Abstract
Because emotions enhance memory processes and music evokes strong emotions, music could be involved in forming memories, either about pieces of music or about episodes and information associated with particular music. A recent study in BMC Neuroscience has given new insights into the role of emotion in musical memory.
Minireview
Music has a prominent role in the everyday life of many people. Whether it is for recreation, distraction or mood enhancement, a lot of people listen to music from early in the morning until late at night, especially since the invention of radio and recordings. Because of its near ubiquity, music has been identified as important in the construction of autobiographical memories and thus for making judgments about oneself and others. But which musical pieces do we remember, and how is music related to our memory? This interesting question has as yet received surprisingly little attention in the scientific literature. Several papers [1-5] have looked at the role of music in memory formation and recall of autobiographical and episodic information, and a recent paper in BMC Neuroscience in particular gives new insights into the role of emotion in musical memory [6]. Collectively, these papers emphasize the enhancing role of music and emotion on memories in various contexts, which I shall focus on in this review.
Music and memory
Musical sounds, like all auditory signals, unfold over time. It is therefore necessary for the auditory system to integrate the sequentially ordered sounds into a coherent musical perception. This series-to-parallel transformation can be considered a mechanism of working memory, which temporarily stores auditory units and combines them into a single percept (such as a sound pattern, rhythm or melody). Interestingly, there seems to be a high degree of overlap between working memory for musical stimuli and for verbal stimuli, as has been shown in recent working-memory experiments [7]. This might be one of the reasons why musicians tend to show a slightly superior verbal working memory – at least in tonal languages such as Chinese [8,9]. Recently, Sluming et al. [10] found that in musicians, compared with non-musicians, there is more gray matter in the part of the frontal cortex known to accommodate neural networks that are involved in several important working memory processes. One might thus conclude that a kind of positive transfer between musical performance and verbal memory functions takes place; in other words, that the process of learning music improves the learning of verbal tasks (see Box 1 for definitions of technical terms used in this article).
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Although hearing music is closely associated with strong emotional feelings, and although music activates the entire limbic system, which is involved in processing of emotions and in controlling memory [11-14], most studies examining musical memory have not focused on the role of emotion in this form of memory. In the foreground of these studies have been questions such as: Is there a difference between implicit (unconscious) and explicit (conscious) musical memory? Which surface parameters of music, such as timbre and tempo, are most relevant for efficiently transferring or encoding musical information into long-term memory and for retrieving it? Are the titles of musical pieces recalled better than melodies, for instrumental or for vocal music?
For example, Halpern and Müllensiefen [1] manipulated timbre and tempo in order to examine their influence on implicit and explicit memory for tunes. After encoding 40 unfamiliar short tunes, participants were asked to give explicit and implicit memory ratings for a list of 80 tunes, which included 40 that had previously been heard. To measure implicit memory, a rating of the pleasantness of old and new melodies was used, whereas to measure explicit memory the researchers used the difference between the recognition confidence ratings of old and new melodies. Half of the 40 previously heard tunes differed in timbre or tempo in comparison with the first exposure. Change in timbre and tempo both impaired explicit memory, and change in tempo also made implicit tune recognition worse. These findings support the hypothesis on which this experiment was based – that there are two different musical memory systems, one implicit and the other explicit [1]. A similar distinction has been drawn by Samson and Peretz [15]. On the basis of a comprehensive analysis of neurological patients suffering from lesions in either the right or the left temporal lobe, they concluded that right temporal lobe structures have a crucial role in the formation of melody representations that support priming and memory recognition, which are both more implicit memory processes, whereas left-sided temporal lobe structures are more involved in the explicit retrieval of melodies.
Other studies have focused on one particular aspect of musical memory, memory for musical pitch. These studies were motivated by investigations into absolute pitch (or perfect pitch), the rare ability of some people to identify or sing a musical note without relating it to a previously played note. Many researchers believe that absolute pitch is a specific kind of musical memory. However, Levitin [2] found that it was more common than previously assumed. He asked a large sample of subjects who did not have absolute pitch to sing popular songs and compared the produced pitch with the actual pitches used in the recordings of these songs [2]. Approximately 50% of the subjects sang the song in the correct pitch, at least in one or two experimental sessions. Forty-four percent were not perfect in producing the correct pitch but they were within two semitones of it. Thus, this study shows that even non-musicians might have relatively stable representations of pitch [2]. Pitch memory can be improved in non-musicians by pitch memory training and can even be enhanced by applying electrical stimulation to the left supramarginal gyrus [16,17]. Although these studies have told us some important things about pitch memory, only a few have focused on memory for longer musical pieces.
Music and memories of associated events
Autobiographical information associated with musical melodies is evoked when we hear relevant music or when we are engaged in conversation about music or episodes and events in our life in which music has been important. Hearing music associated with our past often evokes a strong 'feeling of knowing'. We have this feeling for many songs without knowing the title or text of the songs. We are, however, better at recalling the titles of the tunes we listen to (when the tunes are instrumental) than at remembering a melody by simply reading or hearing its title. The opposite pattern occurs when remembering vocals, for which the titles of the songs are much better cues than the melodies [3]. The finding of this link between text and music, which suggests that music is encoded in semantic memory like text, is of particular importance. Many researchers believe that music is encoded in the brain by the perceptual memory system, which organizes auditory information into melodies and rhythms, rather than by the semantic memory system, which encodes meaning. Nevertheless, musical information could be associated with emotional and semantic information (associative memory), either indirectly or directly, as was shown [3], even if it is not directly related to semantic information.
A more recent paper by Stefan Koelsch and colleagues [18] has elegantly shown that short musical pieces with particular characteristics can prime the semantic language memory system, thereby yielding faster and more efficient recognition of specific words. The general principle of their experiment [18] was to present target words that were preceded by either musical or sentence primes. Electrical brain responses to the target words (the N400 event-related potential, a dip in scalp electrical activity that occurs 400 milliseconds after the target word) were measured. When the musical piece was semantically related to the target word, the brain response to the target word was reduced (representing less neural activation associated with the search in semantic memory), whereas when the musical piece was unrelated to the target word, the response was enhanced. A typical musical prime for the target word 'needle' was a passage of Schönberg's String Terzett, which was written to describe musically the 'stitching' pains during the composer's heart attack. Other musical primes had been chosen on the basis of their musicological terminology; for example, the prime for the word 'narrowness' was an excerpt in which close intervals dominate. Others were chosen because they resembled the sounds of objects (such as birds) or qualities of objects (such as low tones associated with a basement, or ascending steps in pitch with a staircase) [18]. Taken together, these two experiments [3,18] demonstrate that there are bidirectional associations between the memory systems for language and melody.
A specific feature of the perceptually based music memory system is that the stored information is relatively abstract (compared with that in semantic memory), allowing recognition despite changes in instrumentation, loudness, tempo or register. Lesion studies and recent brain imaging studies [19-21] have shown that this perceptual memory system is located bilaterally in the auditory cortex (including the supramarginal gyrus). In addition, the inferior frontal and inferior temporal brain areas have been shown to be important in recognizing familiar tunes. To determine where other kinds of musical memory are stored in the brain, however, a distinction needs to be made between an episodic and a semantic musical memory system. Episodic memory for musical information is defined by Platel and colleagues [5] as "the capacity to recognize a musical excerpt (whether f