Final Thoughts

(Image: Kateryna Kon/Shutterstock)

In late February and early March of this year, scientists knew only the most basic information about the novel coronavirus, SARS-CoV-2. Eight months later, only a year after the initial discovery of the virus, our knowledge has grown exponentially. Yet, there is still more to learn.

This blog has highlighted the neurological effects of COVID-19. Scientists and medical professionals from Wuhan to Paris to Chicago are noting the short- and long-term changes to the brain and nervous system caused by SARS-CoV-2. The myriad of research techniques being employed to understand this virus is an awesome demonstration of the power and flexibility of neuroscience. The findings are a vital reminder of the strong link between our physical and mental well-being.

We leave you with a few final thoughts on what we discovered about neuroscience, COVID-19, and ourselves.

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…I still find it incredible that my brain decided to study itself… -David

Knowing that there’s an entire unknown body of information about the virus, and that it can directly affect the brain, was just scary enough to make me much more cautious. -Parker

…many techniques were working in tandem in the assigned readings, and it became clear that neuroscience research is a symphony of approaches working to reinforce each other, from gene sequencing and biochemical assays to brain imaging and computational modeling. -Annie

Now instead of uneasiness and fear I see it as a challenge, and I am in awe of how rapidly as a society we can learn and adapt to different conditions. Furthermore, I see that COVID-19 is like trying to piece together a large puzzle without the reference picture. -Melanie

Understanding how to read scientific articles has also helped me better understand how to write scientifically. -Mylah

I now know that viruses can have many effects on the brain’s function and could even permanently alter the brain. -John

…it really made one feel useful to the progression of information found about COVID-19… -Felicity

I have already had many meaningful discussions with my family and friends about COVID-19… -Grace

Learning all of these things in the lab about COVID is definitely going to make me more conscientious of other people because if they’ve had COVID they could be dealing with all of these lasting effects and more. -Jordan

I realized that, unlike an ophthalmologist or a neurosurgeon, rigid specialization is not a requirement for a neuroscientist and there is a lot of room for creative approaches … this project reinforced my belief in the diversity of the field of neuroscience and the exciting ways in which we can study the brain. -Navami

Not only has this lab taught me about neuroscience, but it has taught me even more how to work with others … the challenge of the online labs has given our entire class an experience we wouldn’t have gotten previously, and now we know better how to communicate with each other when not in person. -Kyle

I realized that there were so many questions answered through research, and still many more to explore … I realized that formulating my own research questions was more than feasible. -Emma

I originally feared this virus, but now I want to be on the team that helps stop it. -Jessie

Computational Modeling for COVID-19

Computational modeling is the use of mathematics, physics, and computer science to simulate and study complex systems. Computational neuroscience is the branch of neuroscience that uses computational modeling to simulate and understand the various aspects of the nervous system. Typically, computational neuroscientists formulate mathematical equations to describe a specific aspect of how the brain works and then use computers to mimic this in a program. 

An example of a computational model for memory was made by Dr. Christian Fink, a former physicist at Ohio Wesleyan University. This model simulates two of the prominent theories in neuroscience for encoding, storing, and retrieval of memory, namely the Hebbian learning rule and the Hopfield network. According to the Hebbian rule of plasticity, neurons that fire together strengthen their synaptic connections, giving them greater efficiency in activating the same network in future. This principle works best for the retrieval of memories that involve fewer neurons and sparse networks, such as episodic memories of one’s graduation or wedding. On the other hand, in Hopfield learning, neurons that either fire together or stay silent at the same time have excitatory connections, while cells that do opposite things at the same time have inhibitory connections. Hopfield’s model is better at retrieving memories that involve widely distributed networks consisting of interconnected and recurrent neurons, such as procedural memories of parking a car or remembering the way to work. Both models are based on assigning differential weightage for neural connections depending on how often they fire together.

Computational neuroscience can be used to study a variety of brain functions and processes, including the neurological effects of COVID-19. One such model is being developed by Frontera et al. The team of researchers have established the Global Consortium Study of Neurological Dysfunction in COVID-19 (GCS-NeuroCOVID), a worldwide research collaboration that aims to understand the prevalence, manifestations, mechanisms, and prognosis of the neurological effects of COVID-19. They have launched a three-tiered research program to gather data on how SARS-CoV-2 infection affects the brain in both adults and children. Tier 1 of the program is an observational study designed to collect core data elements, such as the onset of neurological symptoms. This tier can be quickly launched in clinical centers around the world due to its cost-effectiveness and expedited approval from ethical boards. Tier 2 will focus on detailed imaging, electrophysiology, and microbiological data that was not collected in Tier 1. This tier will take slightly longer due to the patients’ willingness to consent and the moderate cost associated with data collection. The last tier, Tier 3, will involve advanced data collection from experimental studies and will take the longest time as it can only be carried out in specialized, adequately-funded research facilities. Adults and children with SARS-CoV-2 who had acute neurological symptoms are included in the study.

The GCS-NeuroCOVID study was conceived in late March, and during a 1-month window from March 27th to April 27th, 124 sites representing 17 different countries registered for participation. While data collection and statistical analysis will continue throughout the remainder of the year, this study represents a bold first step into systematically characterizing the neurological effects of SARS-CoV-2 infection. The study design is cost-effective, easily and rapidly deployed, and, perhaps most importantly, adaptive. Thus, data can be collected in real time with each site contributing the greatest level of detail as determined by its resources and capabilities. The global, longitudinal, efficient, and thorough nature of this study is the kind authors have been calling for in studies we have read all semester.

