Anxiety Undermines Good Decision Making, Study Finds

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For people living with anxiety, decision making can be overwhelming. Now, a recent study published in The Journal of Neuroscience has uncovered exactly what’s happening in your brain when you struggle to make a decision in a state of anxiety. 

According to the study, which tested the decision-making skills of anxious rats, anxiety disengages the prefrontal cortex (PFC), a region of the brain that plays an important role in flexible decision making. Researchers injected a mild dose of an anxiety-inducing drug into one group of rats, and a placebo into another, and tested their ability to make decisions in order to reach a reward. At the same time, they monitored the activity of the rats’ PFC to determine exactly how neurons were affected by anxiety. 

Researchers found that both groups of rats performed relatively well in tests. However, any time decision making involved distractions, or the need to ignore unnecessary information, anxious rats began making more wrong choices. Researchers observed numbing of PFC neurons in anxious rats, and believe that this impairment of the PFC is what made it more difficult for the anxious rats to make decisions on the fly. 

A brain locus of vulnerability for these anxiety-induced mistakes was a group of cells in the PFC that specifically coded for choice,” explains researcher Bita Moghaddam. “Anxiety weakened the coding power of these neurons.”

While most of us experience anxiety at some point, chronic anxiety can have a major impact on many aspects of daily life, says Moghaddam. Earlier this month, a study found that people with generalized anxiety disorder were more likely to interpret harmless things as threats. Moghaddam’s work adds to those findings, showing yet another of the subtle, but potentially harmful, effects of anxiety. 

“We have had a simplistic approach to studying and treating anxiety. We have equated it with fear and have mostly assumed that it over-engages entire brain circuits,” explains Moghaddam. “But this study shows that anxiety disengages brain cells in a highly specialized manner.” 

What Caused Pangea to Break Apart?

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Emily Devenport:

There's another way to look at this question. People tend to think in terms of supercontinents forming and then breaking up again due to convection currents in the mantle, hot material rising and causing rifts in weaker spots, possibly in old sutures where the continents were shoved together—but what is really happening is that ocean basins are opening and closing, and the ocean has an active role in subduction.

The opening and closing of an ocean basin is called a Wilson Cycle. It begins when hot material rising from the mantle stretches the overlying crust. As molten material rises, a rift is formed. The rift is widened as material continues to squeeze into it. If that rifting goes on long enough, through a broad enough swath of a continent, ocean water will eventually flow into it, and an ocean basin begins to form. The upwelling of hot material will continue to rise through that thinner area of crust, pushing the plates apart. The Atlantic Ocean is an example of a basin that is well along in the Wilson Cycle; eventually subduction is going to begin at its margins, and the whole shebang will pivot.

This will happen because at the edge of continents, sediments accumulate. The weight of those sediments, combined with the weight of the water, drives the heavier, denser edge of the oceanic plate under the continental crust, which is fatter and lighter. Eventually subduction begins, and the basin begins to close again. The Pacific Ocean is an example of a basin that's closing.

If you look at a map of the oceanic rift zones, you'll notice that the one in the Atlantic is pretty much in the middle of that ocean, but the Pacific rift zone has been pulled all the way over to North America above Central America. Subduction is actively occurring on all margins of that plate.

The simple picture is that the continents are moving toward each other across the Pacific Ocean while the Atlantic Basin continues to widen. The truth is more complicated. When plates subduct, the water in the crust lowers the melting point of those rocks, so partial melting occurs. The partially melted material begins to rise through the overlying rocks, because it's less dense, and decompression melting occurs. Eventually, the upwelling of hot material forms plutons and volcanoes above the subduction zones. Fore-arc and Back-arc [PDF] basins can form. As the oceanic crust is pulled under the continental plate, island chains and other chunky bits get sutured to the edge of the continent along with sediments, making it larger. Our world is ~4.6 billion years old, so our continents are really large, now. They're unlikely to rift through the ancient cratons that formed their hearts.

What will happen if subduction begins on the eastern side of North America before the Pacific Basin closes? The margin next to California is a transform fault; it's not subducting. Will it eventually push itself under that part of North America again, or will the transform zone get bigger? The hot spot that was driving the ancient Farallon Plate under North America was eventually overridden by the southwestern states (Arizona, New Mexico, etc.) forming a rift zone. Will it continue to rift or poop out?

There are computer models predicting what supercontinent may form next. They will continue to change as our understanding of tectonic processes gets more accurate.

This post originally appeared on Quora. Click here to view.

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