William James stated music was no more than “a mere incidental peculiarity of the nervous system, with no teleological significance” (as cited in Dissanayake, 2009, chapter 2, p. 21). James, however, failed to recognize the significance and importance of music in our lives. Music is an important part of our surroundings. Music is ubiquitous, possibly serving an evolutionary function (see,Dissanayake,2009, chapter 2). Individuals listen to music while studying, driving, excersizing, or while relaxing at home. There are those who create and play music as well. Music even has the ability to elicit emotional responses and has been described by many to be a medium of self expression. Have you ever associated a song with an important event in your life (e.g., marriage or death)? Has a song made you cry or liven up your spirit? In addition to the subjective meaning music takes in individuals’ lives, there are physiological correlates known to arise from listening to music, such as the experience of “thrills” (Goldstein, 1980). Even with some of physiological responses to music known, the effects of music at the neurological level needs to be examined. The quote which started this paper was right in one regard—the importance of the nervous system—but not until recently have we been able to test the peculiarities of the nervous system, or of the brain, while listening to music. Specifically, this paper will examine the neurological correlates of emotional responding to music. Music and the effects it has on the brain are robust and too lengthy to explain in this short essay. This is why only pleasant and unpleasant musical effects will be examined.
Two questions will be answered in relation to music and emotional processing in the brain:
1. How does the brain respond to pleasant music?
2. How does the brain respond to unpleasant or noxious music?
Answering those questions will provide an answer as to what happens neurologicaly when one listens to music denoted as pleasing and un-pleasing. Does the brain respond the same to both, or are there separate, distinctive pathways for both?
How does the brain respond to pleasant music?
Before the advent of brain-imaging apparatuses, and before the growing trend to study neurological correlates of behavior, emotional processing of pleasant music was studied through physiological studies. Physiological studies provide an interesting starting point on our way to understanding what is happening in the brain.
When listening to pleasing music, there are certain distinctive physiological characteristics. Krumhansl (1997) found, using a polygraph, “happy” excerpts (music by Valvaidi and Alfen) induced faster breathing compared to sadness and fearful stimuli. It should be noted, however, that the sample was comprised of mostly musicians who had a liking towards the selections played (i.e., classical). In addition, listening to pleasant music can cause an increase in heart rate found through elctromyogram readings (Blood & Zatorre, 2001).Overall, physiological measurements gives us a glimpse into what happens when exposed to pleasant music. (Another study by Goldstein, 1980 provides a little more into the physiological underpinnings of what occurs with pleasant music.) Physiological correlates of pleasant music listening were explored by having participants listen to pleasant, or “thrilling,” musical selections and being injected, in a double-blind manner, with naloxne or saline to see if injections soothed self-report measures of pleasurable emotions (thrills) associated with the musical selections. Naloxne is an opiate antagonist, and attenuated pleasurable experiences, or thrills experienced, while listening to musical selections. Although this study was highly suggestive—relying on self-report measures—it did provide evidence of opiates playing a role in experiencing physiological effects. Therefore, pleasing musical selection.
Opiates can cause or inhibit “thrills” while listening to personal musical selections (Goldstein, 1980). In addition, a correlation exists between physiology and brain activation in reward processing of pleasing music (Blood & Zatorre, 2001). Research using brain-imaging techniques have found areas for reward processing active when participants listen to pleasant music. For example, Blood and Zatorre (2001) used a Positron Emission Tomography (PET) scan and polygraph to study 10 university students with at least 8 years of musical experience. Students listened to musical stimuli—selected by them—and neutral controls, which was of no significance to them. After the experiment, the students self-reported on the “chill” intensity of the stimulus. Activity was found in the left ventral striatum, dorsomedial midbrain, bilateral insula, right orbitalfrontal cortex, thalamus, and cerebellum. All of these areas have been denoted as important reward areas of the brain, and correlate with the physiological underpinnings of pleasant emotional processing (most notably the thalamus). Because PET scans do not have good spatial ability, it is difficult to determine if certain reward processing regions are active while listening to music (i.e., nucleus accumbens or other reward processing regions). Furthermore, the sample used was biased with only musicians being used and the selections played being chosen by participants.
Menton and Levitin (2005) used a sample of 13 non-musician participants to investigate. Stimuli selected were not selections picked by the participants. Pleasant music was rated and picked by a pilot study, and the same selections were scrambled to serve as the control stimuli. Furthermore, functional Magnetic Resonance Imaging (fMRI) was used to denote specific reward areas that were active while participants listened to music—most likely because of its superior spatial and temporal processing. Results obtained saw activation in the nuclues accumbens, ventral tegemental area, hypothamus, left and right inferior front cortex, orbitalfrontal cortex, anterior cingulated cortex, cerebellar vermis, and brainstem. Due to the activation of the nucleus accumbens, without an external reward seen in many drug paradigms, music served as a reward in and of itself (Menton & Levitin, 2005).
