Dual-Task Interaction Between Vestibular Function And Cognitive Processing Using The P300 Event-Related Potential, Laurel Elise Money-Nolan

Graduate Theses and Dissertations (2019 - present)

Previous research has established links between vestibular function and cognitive processing, aging and cognitive function, and aging and vestibular function. Theories of cognitive resource allocation discuss how cognitive resources, such as attention, are devoted towards and divided between tasks when multitasking. This dual-task study, utilizing a balance task and a listening/cognitive task, across the young- and middle-aged adult age range, aimed to evaluate potential relationships between vestibular function, cognition, and age, and to examine how cognitive resources might be allocated under dual-task conditions.

The dual-task protocol in this study utilized an oddball paradigm with tonal stimuli to measure the P300 …

A Rare Delayed Neuropsychiatric Encephalopathy After Hyperbaric Oxygen Treatment For Carbon Monoxide Poisoning: A Couple’S Case Report, Sabrina Kasha, William J. Naber Ii, Michael Reimer

Graduate Medical Education Research Journal

Background: Carbon monoxide (CO) poisoning is caused when carbon monoxide builds up in the blood, most specifically due to its high binding affinity for the heme structure in hemoglobin. This can lead to serious tissue damage and even be fatal. CO poisoning is primarily the result of incomplete combustion of fuels, with common sources domestically and internationally including furnaces, gas heaters, generators, and motor vehicles.2 Symptoms tend to present as neuropsychiatric symptoms, such as dementia, psychosis, parkinsonism, and incontinence. There are few well-researched CO poisoning specific treatments, which suggest supplemental oxygen and hyperbaric oxygen are most effective. We present a …

The Impact Of An Iron-Rich Diet On Fatigue In Menstruating Women With Non-Anemic Iron Deficiency, Meagan Seraydar, Lauren Latimer, Sam Miragliatto

Department of Nutrition Student Projects

Fatigue without diagnosed anemia is prevalent in menstruating women, with iron deficiency being a potential contributor. While iron supplementation is a standard intervention, dietary sources of iron may offer a sustainable alternative. This study aims to assess the impact of an iron-rich diet on fatigue levels in menstruating women. A 12-week randomized controlled trial (RCT) will be conducted, assigning participants to either an iron-rich diet group or a control group following their usual diet without specific iron recommendations. Fatigue will be measured using the Fatigue Severity Scale (FSS) at baseline, six weeks, and twelve weeks, alongside iron status biomarkers, including …

Aging-Related Hearing Decline And Resting State Networks, Cassidy S. T. Ellsworth

College of Education and Human Sciences: Dissertations, Theses, and Student Research

This study investigated the effects of age-related hearing decline on functional networks using resting-state functional magnetic resonance imaging (rs-fMRI). The main objective of the present study was to examine resting-state functional connectivity (rsFC) and graph theory-based network efficiency metrics in forty-nine adults categorized by age and hearing thresholds to identify the neural mechanisms of age-related hearing decline. RsFC within key brain networks and auditory-related brain regions, including the default mode network, salience network, dorsal attention network, and primary auditory cortices, was assessed using region-of-interest (ROI)-based and graph theory approaches. Functional metrics, such as rsFC strength and global and local efficiency, …

Optimizing Interventions For Major Depressive Disorder And Provider Burnout: Self-Speak Exercise Dosing (Sed), Laureen Maloney-Gepfert

Lynchburg Journal of Medical Science

ABSTRACT

Major Depressive Disorder (MDD) is ranked highest among mental illnesses in the United States (US) and significantly contributes to the mental health care crisis. Patients experience resistance to pharmacologic interventions, side effects, co-morbidities, and mental health provider shortages. Subsequently, 33 % of Serious Mental Illnesses (SMIs) are being redirected to Primary Care Providers (PCPs). Concurrently, prescriber mental health is in crisis. Growing workloads for physicians and Advanced Practice Providers (APPs) have increased provider burnout syndrome (BOS). Major Depressive Disorder and BOS are positively affected by exercise, Cognitive Restructuring (CR), and Behavioral Activation (BA). Sports medicine and psychology research shows …

Interactions Between Repetitive Mild Traumatic Brain Injury And Methylphenidate Administration On Catecholamine Transporter Protein Levels Within The Rodent Prefrontal Cortex, Anna Abrimian, Eleni Papadopoulos, Christopher P. Knapp, J. Loweth, Barry Waterhouse, Rachel Navarra

