Researchers at the University of Cambridge have recently published findings in PLoS One that demonstrate the brain's need for a period of "down-time" after a challenging cognitive task in order to return to it's resting state. Barnes and colleagues continuously monitored their subjects' brain activity using fMRI, first having the subject relax for a bit more than 9 minutes, then having the subject perform a cognitive task for 9 minutes, and finally having the subject relax for almost 19 minutes. The cognitive task employed in this experiment was the widely used "n-back" memory game, in which subjects are shown two co-varying stimuli (generally a set of numbers that appear in different locations in a grid) and are challenged to respond correctly when the set of stimuli is a repeat of the set presented "n" times ago. In the version of "n-back" used here, the numbers ranged from 1 to 4 and appeared in a 4-quadrant grid; "n" was either 1 or 2 for different subjects.
Barnes et. al. found that the brain, like the heart, does not simply return to it's resting state immediately following activity. In this experimental design, the brain took approximately 6 minutes to return to its resting state following the task; although there was no statistically significant difference in recovery times between the n=1 and n=2 subjects, the data did indicate that the brain took more time to recover when the cognitive task was more demanding. As the researchers point out in the final paragraph of the discussion, these findings help to clarify further research questions, including testing the performance of subjects engaging in a new cognitively demanding task following a previous task, but before the brain returns to its resting state. For those of us involved in education as classroom teachers or as administrators in charge of the daily schedule of classes for students, this line of research should prompt us to reflect on how we structure the use of time within the classroom, as well as how much time we afford students to return to their resting state in between classes.
Barnes A, Bullmore ET, Suckling J, 2009 Endogenous Human Brain Dynamics Recover Slowly Following Cognitive Effort. PLoS ONE 4(8): e6626.doi:10.1371/journal.pone.0006626