Frontiers in Animal Behavior Research: Scientific Application of Krogh’s Principle
By Kaiming Tan, Neurobiology, Physiology, and Behavior, ‘16
Author’s Note: As a student who is engaged in biological sciences research, I often read research publications and perform experiments in laboratory classes and research projects. A common theme across these studies is that different labs use various model organisms. For instance, labs that research infectious human diseases tend to use primates because of their similarity to humans, whereas geneticists tend to use fruit flies because of their clearly defined and inherited traits. I often wondered what drives the selection of specific model organisms and whether there is any scientific justification behind it. This manuscript introduces Krogh’s principle, a principle which is commonly applied in in vivo research studies to aid in determining the appropriate model organism. Additionally, a brief research proposal is presented to demonstrate Krogh’s principle on a practical level.
Key Words
Krogh’s principle, animal behavior, sensory ecology, Leach’s storm-petrel, bladder grasshopper, research proposal
Introduction
Krogh’s principle is the gold standard used to choose experimental models in the fields of animal behavior and sensory ecology. The principle states that for every research question, there is a preferred model organism to study, which allows researchers to produce experimental results that help to answer the research question. These preferred organisms often have one or more specialized traits that are particularly well-suited for a researcher’s objectives [1]. August Krogh developed this principle in the mid 19th century, and ever since, scientists worldwide have adapted this principle when selecting model organisms for their research studies.
Krogh’s Principle in Use
Dr. Robyn Hudson is a world-renowned scientist and a leading expert on the effects of chemical olfactory cues on animal behavior. Dr. Hudson applied Krogh’s principle in her research on olfactory learning and development by choosing the European rabbit as a model for her research. Rabbit pups are born blind, but they have a fully-developed sense of smell, also known as olfaction. Additionally, baby pups are fed in the dark conditions of their underground nests. They are also altricial, meaning they are entirely dependent on their mother’s brief nursing. In Hudson’s experiment, the rabbit pups were only visited by their mother once a day to be nursed for about three to four minutes [2]. Thus, the pups require olfaction to look for their mother’s nipples for milk in order to survive. Given the natural history of this species, scientists can conclude that the baby rabbit’s ability to search for their mother’s nipples is primarily due to olfaction.
Additionally, Krogh’s principle applies to Dr. Hudson’s choice of research subjects because rabbits are easy to rear and observe in a laboratory setting. European rabbit pups have evolved plastic mechanisms calibrated by circumstantial odor experience in preceding and current environments. Olfactory plasticity allows the rabbits to modify their behavior in response to olfactory cues such as different scents. This enables the rabbits to learn behaviors evoked by odors and makes the behavior easy to measure and manipulate by researchers [2,3]. As a result, scientists can measure the rabbits’ behavioral ecology with respect to foraging, which could make the European rabbits a preferred model for olfactory learning. These rabbits are perfectly suited for this type of study because they are born with an innate sense of olfaction, allowing Dr. Hudson and her research team an excellent opportunity for a study aimed at olfactory learning and development.
Another illustrative example of Krogh’s principle in use comes from the work of Dr. Brian Hoover. Dr. Hoover’s research interests included the role of olfaction as it pertained to determining mating preferences in avian species. Dr. Hoover investigated mating patterns in Leach’s storm-petrel (Oceanodroma leucorhoa) to explore the chemical basis of mate choice through avian olfaction. There are several reasons he chose the Leach’s storm-petrel as the model organism for this study. The Leach’s storm-petrel has among the largest olfactory bulbs of any bird, thus they have an excellent sense of smell [4]. Olfaction is critical for the Leach’s storm-petrel to locate prey [5]. In addition, the Leach’s storm-petrels are genetically monogamous and produce only one chick per year. This scenario allows the offspring to have higher genetic quality. An organism’s genotype must be best-fitted for its survival. As the Leach’s storm-petrel only gives one offspring per year, its genetic makeup needs to be suitable to sustain it in its environment so that its survival rate is high. Thus, scientists can collect data about offspring quality and observe the adults’ mating patterns, thereby simplifying the data collection process while maintaining the accuracy of the mating patterns measured.
The population of Leach’s storm-petrel was abundant in the study, which equated to a large and accessible sample size. Sample size is an important consideration for data analysis as it is the determinant of statistical power, the ability to report findings with statistical confidence. There are other species that could have been used in this study, including the mallards (Anas platyrhynchos) due to their large olfactory bulbs. The mallard’s reproductive behavior is also driven by olfactory cues [6]. However, the mallards are not an ideal model organism compared to the Leach’s storm-petrels in this study because the mallards are polygamous. Therefore, the mallards would not show clear mating preferences compared to the monogamous Leach’s storm-petrel [5,7]. Both Dr. Hudson and Dr. Hoover utilized Krogh’s principle when designing their respective research studies. Applying Krogh’s principle allows for the intersection of practical study methodology, high quality data, and conclusions that are generalizable beyond the species studied.
