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Michael Posner—measuring the mind

The the pinnacle of AAAS Fellow Michael Posner's career was pinning down mental process to regions of the brain. | University of Oregon

Part philosopher, part scientist, Michael Posner is exactly the sort of broad-thinking but nonetheless meticulous investigator you would expect from his body of research, a more than 50-year exploration across multiple lines of inquiry coalescing on a singular purpose: measuring the mind.

An AAAS Fellow since 1976, 79-year-old Posner’s career in psychology began with a series of experiments examining memory. Posner would later produce some of the first studies on how the brain processes written language, leading him to the study of attention, a pursuit he continues to investigate today as professor emeritus in the Department of Psychology at the University of Oregon. Posner’s work has earned him multiple accolades including the National Medal of Science, which President Barack Obama awarded him in 2009. Yet for all this, Posner says his motivation to pursue psychology was simple.

“To be able to measure a thought is intrinsically interesting. [My interest] was probably no greater than that,” he said.

Posner began to measure the mind at the University of Michigan in Ann Arbor, where he studied under Paul Fitts, a groundbreaking psychologist using reaction time to study mental processes. In the late 1960s, Posner used reaction time to reveal just how neurologically complex the reading process is, breaking down reading into a series of discrete steps: visual (seeing written language); phonological (neurologically translating written language into the much more natural spoken language); and semantic (extracting meaning). The work helped propel the study of reading for years. 

“Much more is now known about the reading network, but most of our early observations have turned out to be more or less correct,” Posner said.

Posner’s research suggested that different brain regions were activated during reading, but tracking the location of this activity and other aspects of cognition proved difficult. Lucky for Posner, the tools of his trade were evolving.

In the 1980s, Posner studied patients with damage in the parietal lobe, a large region at the middle and back of the brain. He discovered that by shifting his subjects’ attention from one place to another, he could find damage in different parts of the brain, leading him to discover that attention had different components in different brain areas. He then used Positron Emission Tomography (PET) scans to study healthy persons while performing language tasks. The PET scans, a somewhat new technology at the time, allowed Posner to see brains reacting to stimuli in real time. These results confirmed his earlier suspicions, revealing separate brain areas for the visual, phonological, and semantic aspects of reading. 

One region that showed up again and again in imaging studies was the anterior cingulate cortex, or ACC, a hook-shaped mass of tissue found below the frontal lobe. The ACC is now believed to be essential for attention, a fact partly revealed by work Posner performed with Mary Rothbart, a close colleague of Posner’s and a leading expert in early childhood development.

From the child brain, Posner went on to study the adult brain. Past a certain stage of development, many psychologists considered the adult brain more or less a done deal. But starting in the late 1990s and early 2000s, a wave of studies began to emerge suggesting that the adult brain could be trained and conditioned in much the same way we train and condition our bodies with exercise. Curious to test this idea, in the mid-2000s Posner, then at the University of Oregon, began looking into brain-training methods. It was at this time that Yi-Yuan Tang, a visiting a professor from China, approached him to study meditation.

Starting in 2007, Posner and Tang published the first of what would become a series of studies showing that subjects who meditated for just 20 minutes a day for five days showed significant improvement on a number of measures relating to attention, emotional well-being, and stress. Further studies employing functional magnetic resonance imaging scans (fMRIs) demonstrated that meditation greatly increased activity in the ACC, increased connectivity between the ACC and other brain regions, and surprisingly, increased white matter in the brain—the so-called insulation, or myelin, around nerve cells.

“We found ourselves with this tough question: How does meditation affect white matter,” Posner said.

Posner’s current research seeks to answer that question. His working hypothesis is that meditation produces a particular brain wave in the theta frequency range that fans out from the ACC to the frontal cortex, affecting an enzyme that breaks down proteins, which in turn increases connectivity and white matter, leading to profound changes in behavior and cognition.

He hopes to learn more about the ACC and the role that brain-training techniques, such as meditation, might play in the continuing development of the adult brain. At the same time, the self-described “retired” researcher will continue to indulge his inquiring mind by examining how genetic differences can affect the ACC.

Still, the pinnacle of his career was pinning down mental process to regions of the brain.

“The fact that we could localize these activities to brain tissue, those were important moments in my life,” Posner said.

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<p>The the pinnacle of AAAS Fellow Michael Posner's career was pinning down mental process to regions of the brain. | University of Oregon</p>
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Nathan Gilles