Rowan-Virtua Research Day

It is theorized that low concentrations of dopamine (DA) and norepinephrine (NE) within in the prefrontal cortex (PFC) following traumatic brain injury (TBI) leads to increased risky behavior. Our lab has shown that repeated mild TBI (rmTBI) sex-differentially increases risky behavior in a rodent model. Methylphenidate (MPH) is a psychostimulant drug used to treat symptoms of Attention-Deficit Hyperactivity Disorder (ADHD), also driven by a hypo-catecholaminergic PFC. MPH elevates catecholamine levels by blocking DA and NE transporters, DAT and NET. While the potential of psychostimulants to treat post-TBI symptoms have been explored, the effects of sub-chronic MPH on transporter levels following …

The Impact Of Traumatic Brain Injury On Noradrenergic Innervation Of The Prefrontal Cortex, Jil P. Modi, Christopher P. Knapp, Rachel L. Navarra

Rowan-Virtua Research Day

Traumatic Brain Injury (TBI) is a common cause of death and disability in the United States, and it can occur due to varied reasons including motor vehicle accidents, gunshot wounds, and falls. Following TBIs, patients are often left with lifelong disabilities and cognitive problems that can lead to increased risk-taking behaviors. The main goal of my research was to understand the neural mechanisms that drive increased risk-taking behaviors due to TBIs. The specific areas of the brain I was interested in looking at were the medial prefrontal cortex (mPFC), orbitofrontal cortex (OFC), and/or anterior cingulate cortex (ACC) of the prefrontal …

Single Case Experimental Design Examining Cognitive Behavioural Therapy For Post-Stroke Depression, Liam Alexander Mackenzie Myles, Emma Jones

Journal of Mind and Medical Sciences

Background. Post-stroke depression (PSD) is common in older-age adults and is typically treated with cognitive-behavioural therapy (CBT). However, research has ascertained mixed findings regarding the efficacy of CBT for PSD in older-age adults, with limited evidence in people from global majority backgrounds. Materials and Methods. This case study used single case experimental design methodology to examine the effectiveness of CBT for PSD in a black, older-age man. The effects of health conditions, cohort beliefs, transitions in role investments, socio-cultural context and early experiences on the client’s thoughts, emotions, physical sensations and behaviours were formulated, before behavioural activation was used to …

The Feigned Annoyance And Frustration Test To Activate The Sympathoadrenal Medullary System, Ted W. Gehrig Iii, Lee S. Berk, Robert I. Dudley, Jo A. Smith, Lida Gharibvand, Everett B. Lohman Iii

Physical Therapy Faculty Articles and Research

When perceived as threatening, social interactions have been shown to trigger the sympathoadrenal medullary system as well as the hypothalamic-pituitary-adrenal axis resulting in a physiologic stress response. The allostatic load placed on human health and physiology in the context of acute and chronic stress can have profound health consequences. The purpose of this study was to develop a protocol for a lab-based stress stimulus using social-evaluative threat. While several valid, stress-stimulating protocols exist, we sought to develop one that triggered a physiologic response, did not require significant lab resources, and could be completed in around 10 min. We included 53 …

Autonomic Modulation Of Cardiac Function In Hypertrophic Cardiomyopathy, Jenna Rose Disser

Dissertations, Master's Theses and Master's Reports

Hypertrophic cardiomyopathy (HCM) is the most common genetic heart disorder. HCM is characterized by cardiac hypertrophy, fibrosis, and an increased risk of fatal arrhythmias and sudden cardiac death. Previous studies in humans with HCM have demonstrated increased cardiac norepinephrine spillover and reduced beta-1 receptor (β1R) expression in the left ventricle (LV). We have previously demonstrated that cardiac sympathetic tone is elevated in an alpha-tropomyosin mutant mouse model of HCM. We hypothesized that HCM mice would demonstrate reduced β1R expression in the LV and attenuated heart rate (HR) and dP/dt max responses to ramped infusion of the β1R agonist, dobutamine. …

Can Alternative Medical Methods Evoke Neuro-Functional Somatosensory Responses? A Case Study Suggesting Functional Improvement, Alhasn Otaif, Mashan E. Alshammari, Christine G. Gerin

