!

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