Testing, Testing

What do we know about finding out what we know?

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A National Medal of Science Pedigree

Neuroscientist Mortimer Mishkin's work was vital to the top/bottom theory.

The roots of the Theory of Cognitive Modes lie in a landmark report published in 1982 by cognitive neuroscientist Mortimer Mishkin and Leslie G. Ungerleider, of the National Institute of Mental Health. Mishkin would go on to receive the National Medal of Science from President Obama in 2010.

Widely cited in scientific circles (although relatively unknown in mainstream society), the paper reported the scientists’ research on rhesus monkeys, whose brains process visual information in much the same way as the human brain. These studies involved training the animals to recognize shape in one task and location in another: “what” and “where,” in other words. After each animal had mastered the two tasks, a part of its brain was surgically removed. Some animals had part of the bottom brain taken out whereas others had a part of the top brain taken out.

The results were dramatic: the animals that had a portion of the bottom brain removed no longer could do the shape task—and could not be taught to perform it again—but they could still perform the location task well. The animals that had a portion of the top brain removed had exactly the opposite problem: They could no longer do the location task, and could not relearn how to perform it—but they could still do the shape task well.

Many later studies, including those that relied on using neuroimaging to monitor activity in the human brain while people performed tasks analogous to the ones the monkeys had performed, led to the same conclusion: Processing in the lower portions of the temporal lobe (located in the bottom brain) plays a crucial role in visual recognition—the sense that we’ve seen an object before, that it’s familiar—whereas processing in the back portions of the parietal lobe (in the top brain) plays a crucial role in allowing us to register spatial relations.

These results naturally led to questions such as the following:

-- Why is the human brain organized into top and bottom parts, along the anatomical divide known as the Sylvian fissure (a structure first identified centuries ago, although its significance was long unrecognized)? Why not just one single, large system?

-- And more practically: What insights into human psychology might be gained from what Mishkin and Ungerleider first demonstrated with monkeys?

Many studies – often involving studying deficits that human patients had following brain damage (e.g., due to stroke) and involving neuroimaging – addressed these questions (for a review, see our book). Such research subsequently showed that the distinction that Ungerleider and Mishkin had made, between “what” (for the bottom system) and “where” (for the top), held up well.

The distinction also held up in studies of healthy people. The Harvard Group Brain Project brought normal participants into the lab to study how people who were very good at top-brain spatial skills or bottom-brain recognition skills worked with partners who had the same, or different abilities. This work eventually led to an extensive 2011 meta-analysis of the neuroscientific literature by Kosslyn, Gréogoire Borts and William Thompson – the only one of its kind, and published in American Psychologist – confirmed the essentials of the science on which the Theory of Cognitive Modes is built.

In our next post, we will begin to explore the Theory of Cognitive Modes in greater depth by focusing on Perceiver Mode. For a primer on the theory, see our first post or watch a video. To assess whether your dominant mode is Perceiver, Stimulator, Mover or Adaptor, take the online test.

Read “Two Cortical Visual Systems,” the landmark 1982 paper by Mishkin and Ungerleider.

Citations of other peer-reviewed research by Mishkin and Ungerleider, Kosslyn and others that are incorporated in the Theory of Cognitive Modes are available in the 18 pages of Notes and Bibliography in Top Brain, Bottom Brain: Surprising Insights Into How You Think.

 

 

Testing, Testing