Research Symposium

Somatosensory pathways act as the avenue in transferring information concerning the body and its interaction with the external environment to the brain. We aim to demonstrate that through studying somatosensory, motor cortical and subcortical networks, we can explain functional recovery after stimulations applied as an alternative medical treatment. Those stimulations might have evidenced neural pathways and networks important in recovery of function. Materials and methods: The de-identified medical reports of nine patients with initial presentations of cerebral trauma or stroke inducing paralysis were studied.These included the alternative treatments they received and other available materials such as videos and photographs. Patients …

Massive Loss Of Proprioceptive Ia Synapses In Rat Spinal Motoneurons After Nerve Crush Injuries In The Postnatal Period, Ariadna Arbat-Plana, Sara Bolívar, Xavier Navarro, Esther Udina, Francisco J. Alvarez

Neuroscience, Cell Biology & Physiology Faculty Publications

Peripheral nerve injuries (PNIs) induce the retraction from the ventral horn of the synaptic collaterals of Ia afferents injured in the nerve, effectively removing Ia synapses from α-motoneurons. The loss of Ia input impairs functional recovery and could explain, in part, better recovery after PNIs with better Ia synaptic preservation. Synaptic losses correlate with injury severity, speed, and efficiency of muscle reinnervation and requires ventral microglia activation. It is unknown whether this plasticity is age dependent. In neonates, axotomized motoneurons and sensory neurons undergo apoptosis, but after postnatal day 10 most survive. The goal of this study was to analyze …

Fast Blue And Cholera Toxin-B Survival Guide For Alpha-Motoneurons Labeling: Less Is Better In Young B6sjl Mice, But More Is Better In Aged C57bl/J Mice, Hasan Farid, Weston B. Gleford, Lori L. Goss, Teresa L. Garrett, Sherif M. Elbasiouny

Neuroscience, Cell Biology & Physiology Faculty Publications

Fast Blue (FB) and Cholera Toxin-B (CTB) are two retrograde tracers extensively used to label alpha-motoneurons (α-MNs). The overall goals of the present study were to (1) assess the effectiveness of different FB and CTB protocols in labeling α-MNs, (2) compare the labeling quality of these tracers at standard concentrations reported in the literature (FB 2% and CTB 0.1%) versus lower concentrations to overcome tracer leakage, and (3) determine an optimal protocol for labeling α-MNs in young B6SJL and aged C57Bl/J mice (when axonal transport is disrupted by aging). Hindlimb muscles of young B6SJL and aged C57Bl/J mice were intramuscularly …

Motoneuron Excitability Dysfunction In Als: Pseudo-Mystery Or Authentic Conundrum?, Sherif M. Elbasiouny

Neuroscience, Cell Biology & Physiology Faculty Publications

In amyotrophic lateral sclerosis (ALS), abnormalities in motoneuronal excitability are seen in early pathogenesis and throughout disease progression. Fully understanding motoneuron excitability dysfunction may lead to more effective treatments. Yet decades of research have not produced consensus on the nature, role or underlying mechanisms of motoneuron excitability dysfunction in ALS. For example, contrary to Ca excitotoxicity theory, predictions of motoneuronal hyper-excitability, normal and hypo-excitability have also been seen at various disease stages and in multiple ALS lines. Accordingly, motoneuron excitability dysfunction in ALS is a disputed topic in the field. Specifically, the form (hyper, hypo or unchanged) and what role …

Artificial Gravity Partially Protects Space-Induced Neurological Deficits In Drosophila Melanogaster, Amber M. Paul, Siddhita D. Mhatre, Janani Iyer, Juli Petereit, Roberta M. Dolling-Boreham

Publications

Spaceflight poses risks to the central nervous system (CNS), and understanding neurological responses is important for future missions. We report CNS changes in Drosophila aboard the International Space Station in response to spaceflight microgravity (SFmg) and artificially simulated Earth gravity (SF1g) via inflight centrifugation as a countermeasure. While inflight behavioral analyses of SFmg exhibit increased activity, postflight analysis displays significant climbing defects, highlighting the sensitivity of behavior to altered gravity. Multiomics analysis shows alterations in metabolic, oxidative stress and synaptic transmission pathways in both SFmg and SF1g; however, neurological changes immediately postflight, including neuronal loss, glial cell count alterations, oxidative …

Non-Invasive Transcutaneous Spinal Dc Stimulation As A Neurorehabilitation Als Therapy In Awake G93a Mice: The First Step To Clinical Translation, Morgan M. Highlander, Sherif M. Elbasiouny