Application of Krogh’s Principle: An Experimental Proposal on the Effect of Noise Pollution on Insect Communication
Now that we have examined historical uses, both recent and distant, of Krogh’s principle, we will now examine an application of Krogh’s principle for future research. In light of how useful Krogh’s principle is, it makes sense to propose an additional study on the auditory interference of grasshoppers. This research proposal will explore whether artificial noise in the environment affects insect hearing or communication. Insect perception of a sound is masked by environmental noise pollution. Based on Krogh’s principle, Bullacris membracioides (the bladder grasshopper) will be the model organism for this study due to their anatomical and behavioral advantages. Male and female bladder grasshoppers (Bullacris membracioides) call each other during mating using the duet behavior. The duet behavior occurs when a male grasshopper produces a song that is then repeated by a receptive female. Therefore, perception of the male call by the female can be measured by the female’s reply [8]. Anatomically, female bladder grasshoppers possess a sensitive auditory system of six pairs of ears (A1-A6). The A1 auditory organ contains 2,000 sensilla, which allows them to hear sounds over great distances of up to two kilometers. This is in contrast to other species of grasshoppers (i.e. Achurum carinatum) where females can only hear male calls only within 1-2 meters [9].
Bladder grasshopper female calls range in frequency from 1.5-3.2 kHz [8]. A common habitat for the bladder grasshopper is on the roadside. Road noises from the motorcycles can be loud (110 dB) and within the frequency range (700 Hz to 1.5 kHz) that could interfere with the auditory system of grasshoppers. Bladder grasshoppers typically mate in daytime, which is the same time as peak traffic noises. As a result, common noise pollution may disrupt perception of grasshopper calls and interfere with mating behavior [10] . In addition, it has been shown that grasshoppers exhibit phonotaxi (an organism’s movement in response to sound) in laboratory conditions [8-11]. To test whether artificial noise can disrupt the duetting behavior of the grasshoppers, a female grasshopper will be placed in a glass aquarium in front of an omnidirectional speaker that plays a recording of a male’s song mounted on a parabolic disk. Testing will be done at distance levels such as 100, 200, 500, 1,000, and 2,000 meters to examine whether distance correlates to the amount of time the female takes to respond. The experiment will be repeated with male calls with traffic noise, traffic noise alone, and no sound at all. Studying the effects of noise pollution on the auditory system using the bladder grasshopper is an example of Krogh’s principle because they are easy to raise and rear in a laboratory setting. Bladder grasshopper’s advantageous hearing made them the model organism of choice in relation to Krogh’s principle, making the hearing behavior more practical to measure and manipulate in response to different noise levels.
Conclusion
Krogh’s principle is an important concept to keep in mind while designing research studies. Many scientists, including Dr. Hudson and Dr. Hoover, around the world have applied this principle in their research to better answer research questions. To further elucidate the utility of Krogh’s principle, an experimental proposal was made concerning the effects of noise pollution on insect communication. The anatomical and behavioral characteristics considered in selecting the bladder grasshopper for this experiment were illustrated. Krogh’s principle provides useful guidance for scientists to select the most representative and practical model organism to study.
Acknowledgments
The author would like to thank Dr. Gabrielle Nevitt (Professor of the Department of Neurobiology, Physiology and Behavior at University of California, Davis) for supporting this research project and providing feedback on early versions of this manuscript.
Editor’s Note: A previous version of this article was published on April 18, 2020. The article was updated on June 19, 2020 to correct citation style.
References
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- Kindermann, U., Gervais, R., & Hudson, R. (1991). Rapid odor conditioning in newborn rabbits: Amnesic effect of hypothermia. Physiology & Behavior, 50(2), 457–460.
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- Hoover, B., Alcaide, M., Jennings, S., Sin, S., Edwards, S., & Nevitt, G. (2018). Ecology can inform genetics: Disassortative mating contributes to MHC polymorphism in Leach’s storm‐petrels (Oceanodroma leucorhoa). Molecular Ecology, 27(16), 3371-3385.
- Nevitt, G., & Haberman, K. (2003). Behavioral attraction of Leach’s storm-petrels (Oceanodroma leucorhoa) to dimethyl sulfide. The Journal of Experimental Biology, 206 (Pt 9), 1497-501.
- Corfield, J. R., Price, K., Iwaniuk, A. N., Gutierrez-Ibañez, C., Birkhead, T., & Wylie, D. R. (2015). Diversity in olfactory bulb size in birds reflects allometry, ecology, and phylogeny. Frontiers in Neuroanatomy, 9, 102.
- Doherty, P., Nichols, J., Tautin, J., Voelzer, J., Smith, G., Benning, D., et al. (2002). Sources of variation in breeding-ground fidelity of mallards (Anas platyrhynchos). Behavioral Ecology, 13(4), 543-550.
- Hedwig, B. (2014). Insect Hearing and Acoustic Communication.
