The ventromedial prefrontal cortex and intention representation in prospective memory

Prospective memory (PM) consists of (i) a retrospective component, i.e. memory for the intentions and for the cues that should trigger an action, and (ii) a prospective component of monitoring and identifying these cues and the timely execution of the action. Here, we tested patients with damage to ventromedial prefrontal cortex (vmPFC; N = 5) and matched controls (N = 12) for (i) the presence of an intention superiority effect (ISE) indexing prieviliged processing of memories associated with intended actions (retrospective PM) and (ii) the cognitive cost that monitoring for a prospective cue exerts on performing an ongoing task (prospective PM). We found that control participants showed a clear ISE, which was absent in patients as a group, and individually absent in 4 out of the 5 patients whose lesions encroached on posterior vmPFC. A patient with more anterior mPFC damage had normal ISE. Conversely, all patients showed normal reaction time cost for an ongoing task when a prospective task was added, if the prospective cue was aligned with the ongoing task focus of attention. When prospective cues were outside the focus of attention of the ongoing task, one patient with additional damage to the Caudate Nucleus failed the PM task completely. The other 4 patients continued to perform within normal controls' range. Together these data suggest a unique role for sub-callosal vmPFC in PM, bolstering the implicit processing of environmental cues that are relevant for realizing future intentions. This is consistent with vmPFC's role in context-sensitive value processing based on prior experiences.