THE EFFECTS OF MUSIC ON STRESS

At the most basic level, stress is our body’s response to pressures from a situation or life’s event. Although in short occurrence or at optimum level stress may be considered to have positive effects, excess and prolonged stress can cause physiological as well as psychological health disorders. Stress cannot be avoided or omitted, but one can reduce or manage the level of stress using several relaxation techniques. Through age-long research, listening to music has been proven to be a powerful tool for stress reduction. Music has been reported to have direct effects on nervous system, immunological and endocrine system of the human body. Amongst various neuroimaging techniques,electroencephalogram(EEG) is a useful electrophysiological biomarker to monitor the neuronal activities of the human brain with high temporal resolution. In research setting EEG signals are used in mental stress study. The present article attempts to review scientific literature in support of the pivotal role of music on stress reduction. Discussions on stress and its effects on human health are followed by the quantification of stress by EEG for identification and classification of stress. The role of music on stress reduction has been discussed with a light on musical neurofeedback as an effective measure for stress reduction.

In a stressful situation, the sympathetic nervous system dominates and the brain's natural response is to accelerate from slow alpha and theta waves to fast beta frequencies (Hoffmann, E. 2005). Both decreased and increased in alpha and beta power have been found as a sign of mental stress (Puterman, E. et al. 2011). During rest and relaxation, the parasympathetic nervous system dominates and as a result the brain waves are slowed down from beta to alpha wave frequencies and during excessive parasympathetic activity to theta waves (Hoffmann, E. 2005).
Considering factors like temporal or spatial resolution, specificity and coverage in selecting non-invasive neurological methods for stress measurement, Electroencephalogram (EEG) is an important tool for studying the transient dynamics of the human brain's large-scale neuronal circuits. It is one of the most common quantifiable measures to identify and classify human stress using real-time digital technology to record electrical activity of the brain with high temporal resolution in millisecond scale (Berka, C. et al 2004). The changes in autonomous nervous system can be effectively represented by EEG signals (Seo, S. H. et al. 2010). Long-term stress has been classified with machine learning algorithms using resting state EEG signal recordings (Saeed, S. 2020). The ratio of power spectral densities of alpha and beta bands has been computed for the analysis of physical stress (N H A Hamid et al. 2010). The changes in EEG absolute power and other connectivity measures such as coherence have been observed to analyze stress (Alonso, J. F. et al. 2015). For stress identification and stress state classification using EEG, different computational methods are used (Table 3) 13-32 2-20 or higher Gamma 32-100 3-5 or higher 528 human brain (Seo, S. H. et al. 2010). Slope of EEG linear regression has been a feature to determine the relaxation level of an individual (Teplan, M. et al. 2006) and a combination of EEG Asymmetry and Spectral Centroids techniques has also been used as a feature to detect unique patterns of human stress ( N Sulaiman, et al. 2011).

Music on brain:
From ample research on music and the brain, it is manifested that music has a biological basis and the brain has a functional organization for music (Weinberger, N. M. 2004). Listening to music is reported to influence varied regions in the brain, including multiple cortices (auditory, visual, motor), the cerebellum along with the deeper emotional area (amygdala, orbitofrontal, anterior cingulate cortex), memory (hippocampus), mesolimbic reward structures and dopaminergic neural networks (Koelsch, S. & Siebel, W. A. 2005; Koelsch, S. 2010) and also to alter the dynamical brain responses, i.e. oscillatory component(s) of the EEG signals, particularly theta frequency band. Music-induced chills produce reduced activity in brain structures associated with anxiety (Blood and Zatorre, 2001). Mainly two types of brain waves responsible for mental relaxation and stress reduction are the alpha wave (8-13 Hz) during relaxation and theta wave (4-8 Hz) during deep relaxation. Studies have found that brain waves can be altered by music (Levitin, D. J. & Tirovolas, A. K. 2009). Alpha and theta brain waves increase either by relaxing music or by other relaxation techniques (Jacobs, G. D. & Friedman, R. 2004). Different types of music ( Light, Country, Jazz, Rock) have been reported to cause the decline of the energy intensity of the waves from different areas which strongly supports the hypothesis that different types of music will have different impact on the human brain and EEG waves (Sun, C. et al. 2013). The first neuroscientific study of the effect of listening to archaic sounds (monochord) was done in patients demonstrating the changes in complexity in brain oscillation patterns in comparison with progressive muscle relaxation (PMR) (Bhattacharya, J. & Lee, E. J. 2016). Studies on the effects of music on alpha and theta waves are summarized in Table 4. The relaxation effects of music are also reported to be associated with a change in the total theta power. The effect of music on human subjects under mental stress has been studied (Nawaz, R. et al. 2018) in three different stress levels: low, high and moderate (using congruent, incongruent and mix stroop color test); with and without background music and the corresponding EEG has been recorded. For congruent and mix stroop test higher alpha power is observed in the presence of music indicating a positive effect of music under low and moderate stress conditions whereas for incongruent case the alpha power is reduced in the presence of music indicating the negative effect of music under high stress. The stress behavior of females is reported to be more sensitive to music as compared to males (Asif, A. et al. 2019). Listening to a piece of classical piano music has been reported to evoke activity changes in the amygdala and the orbitofrontal cortex (Koelsch, S. 2014) which plays a pivotal role in stress reduction in daily life. According to the study of Frances H Rauscher and his team (Rauscher, F. H. 1993), significantly better spatial reasoning skills were observed on normal subjects after listening to Mozart's sonata for two pianos (K448) for 10 minutes than after periods of listening to relaxation instructions designed to lower blood pressure or silence (Jenkins, J. S. 2001).
The controlled use of a specific kind of music and its ability to influence behavioral, emotional, and psychological changes in a human being during the treatment of a disability or illness is usually referred to as music therapy Music Therapy has been observed as an evidence-based novel therapeutic tool to reduce stress elating the cognitive, sensory, communicative and emotional domains.

