Friday, October 31, 2008

Article 3-Music-educed mood, Article 4-Intensely pleasure response..

University of Toronto
Course: MUS 2122H: Music and the Brain - Fall 2008
Instructor: Dr. Lee Bartel
Student: Maddie

Portfolio: reference, review, reflect and report.


Article 3 “Music-induced mood modulates the strength of emotional negativity
bias: An ERP study.”
Neuroscience Letters. 28 August 2008
by: Jie Chen, Jiajin Yuan, He Huang, Changming Chen and Hong Li

Article 4 “Intensely pleasurable responses to music correlate with activity in
brain regions implicated in reward and emotion.”
The National Academy of Sciences. September 2001.
by: Anne J. Blood and Robert J. Zatorre
Montreal Neurological Institute, McGill University, Montreal

SUMMARY: Article 3

Aim of the study:
Chen, Yuan, Huang, Chen and Li set out to investigate the effect of music-elicited moods on the subsequent affective processing through a music-prime valence categorization task. This in turn would also investigate whether the processing bias of the brain for negative stimuli is modulated by mood changes in normal individuals.

The neural responses to negative images would be more intense than to positive images, irrespective of music primes. It was also predicted that the strength of emotional negativity bias, as indexed by difference ERRs between negative and positive images, would be increased with negative music prime than positive music prime.

The study used negative (sad) and positive (happy) music pieces, which were believed to elicit a wide range of powerful emotional states. They were used as priming stimuli to induce negative and positive moods. Emotional pictures were used as task-relevant target stimuli. The pictures were selected from the native Chinese Affective Picture System (CAPS) and the mood-inducing musical pieces were selected from the Chinese classical music pool more familiar with Chinese participants, to better guarantee the effectiveness of mood inducement.

Volunteers who participated in the study:
· 12 native Chinese students, 7 women and 5 men, aged 20-25 years.
· All were healthy, right-handed, with normal or corrected to normal vision and audition, and reported no history of affective disorder.

The stimulus material consisted of 7 blocks of 232 prime-target pairs, in which music excerpts served as primes and pictures as targets, and these pairs were divided into four experimental conditions:
· 58 = negative music as prime and negative picture as target.
· 58 = negative music as prime and positive picture as target.
· 58 = positive music as prime and positive picture as target.
· 58 = positive music as prime and negative picture as target.

Picture target consisted of 116 emotionally negative pictures and 116 emotionally positive pictures.
· Volunteers were seated in a quiet room in front of a computer and participated in 12 practice trials (with 3 trials under each condition) to familiarize them with the tasks.
· Electroencephalography (EEG) was recorded from 64 scalp sites.
· EEG activity for correct response in each valence condition was overlapped and averaged separately.
· To break down this interaction, the research team compared the average amplitudes elicited by positive and negative pictures for negative and positive priming conditions, respectively. Negative images elicited more negative deflections than the positive images.
· The difference between negative and positive images was larger with negative musical primes than with positive musical primes during an interval of 500-550 ms.
· The amplitude differences between negative and positive pictures were largest at LEFT FRONTAL SITES.

The study concluded that:
· The processing bias for negative over positive stimuli, as termed as emotional negativity bias, exists stably under different emotional contexts, and the strength of bias might be influenced by individuals’ mood states.
· The findings also provided evidence that the emotional negativity bias occurred not only at early stage of features detection, but also in later cognitive and memory-related stages, independent of music-induced mood states.
· Moreover, the strength of this bias was modulated by individuals’ mood states at each step of the information-processing stream, and negative mood intensified the neural sensitivity of the brain to emotionally negative stimuli.

SUMMARY: Article 4

Aim of the study:
Blood and Zatorre set out to study neural mechanisms underlying intensely pleasant emotional responses to music.

Activity changes in reward\motivation, limbic, paralimbic and arousal brain regions would correlate with the intensity of these chills.

PET (Positron Emission Tomography) scans were used to measure rCBF changes, while subjects listened to music they had selected to predictably elicit the euphoric experience of chills.