The answers resulting from the GCS-NeuroCOVID study will first and foremost allow us to progress from guesswork and anecdotes to quantitative data when it comes to the neurological effects of COVID-19. For example, it is essential that we determine a time frame in which acute neurological deficits arise and how long they last. Laboratory and imaging data may point to certain biomarkers that characterize neurological deficits, predict who will develop them as well as their relationship to the severity of the infection. Interestingly, the global extent of the study design may reveal if there are unique neurological symptoms in different countries, perhaps according to the spread and mutation of the virus over the course of the SARS-CoV-2 pandemic. Additionally, children are commonly seen as differentially affected by the virus with relatively fewer cases and less severe symptoms. They may be overlooked in favor of studying more vulnerable populations, but the pediatric data collected as proposed by Frontera et al. will be crucial in determining if and how children’s nervous systems are affected. The most lingering and worrying question, however, may be only answered over time: will COVID-19 survivors have long-term impairments that interfere with their functional and cognitive status? Thankfully, the lengthy and comprehensive GCS-NeuroCOVID study could be the first to capture the progression of any long-term effects quantitatively in real time, informing future prevention and treatment options.

Electroencephalography and COVID-19

Electroencephalography (EEG) is a research method that records the electrical activity of neurons in the cortex. EEG is a non-invasive technique that uses a cap with electrodes made from conductive metal attached to it. An EEG cap can have a couple of electrodes or up to hundreds spaced around the cap according to the 10-20 system. The 10-20 system is an internationally recognized system that standardizes electrode spacing so that researchers are able to compare their findings across many different studies. An EEG creates a wave based on the electrical signals picked up by the electrodes. These contain summed signals of many neurons in the same area firing from the cortex as well as outside noise. Scientists are able to remove some of this noise in order to make the EEG waves more coherent. Researchers also have to redo the same trial many times and average the results in order to get more meaningful results. EEGs can show a variety of different waves based on the subject’s mental state with high activity resulting in high frequency, low amplitude waves. Event-related potentials (ERPs) use the EEG waves along with the timing of certain events in order to connect the EEG activity to the stimulus. In order to connect the EEG to the timed events, trigger codes are sent from the machine providing the stimuli to the machine graphing the EEG. Researchers look for positive and negative peaks in the EEG within a second of the event in order to draw conclusions about the effect of the event on EEG waves. Using the ERP scientists can see the brain’s response to the stimulus before the subject is consciously aware of it such as the error related negativity that occurs immediately after making an error. Although EEGs and ERPs allow researchers to see direct neurological activity non intrusively, they do have some drawbacks. EEGs are only able to pick up signals from neurons in the cortex and nothing deeper in the brain. EEGs also pick up noise from both inside the cortex and in the environment which distorts the data and requires a multitude of trials for reliable information.

In an attempt to better understand the neurological effects that SARS-COV-2 has on the brain, EEGs have been used to determine if there are patterns of cortical activity that are directly related to its infection. In two letters to the editors, Covid-19 associated encephalopathy: Is there a specific EEG pattern and Pay more attention to EEG in COVID-19 pandemic both examine the history of three patients who tested positive for COVID-19 and had EEGs performed. Initially, two of the three patients observed by Vellieux et al. tested negative for COVID-19 from a nasopharyngeal swab and CT scan tests. They later tested positive with further testing with IgC serology tests or through a second round of PCR testing. The EEG recordings of two of the three patients revealed similar abnormal wave patterns, which consisted of continuous, symmetric, slow(1-2s), delta, and diphasic/triphasic waves. One of the two patients, observed by Flammad et al., was able to fully recover while the other, with more severe symptoms, went into a coma. The third patient observed also showed abnormal cortical activity patterns with periodically short(1-1.5s) triphasic wave activity, which is typically related to respiratory failure. Unfortunately, this patient had a more serious case of COVID-19, which resulted in their death. Overall, although all patients saw different outcomes from their COVID infection, their EEG recordings showed similar abnormal wave patterns, which may be a signature of COVID-19 infection. However, it is important to note that the underlying causes of the abnormal activity are still unknown. Therefore, it is essential to continue to perform EEGs on patients demonstrating the neurological symptoms from COVID-19 infection as it might be able to aid prognosis and might reveal more of the COVID-19 effects on the brain.

With further use of EEG recordings and ERPs, it might be possible to find answers to the many unanswered questions relating to COVID-19 infection. For instance, since the EEG patterns described above share similarities is it possible that an EEG recording could be used to help confirm diagnosis? What are the long term effects of COVID-19 infection on cortical activity? To determine if EEG recordings can be used to confirm or deny the diagnosis of patients an observational study can be performed. The study would involve observing and comparing more EEG recordings to support or disprove that COVID-19 has a signature EEG wave pattern. 

One of the common less severe symptoms of COVID-19 appears to be loss or disruption to one’s ability to smell. Therefore, another interesting question to answer might be how does brain activity in patients with anosmia differ from those who do not have anosmia as one of their symptoms? To study this question, a control group of healthy individuals who have not been exposed to COVID-19 would be used as the baseline comparison. An ERP would be used to show the effects of different scents on the EEG wave. Researchers could then compare the averages of the ERPs for each scent for both groups and compare the results from people with COVID-19 to the control group to find how COVID-19 affects the brain activity when exhibiting anosmia.

