How The Brain Adapts When Goals Shift

Scientists have identified mechanisms that govern how the brain incorporates information about new situations into our existing goals, according to research recently published in Proceedings of the National Academy of Sciences.

Using brain scans of human volunteers, researchers found that updating goals takes place in a region known as the prefrontal cortex, and appears to involve signals associated with the brain chemical dopamine.

When the researchers used a magnetic pulse to interrupt activity in that region of the brain, the volunteers were unable to switch to a new task when playing a game requiring them to push a button after seeing letters pop up on a screen.

“We have found a fundamental mechanism that contributes to the brain’s ability to concentrate on one task and then flexibly switch to another task,” says Jonathan Cohen, professor in neuroscience at Princeton University and co-director of the Princeton Neuroscience Institute. “Impairments in this system are central to many critical disorders of cognitive function such as those observed in schizophrenia and obsessive-compulsive disorder.”

Existing research has shown that when new information is used to update a task, behavior, or goal, this information is held in a type of short-term memory storage known as working memory. Investigators did not know, however, what mechanisms were involved in updating this information.

To find out, Cohen’s team used functional magnetic resonance imaging (fMRI) to scan the brains of human volunteers playing a game where they pressed a specific button depending on a particular visual cue.

If the volunteer saw the letter A prior to seeing the letter X, he or she had to press button 1. But if the volunteer saw the letter B prior to seeing the X, the participant had to press button 2. The A and B served as the new information that the participant used to update their goal of deciding which button to press. Another version of the task required the same participants to press button 1 upon seeing an X regardless of whether an A or B was shown.

With the fMRI, researchers detected activity in the right prefrontal cortex during tasks that required the participants to remember whether they saw an A or a B before pressing the correct button, but not during tasks where the participant only had to press the button when prompted by an X.

These results confirmed findings from a previous study led by Cohen and published in the journal Cognitive, Affective and Behavioral Neuroscience in 2010 that used another scanning method to gauge the timing of the brain activity. Using electroencephalography (EEG), the researchers found that the prefrontal cortex showed a spike in brain electrical activity 150 milliseconds after the participant viewed the context letter A or B.

For the current study, the researchers demonstrated that the prefrontal cortex is indeed the area of the brain involved with updating working memory by sending a short magnetic pulse to the region. This pulse disrupted cortex activity at the precise time—as revealed by the EEG—the researchers suspected that the prefrontal cortex was updating working memory.

When the researchers introduced the pulse to the right side of prefrontal cortex about 150 milliseconds after the volunteers saw the A or B, the participants were unable to press the correct buttons, Cohen says.

“We predicted that if the pulse was delivered to the part of the right prefrontal cortex observed using fMRI, and at the time when the brain is updating its information as revealed by EEG, then the subject would not retain the information about A and B, interfering with his or her performance on the button-pushing task,” Cohen says.

Finally, the researchers explored their theory that dopamine—a naturally occurring chemical involved in motivation and reward among other brain functions—tags new information entering the prefrontal cortex as important for updating working memory and goals.

Cohen and his team imaged a brain region called the midbrain, which contains clusters of nerve cells called dopaminergic nuclei that are the source of most of the dopamine signals in the brain. Using high-resolution fMRI, the researchers probed the activity of these dopamine-releasing cells in the brains of volunteers engaged in the game described above.

The researchers found that the brain activity in these areas correlated both with the activity in the right prefrontal cortex and with the ability of the volunteers to press the correct buttons.

“The remarkable part was that the dopamine signals correlated both with the behavior of our volunteers and their brain activity in the prefrontal cortex,” Cohen says. “This constellation of findings provides strong evidence that the dopaminergic nuclei are enabling the prefrontal cortex to hold on to information that is relevant for updating behavior, but not information that isn’t.”

David Badre, a Brown University assistant professor of cognitive, linguistic, and psychological sciences, says the work is an important step forward in understanding how working memory is updated. Badre is familiar with the work but had no role in it.

In a commentary published online November 9 by PNAS, Badre wrote: “The mechanisms by which the brain achieves an adaptive balance between flexibility and stability remain the basis of much current investigation in cognitive neuroscience. These results provide a basis for new investigations into the neural mechanisms of flexible, goal-directed behavior.”

The research was supported by the Regina and John Scully Center for the Neuroscience of the Mind and Behavior, the National Institutes of Health, Princeton University’s R.W. Crecca ’46 Senior Thesis Research Fund for Molecular Biology, and the Kane Family Foundation.

Researchers from Virginia Tech, Harvard Medical School, Tulane University School of Medicine, the University of California, Los Angeles, and the Neuroscience Cognitive Control Laboratory at PNI contributed to the study.

