Individual differences in retrieval-induced forgetting affect the impact of frontal dysfunction on retrieval-induced forgetting

Introduction: Retrieval-induced forgetting (RIF) paradigms are used to investigate successful forgetting of irrelevant information. Responses to the RIF paradigm can vary substantially, but to date there has been limited investigation of the individual difference factors that contribute to RIF performances. This study investigated whether individual differences in baseline RIF ability impacted on RIF performance after temporarily induced frontal dysfunction. To examine this question, left dorsolateral prefrontal cortex (DLPFC) function was temporarily reduced using transcranial direct current stimulation (tDCS). 

Method: Fourteen individuals received tDCS (sham/active) on two separate occasions and completed a RIF paradigm within 30 minutes of receiving tDCS. 

Results: As expected, the group of individuals who demonstrated high levels of RIF after sham tDCS demonstrated a significant reduction in RIF performance after active tDCS. Unexpectedly, however, those individuals who demonstrated low or reverse RIF effects after sham tDCS showed a significant increase in RIF after active tDCS. 

Conclusions: This is the first study to show that individual differences in premorbid RIF affect RIF performance after temporary reduction in left DLPFC function. These findings suggest that premorbid RIF ability may be an important factor to consider when investigating the impact of frontal dysfunction on RIF in patient populations.