Project Background
In the summer of 2023, I participated in a 6-week research internship with the Max Planck Florida Institute for Neuroscience, where I worked under Sarah Stern with mentors Maria Olvera Caltzontzin and Sebastien Bullich. The Stern Lab uses a feeding behavior model to understand the information-processing function of the insular cortex and its influence on behavior when presented with varying external stimuli.
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To understand the significance of the insular cortex, one must identify the factors that govern behavior. Behavioral expression results from the analysis and synthesis of information received from external stimuli (exteroception) and internal stimuli (interoception). The insular cortex is thought to receive and process interoceptive information, and the subsequent involvement in decision-making accounts for this region's influence on behavior.
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The feeding behavior model addresses the complexity of eating by exploring the factors that determine dietary patterns. A primary example is the interaction between the homeostatic and non-homeostatic (hedonic) feeding systems. Homeostatic feeding involves the desire for nutrients necessary for survival, while non-homeostatic feeding works to satisfy psychological cravings regardless of physiological needs(1).
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​An imbalance between these systems in response to external stimuli contributes to the abnormal behavioral patterns observed in eating disorders. To determine the neural processes of related pathologies, one can examine the neural pathways connected to the insular cortex during altered feeding behaviors.
(1)Stern Lab – Max Planck Florida Institute for Neuroscience. (2023, October 2). Mpfi.org. https://mpfi.org/science/our-labs/stern-lab/
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Gogolla, N. (2017). The insular cortex. Current Biology, 27(12), R580–R586. https://doi.org/10.1016/j.cub.2017.05.010
Research Focus
Principal Investigator: Sarah Stern
Graduate Mentors: Maria Olvera Caltzontzin and Sebastien Bullich
Max Planck Florida Institute for Neuroscience
PROJECT: Decode the circuits of the insular cortex to understand non-homeostatic feeding behaviors.​
Principal Investigator: Sarah Stern
My project was to identify the neural pathways that exhibit the strongest relationship with the insular cortex during non-homeostatic feeding behaviors. These pathways connect the cortex to various brain regions responsible for cognitive, emotional, or sensory processing. Analyzing the activity of individual pathways during specific behaviors highlights the role of different brain regions in particular conditions or pathologies. ​
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I identified 6 brain regions that interact with the insular cortex during non-homeostatic feeding behaviors and numerically defined the relationship. I analyzed and recorded the pixel intensity of neural projections from microscope images of each region.
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This information, and that obtained from similar studies, supports advancements in preventative and treatment methods for eating disorders by revealing the brain regions involved in different pathologies.
Methods
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Retrograde tracing allowed me to identify the origin of neuronal projections received by the insular cortex. This process includes the use of neuronal tracers, chemical probes that follow the path from a synaptic terminal to the original cell body (1).
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Immunohistochemistry enhanced neuron visibility on images by staining the target neuron with a fluorophore. The process includes the use of a primary antibody that represents the intended antigen and a secondary antibody that connects the first antibody and the fluorophore.
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ImageJ was used to determine the relevance of each pathway by quantifying the projection neurons sent to the insular cortex from an individual region.
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​(1)Thompson, N., Mastitskaya, S., & Holder, D. (2019). Avoiding off-target effects in electrical stimulation of the cervical vagus nerve: Neuroanatomical tracing techniques to study fascicular anatomy of the vagus nerve. Journal of Neuroscience Methods, 325, 108325. https://doi.org/10.1016/j.jneumeth.2019.108325
Responsibilities
My responsibilities included the immunohistochemistry process, which involved sample collection, performing the immunohistochemistry assay, and microscopy. I began by slicing six mouse brains using a vibratome. I then stained the samples with a fluorophore to increase the visibility of projection neurons on images, and obtained 48 images with a fluorescent microscope. I measured the pixel intensity of each image with ImageJ, and developed a comprehensive presentation to synthesize my data (linked in the Media section).