Research Article: Competitive Semantic Memory Retrieval: Temporal Dynamics Revealed by Event-Related Potentials

Date Published: February 22, 2016

Publisher: Public Library of Science

Author(s): Robin Hellerstedt, Mikael Johansson, Sabine Windmann.

http://doi.org/10.1371/journal.pone.0150091

Abstract

Memories compete for retrieval when they are related to a common retrieval cue. Previous research has shown that retrieval of a target memory may lead to subsequent retrieval-induced forgetting (RIF) of currently irrelevant competing memories. In the present study, we investigated the time course of competitive semantic retrieval and examined the neurocognitive mechanisms underlying RIF. We contrasted two theoretical accounts of RIF by examining a critical aspect of this memory phenomenon, namely the extent to which it depends on successful retrieval of the target memory. Participants first studied category-exemplar word-pairs (e.g. Fruit—Apple). Next, we recorded electrophysiological measures of brain activity while the participants performed a competitive semantic cued-recall task. In this task, the participants were provided with the studied categories but they were instructed to retrieve other unstudied exemplars (e.g. Fruit—Ma__?). We investigated the event-related potential (ERP) correlates of retrieval success by comparing ERPs from successful and failed retrieval trials. To isolate the ERP correlates of continuous retrieval attempts from the ERP correlates of retrieval success, we included an impossible retrieval condition, with incompletable word-stem cues (Drinks—Wy__) and compared it with a non-retrieval presentation baseline condition (Occupation—Dentist). The participants’ memory for all the studied exemplars was tested in the final phase of the experiment. Taken together, the behavioural results suggest that RIF is independent of target retrieval. Beyond investigating the mechanisms underlying RIF, the present study also elucidates the temporal dynamics of semantic cued-recall by isolating the ERP correlates of retrieval attempt and retrieval success. The ERP results revealed that retrieval attempt is reflected in a late posterior negativity, possibly indicating construction of candidates for completing the word-stem cue and retrieval monitoring whereas retrieval success was reflected in an anterior positive slow wave.

Partial Text

Memories that are associated with a common retrieval cue are reactivated and compete for retrieval when the shared cue is presented. An everyday-example of such competitive cued recall is when someone asks you about your friend’s address. In this situation, the memory of her current address, the target-memory, and memories of previous addresses, competitors, will compete for retrieval. Memory research has suggested that the ability to retrieve the currently relevant target-memory comes at a cost, namely forgetting of the competing memories [1]. The phenomenon that competitive retrieval causes forgetting of related memories is referred to as retrieval-induced forgetting (RIF; for reviews see [2–4]. There is an on-going debate regarding the cognitive mechanisms underlying RIF. The associative blocking account holds that retrieval of the target memory strengthens the association between the target memory and the retrieval cue. The next time the retrieval cue is presented the target memory is more likely to be reactivated than the competitors given that it has a stronger association to the retrieval cue. In this way, the associative blocking account proposes that successful target retrieval causes blocking of competing memories in ensuing retrieval situations involving the same retrieval cue [4]. Another theory, the inhibitory control account [1] has challenged the associative blocking account. According to this theory, inhibitory control is recruited to inhibit currently irrelevant competing memories in order to facilitate retrieval of the relevant target memory. In a previous study, we investigated the ERP correlates of competitor activation and the role of this process in RIF [5]. We here continue this line of research by examining the role of target retrieval for RIF with behavioural and electrophysiological methods. The reason for investigating the relation between target retrieval and RIF is that the two earlier described theoretical accounts of RIF have opposite predictions regarding the relationship between target retrieval and RIF; more specifically, concerning the role of target retrieval success.

The data are available as S1 Dataset.

The phenomenon that competitive retrieval can cause forgetting has been intensively studied for the last 20 years, but there is still an on-going debate of whether such forgetting is caused by associative blocking or inhibition. The present experiment contrasted these two theoretical accounts by investigating the extent to which RIF is contingent upon target retrieval by employing behavioural and electrophysiological methods. Besides investigating the neurocognitive mechanisms underlying RIF, we extend previous literature by isolating the ERP correlates of retrieval attempt and retrieval success in a semantic competitive-retrieval task.

The present study investigated the time course of competitive semantic retrieval and the neurocognitive mechanisms underlying RIF, in particular the role of target retrieval. The behavioural results replicate previous findings and suggest that RIF is independent of target retrieval. The ERP results are however inconclusive regarding the role of target retrieval in RIF. Besides informing theories of forgetting, the present study also isolated the ERP correlates of retrieval attempt and retrieval success in a competitive semantic retrieval task. Retrieval attempt gave rise to an LPN effect whereas retrieval success was evident in a PSW effect. Furthermore, we compared ERP correlates of retrieval success from semantic and episodic memory. The results suggest that similar cognitive processes are involved in retrieval from these two declarative long-term memory systems.

 

Source:

http://doi.org/10.1371/journal.pone.0150091