SCIENCE

Scientists have made an atlas that catalogs where words’ meanings are located in the brain. (NPR)

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Discussion Ideas

• Scientists have produced what is alternatively called a “brain dictionary”, a “cortical map” or a “semantic atlas.” Can you untangle this language?
  • “Cortical” simply means it has to do with the wrinkly outer layer of our brain. The cerebral cortex is associated with higher brain functions such as memory and voluntary movement. (The medulla and the pons, near the brain stem, are responsible for involuntary or simple functions such as heart rate, respiration, and swallowing.)
  • Semantics is the study of meaning, or the relationship between signifiers (words) and the things to which they refer. In the brain, the “semantic system” describes the “group of regions that seem to represent information about the meaning of language.”

• The Nature video identifies the project as a “brain dictionary,” and NPR identifies it as a map, but we think “atlas” is probably the best term. Why?
  • The word “dictionary” doesn’t convey the geographic scope of the project, which is literally mapping the brain using 3D visualizations. The project uses a sophisticated algorithm (called PrAGMATiC—probabilistic and generative model of areas tiling the cortex) to model each section on the brain grid as a voxel. (A voxel—our word of the day!—is the 3D version of a pixel.)
  • The project has not produced a single map, but multiple maps with multiple layers. An atlas is a collection of maps.

• Watch the Nature video or read the NPR article. How was the brain experiment carried out?
  • First, researchers placed seven people in MRI scanners. MRI scanners are big tubes surrounded by powerful magnets. You lie down in the tube during the scan, and scanning technology creates magnetic fields and radio waves. These produce remarkably detailed images of the inside of your body.
  • Research subjects (people in the MRI scanners) listened to two hours of stories from The Moth Radio Hour.
  • Finally, researchers examined the MRI scans. The scans showed that blood flow to specific regions of the brain coincided with when specific words were spoken. Researchers surmised the brain was going to these regions for definitions and context.

• How did words seem to organize in the semantic atlas?
  • Words seemed to organize in “neighborhoods”—in regions with other words associated by context. Researchers grouped 12 categories:
    • ‘tactile’ (a neighborhood containing words such as ‘fingers’)
    • ‘visual’ (‘yellow’)
    • ‘numeric’ (‘four’)
    • ‘locational’ (‘stadium’)
    • ‘abstract’ (‘natural’)
    • ‘temporal’ (‘minute’)
    • ‘professional’ (‘meetings’)
    • ‘violent’ (‘lethal’)
    • ‘communal’ (‘schools’)
    • ‘mental’ (‘asleep’)
    • ‘emotional’ (‘despised’)
    • ‘social’ (‘child’)

• Could researchers point to a specific place (a cortical “lat/long”) where a word or phrase is processed for meaning?
  • No. Words never or rarely have a precise semantic or cortical “lat/long,” because words can have multiple meanings in multiple contexts. Researchers use the example of the simple word “top”: One cortical region is active when “top” refers to clothing (a button-down top), another is active when the context is numbers or measurements (top ten), while another is active when the context is places (on top of the mountain).

• Are words associated with physical senses processed in the same “neighborhood” of the brain that processes the actual sensation? For instance, might the word “stinky” be located in the neighborhood of the olfactory cortex, which processes our sense of smell?
  • Probably. Researchers report the region for words such as stripes or spots is located close to the visual cortex, where the brain processes what we see.

• What was surprising about the semantic atlas?
  • The distribution of semantically selective areas is distributed across both cerebral hemispheres—your right brain and left brain. Many previous studies have indicated that the semantic system is mostly located (lateralized) on the left brain.
  • “The organization of semantically selective brain areas seems to be highly consistent across individuals,” meaning that while there is some variation in each person’s brain, semantic “neighborhoods” are generally consistent.

• How would you apply the navigational tools that helped create the “semantic atlas” to future “brain expeditions”?
  • We love this research, and would love to see it duplicated with more subjects!
  • Study authors suggest that similar semantic neighborhoods may owe to “common life experiences of the subjects, all of whom were raised and educated in Western industrial societies. Future studies [hopefully will] include subjects from more diverse backgrounds.”
  • All the subjects listened to stories/words in English. We’d be interested in how/where different languages are processed, and how/where people who understand more than one language process or even translate words.
  • All the subjects listened to audio stories. We’d be interested to know if our brains mapped musical language differently than spoken language.
  • All the subjects were adults. We’d love a study mapping how infants and children acquire language, and how the elderly or disabled lose it.

TEACHERS’ TOOLKIT

NPR: Scans Show ‘Brain Dictionary’ Groups Words By Meaning

Nat Geo: The Brain quiz

Semantic Maps! Explore the Brain

(extra credit!) Nature: Natural speech reveals the semantic maps that tile human cerebral cortex