The Influence of Varying Sound Pitch on the Brain’s Electrical Activities of Young Nigerian Adults

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The Influence of Varying Sound Pitch on the Brain’s Electrical Activities of Young Nigerian Adults

https://doi.org/10.21203/rs.3.rs-3140799/v1

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There is a considerable interest in understanding the Brain’s electrical activity; at least to better the understanding of arousal and mental wakefulness in different conscious states, including in conditions like seizures. Electroencephalography is a technique for assessing Brain’s electrical function, and has been adapted for use in humans. Desynchronized waveforms occur frequently in humans during the sleep cycle, leading to a substantial alteration in serum levels of neuro-endocrine hormones for proper daily routines. In this study, we assessed the influence of pitch; a key ingredient in sounds on the electrical patterns of the brain of young Nigerian adults. Being a cross-sectional observation study, 400 healthy young Nigerians (16–35 years) from the students’ community of the Delta State University, Abraka, Delta State of Nigeria were exposed to varying pre-recorded sound pitches (30 Hz, 40 Hz, 50 Hz and 60 Hz) for 5 minutes each; haven determined their brainwave patterns [Alpha (α), Beta (β), delta (δ), Theta (θ) and Gamma (γ) rhythms] at rest (baseline) in a sound-proof studio, using the electroencephalogram (EEG). Statistical measures of association (correlation) was conducted, mean differences (ANOVA) computed with the graph pad prison (version 8.1), while adjudging p-value < 0.05 as statistically significant. Results suggest that lower frequency sounds (30Hz, 40 Hz) elicited α, or δ rhythms in relaxed cortical state, although insignificantly. ANOVA returned no significant change (p > 0.05) in brain activities compared to baseline. A weak negative correlation was observed (Pearson’s coefficient) between pitch and participants’ γ, θ and δ waveforms, even though this was insignificant (p > 0.05). Whereas, β and α activities returned strong and weak positive correlation respectively with increasing pitch administration. Thus, varying sound pitch increased brain’s electrical activities in exposed youths, although insignificantly.

Electroencephalogram

Brain waves

Sound pitch

Electrical activity

The human brain has been an optimized system of learning and dynamic recall of events. It is capable of creating new knowledge that can be combined, recombined, and applied in new and novel ways. This intricate machine, or schemas has proven useful in organizing and interpreting the world through efficient break down and information encoding into numerous small blocks of frequencies (rhythms), making it the best-known example of the seat of intelligence [1–3]. However, not very much is known about the neural and electrical processes that allow it to make these fit; especially when it is fed special sensations from the ear (acoustic system), eye, tongue, nose, and even the skin.

Acoustics (Greek akouein, “to hear”) is the science of sound and its associated elements [1, 4] pitch, tempo, amplitude and timbre. Technically, while pitch, tempo, amplitude and timbre are respectively dependent on vibration frequency of sound, velocity (speed), amplitude (loudness) and quality, Recently, the use of pitch, specifically in promoting mental health (music therapy), understanding the brain’s cortical function has gained global attention [5]. There are reports for instance, that music, when augmented with robust rhythmical ingredients can strongly affect cardio-pulmonary activities, respiratory rates, as well as alter circulating levels of neuro-endocrine hormones like endorphin to induce natural painkilling tendencies [6].

Although, the exact mechanism by which music achieves this is yet to be fully understood, there are however pointers to the fact that the human auditory system has special filters in the spiral organ of corti, within the inner ear. These filters, by the activities of their specialized hair cells (kinecilia) are extrinsically depolarized through the turbulence in the endolymph (a fluid within the cochlea, in the inner ear) created by vibrations; to transduce sound waves of different frequencies, tempos, intensity, etc. into a nerve action potential for conscious awareness, emotional response and integration by the brain [7, 8]. Although the limbic system; a deep cortical structure within the brain is responsible for emotional processes of sound, touch, smell, taste, etc., its connections with the prefrontal cortex (responsible for executive functions) and hypothalamic nuclei (responsible for sexual and feeding behaviours) is known to activate the corticospinal, descending analgesic tracts and the anterior, posterior hypothalamic nuclei respectively [9, 10]. By this trajectory, sound is theorized to influence neurones in the limbic system, affecting as such; sexual, feeding, and emotional response to pains as seen in humans.