Neuroscience, Cell Biology & Physiology Faculty Publications

Spinal direct current stimulation (sDCS) modulates motoneuron (MN) excitability beyond the stimulation period, making it a potential neurorehabilitation therapy for amyotrophic lateral sclerosis (ALS), a MN degenerative disease in which MN excitability dysfunction plays a critical and complex role. Recent evidence confirms induced changes in MN excitability via measured MN electrophysiological properties in the SOD1 ALS mouse during and following invasive subcutaneous sDCS (ssDCS). The first aim of our pilot study was to determine the clinical potential of these excitability changes at symptom onset (P90-P105) in ALS via a novel non-invasive transcutaneous sDCS (tsDCS) treatment paradigm on un-anesthetized SOD1-G93A mice. …

Suppression Of Store-Operated Calcium Entry Channels And Cytokine Release By Cannabinoids, J. Ashot Kozak

Neuroscience, Cell Biology & Physiology Faculty Publications

No abstract provided.

The Role Of Microglia In Neuroinflammation Of The Spinal Cord After Peripheral Nerve Injury, Tana S. Pottorf, Travis M. Rotterman, William M. Mccallum, Zoë A. Haley-Johnson, Francisco J. Alvarez

Neuroscience, Cell Biology & Physiology Faculty Publications

Peripheral nerve injuries induce a pronounced immune reaction within the spinal cord, largely governed by microglia activation in both the dorsal and ventral horns. The mechanisms of activation and response of microglia are diverse depending on the location within the spinal cord, type, severity, and proximity of injury, as well as the age and species of the organism. Thanks to recent advancements in neuro-immune research techniques, such as single-cell transcriptomics, novel genetic mouse models, and live imaging, a vast amount of literature has come to light regarding the mechanisms of microglial activation and alluding to the function …

Il-10 And Tgf-Β Increase Connexin-43 Expression And Membrane Potential Of Hl-1 Cardiomyocytes Coupled With Raw 264.7 Macrophages, Cora B. Cox, Mike Castro, Thomas L. Brown, Nancy J. Bigley

Neuroscience, Cell Biology & Physiology Faculty Publications

Cardiac resident macrophages facilitate electrical conduction by interacting with cardiomyocytes via connexin-43 (Cx43) hemichannels. Cx43 is critical for impulse propagation and coordination between muscle contractions. Cardiomyocyte electrophysiology can be altered when coupled with noncardiomyocyte cell types such as M2c tissue-resident macrophages. Using cocultures of murine HL-1 cardiomyocytes and RAW 264.7 macrophages, we examined the hypothesis that cytokine signals, TGF-β1 and IL-10, upregulate Cx43 expression at points of contact between the two cell types. These cytokine signals maintain the macrophages in an M2c anti-inflammatory phenotype, mimicking cardiac resident macrophages. The electrophysiology of cardiomyocytes was examined using di-8-ANEPPS potentiometric dye, which reflects …

A Neurophysiological Investigation Of Listening Effort In Normal Hearing Adults Using Fnirs And Pupillometry, Jessica Defenderfer

Theses and Dissertations (ETD)

Real-world conversations are often accompanied by some sort of interference that challenges the clarity of the speaker’s message, causing listeners to exert more effort to understand speech. Previous research has demonstrated that when listening to speech becomes difficult, various regions of the brain are recruited beyond those which engage during optimal listening conditions. However, the neural correlates that underly listening effort are not fully understood. Importantly, the pupillary response can be used to index listening effort, such that pupil size increases with increasing cognitive demand. I proposed that pupillometry can be used to characterize the cortical response, such that changes …

Acute Oxygen-Sensing Via Mitochondria-Generated Temperature Transients In Rat Carotid Body Type I Cells, Ryan J. Rakoczy, Clay M. Schiebrel, Christopher N. Wyatt

Neuroscience, Cell Biology & Physiology Faculty Publications

The Carotid Bodies (CB) are peripheral chemoreceptors that detect changes in arterial oxygenation and, via afferent inputs to the brainstem, correct the pattern of breathing to restore blood gas homeostasis. Herein, preliminary evidence is presented supporting a novel oxygen-sensing hypothesis which suggests CB Type I cell “hypoxic signaling” may in part be mediated by mitochondria-generated thermal transients in TASK-channel-containing microdomains. Distances were measured between antibody-labeled mitochondria and TASK-potassium channels in primary rat CB Type I cells. Sub-micron distance measurements (TASK-1: 0.33 ± 0.04 µm, n = 47 vs TASK-3: 0.32 ± 0.03 µm, n = …