· McGill University students, aged 20-30, 5 female and 5 male with at least 8 years of music training since this demographic was more likely to experience strong emotional responses to music.
· Each subject was selected on the basis of their reports of frequent, reproducible experiences of chills in response to certain pieces of music.

· Each subject selected one piece of music that consistently elicited intensely pleasant emotional responses, including chills. Music selected was of the classical genre with no lyrics.
· Each subject’s selected music was used as another subject’s emotionally “neutral” control.
· Subjects were asked to rate the emotional intensity of their responses to each of the other nine music selections.

Scanning Procedures:
· PET scans were performed and registered with MRI scans.
· Measurements of heart rate, respiration depth and skin temperature were made during PET scans.
· After each PET scan, subjects rated their emotional reactions to each stimulus.
· Ratings were acquired for “chills intensity”,(0 to 10), “emotional intensity”(0-10) and “unpleasant vs. pleasant “ (-5 to +5).

· Subjects reported experiencing chills during 77% of scans when their own selected music was played. HR and EMG increased significantly during the highest rated chills music condition relative to the control music condition. Skin temperature did not differ significantly between these conditions.
· Chills were never reported for control music, noise or silence conditions.
· Subjects experienced chills of varying intensity while listening to their selected music.
· These chills were associated with increases in HR, EMG, and RESP relative to the control music condition, indicating changes in autonomic and other psychophysiological activity.
· Changes in brain structures that have been associated with brain reward circuitry were identified. These included:
- rCBF increases in left ventral striatum and dorsomedial midbrain and rCBF decreases in right amygdale, left hippocampus/amygdale and VMPF. These structures remained active when control music was removed.
- rCBF increases with chills intensity were also observed in paralimbic regions (bilateral insula, right OfC) and in regions associated with arousal (thalamus and AC) and motor (SMA and cerebellum) processes.
· The pattern of activity observed here in correlation with music-induced chills was similar to that observed in other brain imaging studies of euphoria and/or pleasant emotion.
· The observation of rCBF decreases in the amygdale and hippocampus during music-induced chills was compatible with the key role played by these structures in both reward and emotion.
· Brain structures correlating with intensely pleasant emotion in the present study differed considerably from those observed during unpleasant or pleasant responses to musical dissonance in our previous study.

C- Conclusion
Music recruits neural systems of reward and emotion similar to those known to respond specifically to biological relevant stimuli, such as food and sex, and those that are artificially activated by drugs of abuse.

Reflection on both articles:
Several neuroscientists whose works I am researching are exploring the connection between music and the human brain and argue that “music is fundamental to our species, perhaps even more so than language.” After reading the chosen articles, I asked myself what I had learned about music that would give me a better insight into the marvels of music and its importance in our lives.

The first article took me by surprise as I wondered how being informed that “the brain has a bias for negative stimuli over positive stimuli, independently of music-induced mood states” could enlighten me about how music is fundamental to our species. Negativity is not usually seen as a means to improving our quality of life, or as a necessary ingredient to becoming a healthy individual.

The second article particularly sparked my interest, as it revealed that music could induce intense pleasure. If learning music has the potential to augment the positive aspects of life, what better way to assist our physical and mental well-being. And, if so, how is music capable of creating intense pleasure on the one hand, yet also be incapable of changing the brain’s bias for negative stimuli? Intrigued, I decided to further investigate the significance of the findings of both articles from a biological perspective.

The first article states that our brain exhibits an emotional negativity bias that can best be understood if one considers that all of our experiences are always monitored for danger, the brain’s main function being to keep the individual, of which it is part, alive and reproducing. In The Emotional Brain: The Mysterious Underpinnings of Emotional Life (Simon & Schuster, 1996), Joseph LeDoux notes that sensory signals go directly to the amygdale, bypassing the sensory cortex before we are even aware of them, the amygdale’s role being to monitor our experience of how things are twenty-four hours a day. “This so-called “lower-route” begins to make meaning of our experience before we have begun to understand it cognitively and consciously.”