- Van Staaden, M., & Römer, H. (1997). Sexual signalling in bladder grasshoppers: Tactical design for maximizing calling range. The Journal of Experimental Biology, 200 (Pt 20), 2597-608.
- Chepesiuk R. (2005). Decibel Hell: The Effects of Living in a Noisy World. Environmental Health Perspectives. 113(1): A34-A41.
- Drosopoulos, S., & Claridge, M. (2006). Insect Sounds and Communication: Physiology, Behaviour, Ecology, and Evolution.
Cerebral Palsy: More Than a Neurological Condition
By Anjali Borad, Psychology ‘21
Author’s Note: This paper explores the dynamic relationship between a mother and her son and the complexity of a health condition that the son has. I will look at a specific case of cerebral palsy—my brother—and talk about how his condition came to be and the likely prognosis. I want to delve into the details of how family dynamics play a very important role in the caregiving and caretaking that goes along with having a disabled family member and how that is seen in the relationship between my brother and my mother.
I see two different perspectives of my brother, Sam, and his condition, cerebral palsy: one through his eyes and the other through the eyes of my mother, his caregiver. Observing how my mother has taken care of Sam from the beginning, I began to realize that it takes a lot to be a caregiver and that she plays a significant role in his life. In order to gain more insight into her practices of giving care, I interviewed her. I started off by asking her what it means to be a caregiver and what “care” means to her. She took a deep breath in and expressed her daily routines as a caregiver. “Waking up in the morning, the first thing that you have to do is to attend to him and care for him before yourself,” she said. “You know that from brushing his teeth to giving him a shower and feeding him, we have to do everything from A to Z.”[1] A day in the life of my mother starts and ends with my brother, from getting him out of bed to providing him with basic needs like food and water. She even takes care of specific requests that pertain to his own interests, such as wearing a watch every day and having matching socks and pants.
Cerebral palsy is a neurological disorder. Most cases of cerebral palsy occur under hypoxic conditions during the birthing process. This lack of oxygen to the brain can cause developmental delays and lifelong debilitating conditions [2]. My family and I have experienced the difficulties and limitations that accompany this disease first hand. My brother’s condition of cerebral palsy is in its most extreme form: he has quadriplegia and spasticity. A telltale sign of quadriplegic cerebral palsy is the inability to voluntarily control and use the extremities. Spasticity occurs due to a lesion in the upper motor neuron, located in the brain and spinal cord. It interferes with the signals that your muscles need to move and manifests in the body by increasing muscle tone and making the muscles unusually tight [3]. Dr. Neil Lava, a member of the National Multiple Sclerosis Society and American Academy of Neurology, describes the pathophysiology of a lack of muscular activity. “When your muscles don’t move for a long time, they become weak and stiff,” Lava writes [4]. This physical restraint is evident in my brother’s case because he has been wheelchair-bound since the age of seven.
Upper motor neuron lesions can worsen over time. Major prolonged symptoms include over-responsive reflexes, weakness in the extensor muscles, and slow movement of the body, all of which affect the sensation of balance and coordination. For this kind of condition, occupational and physical therapy can alleviate some of the symptomatic stresses. In the case of therapy, performing the right kind of stretches can help to relax some muscle stiffness. Medication and certain surgical procedures can also treat upper motor neuron symptoms. Some common muscle relaxants prescribed to patients are Zanaflex, Klonopin and Baclofen [5].
At the neurochemical level, “Spasticity results from an inadequate release of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter in the central nervous system,” according to Mohammed Jan [6]. In a normal neural cell, when GABA interacts with and binds to GABA receptors on the postsynaptic neuron, it decreases the likelihood that the postsynaptic neuron will fire an action potential because of the inhibitory nature of GABA receptors. For a condition like cerebral palsy in which some form of insult or damage has occurred to the brain, especially in the upper motor neurons, the result is hyperactive reflexes (as opposed to the calming sensation). At this point, muscle spasticity begins to become detectable. [6]
Apart from the biological mechanism underlying this condition, particularly significant environmental factors also gravely contributed to Sam’s condition. For eight months, my mother was carrying a normally developing fetus in the womb. However, a few weeks before Sam’s delivery date, my mother could not feel any fetal movement for about three days, so she went to check on it. As she was receiving the examination, Sam unexpectedly made a fluttering movement. If he had not moved, my mother would have had to get a Caesarean section immediately. Since he moved inside, the examiners found nothing to be wrong with the fetus and deemed it safe to send my mother home.
