What happens when you overcome distraction and remain focused. The brain can retain its concentration. How? Science Daily (here) reports on a paper by Jacobs and Nieder in Neuron, which shows that one part of the brain ignores the distraction completely while another attends to it very briefly and then returns to the memory task at hand.
Science Daily says, “The monkeys had to remember the number of dots in an image and reproduce the knowledge a moment later. While they were taking in the information, a distraction was introduced, showing a different number of dots. And even though the monkeys were mostly able to ignore the distraction, their concentration was disturbed and their memory performance suffered.
Measurements of the electrical activity of nerve cells in two key areas of the brain showed a surprising result: nerve cells in the prefrontal cortex signaled the distraction while it was being presented, but immediately restored the remembered information (the number of dots) once the distraction was switched off. In contrast, nerve cells in the parietal cortex were unimpressed by the distraction and reliably transmitted the information about the correct number of dots.”
The paper’s highlights and summary were:
- Prefrontal suppression of distractors is not required to filter interfering stimuli
- Distractors can be bypassed by storing and retrieving target information
- Frontal and parietal cortex assume complementary functions to control working memory
Prefrontal cortex (PFC) and posterior parietal cortex are important for maintaining behaviorally relevant information in working memory. Here, we challenge the commonly held view that suppression of distractors by PFC neurons is the main mechanism underlying the filtering of task-irrelevant information. We recorded single-unit activity from PFC and the ventral intraparietal area (VIP) of monkeys trained to resist distracting stimuli in a delayed-match-to-numerosity task. Surprisingly, PFC neurons preferentially encoded distractors during their presentation. Shortly after this interference, however, PFC neurons restored target information, which predicted correct behavioral decisions. In contrast, most VIP neurons only encoded target numerosities throughout the trial. Representation of target information in VIP was the earliest and most reliable neuronal correlate of behavior. Our data suggest that distracting stimuli can be bypassed by storing and retrieving target information, emphasizing active maintenance processes during working memory with complementary functions for frontal and parietal cortex in controlling memory content.
It is interesting that this as not what the researchers expected to find. “The researchers were surprised by the two brain areas’ difference in sensitivity to distraction. “We had assumed that the prefrontal cortex is able to filter out all kinds of distractions, while the parietal cortex was considered more vulnerable to disturbances,” says Professor Nieder. “We will have to rethink that. The memory-storage tasks and the strategies of each brain area are distributed differently from what we expected.””
But I’m sure they found it made sense after thinking about it. We can look at it this way: the ventral intrapariental area is involved with the task, concentrating on the task and little else (bottom-up). The prefrontal cortex on the other hand is involved in somewhat higher level executive operations (top-down). It looks at what is happening, and as it is those researchers trying to distract me, I ignore it and carry on with the task. If on the other hand it is a big machine about to hit me, I will not ignore it and stop the silly dot test while getting out of the way. Something has to be a look-out, take note of things that are happening and decide whether to ignore distractions.