Music on neurotransmitters and immunological stress markers:
Studies (Table 5) suggest that pleasant music releases dopamine, the main neurotransmitter in the reward system. Different music has its effects on the levels of other neurotransmitters like norepinephrine, serotonin, endorphin and cortisol (Table 6)  Anticipation " D2 binding in caudate Abbreviations: D2, dopamine D2 receptor; mPFC, medial prefrontal cortex; NAc, nucleus accumbens; PET, positron emission tomography; rCBF, regional cerebral blood flow; VTA, ventral tegmental area.

Selection of music:
Selection of appropriate music is of huge significance and the effects of different music genres on reducing stress have been explored in several studies. Classical music is found to be more stress relieving than non-classical music such as heavy metal and hard rock (Labbé, E. et al. 2007). Sedative music or silence reduces tension and has a relaxing effect, as compared to stimulative music or noise (Lingham, J. et al. 2009). Listening to self selected music while being in curative radiation therapy has been reported to lower anxiety and treatment-related distress (Clark, M. et al 2006). A meta-analysis of the effectiveness of music use of stress reduction revealed the importance of preferred music in a decrease of arousal due to stress (Pelletier, C. L. 2004). Relaxing music which is specially formulated music with binaural beats (alpha brainwave range, 8-13 Hz) for relaxation (alpha state) has been reported (Phneah, S. W. & Nisar, H. 2017) to produce more alpha brainwaves hence higher alpha power causing a better soothing effect on the participants compared to the participants' favourite music.

Musical neurofeedback in stress reduction:
Neurofeedback, also known as EEG biofeedback, involves utilizing EEG signals to measure brain wave activity with the use of audio or visual signals to reorganize or retrain these brain signals. Musical Neurofeedback has become frequently used technique for treating stress related disorders. (Álvaro J. Bocanegra-Pérez, et al. 2020). It teaches self-control of brain functions to subjects by measuring brain waves and providing a feedback signal. Over the past decade, neurofeedback has been found to be effective in producing significant improvements in medical conditions related to stress such as depression (

Conclusion:-
Stress has been identified as a serious and escalating issue having severe impacts on both individuals and society. Growing experimental evidences show that the effects of music on human brain with precise identification and classification of stress by EEG monitoring could be a potential clinical method to manage and treat the stress related health hazards. Music being a cost effective subjective stimulus, it is quite evident from studies that properly selected music would be beneficial as a therapeutic to the common people suffering from stress related health problems. Musical Neurofeedback training would also cast a new light on stress research.

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A preliminary literature support has been attempted through this review paper to provide the evidences for the effects of music to facilitate stress relief. But there is an absolute need of more focused neuroscientific research to explore the clinical efficacy of music interventions on stress with more detailed insights.The author would have liked to suggest a few ideas where future research needs to be looking next. As levels of stress may vary from mild to moderate to severe, more work is required on the identification of different levels of stress and the effects of music should be observed accordingly for detailed characterization. Comparative studies can also be done with instrumental and vocal music for finding the better option of minimizing stress levels in humans. The review conclusively suggests that on precise identification and classification of stress, music can be considered as a prospective aid to cope with stress. Future investigations would certainly validate the conclusions by exploring exclusive association of music with human brain which would help in achieving a deeper understanding of beneficial effects of music on stress. References:-