Biochemical Assays

A biochemical assay is a test or a procedure that is used to identify the presence of a specific protein in a sample based on its unique properties and functions. These assays can be used to determine the concentration of a protein in a certain substance which  allows for the isolation of specific proteins. It can also be used to measure enzyme activity. There are many different neurological effects of COVID-19 that are being studied and tracked. With the help of biochemical assays, scientists can conduct more specific tests related to the neurological symptoms of COVID-19. Doctors can follow the changes in enzyme levels in order to better understand how these neurological effects are produced. This can also help doctors monitor how quickly the disease moves to different parts of the body, allowing them to track a wide array of symptoms. These techniques can also be utilized in order to prevent the onset of intense psychological symptoms in COVID-19 patients. They would be used to determine levels of inflammatory cytokines that are often present in COVID patients and cause psychiatric symptoms. 

Raony et al. examined previous literature to understand COVID-19’s effect on mental health. This research specifically studied psychiatric symptoms from effects of treatment, social isolation and other stressors such as finances or fears surrounding the growing pandemic. The main conclusion of the study was that endocrine and immune responses are likely causes of the negative effects on mental health associated with COVID-19. This was supported by other research on SARS and MERS, which were diseases that have a lot in common with SARS-COV-2. Many patients that recovered from these viral infections experienced adverse effects after recovery. These included anxiety, depression, PTSD, memory loss and other long term psychiatric effects. Many of these symptoms are being identified in COVID patients and there seems to be a pattern emerging

There was also evidence of changes to the HPA axis, inflammatory responses and the infection of the CNS that resulted in adverse mental health effects. The inflammatory immune response causes an alteration in production of neurotransmitters and neural plasticity and is seen in transgenic mice models as well. The production of cortisol (stress hormone) is also seen to increase.  This study reveals that it is important to understand the long term mental health effects that the infection will cause. A similar bodily response is seen in the uninfected population resulting from stress and social isolation. This highlights the importance of coming up with solutions for individuals suffering from social isolation. The researchers suggest that tighter social bonds, maintained safely, can help mitigate the harmful effects of isolation. There is also research supporting healthy diet, sleep habits and the potential for music to benefit a reduction in inflammatory stress responses. 

There are many directions that future researchers could take with the results of the Raony et al. study.  The main conclusion of this study was that neuroendocrine-immune interactions are the likely cause of  negative impacts of COVID-19  infection and also social isolation on psychiatric manifestations. This should be further investigated by researchers to gain a better understanding of the mechanisms and structures involved in this process.  There are two main techniques areas that would be a good starting point with research; animal models and case studies. The animal model would likely utilize transgenic mice. It would be important to observe the relationship between psychiatric symptoms and elevated cytokines and HPA activity.  This could help us understand if there is a definite connection between these variables in humans.  Mice could also be used to study the effects of immunosuppressants on psychiatric symptoms. Researchers could track the rate and extent of infection while also determining if mice patients given this treatment are less likely to develop neurological symptoms. 

Another potential study would involve case studies.  Patients who are diagnosed with COVID-19 are a valuable resource for the scientific community. They should isolate a population of patients who have had psychiatric symptoms. Participants would begin by completing a self report assessment about their psychological and physical symptoms while infected.  Researchers should specifically evaluate a patient’s levels of proinflammatory cytokines through protein assays, HPA activity and cortisol levels. PET scans would also be helpful to take in order to see brain activity.   These variables could help researchers discover links between them and conduct more targeted research. It would also be important to consider outside stress factors such as depression, threat of job loss, sick loved ones and social isolation because these also cause inflammatory responses and potential psychiatric problems. 

Microscopy and Histology; How We can utilize these techniques to study COVID-19

Histology is the study of microscopic anatomy. Using this technique, researchers would be able to answer questions pertaining to cells or tissues in the body and how they function and/or react to certain environments. A light microscope is one way to look at cells and tissues, this technique uses light filtered through a slide holding the cells being observed so they can be viewed through the ocular lens. Staining is another technique that can be used to color different structures in the cell, allowing the researcher to observe the cell and its structures more clearly. Using histology, researchers would be able to identify which tissues are affected by SARS-CoV-2 and what kind of tissue is involved (skeletal, cardiac, or smooth). Histology is relevant to studying the neurological effects of COVID-19 because it can be used in studying changes to the nervous tissue caused by viral infection, most likely through autopsies. Modifications to nervous tissue, such as changes in shape, can help understand the cause of some of the neurological effects of COVID. It can also help in determining which molecules can cross the blood-brain barrier or can be taken up by the neurons. Histology is a technique that can be used to answer and look into how COVID-19 specifically affects tissues like epithelial cells and neurons. Investigating neural vs. epithelial tissue in SARS-CoV-2 infection would be relevant, for example. Researchers could then determine if certain cell types are differentially affected by the virus.

A study done by Paniz‐Mondolfi et al. (2020) attempted to understand the biological components of the neural effects of COVID-19. The researchers began to understand where SARS-CoV-2 was being detected in neural tissues and which structures it is specifically found in. They discovered in one case study of a patient that had SARS-CoV-2, that virus particles are present in the brain and there is direct propagation of the virus into the brain. The virus particles were found specifically in the brain and capillary endothelial cells and could be seen through a transmission electron microscope. This led the researchers to question the pathway that the virus takes to enter the brain. The two most likely pathways discussed were hematogenous and neuronal retrograde routes, hematogenous meaning transmitted through the blood and neuronal being through neurons. 