The Anti-Inflammatory Agent Bindarit Attenuates The Impairment Of Neural Development Through Suppression Of Microglial Activation In A Neonatal Hydrocephalus Mouse Model, Eri Iwasawa, Farrah N. Brown, Crystal Shula, Fatima Kahn, Sang Hoon Lee, Temugin Berta, David R. Ladle, Kenneth Campbell, Francesco T. Mangano, June Goto

Neuroscience, Cell Biology & Physiology Faculty Publications

Neonatal hydrocephalus presents with various degrees of neuroinflammation and long-term neurologic deficits in surgically treated patients, provoking a need for additional medical treatment. We previously reported elevated neuroinflammation and severe periventricular white matter damage in the progressive hydrocephalus (prh) mutant which contains a point mutation in the Ccdc39 gene, causing loss of cilia-mediated unidirectional CSF flow. In this study, we identified cortical neuropil maturation defects such as impaired excitatory synapse maturation and loss of homeostatic microglia, and swimming locomotor defects in early postnatal prh mutant mice. Strikingly, systemic application of the anti-inflammatory small molecule bindarit significantly supports healthy …

Evaluation Of Hippocampal Allostatic Load-Associated Factors In Animal Models Of Post-Traumatic Stress Disorder: Relevance To Human Ptsd, Dennis Parker Kelley

LSU Doctoral Dissertations

Post-traumatic stress disorder (PTSD) is associated with elevated allostatic load, nearly double the risk for metabolic syndrome, reduced hippocampal volume, and contextual memory processing deficits. Emerging evidence suggests that these stress effects may predispose individuals to the development of PTSD, and there is a known relationship between chronic stress and metabolic dysfunction. In this work, we utilized two rat models of PTSD to explore these connections. We used an acute predator odor stressor to investigate the relationship between PTSD-like behaviors and mitochondrial dysfunction in the hippocampus of rats, and we observed that conditioned place avoidance was associated with reduced mitochondrial …

Ethanol And Opioids Do Not Act Synergistically To Depress Excitation In Carotid Body Type I Cells, Ryan J. Rakoczy, Kajal Kamra, Yoon-Jae Yi, Christopher N. Wyatt

Neuroscience, Cell Biology & Physiology Faculty Publications

The combination of opioids and ethanol can synergistically depress breathing and the acute ventilatory response to hypoxia. Multiple studies have shown that the underlying mechanisms for this may involve calcium channel inhibition in central neurons. But we have previously identified opioid receptors in the carotid bodies and shown that their activation inhibits calcium influx into the chemosensitive cells. Given that the carotid bodies contribute to the drive to breathe and underpin the acute hypoxic ventilatory response, we hypothesized that ethanol and opioids may act synergistically in these peripheral sensory organs to further inhibit calcium influx and therefore inhibit ventilation.

Methods …

Genetic Targeting Of Adult Renshaw Cells Using A Calbindin 1 Destabilized Cre Allele For Intersection With Parvalbumin Or Engrailed1, Alicia R. Lane, Indeara C. Cogdell, Thomas M. Jessell, Jay B. Bikoff, Francisco J. Alvarez

Neuroscience, Cell Biology & Physiology Faculty Publications

Renshaw cells (RCs) are one of the most studied spinal interneurons; however, their roles in motor control remain enigmatic in part due to the lack of experimental models to interfere with RC function, specifically in adults. To overcome this limitation, we leveraged the distinct temporal regulation of Calbindin (Calb1) expression in RCs to create genetic models for timed RC manipulation. We used a Calb1 allele expressing a destabilized Cre (dgCre) theoretically active only upon trimethoprim (TMP) administration. TMP timing and dose influenced RC targeting efficiency, which was highest within the first three postnatal weeks, but specificity was low with …

Nsaids Naproxen, Ibuprofen, Salicylate, And Aspirin Inhibit Trpm7 Channels By Cytosolic Acidification, Rikki Chokshi, Orville Bennett, Tetyana Zhelay, J. Ashot Kozak

