Updating processes in episodic memory

Item type:	Thesis of the University of Regensburg (PhD)
Date:	20 January 2008
Referee:	Prof. Dr. Karl-Heinz Bäuml
Date of exam:	19 December 2007
Institutions:	Human Sciences > Institut für Psychologie > Lehrstuhl für Psychologie IV (Entwicklungs- und Kognitionspsychologie) - Prof. Dr. Karl-Heinz Bäuml
Keywords:	Episodisches Gedächtnis , Theta-Aktivität , Alpha-Rhythmus , Vergessen , Elektroencephalogramm , , Episodic memory , forgetting , electroencephalogram , alpha , theta
Dewey Decimal Classification:	100 Philosophy & psychology > 150 Psychology
Status:	Published
Refereed:	Yes, this version has been refereed
Created at the University of Regensburg:	Yes
Item ID:	10698

Abstract (English)

The efficient use of episodic memory does not only require to remember new information, it also requires to forget old information. That such memory updating is part of our memory system is suggested by behavioral studies examining both contextual and intentional memory updating. The electrophysiological correlates of episodic memory updating, however, still remain elusive. To investigate ...

Abstract (English)

The efficient use of episodic memory does not only require to remember new information, it also requires to forget old information. That such memory updating is part of our memory system is suggested by behavioral studies examining both contextual and intentional memory updating. The electrophysiological correlates of episodic memory updating, however, still remain elusive. To investigate episodic memory updating, the context-change paradigm and the directed-forgetting paradigm can be used. In the directed-forgetting paradigm, subjects are cued to intentionally forget a previously learned item list and to learn a new list of items instead. In the context-change paradigm, subjects are cued to change their internal context between the learning of two lists. Both forms of cuing typically lead to forgetting of the first list and to memory enhancement of the second. The standard explanation of these effects is that forgetting and enhancement are mediated by a single mechanism: context differentiation in contextual memory updating and retrieval inhibition in intentional memory updating. In four experiments the necessity of new learning after cue presentation and the electrophysiological (EEG) correlates of forgetting and enhancement as they occur in these paradigms were explored. In both paradigms, forgetting of the first list was only observed when a second list was learned after cuing. Analysis of oscillatory EEG activity revealed that the forgetting in contextual memory updating was accompanied by an increase of theta phase coupling between scalp electrodes which is suggested to reflect the establishment of a new mental List-2 context. On the other hand, the forgetting in intentional memory updating was accompanied by a decrease of upper alpha phase coupling which is suggested to reflect an inhibitory disintegration of the to-be-forgotten information. Thus, phase coupling mediated the forgetting both in contextual and intentional memory updating, but in different frequency bands. In both paradigms, memory enhancement was accompanied by an increase in upper alpha band power which is suggested to reflect a change of encoding strategy after cuing. In sum, the present experiments revealed separate neural origins of forgetting and memory enhancement and thus point to a two-mechanism view of episodic memory updating.

Translation of the abstract (German)

Updating im episodischen Gedächtnis beschreibt das Erinnern relevanter Information und das Vergessen irrelevanter Information. Um Updating-Prozesse experimentell zu untersuchen, können das Kontextwechsel-Paradigma und das Gerichtete-Vergessen-Paradigma verwendet werden. Beim gerichteten Vergessen erhalten die Versuchspersonen nach dem Lernen einer ersten Itemliste die Instruktion, diese wieder zu ...

Translation of the abstract (German)

Updating im episodischen Gedächtnis beschreibt das Erinnern relevanter Information und das Vergessen irrelevanter Information. Um Updating-Prozesse experimentell zu untersuchen, können das Kontextwechsel-Paradigma und das Gerichtete-Vergessen-Paradigma verwendet werden. Beim gerichteten Vergessen erhalten die Versuchspersonen nach dem Lernen einer ersten Itemliste die Instruktion, diese wieder zu vergessen und sich stattdessen eine neue Liste einzuprägen. Im Kontextwechsel-Paradigma werden die Versuchspersonen instruiert ihren mentalen Kontext zwischen dem Lernen zweier Itemlisten zu wechseln. Beide Instruktionen führen typischerweise zum Vergessen von Liste 1 und zum besseren Erinnern von Liste 2. Vier Experimente sollten über die zugrundeliegenden elektrophysiologischen (EEG) Mechanismen von Updating im episodischen Gedächtnis Aufschluss geben. In beiden Paradigmen zeigte sich das Vergessen von Liste 1 nur wenn in der Folge eine zweite Liste gelernt wurde. Die Analyse oszillatorischer Aktivität zeigte, dass das Vergessen im Kontextwechsel-Paradigma mit einer Zunahme an Theta-Phasenkopplung einherging. Andererseits führte der Vergessenshinweis im Paradigma des gerichteten Vergessens zu einer Abnahme an Alpha-Phasenkopplung. In beiden Paradigmen ging die Förderung von Liste 2 mit einer Zunahme der Alpha-Signalstärke einher. Die Ergebnisse deuten somit auf unterschiedliche Mechanismen von Vergessen und Förderung beim Updating im episodischen Gedächtnis hin.

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