In a piece of scientific literature written by Brann et al. (2020), the researchers went more in-depth trying to find how SARS-CoV-2 enters the body and the brain. Brann’s literature included figures and a table to display their findings on how nasal passages and olfactory neurons play a role in SARS-CoV-2 entering the body and making its way into the brain. The results from their experiments showed that the neurons themselves didn’t carry the virus but their supporting structures were carrying the virus. The ACE2 receptor was also researched further in this article, which has been suspected for several months of making a person more immune to contracting SARS-CoV-2, and the results of their study using mice further supported this statement.

A question that still remains is the extent of damage that persists in people who have recovered from SARS-CoV-2 infection but have lingering neurological symptoms. A follow-up longitudinal case study may look to investigate the quality of the neural tissue that remains post-infection. This study would aim to examine if SARS-CoV-2 produces lasting changes to neural tissue that facilitate the persistent neurological symptoms that remain. Sampling methods may be employed to collect tissue from the neural areas in question postmortem. Microscopy and staining techniques such as those examined today may be utilized to determine whether or not lasting changes are visible that may compromise the integrity of the neural tissue.

 

Animal Modeling of SARS-CoV-2 and Optogenetic Alteration of Neural Circuitry

For this week’s lab, Dr. Chelsea Vadnie presented some of her extensive research on circadian rhythms and how optogenetics have been useful in those studies. She also touched upon the use of animals for scientific and clinical research inquiries, primarily on why mice are used most often. The first technique that was evaluated was the use of animal models, primarily mice, as a method of conducting research. Animal models have been significant in creating vaccines and therapies, and mice are of particular interest due to their 85% genome similarity to humans (Vadnie). Furthermore, mice breed and mature rapidly, allowing for large colonies to be spawned quickly. Thus far, mice have not seen much use in SARS-CoV-2 research due to failure of the spike protein to adhere to the ACE2 receptor. Scientists have attempted to bypass this by genetically engineering mice to possess the ACE2 receptor of humans. Another attempt at solving this problem has been to use an adeno-associated viral vector with SARS-CoV-2 genes to infect and cultivate mice that are susceptible to SARS-CoV-2. Essentially, think of the adeno-associated viral vector as a car, and the persons inside it as the SARS-CoV-2 genes. The car (adeno-associated viral vector) will transport the people (SARS-CoV-2 genes) into the mice and allow for the genes to be replicated. Another research technique that was examined this week is the use of optogenetic approaches. Optogenetics have “disentangled intricate neuronal circuits at spatio-temporal precision unmatched by other techniques”, meaning that optogenetics have enabled more precise research of neuronal circuitry in the brain (Deubner, Coulon, Diester 1). Optogenetics allows researchers to control neuronal circuits using light-sensitive microbial proteins called opsins after injecting a viral vector into a specific brain region. This viral vector contains modified genetic constructs that allow for alterations to be made to specific regions of the brain. This technique can be utilized to examine how neurons work together by controlling the expression of certain neurons and monitoring the responses of the other neural structures. Overall, this will provide researchers with a better understanding of how certain regions as well as the brain as a whole function.

Since the first case of COVID-19, scientists have been tirelessly working on a possible vaccine as well as therapeutic agents. There are not always willing participants to try new and untested therapies. This is why animal models are essential to find the most effective drug to aid against this deadly virus. The article “Animal models for COVID-19” explores the many different kinds of animals that can be utilized. Finding an ideal animal model has been proven difficult. Mice are commonly used to create vaccines and therapies, as detailed above. Many issues have arisen as SARS-COV-2 does not present the same way in mice as it does in humans. Another animal that scientists have shown interest in is syrian hamsters. They are cost effective and have been used before as models for respiratory viruses. There is however a lack of research tools, which does not make them an ideal candidate. Perhaps the most promising animal model is the ferret. They have provided consistent results and the ferrets presented with similar symptoms to humans. The most important finding is where the infection is located; “SARS-CoV-2 infection results in a predominantly upper-respiratory-tract infection in these animals.” This can lead to the testing of experimental drugs that help prevent infection and transmission to the upper airway. This article looks at other animals as well that have varying results. The research being conducted is important as it can allow for the approval of therapeutic drugs as well as a possible vaccine.

Animal models are not only being utilized to aid in the fight against COVID-19. Along with models, optogenetic approaches are used to help better understand the brain physically and physiological. The article “Optogenetic approaches to study the mammalian brain” discusses possible ways that this approach can help the brain’s physically damaged parts, such as possibly restoring a blind person’s sight. However, others have looked at how it can help the brain physiologically. Dr. Vadnie, a professor at Ohio Wesleyan, conducted research to try to determine what portion of the brain is a major contributor in regulating symptoms of psychological disorders. To do this, she utilized animal models and the optogenetic approach. The approach looked specifically at the role of the suprachiasmatic nucleus (SCN). By using two optogenetic approaches, Dr. Vadnie was able to control the amount of stimulation the SCN was receiving. The animal models (mice) were then put into situations which may cause anxiety or depression. Through many tests, it was discovered that with a decrease in stimulation of the SCN was clearly correlated with an increase in anxious behavior. However, there was not a direct relationship between the amount of stimulation of the SCN and depressive behaviors. From this, they concluded that the dampening of the SCN is synonymous with increased anxious behavior, but not with depressive behavior.

While the WHO continues to explore the efficacy of animal models to test vaccines and therapeutic agents, an ideal model that presents many of the characteristics of COVID-19 in humans remains to be found. However, some aspects of the disease in humans can be accurately modeled in animals, and the species can be selected depending on the research question. For example, Syrian hamsters and non-human primates both produce the same characteristic chest imaging patterns that we observed earlier in humans, and thus it may be worth considering these species as subjects in studies of severe respiratory infection and pneumonia. Animal models have also been shown to mimic demographic trends among human transmission. Male hamsters experience more severe disease, and older hamsters and non-human primates also experience more severe disease. Dr. Vadnie also suggested that mice aged 10-14 months can be used to represent humans in their late 30s-40s, and mice between 18-24 months can represent older adults in their 50s and 60s. Age-related trends in disease severity can then be readily testable as mice are cost-effective and breed quickly.