Although it has been reported that the serum levels of circulating neuro-endocrine hormones that influence physiological states across numerous body systems is dependent on the brain’s cortical waveforms [alpha (α), beta (β), delta (δ), theta (θ), gamma (γ) rhythms] at any point in time [10, 11]. In the light of this, it will therefore be difficult to exaggerate the importance of understanding the influence of sound, specifically its pitch element on the brain’s electrical activity that ultimately alters functional states in humans. Nonetheless, to what extent, and at what specific dose will pitch achieve this fit remains a puzzle. In this study, the changes in the brain electrical patterns [α, β, δ, θ, γ rhythms] in administration of pre-recorded sound pitch at varying doses were investigated in young Nigerian adults. The study also examined the relationship (correlation) between sound pitch and the brain’s electrical patterns over a period of listening.

Study Area

This observational, cross-sectional study was conducted on the student population of the Delta State University, Abraka, Delta State, Nigeria. Abraka is one of the 25 Urhobo kingdoms in Delta State, Nigeria, with geographical co-ordinates of 5⁰ 47` 0 North, 6⁰ 6` 0 East.

Ethical Clearance

Prior to investigation, Ethical clearance, dated 16/11/2020 was sourced from and approved (REC/FBMS/DELSU/20/78) [12] by the research and ethics committee of the Delta State University, Abraka. In this study, the procedures for dealing with human subjects was in accordance with the ethical standards stipulated by the National Health Research Ethics Committee of Nigeria (NHREC); a national organization that provides guidance on research ethics to Federal and State Health Ministries in Nigeria; setting guidelines and criteria for the conduct of human and animal experiments. The protocols adopted was in accordance with the Helsinki Declaration of 1975, as revised in 2008 [13].

Informed Consent

Before selection for participation, a carefully structured consent form was issued to participants to seek their permission to partake in the study. Only subjects who consented to cooperate (haven been briefed on the rules and nitty gritty of the study) were included into the study. The consent form was written in plain language, free from unnecessary words, granting allowance for eligible participants only after clearly responding to each of the following points;

1. that He / She (Participants) has been briefed, read and understands key information about the study.

2. that He / She has been given the opportunity to ask questions whenever and however they dim fit, relating to the study.

3. that He / She (Participants) voluntarily agrees to oblige the researcher with relevant supports and/or access to procedural rules relating to the study in accordance with the briefing

4. that He / She (Participants) understands that they can withdraw at any time of their choice with no compulsion, and without facing any penalty.

5. that confidentiality issues were firmly explained to them before actual participation (using no actual names but pseudonyms for purpose of data anonymization)

6. that the use of obtained data in research, publications, sharing and archiving were explained; even though the public will be blurred from assessing their private information

Participants

The study was targeted at the young student population of the institution. Ages fell between 16 – 35 years. This population was 19,657 for the 2019/2020 academic year as obtained from the office of the Director of Academic Planning, Delta State University, Abraka, Delta State, Nigeria(Academic Planning Unit, 2020) [12].

Study Design

Simple randomization was used to select eligible participants into four (4) groups of hundred (n = 100) subjects each. Each group were first assessed (in a strictly controlled sound-proof studio) for baseline values of their brainwave, using the electroencephalogram (EEG) to served as control. Thereafter, participants were fed with incremental doses of pre-recorded pitch notes [30 Hz, 40 Hz, 50 Hz, and 60 Hz] for 5 minutes.

Participants’ Eligibility

To be eligible for participation, only subjects without medical record(s) of ear loss (partial or total deafness) were included in the study. This was necessary because the number of auditory hair cells (kinecilia) in the inner ear (organ of corti) reportedly decreases at about 37-40 years [14]. Subjects undergoing treatments with ear medications were also excluded from the study.

Protocol

Technically, the electronic musical rhythm / bits synchronization device (metronome – 9 type: rhythm 410-460 Hertz, A4 frequency; falling tone selection; 1 * Tuner; 1* Booklet; 1* pickup peg and ± 0.5 % Accuracy) with LCD display feature was used to generate sound pitch of aforesaid frequencies, while saving on electronic mp3 player and administration on subjects’ ear with a mini headphone (wireless) of Bluetooth V4.1 Stereo Binaural earpiece (Model: Freeheat_001; Impedance: 32 ohms; Frequency 2.4 Giga Hertz; Temp 10-55⁰C; input 5V).