Neuroscience, Cell Biology & Physiology Faculty Publications

Non-steroidal anti-inflammatory drugs (NSAIDs) are used for relieving pain and inflammation accompanying numerous disease states. The primary therapeutic mechanism of these widely used drugs is the inhibition of cyclooxygenase 1 and 2 (COX1, 2) enzymes that catalyze the conversion of arachidonic acid into prostaglandins. At higher doses, NSAIDs are used for prevention of certain types of cancer and as experimental treatments for Alzheimer’s disease. In the immune system, various NSAIDs have been reported to influence neutrophil function and lymphocyte proliferation, and affect ion channels and cellular calcium homeostasis. Transient receptor potential melastatin 7 (TRPM7) cation channels are highly expressed in …

Placenta-Specific Slc38a2/Snat2 Knockdown Causes Fetal Growth Restriction In Mice, Owen R. Vaughan, Katarzyna Maksym, Elena Silva, Kenneth Barentsen, Russel V. Anthony, Sara L. Hillman, Thomas L. Brown, Rebecca Spencer, Anna L. David, Fredrick J. Rosario, Theresa L. Powell, Thomas Jansson

Neuroscience, Cell Biology & Physiology Faculty Publications

Fetal growth restriction (FGR) is a complication of pregnancy that reduces birth weight, markedly increases infant mortality and morbidity and is associated with later-life cardiometabolic disease. No specific treatment is available for FGR. Placentas of human FGR infants have low abundance of sodium-coupled neutral amino acid transporter 2 (Slc38a2/SNAT2), which supplies the fetus with amino acids required for growth. We determined the mechanistic role of placental Slc38a2/SNAT2 deficiency in the development of restricted fetal growth, hypothesizing that placenta-specific Slc38a2 knockdown causes FGR in mice. Using lentiviral transduction of blastocysts with a small hairpin RNA (shRNA), we achieved 59% knockdown of …

Intensity-Dependent Changes In Quantified Resting Cerebral Perfusion With Multiple Sessions Of Transcranial Dc Stimulation, Matthew Sherwood, Lindsey Mcintire, Aaron T. Madaris, Kamin Kim, Charan Ranganath, R. Andy Mckinley

Neuroscience, Cell Biology & Physiology Faculty Publications

Transcranial direct current stimulation (tDCS) to the left prefrontal cortex has been shown to produce broad behavioral effects including enhanced learning and vigilance. Still, the neural mechanisms underlying such effects are not fully understood. Furthermore, the neural underpinnings of repeated stimulation remain understudied. In this work, we evaluated the effects of the repetition and intensity of tDCS on cerebral perfusion [cerebral blood flow (CBF)]. A cohort of 47 subjects was randomly assigned to one of the three groups. tDCS of 1- or 2-mA was applied to the left prefrontal cortex on three consecutive days, and resting CBF was quantified before …

Current State Of Preeclampsia Mouse Models: Approaches, Relevance, And Standardization, Christopher A. Waker, Melissa R. Kaufman, Thomas L. Brown

Neuroscience, Cell Biology & Physiology Faculty Publications

Preeclampsia (PE) is a multisystemic, pregnancy-specific disorder and a leading cause of maternal and fetal death. PE is also associated with an increased risk for chronic morbidities later in life for mother and offspring. Abnormal placentation or placental function has been well-established as central to the genesis of PE; yet much remains to be determined about the factors involved in the development of this condition. Despite decades of investigation and many clinical trials, the only definitive treatment is parturition. To better understand the condition and identify potential targets preclinically, many approaches to simulate PE in mice have been developed and …

The Role Of Action Potential Waveform In Failure Of Excitation Contraction Coupling, Xueyong Wang, Murad Nawaz, Steve R.A. Burke, Roger Bannister, Brent D. Foy, Andrew A. Voss, Mark M. Rich

Neuroscience, Cell Biology & Physiology Faculty Publications

Excitation contraction coupling (ECC) is the process by which electrical excitation of muscle is converted into force generation. Depolarization of skeletal muscle resting potential contributes to failure of ECC in diseases such as periodic paralysis, ICU acquired weakness and possibly fatigue of muscle during vigorous exercise. When extracellular K+ is raised to depolarize the resting potential, failure of ECC occurs suddenly, over a range of several mV of resting potential. While some studies have hypothesized the sudden failure of ECC is due to all-or-none failure of excitation, other studies suggest failure of excitation is graded. Intracellular recordings of action potentials …