Perhaps more interestingly, mice and non-human primates had pro-inflammatory cytokines and thus could help answer questions regarding the virus’ central mechanism of attack on the body’s organ systems, whether by direct infection or indirectly by means of the cytokine storm. Mice genetically modified to express human ACE2 have developed anosmia and encephalitis ranging from undetectable to lethal. Therefore, they are a promising candidate for the investigation of SARS-CoV-2’s entry into the nervous system where studies on humans, given their complex anatomy, may prove difficult.

Optogenetics should also be considered as a tool for future COVID-19 research. Dr. Vadnie speculated that the severity of the disease may depend upon when the infection took place (day or night). Among 332 human proteins associated with circadian rhythms, about 30% are thought to interact with SARS-CoV-2. Furthermore, symptoms of anxiety-like behavior in mice such as in Dr. Vadnie’s research include a reduction in weight gain, reduced self-grooming, adn stress hormone dysfunction. Mice expressing human ACE2 experienced weight loss and hunching upon infection with SARS-CoV-2, and hamsters experienced lethargy, ruffled fur, and a hunched posture as well. The overlap between anxiety-like symptoms and COVID-19 symptoms warrants further research. Optogenetics and animal models can answer questions regarding the role of the SCN and circadian rhythms in infection severity and anxiety in COVID-19 patients.

More Brain Imaging techniques and Clinical Assessment in Relation to COVID-19

Medical professionals and researchers often use different imaging techniques to help diagnose or detect various abnormalities in the brain or body. Some common imaging techniques used are MRIs, fMRIs, and PET scans. When deciding what imaging technique to use a researcher or medical professional takes into account the price, the function of the technique, and how accessible it is. MRIs are often used to study abnormalities in the structure of the brain by using a magnet and radio waves to create a 3D image (“How does an MRI machine work?”). An fMRI on the other hand, can reveal and measure what areas of the brain are active by tracking the oxygenated blood flow to the brain (“fMRI – How it Works and What it’s Good For”). Like an fMRI, a PET scan is also able to track brain activity and produce a 3D image. However to perform a PET scan a radioactive tracer is made to track specific molecules and is injected into the bloodstream this allows them to track brain activity and produce a 3D image (“How does a PET scan work?”). A PET scan might be more beneficial since it can track brain activity, create a 3D image, and track metabolic features. Unfortunately, it requires the production of a tracer molecule, which is time consuming to produce and can be more expensive in comparison to the other two techniques. Moreover, although MRIs and fMRIs have fewer functionalities they don’t require the injection of the radioactive tracer, are less expensive, more accessible, and may be more beneficial for diagnosing certain patients and for research. These imaging techniques can be used by researchers studying the trends of COVID-19 patients with have neurological symptoms such as anosmia, altered mental states, headaches, and strokes. An fMRI could be used to compare brain activity between patients to see if anything is altered. While MRI can be used to detect strokes and hemorrhages by analyzing the brain structure from the 3D image of the brain created.

Due to how little we know about COVID-19 researchers have begun using these neuroimaging techniques to find neurological trends between patients. The study: ‘Imaging in Neurological Disease of Hospitalized COVID-19 Patients: An Italian Multicenter Retrospective Observational Study,’ done by Adbelkader Mahammedi, Roberto Gasparotti, and others included images from 725 consecutive hospitalized patients with a confirmed COVID-19 infection between February 29th and April 4th. In this group, 108 (15%) had serious neurological symptoms and underwent brain or spine imaging. Most patients (99%) had brain CT scans, 16% had head and neck CT imaging, and 18% had a brain MRI scan. It was found that 59% of patients reported an altered mental state and 31% of patients experienced a stroke. These were found to be the most prevalent symptoms in patients (strokes specifically being ischemic), as well as altered mental status being more common in older adults. Patients also had symptoms of headaches (12%), seizures (9%) and dizziness (4%). 

Of the 108 experiencing neurological symptoms, 31 patients (29%) had no past medical history, whereas 77 (71%) had at least one of the following chronic disorders: coronary artery disease (23%), cerebrovascular disease (14%), hypertension (51%), and diabetes (28%). Of the 31 patients with no past medical history, aged 16 to 62, 10 experienced acute ischemic strokes and 2 patients experienced an intracranial hemorrhage (brain bleeds). When neuroimaging took place, the main factor was acute ischemic infarcts. Of the infarcts, 19 (18%) were large, 11 (10%) were small, 3 (3%) were cardioembolic, and 1 (1%)  had a hypoxic-ischemic encephalopathy pattern. Out of the 6 patients (6%) who experienced intracranial hemorrhages, 3 patients (3%) experienced subarachnoid hemorrhages. 71 patients (66%) had no findings on a brain CT scan, the remaining 7 (35%) had brain MRI’s in which acute abnormalities were shown. There was a statistically significant association between the prevalence of altered mental status and the age of the patient.

