Musical memory and its relation to emotions and the limbic system

The retrieval of music rated as emotional or non emotional (arousal and valence) from long-term memory was investigated behaviourally in three experiments by recognition tasks. A neuroimaging study (functional magnetic resonance imaging (fMRI)) examined the neural underpinnings of this process and of musical long-term memory in general. The main hypothesis was that music rated as highly arousing and very positive would be remembered better and could be retrieved more easily. A first attempt was made to define structural features possibly influencing memory performance. Music is able to elicit strong emotions in the listener and many people listen to music because of the emotional richness it adds to their lives. Possibly in connection with these emotions, music can be remembered even years later. For emotional words, pictures, and events there is convincing evidence that they are remembered better and are more readily retrieved from long-term memory than non emotional ones. However, for music this relation has not yet been examined. The studies in this thesis were based on a dimensional model of emotions comprising the two dimensions “arousal” and “valence”. “Arousal” describes the excitation elicited by the music (from calming to exciting) while “valence” refers to the pleasantness of the music (from negative to very positive). Both variables were rated on five-point-scales. It was asked for the emotion elicited by the music in the listener. Participants of all experiments were non musicians with either little or no musical training. In the first experiment, 10 participants listened to 30 short musical excerpts of piano music by J.S. Bach and were asked to rate valence and arousal elicited in them by the music (encoding phase). After a delay phase of two weeks participants listened to the pieces of the encoding session randomly intermixed with 30 similar new pieces and performed a classical recognition task (recognition phase). Additionally, they again rated arousal and valence. Stimuli had been selected by pretests according to their emotional effect and were kept as similar in structure as possible for minimizing an effect of structure on recognition performance. In studies two and three shorter excerpts of symphonic film music were used as stimuli and the retention phase was cut-down to one week (experiment two) and to two days with one more encoding phase in-between (experiment three) in order to enhance recognition performance. In the second experiment 20 participants listened to 104 pieces, in the third experiment, 24 participants listened to 80 pieces. In the second experiment additionally the levels-of-processing effect in music was examined by dividing the participant group in the encoding phase into one group who rated arousal and valence (deep elaboration) and one group who rated the total length and loudness of the pieces (shallow processing). Recognition performance and emotion ratings of the recognition session, in which both groups were asked to rate emotions again, did not differ between the groups. In the third experiment, additional psychophysiological measures (skin conductance level, skin conductance response, heart rate, and breathing rate) were collected to gain a supplementary and more objective control of the rated emotions. A first detailed structural analysis of the music pieces was conducted. The main finding of these three studies was that valence ratings were significantly related with recognition performance whereas there was no such effect for arousal. This is surprising because studies about memory and emotion in other domains had found arousal to be the most important variable in recognition memory of emotional events. No levels-of-processing effect was found which confirms other studies in the musical domain. In the third study, significantly higher skin conductance levels and skin conductance responses for pieces rated with high arousal and valence compared to low arousal and valence provided a further prove that the emotions had been elicited in the listeners. Interestingly, heart rate was significantly higher for new pieces (distractors) than for old pieces in the recognition session. Concerning the structural analysis, in this pool of pieces only the structural variable “strong accents” seemed to influence recognition performance. This might be due to the selection procedure and confirms that stimuli were structurally very similar as was intended. The continous changes and improvements in design and methods with each experiment as well as the results obtained, finally allowed to conduct an fMRI study using a similar design as described above. However, this time only valence was varied from less positive to very positive while arousal was kept on an equally high level for all pieces. Participants listened to 30 target pieces in the encoding session outside the scanner and again rated valence and arousal. One day later, the recognition phase took place in the scanner where the participants listened to 60 pieces and performed the recognition task without another emotion rating. Probably due to the artificial listening situation in the scanner and a rather low recognition rate, no significant valence effect was found. The comparison of old to new pieces yielded thalamic and midbrain activity while the contrast of recognized vs. not recognized pieces showed activation in the right inferior frontal gyrus. Retrieval processes from long-term representations of music tend to engage inferior frontal regions. Like in other studies before, a mainly left-lateralized activation of the frontal and temporal gyrus as well as the cingulate cortex was found for the processing of very positive valence. Contrasting recognized positive versus recognized less positive stimuli confirmed the role of the posterior cingulate gyrus in emotion control as well as the role of frontal regions and the right temporal pole in the processing of (the valence) of complex stimuli. Taken together, more brain areas were active during the processing of the very positive stimuli. The results of the experiments provide evidence for a relation between valence elicited in the listener by music and the retrieval of this music from long-term memory. Music inducing very positive emotion is recognized better. The left inferior frontal gyrus seems to be involved in the retrieval of music from episodic memory and more (frontal and limbic) brain areas are active during the retrieval of very positive compared to less positive music.