On the role and nature of retroactive interference in anterograde amnesia
Recent research has elucidated significantly improved delayed recall in patients with severe anterograde amnesia following an unfilled as opposed to a filled retention interval. Such findings are of great interest as they suggest that some anterograde amnesiacs are able to retain material for much longer than usual when Retroactive Interference is kept minimal. The research thus provides a novel cognitive hypothesis for the severe forgetting in anterograde amnesia, namely a greatly heightened susceptibility to Retroactive Interference. The aim of this thesis was to further examine such phenomenon and hypothesis. More specifically the main aim was to (a) investigate which cognitive conditions are required for a benefit of minimal Retroactive Interference to emerge in anterograde amnesiacs; and thus how specific their susceptibility to Retroactive Interference is, and (b) which cognitive processes underlie the benefit of minimal Retroactive Interference in such patients. A secondary aim was to review and further explore Müller and Pilzecker’s (1900) original research and theory of Retroactive Interference in forgetting in healthy people, to investigate the effects of Retroactive Interference on age related memory decline as well as to examine potential neural correlates of the benefit of minimal Retroactive Interference. Various samples of anterograde amnesia patients (Focal injury and MCI) and healthy participants were tested by means of a range of experimental manipulations in order to explore these questions. The research elucidated that any material or distraction (‘diversion Retroactive Interference’) had to be removed during the delay interval for anterograde amnesiacs to show improved delayed recall. Moreover the results of this thesis strongly suggest that minimal Retroactive Interference allows for improved Long Term Memory formation in at least some anterograde amnesia patients. These two main findings were also made for the healthy participants, albeit to a greatly reduced extent. In conclusion, the present research provides further and novel detailed evidence for a ‘diversion’ Retroactive Interference hypothesis of forgetting in pathological and normal forgetting alike.