It was also demonstrated that the neuroimaging features of COVID-19 patients (and specifically the patients studied) were variable and without a specific pattern, but “dominated by acute ischemic infarct and intracranial hemorrhages.” Overall, scientists studying this have a poor mechanistic understanding of the neurological symptoms in COVID-19 patients, and whether or not these neurological symptoms are coming from a critical illness or directly from the infection invading the central nervous system (CNS). The study also quotes, “Accumulating evidence suggests that a subgroup of patients with severe COVID-19 might have a cytokine storm syndrome which could be a trigger for ischemic strokes.” The results of the study showed a lower prevalence of CNS symptoms than Wuhan’s study(15% versus 35%), although the prevalence of ischemic strokes was higher in this study (31% versus 11%). Findings also suggest the potential of COVID-19 being associated with Guillain-Barre syndrome.

COVID-19 can have long lasting neurological effects, but we are unsure what exactly the long term effects may be. For example many COVID-19 patients have reported a “brain fog”, but why does COVID-19 do this? One way we could find answers to this question would be to potentially have COVID-19 patients, or even recovered people, complete cognitive tasks while undergoing an fMRI to see what parts of the brain were more affected, and how they behaved differently compared to people who never had COVID-19. Any changes in brain activity in COVID-19 patients compared to those who never had COVID-19 would help us identify what parts of the brain are affected more by COVID-19, and further help us treat COVID-19 patients.

Brain Imaging and Clinical Assessment

Both CT scans and cerebral angiograms can be helpful tools when detailed images of the brain are required. A cerebral angiogram is specifically used when a medical professional needs to examine the blood vessels in the head and neck. It can determine if the blood flow to the brain is sufficient. Looking at these scans, a doctor can determine if there is an aneurysm (bubble in the brain caused by weak blood vessels) present or identify a brain bleed (“Diagnostic Cerebral Angiography”). On the other hand a CT scan is utilized for many different reasons. It provides a detailed image of the soft tissue present in the brain. It can identify many things about the brain including the presence of tumors, strokes, or infections. CT scans are good for emergencies as they are quick to provide images. They are also beneficial as they are non-invasive and provide more detail than a traditional X-ray. A downside is that CTs utilizes a high amount of radiation which can be harmful to the person being exposed. Another issue with a CT scan is that it cannot identify brain activity (“Computed Tomography (CT) Scan of the Brain”). As more studies are conducted, scientists are discovering that neurological effects are a common symptom of COVID-19. One common symptom affecting COVID-19 patients is the formation of blood clots. A CT scan can show if this is happening in the brain. Scientists can also use these techniques to discover other neurological symptoms that are common with patients who have contracted COVID-19. 

Previous research about SARS-COV-2 has focused on the symptoms that relate to respiratory issues or common illnesses.  Studies have analyzed the common symptoms of the virus, but no one has considered the neurological effects until recently.  Mao and colleagues were the first to look into neurological symptoms associated with COVID-19 and determine if they are common. The purpose of this study was to analyze neurological symptoms in patients diagnosed with COVID-19. After reviewing many case files, the researchers concluded that neurological symptoms do indeed often accompany COVID-19. Although it was originally thought to be a disease that mainly impacted the respiratory tract, it seems that there is another level to this illness. Patients with more severe infections were more likely to experience neurological symptoms, which affected the central nervous system, peripheral nervous system, and skeletal muscular system.  Seventy-eight of the 214 patients reviewed had neurological issues present when diagnosed with COVID-19. The study also divided the participants into severe and nonsevere cases. Those who experienced severe cases had much higher rates of reporting neurological symptoms and typically also had a higher age and more additional conditions. Forty of 88 patients with severe infection had neurological symptoms, while only 38 of 129 nonsevere group reported similar symptoms. The study confirmed that many patients experienced a range of symptoms from nonsevere to very severe. The researchers took these results and suggested that doctors consider testing patients who present with neurological symptoms for COVID-19 so as not to overlook the disease when determining a course of treatment. This study shows that the management of this pandemic is very important because even after recovering, patients may experience long term neurological symptoms. 

With these symptoms (and their extremely high variance), many questions arise. Why and how do we find these symptoms in patients? Are these neurological effects the result of SARS-CoV-2 specifically targeting the nervous system, or is the outcome just collateral damage from other symptoms of the body’s immune response? A study that could help us answer this last question would focus on determining if the olfactory bulb is infected with SARS-CoV-2.  This is an important area because if it is infected, this shows that COVID-19 is directly affecting the nervous system. CT scans could be used for viewing structure, fMRI for activity and self report for neurological symptoms. The combination of these strategies could cause researchers to conclude if the olfactory bulb is different for those infected with COVID-19 compared to healthy individuals.  As underlying health conditions and other factors that put patients at risk of severe SARS-CoV-2 infection can also be precursors for some of the neurological symptoms observed (This Is What Coronavirus Can Do to Your Brain), the degree to which these neurological symptoms are directly caused by COVID-19 can’t yet be precisely described. It may take a great deal more observation to get a deeper look into what’s going on in the brains of COVID-19 patients. CT scans and cerebral angiograms will be indispensable tools in doing so considering the aggressive effects of COVID-19 on the cardiorespiratory system and the nature of neurological symptoms found in COVID-19 patients.

Molecular and Cellular Neuroscience in respect to COVID-19

This week we learned more about techniques used in molecular and cellular neuroscience from Ohio Wesleyan University professor, Dr. Suren Ambegaokar. While Cellular Neuroscience focuses on the inner workings of a single cell or the system level integration of multiple cells, Molecular Neuroscience looks at the function of individual components of the cells, like genes and proteins. Dr. Ambegaokar’s work is more closely aligned with Molecular Neuroscience. 

