Directed forgetting of emotional material : cognitive and neural mechanisms

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HAUSWALD, Anne, 2008. Directed forgetting of emotional material : cognitive and neural mechanisms

@phdthesis{Hauswald2008Direc-10528, title={Directed forgetting of emotional material : cognitive and neural mechanisms}, year={2008}, author={Hauswald, Anne}, address={Konstanz}, school={Universität Konstanz} }

deposit-license Hauswald, Anne Directed forgetting of emotional material : cognitive and neural mechanisms application/pdf Gerichtetes Vergessen von emotionalem Material - kognitive und neuronale Mechanismen Hauswald, Anne eng Directed forgetting refers to people s ability to intentionally forget material designated as unimportant. Two paradigms are usually used to explore this ability: The item and the list method. In the item method, stimuli are presented individually, each followed by an instruction to forget or remember the previous item. In the list method, two lists of stimuli are presented. The first list is either followed by a forget instruction or a remember instruction. Memory is tested for all items regardless of initial instruction. Directed forgetting occurs as reduced recall of to-be-forgotten compared to to-be-remembered stimuli in the item method and as reduced recall of the to-be-forgotten first list compared to a to-be-remembered first list. Although directed forgetting paradigms have been used widely, some important issues have been neglected and are less well understood: (1) Is directed forgetting material-specific? (2) Is directed forgetting modulated by emotional material? (3) What are the electrophysiological dynamics of directed forgetting?<br />Six experiments will be presented, aiming at answering these questions. Two experiments (chapter 1) investigated item method directed forgetting of complex colorful pictures. Directed forgetting has been shown with verbal material, but no previous study explored item method directed forgetting of complex and colorful pictures. Exp. 1 investigated item method directed forgetting of neutral complex pictures. Further, exp. 2 focused on behavioral and electrophysiological effects of item method directed forgetting of neutral compared to unpleasant complex pictures.<br />Four experiments (chapter 2) explored list method directed forgetting of words varying in emotional content. Although there are several studies on list method directed forgetting of emotional material, the findings are inconclusive as systematic investigations on healthy participants are missing. Thus, list emotionality was systematically varied in experiments 1-4 exploring the influence of emotion on directed forgetting. In exp. 1, both lists comprised neutral words and unpleasant words in experiment 2. In exp. 3, the first list consisted of neutral words and the second list of unpleasant words, while in exp. 4, the assignment was vice versa. Electrophysiological measures were assessed in all four experiments.<br />The experiments of chapter 1 found item method directed forgetting for neutral but not for unpleasant pictures. Successful forgetting of neutral pictures was related to enhanced electrophysiological positivity in frontal regions, which occurred during encoding of the forget instruction following neutral pictures. The lack of directed forgetting for unpleasant pictures was associated with late positivities reflecting enhanced encoding already during picture presentation and less frontal positivity during encoding of the forget instruction for unpleasant pictures. Further, regardless of previous picture valence, remember instructions evoked late positivities, which have been related to enhanced encoding processes.<br />In all experiments on list method directed forgetting, directed forgetting was found regardless of list emotionality. Moreover, memory effects of context change occurred, when the emotional content was changed between the first and the second list (exp. 3 and 4). Electrophysiologically, increased activity was found during the presentation of words that followed forget instructions compared to words following remember instructions. This activity difference occurred as late positivities, which have been associated with encoding and attentional processes.<br />These findings provide new insights for the above raised questions: (1) Directed forgetting is not restricted to verbal material but also occurs for complex neutral pictures. (2) Directed forgetting occurs for emotional and neutral words equally, while complex pictures depicting unpleasant content are exempt of directed forgetting. (3) The EEG data suggest that successful item method directed forgetting is associated with late positivities during remember instructions and frontal activity enhancement during forget instructions. In list method directed forgetting, late positivities occurred following the forget instruction.<br />Thus, the findings support a two-factor for both the item and the list method: Processes of selective rehearsal and inhibition can explain item method directed forgetting. Late positivities, which are associated with enhanced encoding, indicate selective rehearsal. These potentials occurred during presentation of unpleasant pictures and of remember instructions. Inhibitory processes are suggested by frontal positivities during forget instructions, which were particularly enhanced following neutral pictures. List method directed forgetting can be explained by attentional focusing, which is supported by the occurrence of late positivities after the forget instruction, and by memory effects of context change. 2011-03-25T09:18:51Z 2008 2011-03-25T09:18:51Z

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