To assess the brain’s electrical activities due to fluctuations in intracranial ionic currents, EEG electrodes (Figure 1) were first connected to the Cyton Bioseng Board of the open BCI, next interfaced with participants’ scalp and then tracked via the open BCI graphical user interface (GUI) in accordance with the OpenBCI guidelines. In any case, participants’ data were logged to a notepad file with other relevant details over the period of listening for subsequent sorting and analysis.

Statistical Methods

All parameters were reported as means ± standard deviation in accordance with statistical analyses carried out with the Graph Pad Prism version 8.1 software. At p < 0.05, means were deemed to be statistically significant. The Kolmogorov-Smirnov test was used to determine whether all definite parameters had a normal distribution. The Log transformation was used to evaluate variables with non-Gaussian distributions. Our data collection included repeated measures with various numbers of repeats for each individual. Analysis of variance (ANOVA) was used to compare the means after data collection, and the Pearson product moment correlation coefficient was employed to establish the relationship (correlation).

Table 1: Comparative Changes in Mean Values of Brain Electrical Activity for Varying Pitch Administration

Pitch	Brain Activities
Pitch	Gama γ (Hz.)	Beta β (Hz.)	Alpha α (Hz.)	Theta θ (Hz.)	Delta δ (Hz.)
I (Baseline)	32.42±0.09	28.16±0.13	9.14±0.07	4.73±0.04	1.03±0.05
II (30 Hz.)	32.39±0.09	28.02±0.14	9.36±0.07	4.71±0.04	2.08±0.08
III (40 Hz.)	32.42±0.09	27.85±0.15	9.32±0.08	6.00±0.09	0.94±0.05
IV (50 Hz.)	32.48±0.85	27.94±0.14	10.98±0.09	4.74±0.05	1.01±0.05
V (60 Hz.)	32.36±0.09	29.96±0.21	9.30±0.08	4.68±0.04	0.96±0.05
ANOVA (p-values)	0.9052^#	0.1001#	0.4008 ^#	0.2000 ^#	0.1000 ^#

^#= Insignificant.

Values are presented as Mean ± Standard Deviation (SD)

From the table above, ANOVA returned no significant change (p > 0.05) in brain activities, following administration of varying sound pitch (30 Hz, 40 Hz, 50 Hz and 60 Hz) on participants; relative to baseline

Table 2: Relationship [Pearson’s Correlation Coefficient (r)] between Sound Pitch and Brain’s Electrical Patterns

Pearson	Brain Rhythms
Pearson	Gama γ (Hz.)	Beta β (Hz.)	Alpha α (Hz.)	Theta θ (Hz.)	Delta δ (Hz.)
R	-0.1060	0.6272	0.4010	-0.0192	-0.3896
R squared	0.0114	0.3935	0.1608	0.0004	0.1518
P value	0.8650	0.2570	0.5030	0.9750	0.5170
Remark	WN	SP	WP	WN	WN

p-value < 0.05 = statistically significant

Key: r = Pearson Correlation Coefficient, WN = Weak Negative Correlation, SP = Strong Positive Correlation, SN = Strong Negative Correlation

From the table above, weak negative correlation was observed for Pitch on γ, θ, and δ brain activities, although this was insignificant (p > 0.05) for each case. Also, a statistically insignificant, Strong Positive and Weak Positive correlations were respectively observed for β and α waveforms with increasing pitch administration on subjects.

Table 3: Multiple Regression Equations for Envisaging Brain’s Electrical Activities from Sound Elements (Pitch, Tempo, Amplitude and Timbre) Over a Period of Listening (Min)

Brain Activity

Reg. Eqn.

