Two new mechanisms responsible for the balance between speed and accuracy in the humans' decision-making process have been identified. Researchers have brought new insight on how quickly a decision can be made and on the amount of information necessary to make it.
The research, conducted by scientists from the Medical Research Council Brain Network Dynamics Unit at the University of Oxford, was published in the journal eLife, and it explains in greater detail a type of brain wiring that could be employed in treating neurological disorders, such as Parkinson's disease.
Accuracy And Speed In Making Decisions
The main connection between accuracy and speed in the decision-making process has been subjected to research throughout an entire century, and a series of studies pointed out that a highly important role belongs to the subthalamic nucleus region in the brain.
"We wanted to address this by measuring the exact location and timing of electrical activity in the subthalamic nucleus and comparing the results with behavioral data collected while a decision-making task is being performed," noted Peter Brown, senior author of the research, from the University of Oxford.
The research team started to study the time of reaction in 11 patients who suffered from Parkinson's disease, as well as in other 18 healthy subjects. Each of them was asked to carry out a task consisting of assessing whether a cloud of moving dots was shifting toward the right or the left.
"Task difficulty was manipulated by changing the percentage of dots moving coherently in one direction (8 percent or 50 percent). Before the onset of the moving dots, subjects were either instructed to respond as quickly or as accurately as possible," noted the research.
The researchers also changed the level of difficulty of the task by modifying the number of dots shifting toward one direction. The subjects were given instructions for the task related to either accuracy or speed — these instructions were randomly alternated.
As part of this test, the researchers discovered that it was much easier for the subjects to make their decisions when the task was easier, such as the dots shifting toward one direction. The participants also made better decisions regarding the rapidity of their choice rather than accuracy.
The subjects were also instructed to stress on the accuracy of their decision. This made the decision-making process take longer and the subjects' outputs contained more errors.
Decision-Making Processes, Two Neural Paths Found
The next step of the research was understanding which networks were activated on behavioral modifications, in the context of the shift between a decision that had to be accurate and one that had to be fast. To analyze this, the researchers measured the electrical activity of nerve cells in the subthalamic nucleus among the 11 subjects who suffered from Parkinson's disease. The patients had been treated with brain stimulation prior to the experiment.
As a result of this analysis, two different neural networks were found. These networks are significantly distinct, both when it comes to their wiring and to the response to tasks.
"Increases of subthalamic nucleus (STN) low-frequency oscillatory (LFO) power preceding the response predicted increased thresholds only after accuracy instructions, while cue-induced reductions of STN beta power decreased thresholds irrespective of instructions. These findings indicate that distinct neural mechanisms determine whether a decision will be made in haste or with caution," also noted the research.