The development of a method to accurately characterize the activity of specific neuronal populations under both experimental and naturalistic conditions is described in this week’s Nature Communications. The approach provides a means for exploring human brain activity in complex social settings and the reconstruction of natural experiences from brain signals - something that has not previously been possible outside of a laboratory setting.

Approaches for recording brain activity, such as functional magnetic resonance imaging, are mostly used in experimental settings in which the influence of the natural environment is substantially reduced. Ever-changing environmental factors and social interactions that occur in real-life situations therefore pose significant limitations on the study of brain activity as it changes during real life settings. To solve this problem, Josef Parvizi and colleagues obtained intracranial brain recordings from three epileptic individuals with pre-implanted electrodes. They recorded neural activity in the patients when they were participating in an arithmetic exercise and during social conversations that include numerical content. They found that electrodes with the strongest and most selective responses during the experimental arithmetic exercise were also the ones that had the most sparse and selective activation patterns during real life settings. In other words, the authors were able to identify neural correlates of not only explicit thought processes, but implicit thought processes too.

Although the authors acknowledge that the responses recorded by the electrodes did not always follow this rule, they hope that their study will help to develop more sophisticated and less invasive methods for assessing more complex brain activity.