ERPs and their brain sources in perceptual and conceptual prospective memory tasks: Commonalities and differences between the two tasks

Abstract

The present study examined whether Event-Related Potential (ERP) components and their neural generators are common to perceptual and conceptual prospective memory (PM) tasks or specific to the form of PM cue involved. We used Independent Component Analysis (ICA) to study the contributions of brain source activities to scalp ERPs across the different phases of two event-based PM-tasks: (1) holding intentions during a delay (monitoring) (2) detecting the correct context to perform the delayed intention (cue detection) and (3) carrying out the action (realisation of delayed intentions). Results showed that monitoring for both perceptual and conceptual PM-tasks was characterised by an enhanced early occipital negativity (N200). In addition the conceptual PM-task showed a long-lasting effect of monitoring significant around 700 ms. Perceptual PM-task cues elicited an N300 enhancement associated with cue detection, whereas a midline N400-like response was evoked by conceptual PM-task cues. The Prospective Positivity associated with realisation of delayed intentions was observed in both conceptual and perceptual tasks. A common frontal-midline brain source contributed to the Prospective Positivity in both tasks and a strong contribution from parieto-frontal brain sources was observed only for the perceptually cued PM-task. These findings support the idea that: (1) The enhanced N200 can be understood as a neural correlate of a ‘retrieval mode’ for perceptual and conceptual PM-tasks, and additional strategic monitoring is implemented according the nature of the PM task; (2) ERPs associated with cue detection are specific to the nature of the PM cues; (3) Prospective Positivity reflects a general PM process, but the specific brain sources contributing to it depend upon the nature of the PM task.

Involvement of the anterior cingulate cortex in time-based prospective memory task monitoring: An EEG analysis of brain sources using Independent Component and Measure Projection Analysis

“…We analysed EEG data in relation to changes in voltage (ERPs) and frequency (ERSP) at a source-resolved level, using ICA and MPA. This study complemented our previous experiments where we investigated neural correlates of strategic monitoring using event-based prospective memory tasks [ 31 ].…”

“…Considering the behavioural results in the context of the series of experiments we have performed in our laboratory can help allay this concern. In the present and previous experiments [ 31 ] we used a fixed order of a control condition before the PM task condition, to avoid contaminating the control block with any long lasting intention maintenance effect evident in other studies [ 29 , 37 ]. Thus, the same semantic ongoing task was performed concurrently with a time-based PM task (current study), a perceptual event-based PM task (detection of a capitalized letter) and a conceptual event-based PM task (detection of an animal word) [ 31 ].…”

“…No changes in the perceptual PM task condition. For details see [ 31 ]. Note that the ongoing task is exactly the same across the three PM task conditions.…”

“…The imprecise spatial resolution of EEG does not allow conclusions regarding what are the neural generators of the ERP modulations reported so far in the PM literature. To deal with this spatial limitation, in a previous study we applied Independent Component Analysis (ICA) and a source localization algorithm [ 31 ] to two different event-based PM tasks, embedded in the same semantic ongoing task: one aimed at detecting perceptual PM cues (upper-case letters) and the other aimed at detecting conceptual PM cues (animal words). We found neural correlates of monitoring mechanisms with their probable brain source generators: during the PM block, ERPs time-locked to the ongoing task events showed an enhanced negativity around 200ms, with common occipital generators for perceptual and conceptual PM tasks, but also a distinct left temporal generator (i.e., located in or near BA 22/BA21) for the conceptual PM task.…”

“…The retrieval mode was operationalized as performance of an ongoing task while holding a time-based intention and target checking was operationalized as clock checks. We asked people to reset a clock every four minutes while performing a non-related ongoing task [ 31 ]. We hypothesised that some attentional resources [ 11 , 16 , 35 , 36 ] would be devoted to monitoring time–in order to identify the moment to execute the intention–instead of evaluating ongoing trials (in contrast to event-based PM tasks where ongoing trials evaluation is essential to detect the PM event).…”