SEM

t-stat

p-value

R²

Remark

Y = b₀ + b₁x₁ + b₂x₂

3.37 + 0.03 * Pitch + (-0.02) * Min

0.13

72.48

0.0018

0.0243

Significant

Y = Predicted Brain Activity (α, β, δ, θ or γ), b_{0 =}regression intercept, b₁ = regression coefficient for (Pitch, Tempo, Amplitude (Amp) and Timbre), b_{2 =}regression coefficient for listening duration, x₁ = Administered Sound Elements [Pitch (Hz), Tempo (BPM), Amplitude (Decibel) and Timbre (Hz)], and x₂ = Duration of listening (Min). Here, Y between 1-3.9 Hz is predictive of Delta wave, whereas 4-7.9 Hz, 8-11.9 Hz, 12-24.9 Hz and 25+ Hz are predictive of Theta, Alpha, Beta and Gamma Activities respectively.

Table 4: Comparative Mean and Percentage Cortical Performance in Varying Pitch Administration

Lobes	Α	β	δ	θ	γ	Percentage Performance (%)
Baseline	9.74±2.13	28.16±5.37	--	4.73±0.48	-	42.03

Occipital	8.14±2.29	--	0.81±0.23	4.01±3.37	-	12.96
Frontal	--	25.02±4.29	--	1.41±0.15	-	26.43
Parietal	7.37±2.54	--	1.27±0.47	--	-	8.64
Temporal	8.32±2.48	1.18±0.25	--	0.43±0.12	-	9.93
p-value (ANOVA)	0. 6002	0.0003*	0. 1027	0.0030*	-

*: significant

A close look at the above table reveals that pitch administration had a significant change (p < 0.05) on percentage cortical performance of β and θ waveforms across different cerebral cortices, especially influencing the frontal (Motor) and temporal (auditory) areas’ β waves relative to baseline, while causing 26.43% and 9.93% performances respectively as against the baseline counterparts.

It is known that the human brain emits electrical energies under any situation of consciousness (tired, awake, or sleep). These waves are nothing but electrical signals (wave patterns) due to depolarization of neurones that fire messages to one another in a complex pattern among various brain areas [15]. Worthy of note is that simultaneous firing of these neurons increases the frequency of the wave, whereas, the more synchronous they fire, the higher their amplitudes [16]. In this study, the effects of listening to varying sound pitch on the electrical activities of the brain was investigated in young humans; especially relative to the firing at each cortical area.

At baseline, the mean values of participants’ α, β, δ, θ and γ waveforms met the standard values, just before administration of varying pitch notes. On the average, β waveform fell between 19 Hz and 30 Hz at baseline as compared to known, normal ranges of 12 Hz and 38 Hz [17]. This was expected for fully awakened and consciously aroused minds as characteristically stated by Worrell and Gotman, (2011) [18]. Even with alpha wave, theta waveforms were most frequently desynchronized at baseline. One explanation for this is traceable to the fact that subjects were in their conscious wakeful state before sound administration [17, 19] especially considering that they were young people who were co-opted into the studios, just immediately after mental, class activities.

Normally, alpha (α) and beta (β) waveforms ranges between 8−13 Hz and 13−22 Hz respectively under normal wakeful state [18]. In this study however, exposure of participants to 30 Hz, 40 Hz, 50 Hz and 60 Hz pitch notes returned a statistically insignificant (p > 0.05) decrease in β activity, except for 30 Hz note, which increased insignificantly compared to baseline value (table 4). Contrarily, Alpha (α) waveform returned an insignificant (p > 0.05) increase across board, irrespective of administered pitch note as compared with baseline. This observation, is suggestive that α and β activities may be affected by sound pitch in a music listener, even though this was insignificant.

This observation complies with Dan's earlier article [20]. Dan’s report showed no specific method that describes the practical localization and mechanism of human pitch production. The implication of having pitch influence alpha and beta waveforms (as noticed in this finding) is that, a dream state of paradoxical rapid eye movement (REM) sleep may be induced, probably as a result of improper synchronization of alpha wave, and / or replacement of a synchronized alpha wave with beta waveform from time to time (alpha block). It is noteworthy that in a typical wakeful state, alpha and beta waveforms differ between 8-13 Hz and 13-22 Hz, respectively [21]. However, the exposure of participants to pitch notes of 30 Hz, 40 Hz, 50 Hz showed a statistically insignificant (p > 0.05) decrease in β activity, with the exception of the 60 Hz regimen, which significantly increased relative to the baseline value. An insignificant (p > 0.05) increase in all but 50 Hz pitch note was returned by alpha waveform which proved important compared to baseline records.