The amygdale is also called the fear centre, the danger centre or the negative emotion centre, because it ensures that we react to bad developments. Its role is to help decipher the incoming information’s meaning. When it senses danger, the amygdale sends signals directly out to the body. These subconscious signals produce body language, and in extreme cases, may directly trigger body movements that can evolve to fight or flight responses.

This is the first pathway that basic emotions follow, because its quick response assures that we are automatically protected. However, this pathway often makes mistakes in its evaluation, so a second pathway, which leads to the sensory cortex, also processes the stimuli. In the cortex, the situation is considered more carefully to better conclude how “real” the danger is to the individual and determine the appropriate response.

Viewed from the biological perspective of a survival-related brain system, the negativity bias does have a positive foundation. Consider our ancestors who lived with hungry predators lurking in every shadow. Negative emotions such as fear and anger allowed them to react very swiftly to danger and survive. We no longer need to hunt and kill our prey to eat; we simply go to the grocery store. The expression of negative emotions such as fear and anger do not prove as beneficial in our society, as they tend to develop into phobias or depression as modern-day mental stress levels engulf our lives.

So, is this survival-related brain system as relevant today since its programming tends to solicit certain behaviours no longer called upon, given the different social context in which we live? And, why is it that the positive music introduced to the subjects in the first article could not change the negative moods of the subjects during the experiment, while in the second article, listening to positive music brought intense pleasure to the musicians?

Of course, the subjects in the first article were shown a negative picture which triggered their brain’s survival mechanism, but why did they react to such an extent that positive music could not transform their negative thoughts into positive ones? After all, the subjects were in no danger; in fact, they were in a very safe controlled laboratory environment. Why couldn’t they shake off the primitive pattern?

Shouldn’t we then be looking at different ways to reprogram this brain related-survival mechanism? It seems evolution hasn’t been able to keep up with man’s ingenuity. And, if an automatic survival system can trigger unsolicited emotions and behaviours, it can certainly inhibit behaviours of which we are unaware and which could prove to be more beneficial to us.

Could this also be the case with music? In the first study, positive music couldn’t change the subjects’ moods, yet, in the second study, was quite capable when the survival mechanism wasn’t activated, no negative stimuli being introduced. Does this mean that activating the survival mechanism inhibits music from engaging its positive mechanisms, which could prove to be very beneficial in today’s complex society?

In the second article, music induced intense pleasure for the musician “by recruiting neural systems of reward and emotion similar to those known to respond specifically to biologically relevant stimuli, such as food, and sex, and those that are artificially activated by drugs of abuse.” Why did the subjects’ brains respond to positive music in the same way they would when our physical needs are met? After all, music is not a biological relevant stimulus like food, sleep and sex. In fact, music is neither strictly necessary for biological survival nor reproduction. It is an abstract stimulus that appears to express the motives and feelings of communication itself. Could this be an example of a behaviour that is usually inhibited by our brain-related survival mechanism, yet once allowed to express itself, proves to be beneficial to our mental well-being?

Given the right conditions, a positive environment that doesn’t trigger the survival mechanism and a trained musician who appreciates the harmony of a musical piece, music has the potential to influence the brain to assign meaning to abstract stimuli that are of higher cognitive functioning. The end result is that musicians can experience intense pleasure, not because they are satisfying a biological need, but because they have created a state a mind by listening to a piece’s particular patterns, evoking feelings and images which create order in their consciousness, and that, quite simply, feels good.

Could this be the almost mystical power that some believe music wields over the human mind? If so, as we further investigate how to control our brain-related survival mechanism and begin to tap into music’s immense potential, we may hopefully one day develop the ability to override our consciousness’ genetic instructions manual and set our own independent course of action.

1 comment:

Lee said...

These are fascinating studies - and so relevant to our consideration of music and emotion. That link is in my opinion the most potent and probably one of the least expplored by music and brain researchers. Thank you for bringing these studies to our attention - and for the very thorough review. I think your personal ruminations are potent with inquiring thought.