Via: "Futurity"

Source: Princeton University

The Architecture Of Memory

Most of us think of memory as a chamber of the mind, and assume that our capacity to remember is only as good as our brain. But according to some architectural theorists, our memories are products of our body’s experience of physical space. Or, to consolidate the theorem: Our memories are only as good as our buildings.

In the BBC television series “Sherlock,” the famous detective’s capacious memory is portrayed through the concept of the “mind palace“—what is thought to be a sort of physical location in the brain where a person stores memories like objects in a room. Describing this in the book A Study in Scarlet, Holmes says, “I consider that a man’s brain originally is like a little empty attic, and you have to stock it with such furniture as you choose…”

The mind palace—also known as the memory palace or method of loci—is a mnemonic device thought to have originated in ancient Rome, wherein items that need to be memorized are pinned to some kind of visual cue and strung together into a situated narrative, a journey through a space. The science writer and author Joshua Foer covered this technique in depth in his book Moonwalking with Einstein, in which he trained for and ultimately won the U.S. Memory Championship. To memorize long lists of words, a deck of cards, a poem, or a set of faces, mental athletes, as they’re called, fuse a familiar place—say, the house they grew up in—with a self-created fictional environment populated by the objects in their list. In an excerpt from his book published in the New York Times, Foer describes his own palace construction:

I was storing the images in the memory palace I knew better than any other, one based on the house in Washington in which I grew up. Inside the front door, the Incredible Hulk rode a stationary bike while a pair of oversize, loopy earrings weighed down his earlobes (three of clubs, seven of diamonds, jack of spades). Next to the mirror at the bottom of the stairs, Terry Bradshaw balanced on a wheelchair (seven of hearts, nine of diamonds, eight of hearts), and just behind him, a midget jockey in a sombrero parachuted from an airplane with an umbrella (seven of spades, eight of diamonds, four of clubs). I saw Jerry Seinfeld sprawled out bleeding on the hood of a Lamborghini in the hallway (five of hearts, ace of diamonds, jack of hearts), and at the foot of my parents’ bedroom door, I saw myself moonwalking with Einstein (four of spades, king of hearts, three of diamonds).

According to Foer, in order for this technique to work, the features of the memory palace must be hyperreal, exaggerating the edges of normalcy in order to stand out in the mind. Whether the palace is a modernist bungalow or a faux-Italianate McMansion or a mobile home doesn’t matter, so long as it is memorable, which is to say, so long as it is a place.

The philosopher Edward S. Casey defines a “place”—as distinct from a “site”—as a physical location where memories can be contained and preserved. An empty lot, for example, would be considered a site—a generic, boundless locale which “possesses no points of attachment onto which to hang our memories, much less retrieve them.” By contrast, a place is “full of protuberant features and forceful vectors—and distinct externally from other places…We observe this when an indifferent building lot, easily confused with other empty lots, is transformed into a memorable place by the erection of a distinctive house upon it.”

From an architect’s perspective, the transformation of a site (or you could call it a space) into a place is a two-way process. Erecting a structure enables the space to contain memories, and the installation of memories turns that structure into a place. In his essay in the book Spatial Recall: Memory in Architecture and Landscape, UC Berkeley architecture professor Donlyn Lyndon explains, ”‘Place,’ as I understand it, refers to spaces that can be remembered, that we can imagine, hold in the mind, and consider.”

Lyndon argues that “Good places are structured so that they attract and hold memories; they are sticky—or perhaps you would rather say magnetic.” He suggests that buildings which try too hard to control the experience of the user ultimately fail to become true places. “Seeking to make each place a singular, memorable work of art often makes the insistence of its vocabulary resistant to the attachment of memories—to the full engagement of the people who use and live with the building.”

This is perhaps why, when building a mind palace, we are told to enhance and distort the standard features of our design. As we add character and color, our own emotions and reactions become the plaster between the walls of our palace and the hooks on which we hang the ace of hearts or the Prince of Wales or the breakfast cereal. Just as we usually think of memory as the property of the head, we often place emotion in the heart and reaction in the gut, and suddenly through this process, the whole physical body becomes integrated into memorization.

In another essay in Spatial Recall, Finnish architecture professor Juhani Pallasmaa asserts, “Human memory is embodied, skeletal and muscular in its essence, not merely cerebral,” later punctuating his point with a quote from Casey, the philosopher: “[B]ody memory is…the natural center of any sensitive account of remembering.”

In other words, while the mind palace technique may seem charmingly counterintuitive to the average rememberer of grocery lists, it is probably the most innate method of recall we have, if we learn how to use it. Which is, of course, why Sherlock Holmes was able to mentally reconstruct crimes in order to solve mysteries, and why Joshua Foer had a relatively short road to becoming a national memory champion.

Via: "Smithsonian Mag"