June 20, 2014
Humans, Monkeys Share Same Neural Processes In Decision Making
Alan McStravick for www.redorbit.com - Your Universe online
The many similarities between humans and monkeys got another addition recently. It appears a new study by researchers from New York University (NYU) and Stanford University (SU) has pitted their monkey results against a 2009 study of human decision making and found both humans and monkeys experience the same neural processes when changing their minds during the decision making process. The study results were recently published in the journal Current Biology.
“The methods used in this study allowed us to see the idiosyncratic nature of decision making that was inaccessible before,” lead author for the study and assistant professor in NYU's Center for Neural Science, Roozbeh Kiani stated. The methods employed and results achieved could very well offer new insights into how we ultimately arrive at decisions as well as pointing to innovative ways to study the decision making process in the future.
Other authors on the study were Christopher Cueva and John Reppas of Stanford's Department of Neurobiology and William Newsome, of both Stanford University and the Howard Hughes Medical Institute at Stanford's School of Medicine.
The 2009 human-centric study on the neuronal processes associated with decision making uncovered changes of mind in the human participants that were, in certain conditions, more frequent, leading to quick corrections of initial mistakes. They also found the flash of activity in the neurons was more likely to occur early on in the decision making process.
Other monkey studies, which focused on a plan of action based on evidence, prior knowledge and payoff, had been methodologically limited, the research team claims. In those studies, an analysis of only one neuron at a time was conducted by scientists. After they collected their data across all individually studied neurons, the previous teams simply applied an average of the results in the hope of painting an understanding of the activity. This would be like the difference between photographic and video evidence of a rocket launch. Sure the photos would show that the craft shot into the sky, but the constantly streaming video would paint a far clearer picture for the observer.
This most recent study was able to provide that “video” observation to the researchers due to their observation of many neurons at one time. This was able to give them a more detailed and nuanced understanding of the decision making process in their study cohort of monkeys.
"Now we can look at the nuances of this dynamic and track changes over a specified period," explains Kiani. "Looking at one neuron at a time is 'noisy': results vary from trial to trial so you cannot get a clear picture of this complex activity. By recording multiple neurons at the same time, you can take out this noise and get a more robust picture of the underlying dynamics."
For their study, the NYU and Stanford researchers observed the decision making process of macaque monkeys by running them through a series of tasks while monitoring the animals' neuronal workings.
Placed before a computer screen with randomly moving dots, the monkeys were given a “Go” signal following the stimulus. After receiving the “Go” signal, the monkeys were expected to report the motion direction of the dots using their eyes to indicate direction. The researchers, using the neuronal processes recorded during the randomized stimulus, sought to predict the decisions of their individual subject monkeys. What they found was that their model was able to achieve highly accurate predictions of the upcoming decisions.
The researchers then used the exact same prediction model to study the potential dynamics at play in the monkeys' decision at different times before the “Go” signal. Confirmation of the model's predictions were able to be made by the stopping of the decision making process at arbitrary times followed by a comparison of the model predictions with the actual decisions made by the monkeys.
Much like what was learned in the 2009 human study, the monkeys' decisions were not always stable. In fact, they occasionally vacillated from one choice to another, indicating so-called covert changes of mind during the decision making process.
This study was funded in part by the Howard Hughes Medical Institute, the Air Force Research Laboratory, a Berry Postdoctoral Fellowship and a Sloan Research Fellowship.