Just a few days later, my mom was rushed to the hospital after her labor pain started. At the time, the primary medical staff mostly consisted of medical interns still honing in on decision-making skills during critical situations. From the time of my mother’s arrival at the hospital, 13 hours passed before a team of doctors and interns determined that she needed a C-section. Once this decision was made, additional time was required by the medical professionals to prepare the room for surgery. All the while, my mom was in labor pain and, unbeknownst to her, the fetus had become separated from the placenta while the umbilical cord suffered damage. By the time the surgery finally ended, Sam had suffered from asphyxiation. According to the Cerebral Palsy Guide, “asphyxiation that occurs during labor or delivery may have been caused by medical malpractice or neglect. Early detachment of the placenta, a ruptured uterus during birth or the umbilical cord getting pinched in a way that restricts blood flow can cause oxygen deprivation.” [7]
The most important aspect of a disease, once established and diagnosed, is treatment and therapy. Asking questions about how to manage pain, how to make daily routines easier to perform, and how to accommodate family members in raising a child with a disability all goes into the planning process of treatment as well. These individuals need more than mere pills in order to get through their daily lives. This is where therapists (i.e. occupational, behavioral, speech, physical, and vocational therapists) and related health advocates, including family members, come into play. While therapists cannot completely remove the condition, they provide a strategy to alleviate psychological symptoms, including feelings of loneliness, fear of who will care for you, or resentment towards oneself. Family psychologists can help children with cerebral palsy by providing an initial assessment in an attempt to gain more insight into the family dynamics. If there seems to be a lack of parental support or lack of child attachment, a family psychologist can address this through therapy sessions with the parents. Therapy sessions allow for parents to individually discuss what they think is working well for the child and other areas that can be improved. The parents are also free to talk about their own personal issues, permitting the psychologist to gain a better understanding of certain triggers for the parents. These triggers can affect caregiving for the child with special needs.
Cerebral palsy is more than just a neurological condition. It is a way of life that, for Sam, is entangled in a web of personal, social, familial, caregiver and medical challenges. One noteworthy concept heavily emphasized in the healthcare field today is the importance of a family-centered management model. The notion of a family-centered approach strives to improve the way of life for individuals with the condition in the family in a mutual way. For a family, it can be quite taxing physically and emotionally to have to take care of someone for the rest of their lives. While it is considerably easier for the receiver to reap the benefits of the caregiver, it is more difficult for the caregiver to constantly provide. The family-centered approach tries to find a middle ground where the caregiver or family and the care-receiver are benefitting from each other as much as possible. In a holistic family-centered model, the needs of each family member are taken into consideration.
A study by Susanne King details the role of pediatric neurologists, therapists, and family members, especially parents, in caring for children with cerebral palsy. This study mainly emphasizes the limiting restraints cerebral palsy places on individuals. For example, families with special needs children often have specific ways of communicating, specialized equipment used at home, and a support system consisting of the family members, therapists, and guidance counselors. The heavy emphasis on familial involvement with medical guidance from professionals is the root of family-centered care. King describes that “these children often have complex long-term needs that are best addressed by a family-centered service delivery model.”[8] Oftentimes, we see that those families who have disabled family members are suffering. Some parents, for example, experience great distress because they do not completely understand what is happening to their child and, thus, fail to acknowledge their limitations at times. Others feel that they are incapable of looking after their child but cannot bear the idea of sending them away to an institution.
King also discusses the lack of investigation of families as a whole practicing care-giving. “Although there is much evidence supporting a family-centered approach in the area of parental outcomes, there has been little work reported on the family unit as a whole,” King writes. “The most common outcome is better psychological well-being for mothers (because they generally were the participants in most of the studies).”[8]
In my family, I can actively see family-centered management of my brother’s condition occurring. I see how both my parents have certain roles in my brother’s life that collectively enable or mobilize him to feel included and respected. I like to call my parents the arms and legs for my brother in a figurative sense, and I like to call myself the eyes for my brother. Working together to the best of our ability, we enable him to see the outside world in a way that’s similar to the way we experience it.
All my life, I have seen my mother perform the role of a caregiver. I have seen so many ups and downs in her situation, and I would always ask myself the following questions. What makes her get up every morning and continue to give the care she does? What makes her not give up? She told me, “I have faith in God, and I know that He creates pathways for me to deal with the physical implications of taking care of a disabled family member and see, I have never had any major problems with your brother. I will continue to give care for as long as my body will allow for me to do so.”[1] Annemarie Mol and John Law of Duke University collaboratively published a research paper detailing how people are more than just the definitions of their disorders or conditions. According to Mol and Law, people actively create and construct their life in a way that either enhances or minimizes the intensity of their conditions. Mol and Law also explain that “there are boundaries around the body we do…so long as it does not disintegrate, the body-we-do hangs together. It is full of tensions, however.”[9] Their conclusion on what makes a person pull through encapsulates the reason my mother still continues to care for my brother.
The definition of cerebral palsy as a condition is very limited. Oftentimes people who have debilitating conditions are missing a network or a support system of people, that once established, can essentially improve that family member’s way of life. With the family-centered approach to managing care, one is essentially enabling the disabled family member by actively being a part of their life, including their day-to-day life activities. For example, through the support system we provide for Sam, he can feel that he is in good hands and that he has established emotional and personal security. Although his condition is permanent, it is comforting to know that our family dynamics allow for an environment in which he can thrive while remaining mentally healthy.