Also from this study, it was observed that 40 Hz and 50 Hz pitch administration caused an increase in theta (θ) and delta (δ) activities, attenuating the apparently increasing levels of other activities of low amplitude waveforms. This implies an irregular pattern for pitch effects on theta and delta waveforms, a situation only possibly accounted for by the state of mind of participants while listening, especially with respect to deep cortical (sub-cortical) activities.

From our result, it was observed that 40 Hz and 50 Hz pitch administration caused an increase in theta (θ) and delta (δ) activities, attenuating the apparently increasing levels of other activities of low amplitude waveforms. Though this alteration was significant and insignificant for theta and delta rhythms respectively; however, 5 Hz frequency sound administration caused a statistically insignificant increase in the delta wave pattern of listeners as compared with baseline. This implies an irregular pattern for pitch effects on theta and delta waveforms, a situation only possible accounted for by the state of mind of participants while listening, especially with respect to deep cortical (sub-cortical) activities.

Clearly, the effect of the pitch note on theta wave was slightly decreased for different frequency, while 40 Hz pitch administration increased insignificantly relative to baseline value. However, 50 Hz and 60 Hz pitch notes caused a statistically insignificant increase in theta activity to hit the maximum de-synchronization point (table 1). In a similar development, delta waves are known to occur either in the thalamus or in the cortex. They are thought to occur in combination with the reticular formation in the thalamus [22], with the suprachiasmatic nuclei haven been shown to control delta waves in the cortex. Though lesions in this region have been shown to significantly interrupt delta activity, however, delta waves display lateralization, with superiority of the right hemisphere during sleep.

In the report from table 1, 40 - 60 Hz pitch caused a notable attenuation in delta activity of subjects. Although this effect was insignificant for 30 Hz frequency sound, a state of deep sleep (Non-REM stage 3) is actually implicated. One possible explanation for this is in part due to the opening of T-type calcium channel. By this effect, cortical neurons are generally inhibited via the release of gamma-aminobutyric acid (GABA) to trigger wave sleep [22]. Delta activity also reportedly induces the release of many hormones, including the hormone releasing growth hormones GHRH and prolactin (PRL). GHRH is released from the hypothalamus and, in turn, induces the pituitary production of growth hormone (GH). The secretion of (PRL) is also controlled by the pituitary, which is closely associated with (GH). In response to delta-wave signalling, thyroid stimulating hormone (TSH) release is expectedly reduced, impacting heavily as such, on the basal metabolic rate and heart rate [23-25].

Scepticisms have always been before now, that listening to sound at varying levels can alter the brain’s electrical patterns. Although the role of varying pitch on EEG parameters has remained vague. In this study though, varying pitch administration increased the Brain’s electrical activities in exposed youths. Although insignificantly, a notable significant change was observed in frontal and temporal cortical performance as exemplified via beta and theta activity relative to baselines. Clearly, the effect of pitch note on theta wave was slightly decreased at different frequency, with 40 Hz pitch increasing it insignificantly compared to baseline. However, 50 Hz and 60 Hz pitch caused a statistically insignificant increase in theta activity, hitting the maximum de-synchronization wave at that frequency.

Authors’ Contribution

Be it in the conception, design, use, collection, analysis, and interpretation of data, or in all these areas, all authors made a substantial contribution to the study. They also chose the journal to which the paper was submitted, took part in the article's drafting, revision, or critical review, provided their final approval for the version that would be published, and elected to be held responsible for every aspect of the work.

Funding

This study was exclusively self-funded by authors and received no funding of any sort from any agency

Availability of data and materials

Codes used in this study are available from the authors upon request.

Ethics approval and consent

All experimental procedures were authorized (REC/FBMS/DELSU/20/78) [12] by the research and ethics committee of the Faculty of Basic Medical Sciences, College of Health Sciences, Delta State University, Abraka, Delta State, Nigeria.

Consent for Publication

The final draft was examined and authorized by all authors, who also agreed to take responsibility for any inaccuracies or problems with the work's integrity.

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No competing interests reported.

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The Influence of Varying Sound Pitch on the Brain’s Electrical Activities of Young Nigerian Adults

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