Music is known as a universal language that is able to cross cultural boundaries. It is a disciplinary that does not always require high cognitive function and extensive knowledge. The extensive nature of music allows it to be a tool that can be added to clinician’s tool boxes all over the world, and possibly for organisms across all kingdoms. While music therapy is a relatively new field, research is beginning to join animal studies as well. Current research on both humans and mammals suggest that music therapy is able to significantly improve psychological state, rehabilitation, motor function, and cognitive function. However, there is very little, if any, research on how music therapy affects sea turtles.
Rhythm Processing in Humans
Rhythm processing and beat detection in humans can result in improved motor function. Due to its universal nature, music can spontaneously induce movement, and activates various areas in the brain. Beat perception is a psychological process as it is not defined as a stimulus. However, this sensitivity to rhythm may be unique to humans. The maximal activity in humans is with audio around 500-700 ms. This tells us that there is a frequency that best induces a sense of beat. This is corroborated with less activity in motor regions of the brain as music becomes too fast to feel a beat. The areas activated by rhythm are the supplementary motor area, premotor cortex, basal ganglia, and cerebellum. Specifically, beat based rhythms improve basal ganglia function .
Music Therapy and Stroke Rehabilitation
Music therapy (MT) has resulted in significant rehabilitation improvements in human stroke patients. About 75% of stroke patients are left unable to work. Strokes result in increased defect signaling in the central nervous system (CNS) . However, music aids neural connections and neural reorganization of the sensorimotor cortex. This can result in improved motor and cognitive function, and psychological state. Simply listening to preferred music can advance cognitive recovery and mood improvement . Music is processed in various brain areas, but specifically music therapy increases cerebral function and motor activity. Because of music’s extensive domain over the brain, listening to music may compete with the focus of a pathological dominant, which could result in that dominant being weakened. It has also been concluded that melodic music at a low volume can have a sedative action on stroke patients . Yakupov et. al (2019) concluded that music therapy results in significant recovery of motor, speech, and autonomic function in ischemic stroke. Raglio et. al (2017) deduced that music therapy increases quality of life, gross mobility, and cognitive function. As well as significantly decreasing anxiety and depression levels. Thus, music therapy results in both physiological and psychological improvements in human stroke patients.
Music Therapy in Rats
Music therapy has been found to positively affect behavior in Wistar rats. Due to the beliefs that music therapy can possibly decrease psycho-behavioral complications in human patients, the effects of music therapy on the CNS in rats was studied. It was found that music therapy decreases stress and depression in rats and contributes to their rehabilitation. As many music therapy studies use Mozart’s K.448 as the stimulus, the increase in spatial and temporal reasoning with music therapy is known as the, “Mozart Effect.” It is believed that music therapy can help with cognitive maintenance and function, but no significant effects have been found in rats. However, music therapy can offer a window into the emotional state of a subject. This is manifested through hormone levels. Both cortisol and beta-endorphin levels are altered with music therapy . Sampaio et. al (2017) found no significant effects in cognitive function of locomotion in rats, but found significant decreases in stress, and significantly more positive behavior. This parallels with the general uses of music therapy: improving and maintaining quality of life, managing stress, and controlling negative emotions.
Music therapy has resulted in significant improvements in rats with bone cancer. Gao et. al (2016) found that rats given bone cancer and music therapy had significantly less weight loss, smaller tumor volume, higher feed efficiency, less spontaneous foot withdrawal, higher heat pain threshold and free walking pain scoring, and lower p38a and p38ß expression. p38 is the signaling pathway in spinal microglia cells, which gives insight into the process of chronic pain. These results suggest that music therapy can have a significant effect on the treatment of chronic cancer pain, along with a therapeutic effect. The goal is for music therapy to improve the anxiety, pain, prognosis, and survival of cancer patients .
Music Therapy in Dogs
It has been discovered that music specifically tailored for dogs can result in a calming and therapeutic effect through changing the environmental acoustics. Music therapy for dogs has been used most notably in clinics and rescue shelters. Especially pre-surgery, the dog’ environment can negatively affect their physiological and psychological state. Thus, by shifting the acoustic stimuli, clinics and shelters can alleviate pain . In fact, a CD specifically meant for dogs, Through a Dog’s Ear, has been created in order to create a more calming environment for shelters and clinics. It has proved to be twice as effective than regular classical music as it is tailored to dogs’ hearing sensitivity range .
Sea Turtle Sensory Biology
Like other members of the animal kingdom, sea turtles have ears and can process auditory stimuli. Their ear canals are just covered by extended facial tissue called, the tympanum . Underneath the tympanum is a layer of sub tympanic fat. This layer is unique to sea turtles and is what increases their sensitivity to low frequencies. Between this and the tympanum is the cutaneous plate; this is the sound receiving surface. The sound moves from this layer through the fatty layer which acts like a fluid and transmits the sound pressure inward [9-10]. As well as having that layer of fat, sea turtles are unique in that they lack an ossicular mechanism, and their lower tympanic membrane to oval window ratio is lower than other turtles . Sea turtles’ ears leave them with a narrow range of low frequency hearing. It is believed that they use both auditory and vibrational stimuli, and use their whole body as a receptor when underwater .