One technique used in this field is the transgenic model, which is an animal model where new genetic information is injected into the embryo and then researchers can see what functions of the animal have changed. Dr. Ambegaokar gave the class an example of fruit flies being genetically malleable and used in studies often. The fruit fly’s eyes are mostly neural tissue making it an external neuron. In this example the fruit fly is used to study the effect of a gene found to be part of causing Alzheimer’s disease in humans. Dr. Ambegaokar explained autophagy related to these studies. Autophagy is the process that targets things that are having harmful effects. In the case of Alzheimer’s disease, it has been discovered through a variety of studies that this process of autophagy is disrupted. 

Transgenic animal models are used to study a variety of neurodegenerative diseases and their effects. ShihuaLia reviews the use of several transgenic models, for example transgenic mice. The transgenic mice are known to show very similar neuropathology and phenotypes expressed in their respective diseases. In this article it expresses how these animal models are used to look at the neurodegenerative effects of Huntington’s disease. There are differences between the larger or smaller animals used. Larger animals could experience a toxic effect from a specific change in their proteins whereas the smaller animals, such as mice, might not. On the other hand, some neuropathologies are more easily uncovered in larger animals than they are in smaller ones. Transgenic animal models are a vital aspect of molecular and cellular neuroscience; they help continue to help us understand the cellular and molecular pathways of diseases and reveal potential treatments. 

Dr. Ambegaokar discussed how interaction between different eye pigment genes and tau induced neurodegeneration in drosophila melanogaster. Dr. Ambegaokar’s studies have demonstrated how white, brown, and rosy genes dose dependently affected the tau-induced eye phenotype, tau phosphorylation, and GSK-3b activity. They also explored how the w1118 homozygotes showed a significant reduction in eye size increased ommatidial disorganization as compared to w+/w1118 heterozygous flies. He described his studies on white and brown, and how the loss of function mutations in these colors induce tau-induced toxicity. As he got deeper into his studies, he discovered that granules with improper pigment balance due to white, brown, or scarlet mutations become autolysosomes. This in turn caused lysosomal dysregulation, which is a characteristic feature of Niemann–Pick disease type C and Sanfillipo syndrome type B, both tauopathies. In conclusion, this shows that studies on how fruit fly genetics affect neurodegeneration can be used in similar instances in human cases.

Based on our discussion with Dr. Ambegaokar, we wondered how this kind of research might be applicable to COVID-19; how can we use fruit flies to study human diseases, especially COVID-19? Although it might seem peculiar at first, Wong et al. and Chan et al. have used fruit flies to study how SARS-CoV-1 from the 2003 outbreak causes cell death. Researchers have even studied HIV Tat protein using fruit fly models, and their findings have been observed in mammalian cells as well, thereby demonstrating that transgenic models as simple as fruit flies can be successfully used to study viral gene expression. Dr. Ambegaokar, too, believes that it is possible to make transgenic models that express human proteins targeted by Sars-CoV-2, such as the ACE2 receptor protein. “There are some people trying to work on animal models for COVID, and the way they’re doing that is by trying to express the human ACE2 receptor in mice or other animals.” Mice have a slightly different version of ACE2 that is enough to make them less susceptible to SARS-CoV-2. “By copying the human gene into a mouse you’re more likely to be able to get a mouse to be actually infected with the virus.”

However, Dr. Ambegaokar points out that “you always have to control where it is going to be expressed and what tissue it is going to be expressed.” It is important to limit the gene expression to a specific tissue, such as the lungs, the gut, or the blood vessels of the mice. “It is hard to get it to be expressed in exactly the same pattern as it would be in humans. So, most of our genetic regulation control is to either express it in one tissue or express it in everything.”

Transgenic models are excellent for studying molecular pathways, but the knowledge gleaned from them cannot always be quickly translated into treatment for humans. This, unfortunately, is the case for Dr. Ambegaokar’s research on Alziehemer’s. “Even though we know or we feel pretty confident that this is what’s happening in the brains, it’s unclear how you would treat it in a way that would be safe and helpful.” If something goes wrong, it might cause damage to healthy cells or trigger unwanted immune response. “When you’re talking about COVID in the brain, inflammation is a massive risk.” Since these factors need to be taken into account, it often takes a long time to make drugs and vaccines.

Nevertheless, can transgenic models potentially help us design methods to treat damage done by COVID-19 infection or even create vaccines? The answer is yes. Transgenic COVID models can help us identify which molecules or pathways are affected by the virus, which can be potential targets for drugs or vaccines. This is where another technique used in molecular and cellular biology can help us answer this question. Dr. Ambegaokar explains that it is possible to make antibodies that identify only the virus protein or a molecule altered by the virus while ignoring other healthy forms of the protein. This allows our immune system to find the viral protein or the impaired molecule and clear it.  “[In the case of Alzheimer’s] It has worked well in animal models and it has been tested a few times clinically in patients but so far, thankfully, it hasn’t caused anything worse.”

How does this apply to treating the effects of COVID on the brain? According to Dr. Ambegaokar, these methods can potentially help in treating the disease, but they cannot recover the neurons that have already been damaged. “We have very little knowledge or idea of how to restore neurons to health”, and so it is important to look into the prevention of the disease. Stem cells are another possibility for future research in molecular and cellular biology that can help us study ways to prevent neural damage. For now, it is important to prevent the spread of the disease by means already available to us.

Genetic Sequencing and COVID-19

Researchers utilize a machine called a genetic sequencer to compile the genomes of viruses, whereby the sequencer breaks the genetic strands into lengths of around 600 bases and tags them before reading and integrating them into the computer. This allows them to determine the RNA construction and evaluate the genetic bases. (“What is Genomic Sequencing?”). The full gene is then reconstructed from the segments. After sequencing the COVID-19 gene, researchers can then compare its genome with the other viruses’ and find similarities and differences in the genetic sequences.

