How the Brain Handles Different Goals

The best-laid plans: How we update our goals based on new information

Princeton University researchers have identified mechanisms that govern how the brain incorporates information about new situations into our existing goals…. updating goals takes place in a region known as the prefrontal cortex, and appears to involve signals associated with the brain chemical dopamine. …”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,”

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.

….. 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.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

“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,”

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.  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.”

“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.”

More information: The paper, “Role of prefrontal cortex and the midbrain dopamine system in working memory updating,” was published Dec. 4 by the Proceedings of the National Academy of Sciences.