References
- Borad, Geeta. “Practices of Care, Interviews.” 8 Dec. 2018.
- Debello, William, and Lauren Liets. “Motor Systems.” Lecture, NPB 101, Davis, CA, 20 Jan. 2020.
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- Lava, Neil. “Upper Motor Neuron Lesions: What They Are, Treatment.” WebMD, 11 May 2018, https://www.webmd.com/multiple-sclerosis/upper-motor-neuron-lesions-overview#1.
- Chang, Eric et al. (2013). “A Review of Spasticity Treatments: Pharmacological and Interventional Approaches.” Critical reviews in physical and rehabilitation medicine vol. 25, 1-2: 11-22.
- Jan, Mohammed M S. (2006). “Cerebral palsy: comprehensive review and update.” Annals of Saudi Medicine. vol. 26, 2.
- Cerebral Palsy Guide. “Causes of Cerebral Palsy – What Causes CP.” Cerebral Palsy Guide. 21 Jan. 2017, https://www.cerebralpalsyguide.com/cerebral-palsy/causes/.
- King S, Teplicky R, King G, Rosenbaum P. (2004). “Family-centered service for children with cerebral palsy and the families: a review of the literature.” Semin Pediatr Neurol. Science Direct.
- Mol, A & Law, J. (2004). “Embodied Action, Enacted Bodies: the Example of Hypoglycaemia.” Body & Society, 43–62.
How Expectations Shape Perception
By Neha Madugala, Cognitive Science, ‘21
Author’s Note: Previous studies in neuroscience have suggested that our expectations and prior experiences impact how we perceive reality and current tasks. This idea is embedded in Bayesian integration, also referred to as multisensory integration, which essentially studies how the brain combines information obtained from sensory neurons to affect perception and create a distinct outlook on an organism’s surroundings. It defines how we view and think about our environment.
This topic was particularly interesting to me because expectations can serve to aid our further understanding of incoming information, but can also inhibit our understanding if the new information contradicts our predictions.
Scientists classify expectations as essentially creating a placebo effect. The idea is that an individual’s expectations can influence the outcome of a certain treatment, their personal performance, or their feelings towards a person, place, or object. These “prior beliefs” can shape our reality and influence our perception of things we encounter in our daily life. The source of this placebo is argued to either be due to a conditioned response, where a situation has occurred multiple times with the same outcome (behaviorist approach) or that the placebo is a result of expectancy (expectation approach) (4).
In a recent study by MIT, researchers argued for the latter hypothesis suggesting that expectations are the suspect for shaping our interpretation of our surrounding environment. MIT neuroscientists were inspired by the idea of Bayesian integration, which is the process of incorporating prior knowledge with new and uncertain information (6). Jazayeri et al. trained monkeys in a task called “ready-set-go.” The monkeys are shown a starting signal and ending signal. After seeing both signals, they are expected to press a button after the same time interval between the starting and ending code has passed (6). The neuroscientists had short intervals, which spanned from 480 to 800 milliseconds and long intervals, which were 800 to 1,200 milliseconds. The monkeys were given a visual cue at the start of each trial signalling whether the trial would be a “short” or “long” scenario (6).
Monkeys were trained in either the short or long intervals. Each prior condition consisted of four blocks and then was followed by the 800 msec block. When all the monkeys were given an interval of 800 msec, those trained with a shorter interval gave an average response that was a little less than 800 msec and those trained with a longer interval gave an average response that was a little longer than 800 msec (6). These results reveal that monkeys trained under longer time intervals had an expectation for the 800 msec time interval to be longer, and those trained under a shorter time interval had an expectation that the 800 msec time interval would be shorter. This experiment was reproduced in humans and they found similar results (6).
The MIT researchers wanted to further determine which areas of the brain are responsible for the influence of expectations from the short and long trials affected the perception of the length of time for the 800 msce interval. Jazayeri et al, found that prior experiences strengthen a pattern of synaptic connections in a region located in the frontal cortex, which has previously been determined to be involved in temporal resolution (6). These patterns of synaptic connections were further computationally modeled. These models were found to perform the tasks in the same manner as the monkeys used in the previous experiments.
In another study at the University of Wisconsin, researchers conducted a similar study in humans testing how prior expectations of taste can influence an individual’s perception of the taste. Sarinopoulos et al. tested how subjects responded to an aversive taste, which was a diluted solution of quinine hydrochloride, with deceiving and accurate cues to test how placebo altered the participants’ responses. One group was informed that they were about to receive a highly aversive taste, while the other group was deceived and told they would receive a less aversive taste. The group told that they would receive a less aversive taste acted as the experimental group and were used to test whether placebo is altered by expectations or further stated if expectations affect our perception. Sarinopoulos et al. compared the expectancy effect from the highly aversive to less aversive groups by measuring changes in the insula and the amygdala, which are activated by aversive tastes (5).