There seems to be a strong connection between music and reward; however, there are some adverse research findings. Some studies did not show activation in the nucleus accumbens or ventral tegemental area—both important areas for reward processing (Blood & Zatoore, 2001; Mitterschiffthaler, Fu, Dalton, Andrew, & Williams, 2007). Moreover, Flores-Gutierrez, Diaz, Barrios, Favila-Humara, Guevara, Rio-Portilla, and Corsi-Cabrera (2007) suggest that different brain activity occurs when participants listen to what they termed as “musical masterpieces.” In their study, by combining fMRI and EEG, a picture of activity when novices (i,e., never heard the songs before and never were musicians) listened to classical songs (Prodromides, Bach, and Mahler were composers chosen for this study) denoted as pleasant or unpleasant. Contrary to other studies (e.g., Blood & Zatorre, 2001; Menon & levitin, 2005), predominate left hemisphere activity has been denoted in the primary auditory cortex, temporal gyrus, frontal gyrus, cuneus, hypothalamus, among others (Flores-Gutierre et al., 2007; Mitterschiffthaler et al., 2007). These areas create a significantly different picture when exposed to pleasant music. It could be possible that some music does not elicit euphoric states equivalent to drug induced states. It could be assumed that the participants in the study were so novice to the musical selections that did not induce rewarding effects, or it could be the combination of equipment gives more in-depth information. Further, it could be that different musical selections induce different activity in different regions. Often, different methodologies and paradigms provide varying results, thus it is hard to know definitively what areas of the brain are active when listening to pleasurable music.
How does the brain respond to unpleasant or noxious music?
What happens physiologicaly and neurologicaly when listening to a selection that provokes fear? There are some physiological signs, which manifest, such as increases in pulse transmission and amplitude, faster breathing, increased heart rate, lower skin conductance, and finger temperature when listening to music (Krumhansl, 1997). There are also changes in the startle reflex when participants are exposed to unpleasant music (higher amplitude and shorter latencies) and activity of the corrugators muscle (Roy, Mailhot, Gosselin, Paquette, & Peretz, 2009). The most interesting, however, is what happens in the brain when exposed to stimuli meant to be un-pleasant.
When examining musical selections which are un-pleasurable, areas compensatory to pleasurable areas become active. Where some studies located reward areas active (Blood & Zatorre, 2001; Menton & Levitin, 2005), or predominate left hemisphere activation (Flores-Gutierrez et al., 2007), the opposite is true for un-pleasurable stimuli. There seems to be significant activation in the right hemisphere when exposed to fearful or negative stimuli found using EEG and fMRI (Flores-Gutierrez et al., 2007). Furthermore, areas observed to be active are: the left hippocampus, amygdale, prefrontal cortex, auditory cortex, right auditory association area cuneus, right superior frontal gyrus, and precuneus, amongst others (Blood & Zatoore,2001; Flores-Gutierrez et al., 2007;Mitterschiffthaler et al., 2007). These areas show significantly different activity than when listening to pleasurable music.
There are many areas that are active when listening to negative or un-pleasurable stimuli, but the most significant to emotional processing of negative stimuli would be the temporal and hippocampal areas of the brain (Gosselin,Peretz, Noulhiane, Hasboun, Beckett,Baulac, & Samson, 2005; Gosselin,Samson, Adolphs, Noulhiane, Roy, Hasboun, Baulac, Peretz, 2006).When listening to pleasurable music, the amygdale or hippocampal areas are not active, or there is attenuated activity (Blood & Zatoore, 2001; Flores-Gutierrez et al., 2007; Menton & Levitin, 2005; Mitterschiffthaler et al., 2007). However, the amygdale and hippocampus are important structures for processing negative emotions, and studies on patients with their amygdales removed have purported that these structures are important. Gosselin et al. (2005), examined participants who had bilateral removal of their temporal lobes. Participants were asked to listen to un-pleasurable music. Participants gave more pleasurable ratings to un-pleasant stimuli; therefore, denoting the importance of temporal lobe structures in discerning pleasurable from un-pleasurable stimuli. Congruently, similar results were found when exposing participants to music deemed as “scary” (Gosselin et al., 2006). It should be noted with previous research (i.e., Gosselin et al., 2005, 2006), brain imaging was not done concurrently while listening to stimuli or giving ratings. It would have been more beneficial to get scans of the brain while engaging in the listening task to draw more defining conclusions about the role of the temporal lobes in discerning un-pleasurable stimuli. Quite apparent is the paramount role of temporal areas in the processing negative or un-pleasurable stimuli. When these areas are absent, there are deficits in responding appropriately to negative stimuli.
Conclusion
This paper set out to answer questions on the neurological correlates of pleasurable and un-pleasurable processing in the brain. The questions have been answered as best they could in this short paper. Much of the research on emotional processing is ambiguous; there are no definitive areas active across different paradigms or methodologies for pleasurable and un-pleasurable stimuli. Yes, there are some overriding areas associated with pleasurable music listening, such as left hemisphere localization (Flores-Guiterrez et al., 2007) and the activation of reward areas of the brain (Blood & Zatorre, 2001; Menton & Levitin, 2005). Moreover, there are areas important for the processing of un-pleasurable music, such as temporal lobe structures (Gosselin et al., 2005, 2006) and right hemisphere localization (Flores-Guiterrez et al., 2007). It can be suggested, however, that when listening to pleasurable music there is activation that is comparable to receiving reward or even drugs. Conversely, un-pleasurable music activates areas of the brain important for evaluating negative stimuli. Humans do not like dissonance, and it is important that we have areas which alert us to unpleasant stimuli. Yet, due to the different paradigms and apparatuses used, it is hard to know what is happening definitively.
Some consistency in paradigm development needs to be implemented in future research. There needs to be similar song selections across experiments as well as similar brain-imaging machinery used. It would be important use apparatuses that measures both physiological and neurological correlates, as they seem to be related. Moreover, in the literature surveyed song selections were limited to classical music. To make it more ecological valid—as not many listen to classical and or popular music needs implementation to see if it has similar effects. Furthermore, what happens to healthy individuals who have an affinity for the more abrasive forms of music? By logic abrasive music is dissonant and should induce un-pleasurable effects in the brain; however, many find this kinds of music pleasurable. Hopefully, future research will explore and implement some the ideas mentioned herein.
References
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