Changing Emotional Responses By Direct Suppression Of Unwanted Memories

We have many emotional memories.When negative memories invade consciousness involuntarily,we experience negative emotions.Direct suppression is a method that purges intrusive memories from consciousness when the memory cue is present.In the mental process of direct suppression,individuals try to stop the process of memory retrieval,prevent unwanted memories from entering the mind,or limit the duration of unwanted memories in consciousness.Hence,direct suppression may relieve negative emotions aroused by negative intrusive memories.The neural architectures of the direct suppression process are similar to that during some ways of emotion regulation,such as emotion suppression.Therefore,there may be an unexplored link between direct suppression and emotion regulation.However,few previous studies explored the changes of emotional response brought by direct suppression.In study 1,for exploring whether direct suppression of unwanted memories impacts emotional response to the suppressed memories(target),we used TNT(Think/No Think)paradigm and EEG recording.We first asked participants to learn “neutral word(cue)-negative picture(target)” parings.Then,participants needed to recall(Think)or not to recall(No-Think)the target when the cue is presented.At each trial,participants were asked to report the frequency of the target memory intrusion.Some cues didn’t appear at this stage(Baseline condition).After that,participants had to assess emotional valence of the targets.Finally,memory test was performed.No effect is found on emotional valence.And event-related potentials(ERPs)show that there is no difference among Think,No Think and Baseline on P2(230~280ms),P300(300~400ms)and LPP(500~700ms)amplitudes which reflect emotional response.Besides,the forgetting of the suppressed memory is proved by results on recall accuracy and reaction time.The result on P2(150 ~ 200ms)amplitudes which reflect trying to retrieve memories and LPP(450~650ms)amplitudes which reflect retrieving memories show that Think is larger than No-Think.And No-Think enhances N2(250~350ms)amplitudes which reflect response inhibition.The intrusion frequency under Think is higher than No-Think.And the difference of LPP amplitudes between Think and No-Think is positively related to the difference of intrusion frequency.These results prove that the direct suppression and memory retrieval have been successfully performed,and the negative results on emotional response are reliable.In study 2,we aimed to explore whether direct suppression of unwanted memories impacts emotional response to negative or neutral extraneous stimulation.The procedure included the learning phase,the TNT phase,and the post-test phase.The learning phase is the same as that in study 1.In the TNT phase,we presented negative or neutral extraneous pictures after two consecutive Think or NoThink trails and asked participants to assess their emotional valence.Similar to study 1,participants had to report the frequency of the target memory intrusion.To explore whether the direct suppression has a lasting effect on the emotional response to extraneous stimulation,we asked participants to assess the emotional valence of the extraneous pictures again which appeared in the TNT phase.The EEG signals were recorded during TNT and post-test phases.Behavior results show that the emotional valence of neutral extraneous stimulation under No-Think condition is more positive than Think condition in the post-test phase,while there is no significant difference between Think and No-Think in the TNT phase.There is no effect on negative extraneous stimulation.ERPs results show that there was only the main effect of emotion on P2(210-260ms)and P300(330-450ms),indicating that the negative stimuli attract more attention than neutral stimuli.In both TNT phase and post-test phase,the neutral extraneous pictures under No-Think condition induce bigger LPP(700~900ms)in the parietal area than Think condition,indicating the higher emotional arousal,while no significant results are found on negative extraneous pictures.Furthermore,in TNT phase rather than post-test phase,the neutral extraneous pictures under No-Think condition enhance N2(225~300ms)in left frontal area,and this effect can be also observed on 300~1000ms time window.We consider this result reveals the left frontal lobe may be involved in the inhibition process of neutral extraneous stimulation after direct suppression of unwanted memories,and this inhibitory processing may explain how the direct suppression impact emotional response to neutral extraneous stimulation.And we also verify the direct suppression and memory retrieval have been successfully performed in study 2 by intrusion frequency,N2 and LPP results which is similar to that in study 1.In conclusion,we find that(1)direct suppression can weaken the memory trace of the suppressed negative content,but cannot change its emotional response;(2)direct suppression of negative memories has a positive effect on the emotional response to neutral extraneous stimulation compared to memory retrieval.Our study adds empirical results to the research on the relationship between direct suppression and emotion regulation.And our results may provide ideas for the interpretation and treatment of emotional symptoms in posttraumatic stress disorder.