The insula is associated with pain processing, which explains the presence of many sensory receptors for visceroceptive, referring to signals received from the heart, lungs, stomach, bladder, and other internal organs near the trunk region, and interoceptive inputs, including regions of the brain such as the thalamus, brainstem, insula, somatosensory, and anterior cingulate cortex (2). The amygdala, located near the insula, specifically the medial temporal lobe forms a part of the limbic system and plays a fundamental role in emotion processing, specifically fear and pleasure (1).
The study was conducted using rapid event-related fMRI design. In order to create a basis of comparison, the study included various conditions with different levels of aversion and manipulation – totaling to seven experimental conditions. The wide array of conditions allows Sarinopoulos et al. to eliminate differences if the perception involves a more aversive or less aversive taste by including both aversive and pleasant taste with varying perceptions.
They found that subjects demonstrated a consistent pattern of rostral anterior cingulate cortex (rACC), which plays an important role in decision-making and attention, and orbitofrontal cortex (OFC), which is also involved in decision-making, activation when presented with the misleading cue, followed by a decrease in the bilateral insula responses to the highly aversive taste. It was also associated with a smaller amygdala response. These findings suggest that the rACC and OFC are both correlated with the placebo effect and are associated with the aversive and pleasant perception of taste.
References
- “Amygdala.” ScienceDaily, ScienceDaily, www.sciencedaily.com/terms/amygdala.htm.
- D.P.Papoiu, Alexandru. “Functional MRI Advances to Reveal the Hidden Networks Behind the Cerebral Processing of Itch.” ScienceDirect, Academic Press, 5 Aug. 2016, www.sciencedirect.com/science/article/pii/B9780128028384000285.
- “Figure 2f from: Irimia R, Gottschling M (2016) Taxonomic Revision of Rochefortia Sw. (Ehretiaceae, Boraginales). Biodiversity Data Journal 4: e7720. Https://Doi.org/10.3897/BDJ.4.e7720.” doi:10.3897/bdj.4.e7720.figure2f.
- Haour, France. “Mechanisms of the Placebo Effect and of Conditioning.” Neuroimmunomodulation, vol. 12, no. 4, 2005, pp. 195–200., doi:10.1159/000085651.
- Sarinopoulos, Issidoros, et al. “Brain Mechanisms of Expectation Associated with Insula and Amygdala Response to Aversive Taste: Implications for Placebo.” Brain, Behavior, and Immunity, U.S. National Library of Medicine, Mar. 2006, www.ncbi.nlm.nih.gov/pubmed/16472720.
- Trafton, Anne, and MIT News Office. “How Expectation Influences Perception.” MIT News, 15 July 2019, news.mit.edu/2019/how-expectation-influences-perception-0715.
panelC.A.HanlonL.T.DowdleJ.L.Jones, Author links open overlay, et al. “Biomarkers for Success: Using Neuroimaging to Predict Relapse and Develop Brain Stimulation Treatments for Cocaine-Dependent Individuals.” ScienceDirect, Academic Press, 25 July 2016, www.sciencedirect.com/science/article/pii/S0074774216301131.
A Regenerative Cocktail: Combination of Drugs Promotes the Conversion of Glial Cells to Neurons
By Reshma Kolala, Biochemistry & Molecular Biology ‘22
Author’s Note: While browsing recent findings in Neuroscience, I came across research investigating the possible conversion of glia to neurons. Although the conventional idea that neurons are irreplaceable has been overturned in multiple research studies, I was immediately intrigued by the possibility for neighboring glia to be the source of neural regeneration. The implications of this research could completely transform how treatment is approached in the neuroscience field of medicine.
This is Your Brain on Music
By Timur Katsnelson, Neurobiology, Physiology, and Behavior, ‘19
Author’s Note: Like everyone else, I love music- especially the works of my favorite artists. There is nothing better than listening or jamming out to your favorite song. The human love for music is a powerful binding force, but why do we even like it? What are the underlying physiological responses of our enjoyment? I wanted to explore the functions of our brain as they relate to enjoying music, and found some interesting results about what scientists have uncovered thus far.
One of the most distinguishing characteristics of the human brain is the ability to interpret and feel emotions regarding complex environmental stimuli such as visual arts and music. Even more interesting is the seemingly infinite amount of variation in how each individual perceives these stimuli, or rather, the reason why one person may love to listen to Vampire Weekend while another casually listens to a lo-fi playlist. There are structural similarities shared by all humans, crafted over millions of years of evolution, but they do not account for different tastes. Neuroscientists who study dopaminergic pathways and other neural structural mechanisms have made several initial steps in understanding what physiological functions music serves to humans. So far, it has been established that musical appreciation and preference are related to the connectivity of white matter between regions in the auditory cortex and the regions processing emotion; variations in activity from neurons related to emotional communication could explain our differences in musical taste. Answering questions about the effects of music on the brain will undoubtedly help to answer larger questions about music’s evolutionary purpose and its profound impact on human cultures.