Wang discusses the genetic sequencing of COVID-19 and compares it with the genetics of the SARS and MERS coronavirus as well as two coronaviruses found in bats in his article, The Genetic Sequence, Origin, and Diagnosis of SARS-CoV-2. COVID-19 was found to be more similar to the bat coronaviruses than the SARS and MERS viruses found in humans. By continual sequencing of COVID-19 genes, scientists can track the mutations of the virus as it spreads through the human population. In the article What the SARS-CoV-2 Genome Reveals, Kelly Malcom mentions that researchers have found 20 mutations in the COVID-19 genome so far. By looking at these mutations, they are able to trace the spread of the virus as it mutates.

The article The Genetic Sequence, Origin, and Diagnosis of SARS-CoV-2 authored by Huihui Wang and colleagues describes COVID-19 as a viral agent capable of inducing severe acute respiratory syndrome (SARS) in patients who encounter it. The article then details the origins of SARS-CoV-2, stating that it spawned from a wholesale seafood market in Wuhan, Hubei province, China and was first noted when doctors began observing cases of pneumonia that came from an unknown etiology. Further investigation from the Chinese Center for Disease Control and Prevention (China CDC) led to the discovery that only about 1% of COVID-19 patients had direct contact with the Wuhan seafood market. This suggested that the virus was being spread on a person-to-person basis. Further research isolated COVID-19 and allowed it to be properly identified. It was then noted that SARS-CoV-2 is remarkably similar to SARS, another type of coronavirus that caused a pandemic in 2003. Additionally, SARS-CoV-2 and SARS also share the same cell entry receptor, angiotensin-converting enzyme 2 (ACE2). Despite sharing remarkable similarities, difficulties still exist in diagnosing and treating patients who have fallen ill. Current criteria to be diagnosed with COVID-19 include fever, respiratory symptoms, fatigue, headache, diarrhea, vomiting, dyspnea, lymphopenia, hypoalbuminemia, ground-glass opacity chest imaging, and epidemiological history RT-PCR assays were then constructed based on RNA-dependent RNA polymerase gene of the SARS-CoV-2 genome. 

The article SARS-CoV-2: Underestimated Damage to Nervous System by Lingyan Zhou and colleagues describes the SARS-CoV-2 as a Betacoronavirus that shares many similarities and pathogenesis with SARS-CoV and MERS-CoV. The article then details that SARS-CoV-2 can invade the central nervous system (CNS) via hematogenous dissemination or neuronal retrograde dissemination, the latter of which is more concerning. Hematogenous dissemination is the spread of a virus via blood. Neuronal retrograde dissemination is the spreading of disease to the rest of the body from the brain or neuronal tissue. A disease that is similar to this is the varicella-zoster (chicken pox/shingles) virus that can lay dormant for years after the initial infection and then re-emerge as shingles. The author then describes that COVID-19 may act as a trigger for other neurological diseases and has the potential to be latent for several years before arising again.

The last article, What the SARS-CoV-2 Genome Reveals, by Kelly Malcom discusses how the original U.S. epicenter was most likely New York City. This was determined by using the genome of the virus and seeing how “things were similar or different” (Malcom 2). This is done by collecting various samples of the virus and constructing what is known as a phylogenetic tree, which helps researchers pinpoint where certain strains of a virus originated from. The author also discusses that patient zero was likely infected by a bat coronavirus that mutated, which shares a 96% genome similarity with SARS-CoV-2. However, Malcom notes that SARS-CoV-2 and other coronaviruses are unique in the sense that they are able to proofread their genetic code, which prevents the virus from mutating as rapidly, thereby allowing researchers to look at it more closely. Thus far, only 20 mutations have occurred to the genome of SARS-CoV-2, yet this still allows for genetic tracing to be performed.

COVID-19 is a novel disease, the outbreak of which is unprecedented in living memory. With that fact, it is important to note that our knowledge of COVID-19 and its effects is limited to the short term, and it may have a side we all have yet to see. According to Zhou et al., SARS-CoV-2 – the virus responsible for the disease we call COVID-19 – may have long-term neurological effects beyond those in the short term that have been observed. 

Looking at the genetic characteristics of SARS-CoV-2 – the data that describes how it behaves, what sort of cells and organisms it affects, and all of the other major characteristics of the virus – it’s spookily similar to MERS-CoV and SARS-CoV. SARS-CoV-2 invades cells very similarly to how SARS-CoV does, and as some previous studies have shown, coronaviruses such as SARS-CoV infect the nervous system. SARS-CoV is neuroinvasive and neurotropic – meaning that not only can it infect the nervous system, it specifically targets it. This information, combined with SARS-CoV-2’s similarity to SARS-CoV, suggests neuroinvasive properties in the virus responsible for COVID-19. 

What long-term neurological effects can we expect in patients that have had COVID-19? Will SARS-CoV-2 create new neurological problems in otherwise healthy individuals, or will it only trigger or exacerbate present conditions? 

Likely the best way we could answer these questions is through a long-term field study. Finding correlations in neurological complications that patients face later in life could lead us to a better understanding of how COVID-19 affects the brain, and over what time frame it does so. For now, however, SARS-CoV-2 has left us with some more pressing concerns. It is probably best that we try to limit the spread of the disease to the best of our ability, especially not knowing how it will still be affecting us down the road.