Human anterior prefrontal cortex encodes the 'what' and 'when' of future intentions

On a daily basis we form numerous intentions to perform specific actions. However, we often have to delay the execution of intended actions while engaging in other demanding activities. Previous research has shown that patterns of activity in human prefrontal cortex (PFC) can reveal our current intentions. However, two fundamental questions have remained unresolved: (a) how does the PFC encode information about future tasks while we are busy engaging in other activities, and (b) how does the PFC enable us to commence a stored task at the intended time? Here we investigate how the brain stores and retrieves future intentions during occupied delays, i.e. while a person is busy performing a different task. For this purpose, we conducted a neuroimaging study with a time-based prospective memory paradigm. Using multivariate pattern classification and fMRI we show that during an occupied delay, activity patterns in the anterior PFC encode the content of 'what' subjects intend to do next, and 'when' they intend to do it. Importantly, distinct anterior PFC regions store the 'what' and 'when' components of future intentions during occupied maintenance and self-initiated retrieval. These results show a role for anterior PFC activity patterns in storing future action plans and ensuring their timely retrieval.