Neuroscience of Pleasure and Reward
Motivation, emotion, and arousal can all be attributed to elevated activity in the reward centers of the brain. As these traits are known to have implications in addiction, their cellular manifestations have been studied for several decades. The ventral striatum, midbrain, amygdala, and some areas of the prefrontal cortex have all been demonstrated, in varying degrees, to being recruited in instances of drug use. The dopaminergic pathways of the brain refer to a series of densely-packed neuronal connections that are stimulated by the neurotransmitter dopamine to propagate signals. Collectively, these regions of the brain are responsible for our response to natural stimuli and our actions to either seek or avoid them.
The brain’s reward centers are also known to be active in communal interactions, suggesting that there is a benefit to acting in a socially-positive way. Interestingly, the emotions experienced by humans when listening to their favorite music is correlated to the engagement of the same dopaminergic pathways as those that are stimulated during drug use or social interactions. It is important to note that the similarities between which parts of the brain are engaged when listening to music, using drugs, or being with people do not imply that the physiological or psychological effects are closely mimicked in the process. Neurons communicate via action potentials. These synaptic changes in membrane voltage effectively signal messages to neighboring neurons, but nothing about them is inherently meaningful. Since all action potentials are the same, it is the frequency of their appearances that convey messages. As it relates to the similarities in regions activated by both drug use and music, increases in activity do not necessarily equal the same frequencies of action potentials. Nonetheless, positron emission tomography (PET) scans observing pleasurable responses to music in animals and humans show the same regions of the brain being activated. Increases in dopaminergic pathway activity in the nucleus accumbens (NAc), ventral pallidum, ventral tegmental area, amygdala, hippocampus, and other areas of the midbrain collectively correlate to the reward process [3].
The Brain’s Response to Music
There are several experiments that examine the neural response to music, or “aesthetic responses” as some scientific literature has described. PET studies visualized the neural relationship with ‘intensely pleasurable’ responses to music [2]. Intensely pleasurable responses are defined as euphoric sensations in reaction to music, characterized by “shivers-down-the-spine” or “chills” [1]. In addition to observing activity levels within the brain, researchers monitored heart rate and blood flow in the brain. When excited by external stimuli, the central nervous system commands a response throughout the body to heighten the senses and increase awareness. A study by Blood et al. measured heart rate and cerebral blood flow of subjects listening to chill-inducing songs. Increases in the intensity of stimulation from a song were shown to increase blood flow in areas of the brain’s reward centers, as well as the heart rate. It is known that pleasure derived from music activates regions between the brain’s auditory region, specifically the superior temporal gyrus, and the reward centers such as the ventral and dorsal striatum. Parts of the basal ganglia, the ventral and dorsal striatum are largely responsible for motor function as it relates to desire and reward. Despite these findings, the exact connection between physiological sensations and aesthetic responses in the brain are ambiguous [1].
Evolutionary Advantage?
The question of music’s evolutionary purpose has been postulated for over a century, including in Darwin’s The Descent of Man, and Selection in Relation to Sex [3]. To some experts, music is considered to be the result of an evolutionary exaptation. That is, music’s purpose was not selected for its current use by humans. Rather, it came about as a result of excited neural pathways that engage emotional responses [1]. Others suggest that music is an important communicative tool that possibly preceded speech and language [5]. In this case, the chills elicited by music are physiologically measurable emotional responses, which signify that music is effectively a resource for communicating emotions [3].
Based on this idea, some researchers wanted to examine responses to music between individuals and compare them to the structural foundations of their emotional expressiveness capacity. Musical anhedonia is used to describe a condition for those who do not exhibit any pleasure from music, as there is no dopaminergic response from the reward centers. The flat affective response of individuals with this condition could be compared to the brains of subjects with affective responses to music. One such study found that patterns of white matter networks between the superior temporal gyrus through the ventral and dorsal striatum predicted the amount of reward response elicited by music. As the name suggests, the superior temporal gyrus is part of the temporal lobe- which is associated with the auditory cortex. This path of white matter moves from the auditory processing system to the basal ganglia. The aforementioned ventral and dorsal striatum, both parts of the basal ganglia, are involved in motor function. However, there could be other reward-related responses elicited from these structures, such as chills. Some researchers postulate that music may have had its origins from chill-responses to pleasurable sounds in the evolutionary environment, which may have motivated our ancestors to create their own response-evoking sounds [3]. Chills are viewed as a form of communication, demonstrating a positive response to sounds. Therefore, finding this white matter network may suggest that, in addition to emotion, there is a structural aspect of music involved in communication [3].
