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- Creators: Barrett, The Honors College
Description
Optogenetics presents the ability to control membrane dynamics through the usage of transfected proteins (opsins) and light stimulation. However, as the field continues to grow, the original biological and stimulation tools used have become dated or limited in their uses. The usage of Organic Light Emitting Diodes (OLEDs) in optical stimulation offers greater resolution, finer control of pixel arrays, and the increased functionality of a flexible display at the cost of lower irradiance power density. This study was done to simulate methods using genetic and optical tools towards decreasing the threshold irradiance needed to initiate an action potential in a ChR2 expressing neuron. Simulations show that pulsatile stimulation can decrease threshold irradiances by increasing the overall duration of stimulus while keeping individual pulse durations below 5 ms. Furthermore, the redistribution of Channelrhodopsin-2 (ChR2) to the apical dendrites and a change in wavelength to 625 nm both result in lower threshold irradiances. However, the model used has many discrepancies and has room for improvement in areas such as the light distribution model and ChR2 dynamics. The simulations run with this model however still present valuable insight and knowledge towards the usage of new stimulation methods and revisions on existing protocols.
ContributorsKyeh, James (Author) / Muthuswamy, Jitendran (Thesis director) / Crook, Sharon (Committee member) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The development of computational systems known as brain-computer interfaces (BCIs) offers the possibility of allowing individuals disabled by neurological disorders such as Amyotrophic Lateral Sclerosis (ALS) and ischemic stroke the ability to perform relatively complex tasks such as communicating with others and walking. BCIs are closed-loop systems that record physiological signals from the brain and translate those signals into commands that control an external device such as a wheelchair or a robotic exoskeleton. Despite the potential for BCIs to vastly improve the lives of almost one billion people, one question arises: Just because we can use brain-computer interfaces, should we? The human brain is an embodiment of the mind, which is largely seen to determine a person's identity, so a number of ethical and philosophical concerns emerge over current and future uses of BCIs. These concerns include privacy, informed consent, autonomy, identity, enhancement, and justice. In this thesis, I focus on three of these issues: privacy, informed consent, and autonomy. The ultimate purpose of brain-computer interfaces is to provide patients with a greater degree of autonomy; thus, many of the ethical issues associated with BCIs are intertwined with autonomy. Currently, brain-computer interfaces exist mainly in the domain of medicine and medical research, but recently companies have started commercializing BCIs and providing them at affordable prices. These consumer-grade BCIs are primarily for non-medical purposes, and so they are beyond the scope of medicine. As BCIs become more widespread in the near future, it is crucial for interdisciplinary teams of ethicists, philosophers, engineers, and physicians to collaborate to address these ethical concerns now before BCIs become more commonplace.
ContributorsChu, Kevin Michael (Author) / Ankeny, Casey (Thesis director) / Robert, Jason (Committee member) / Frow, Emma (Committee member) / Harrington Bioengineering Program (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor) / School for the Future of Innovation in Society (Contributor) / Lincoln Center for Applied Ethics (Contributor)
Created2016-05
Description
A reliable method for real-time blood flow monitoring in vivo is critical for several medical applications, including monitoring cardiovascular diseases, evaluating interventional procedures and surgeries, and increasing the safety and efficacy of neuromodulation procedures. High-speed methods are particularly necessary for neural monitoring, due to the brain's
heightened sensitivity to hypoxic and ischemic conditions. High-speed CBF monitoring methods may also provide a useful biomarker for the development of a closed-loop deep brain stimulation (DBS) system. Current methods such as laser Doppler, bold fMRI, and positron emission tomography (PET) often involve cumbersome instrumentation and are therefore not well-
suited for chronic microvasculature monitoring. The purpose of this study is to develop a method for real-time measurement of blood flow changes using electrochemical impedance spectra (EIS). Utilizing EIS to measure CBF has the potential to be included in a chronic, closed-loop DBS system that is modulated by fluctuations in CBF, using minimal additional instrumentation. Five experiments in rodents were conducted, with the objective of 1) determining whether electrochemical impedance spectra showed impedance changes correlated with changes in blood flow, assessing the sensitivity, specificity, and limitations of detection of this method, and 2) determining whether cyclic voltammetry-based method could be used to produce EIS more rapidly than current methods. The experimental set-up included electrodes in the femoral artery with the administration of endothelin (ET-1) to induce blood flow changes (N=1), electrodes in the motor cortex using isoflurane variation to induce blood flow changes (N=3), and electrodes in the femoral artery with the administration of nitroglycerin (NTG) to induce blood flow changes (N=1). Preliminary results suggest that impedance changes in the higher frequencies (over 160 Hz) demonstrated higher sensitivity to blood flow changes in the femoral artery model compared to <100 Hz frequencies, with inconclusive results in the motor cortex model. Future in vivo experiments will be conducted using endothelin-1 to further establish the relationship between impedance and cerebral blood flow in the brain.
ContributorsJitendran, Elizabeth (Author) / Greger, Bradley (Thesis director) / Kodibagkar, Vikram (Committee member) / Muthuswamy, Jitendran (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor)
Created2024-05