Sea turtles have both a lower and more restricted range than human ears. The human auditory range is 20-20,000 Hz . On the other hand, green sea turtles’ range is 50-1600 Hz underwater . Ridgway et. al (1969) found that the highest sensitivity range for green turtles in an aerial setting is 300-500 Hz. Similarly, Piniak et. al (2016) found that green turtles have highest sensitivity from 300-400 Hz in the air, and 200-400 Hz underwater. Specifically, Pacific green turtles’ maximized range is 200-400 Hz. Outside of these ranges there is a rapid decline of sensitivity, especially in higher frequencies . Sensitivity range is also restricted in aerial settings. Rather than 1600 Hz, they can only detect up to 800 Hz. This makes sense as sea turtles spend the majority of their lives in marine environments . Lavender et. al (2014) found that there is no ontogenetic shift in loggerhead turtle hearing sensitivity. This species is also a low frequency specialist, and their range is 50-1000 Hz. Their maximized sensitivity range is 100-400 Hz . Based on this data, a more universal range between species and environment type seems to be 300-400 Hz. The best instruments for this range would be mid-range piano, mid range acoustic guitar, mid to high-range cello, tenor saxophone, and tenor vocals .
Sea turtle audiation continues to be an important factor to sea turtle biology as human impact increases. Acoustic stimuli may provide cues for sea turtles, and may be used for navigation, locating prey, avoiding predators, and general environmental awareness. At the very least these reptiles are able to detect and process auditory stimuli . However, their sensitivity and detection capabilities may be limited due to the increase in anthropogenic sound in oceans; this includes shipping traffic and military sonar operations. This sound pollution could alter behavior, mask biologically significant sounds, and cause trauma to both the auditory apparatus and non-hearing tissue . However, understanding sea turtle aural skills could also help to make music therapy techniques as effective as possible. Just as music has been composed to fit dog sensitivity ranges , a CD can be made to fit sea turtles’ range of 300-400 Hz using the instruments mentioned earlier. This CD could help to combat anthropogenic sounds and fishery bycatch.
Possible Research in Sea Turtles
Alternative medicines, such as music therapy, for sea turtles should be looked into as Western clinical techniques are not always successful. For example, when the New England Aquarium were rehabilitating two sea turtles suffering from hypothermia they were given acupuncture treatments. Conventional techniques, such as laser therapy and antibiotics, resulted in no improvements; both were still not eating and had difficulty moving. However, after three acupuncture treatments, the turtles had improved limb use and were able to eat on their own. Acupuncture is commonly used on humans in order to relieve pain or treat disease. While it is not a common practice, it can have significant positive results . Thus, alternative medicines can be beneficial to sea turtles, and focus doesn't need to remain on the conventional Western techniques.
Music therapy may result in significant improvements in sea turtle physiology and psychological state. Similar to mammals such as rats and humans, sea turtles can fall victim to cancer. An example being Fibropapillomatosis (FP) in Hawaii and Florida. As well as biological factors, such as illness, parasites, and disease, sea turtles are buckling to habitat degradation, pollution, fisheries bycatch, trade, consumption, and climate change . These added stressors may be hindering the psychological state and physiological health of sea turtles all over the world.
Many animals respond to sound similar to humans. Entrainment, the process of synchronizing physiologic processes to external rhythms, has been found in dogs and rats already, with rhythm being used to facilitate rehabilitation due to sound stimulating hard-wired circuits in the CNS. Even simply changing or adding music in a rehab facility can significantly improve patients’ progress and comfort [1-7]. Music therapy can be used to help facilitate sea turtle rehabilitation by decreasing stress and depression levels, as well as possibly decreasing their physical pain. For example, music therapy can be used during stressful procedures such as laparoscopy in order to lower their cortisol levels and create a more calm environment. The hormone levels of sea turtles can be collected before and after music therapy in order to see if there are any significant results. Research on the physiological and psychological states of sea turtles in rehabilitation centers should be conducted in order to see if they too can benefit from this alternative medicine. If anything, these studies will hopefully result in a new tool being added to a sea turtle veterinarian’s tool box to help with the symptoms and stresses that marine turtles can experience.
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- Lavender, A. L., Bartol, S. M., & Bartol, I. K. (2014). Ontogenetic investigation of underwater hearing capabilities in loggerhead sea turtles (Caretta caretta) using a dual testing approach. The Journal of Experimental Biology, 217, 2580-2589.
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