Music’s Effect on Other Species
A less studied and even less understood aspect of music is its meaning and interpretation by other species. Understanding the effect of music on other animals could provide a glimpse into music’s inherent biological meaning. Although it is clear that the pleasures that humans experience from music are not necessarily akin to the experience of animals, research suggests that music genres can affect the mood or behavior of captive animals. Country music has been shown to improve the mood and well-being of cattle, as opposed to more harsh or erratic-sounding music such as rock and jazz. One study specifically showed that cows more readily entered milking parlours when exposed to country music. However, these foundational animal studies have strictly been observant of the behavior and activity of the cattle [4]. Examining the neurological differences in musical preference or indifference in cattle would provide more concrete evidence of the neurological change that leads to the observed behaviors.
Further Discussions and Research
The research discussed thus far provides clues into the baseline purposes of music and the nature of its evolutionary impact. Yet, there are still many interesting existential discussion topics surrounding the origins of music and its purpose. Grounded biological inquiry, however, will be the most essential tool to get closer to understanding the extraordinary impact of music on human culture, communication, and evolution. Moving forward, researchers should continue to address the differences between individual preference and capacity to respond to music by studying differences in neural matter and structure. Most evidence suggests that music has a strong correlation to emotional expression, so examining the mechanisms of communication and interpreting abstract stimuli as emotional cues will help researchers understand how music can be physiologically deciphered and responded to. On a broader scale, examining global differences in musicality could provide insight into how different cultures and languages relate to their historically popular forms of music and rhythms. Could phonetic or rhythmic patterns in language correspond to preferences for certain tempos, measures, rhythms, or lyrics in music? These questions would be better served in a separate discussion but for now, go back to enjoying your favorite song.
References:
- Blood, A. J., & Zatorre, R. J. (2001). Intensely pleasurable responses to music correlate with activity in brain regions implicated in reward and emotion. Proceedings of the National Academy of Sciences of the United States of America, 98(20), 11818-23.
- Matthew E. Sachs, Robert J. Ellis, Gottfried Schlaug, Psyche Loui (2016). Brain connectivity reflects human aesthetic responses to music, Social Cognitive and Affective Neuroscience, Volume 11, Issue 6, Pages 884–891.
- Psyche Loui et al. (2017). White Matter Correlates of musical Anhedonia: Implications for Evolution of Music. Frontiers in Psychology, Volume 8, Article 1664.
- Deborah L. Wells (2009). Sensory Stimulation as Environmental Enrichment for Captive Animals: A Review. Applied Animal Behaviour Science. Volume 118, Issues 1-2, Pages 1-11.
- Steven Mithen (2007). The Singing Neanderthals: The Origins of Music, Language, Mind, and Body.
Erasing Cue-Associated Memories
By Neha Madugala, Cognitive Science, ‘22
Author’s Note: While working on a different paper, I became interested in treatment and therapy for drug addiction. Addiction continues to increase, yet there seem to be limited viable options to actually overcome this problem. One of the main issues in the recovery process is relapses. I found this study interesting and promising for drug therapy because it directly targets relapses, an important step in preventing and treating drug addiction more effectively.
“Gut Feeling”: How Does Modulation of Gut Microbiome Affect Depression Pathophysiology and Status?
By Raida Aldosari, Nutrition Science (Biology option) ’18
Author’s Note: I wrote this literature review as part of my UWP 104F class with Dr. Lisa Sperber. The assignment was to choose a clinically-relevant topic, review the existing body of literature on this topic, and choose a specific area to write on. My topic of interest was about the relationship between gut microbiome and the brain. I became interested in this topic after reading an article about the differences between the microbial composition of individuals with depression. By the end of the quarter, my research question evolved from “how does our diet affect our brain or mood?” to “how does modulation of gut microbiome affect depression pathophysiology?” I enjoyed the flexibility of the assignment, and I greatly benefited from the guidance provided by Dr. Sperber. I would recommend this class to anyone interested in health-related fields, especially in research!
Cause of Seizures in Individuals with Angelman Syndrome
By Neha Madugala, Cognitive Science, ‘22
Author’s Note
While browsing recent scientific achievements and breaking news in the scientific community, I came across an article declaring that the 125-year-old neuroscience mystery surrounding perineuronal nets (PNNs) is finally resolved. PNNs have stumped neuroscientists for decades, yet their importance is undeniable. To understand the extent of this discovery, I read more about PNNs and found that they have a key connection to Angelman syndrome, which causes severe epileptic seizures in children. The new findings from the Philpot Lab identifying the purpose of PNNs draw a connection between PNNs and seizures, and this information can lead to improved medications and therapeutic treatment methods.
Neural Mechanisms of Axon Degradation
By Timur Katsnelson, Neurobiology, Physiology, and Behavior, ‘19
Author’s Note
This topic was brought up during our discussion on the development of the nervous system in my neurobiology foundations class. I found it to be interesting because of its significance in the earliest stages of our lives. Further research into scientific literature discussing the role of pruning in neurodevelopment led me to learn more about its mechanism, distinctions from other forms of axon degrading, and its use in adult organisms.
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