Breaking News
August 17, 2018 - Female mosquitoes quickly evolve selective mating behavior when faced with threats
August 17, 2018 - FDA Grants Breakthrough Therapy Designation to Daiichi Sankyo’s FLT3 Inhibitor Quizartinib for Relapsed/Refractory FLT3-ITD AML
August 17, 2018 - Resistance training and exercise motivation go hand-in-hand
August 17, 2018 - A lesson for future doctors: Listen to and learn from your patients
August 17, 2018 - NUS study discovers a bidirectional regulator and shines light on A-to-I RNA editing in cancer cells
August 17, 2018 - Research shows link between high blood levels of omega-3s and better brain function in children
August 17, 2018 - Researchers propose new theory for how rare gene mutations cause Alzheimer’s disease
August 17, 2018 - Digital psychiatric therapy can ‘rewire’ the brain in children with ADHD, study shows
August 17, 2018 - Psychologist to assess how the brain maintains precise short-term and long-term memories
August 17, 2018 - Eating white button mushrooms could improve regulation of glucose in the liver
August 17, 2018 - Scientists identify mutational signatures in ovarian cancer
August 17, 2018 - Sun Pharma receives U.S. FDA approval for CEQUA to treat patients with dry eye disease
August 17, 2018 - Teva Announces Updated Indication and Vial Presentation for Granix (tbo-filgrastim) Injection in United States
August 17, 2018 - Study shows DNA methylation related to liver disease among obese patients
August 17, 2018 - Life on the border: Back at Stanford, ready to pitch in
August 17, 2018 - New device for accurately placing hemodialysis catheters on kidney patients
August 17, 2018 - New strategy accelerates, automates process of prototype molecule optimization
August 17, 2018 - Study finds role of autoimmunity in development of COPD
August 17, 2018 - Researchers transform research tool to study neuronal function
August 17, 2018 - Cognitive impairment does not equate to unhappiness in older adults
August 17, 2018 - Peer Comparisons Can Decrease Risky Prescribing Patterns
August 17, 2018 - Susceptible genes identified for childhood chronic kidney disease
August 17, 2018 - Research uncovers miscarriage cause, identifies potential targets for treatment
August 17, 2018 - Bacterial armor could be new target for antibiotics | News Center
August 17, 2018 - FDA expands approval of Vertex’ cystic fibrosis medicine to treat children aged 12 to
August 17, 2018 - Give Your Child a Head Start With Math
August 17, 2018 - Ground-breaking study tests whether rejected livers can be made viable for transplantation
August 16, 2018 - New algorithm could improve diagnosis of rare diseases | News Center
August 16, 2018 - SCHILLER introduces latest generation of ECG device, CARDIOVIT AT-102 G2
August 16, 2018 - Proper treatment, refraining from smoking can reduce heart disease risk from type 2 diabetes
August 16, 2018 - Mount Sinai study could transform treatment for patients with retinal degenerative diseases
August 16, 2018 - Penn researchers develop first mouse model of idiopathic pulmonary fibrosis
August 16, 2018 - Four tips to help prevent fall allergy symptoms
August 16, 2018 - Women’s Preventive Services Initiative says screen all women annually for urinary incontinence
August 16, 2018 - At Stanford, patient discovers the source of her headaches, nausea | News Center
August 16, 2018 - To Prevent Injuries in Young Baseball Players, Chris Ahmad Reaches Out to Parents
August 16, 2018 - Restoring blood flow may be linked to longer survival in patients with critical limb ischemia
August 16, 2018 - New model of genetically engineered immune cells may help fight solid tumors
August 16, 2018 - Maternal stress increases anxious and depressive-like behaviors in female offspring
August 16, 2018 - Childhood exposure to secondhand smoke increases risk of COPD death in adulthood
August 16, 2018 - Scientists uncover key control mechanism of DNA replication
August 16, 2018 - NIH begins first-in-human trial of experimental live, attenuated Zika virus vaccine
August 16, 2018 - Two diabetes medications don’t slow progression of type 2 diabetes in youth
August 16, 2018 - 5 Questions: How Stanford research is making MRI scans safer for kids | News Center
August 16, 2018 - Columbia Celebrates 25th Anniversary of White Coat Ceremony
August 16, 2018 - Phonak’s new smallest and most discreet Virto B-Titanium hearing aid
August 16, 2018 - New project aims to study growth of water-based microorganisms
August 16, 2018 - Immune cell found to play important role in photosensitivity
August 16, 2018 - Higher social dominance linked to faster decision-making in men
August 16, 2018 - Blood test in early pregnancy could determine a woman’s later risk for gestational diabetes
August 16, 2018 - New research confirms link between DDT exposure and autism
August 16, 2018 - Neurodevelopmental Anomalies, Birth Defects Linked to Zika ID’d
August 16, 2018 - Risk of heart failure up in ALVSD patients with diabetes
August 16, 2018 - Exercise reduces symptoms and fatigue in patients with chronic kidney disease
August 16, 2018 - Study reveals role of RUNX proteins in DNA repair
August 16, 2018 - New research finds no harm from average salt consumption
August 16, 2018 - Researchers develop new way of testing bacterial resistance to antibiotics
August 16, 2018 - Magnetic gene in aquarium fish could open doors to treatment for epilepsy, Parkinson’s
August 16, 2018 - Five tips for successful long-term breastfeeding
August 16, 2018 - Researchers identify brain networks involved in object naming
August 16, 2018 - Promoting HPV Vaccine Doesn’t Prompt Risky Sex by Teens: Study
August 16, 2018 - Treating Rheumatoid Arthritis: Search for a Cure
August 16, 2018 - Research shows in the long run, charcoal toothpaste likely won’t whiten teeth
August 16, 2018 - Seattle Children’s opens new clinic to provide convenient access to pediatric specialty care services
August 16, 2018 - Curious case of the lost contact lens
August 16, 2018 - GN Hearing unveils world’s first Premium-Plus hearing aid
August 16, 2018 - Parental life span linked with increased longevity and health in daughters
August 16, 2018 - Health leaders reveal ten most important medicines in NHS history
August 16, 2018 - Mobile health devices diagnose hidden heart condition in at-risk populations
August 16, 2018 - When it comes to shedding pounds, it pays to think big
August 16, 2018 - Liva Healthcare announces appointment of Thomas Cooke as clinical services manager in the UK
August 16, 2018 - New digital pharmacy aims to help people living with chronic care conditions
August 16, 2018 - Preventing ACL injuries in high school athletes
August 16, 2018 - Experts provide insight into novel concepts and approaches for stroke rehabilitation
August 16, 2018 - Scientists reverse congenital blindness in mouse model
August 16, 2018 - Study shows link between use of benzodiazepines and increased risk of Alzheimer’s disease
August 16, 2018 - Study provides new insight into how ‘trash bag of the cell’ traps and seals off waste
August 16, 2018 - Trial shows PARP inhibitor as novel treatment option for patients with advanced breast cancers
August 16, 2018 - Prenatal exposure to violence increases toddlers’ aggressive behavior to their mothers
August 16, 2018 - Can manipulating gut microbes improve cardiac function in patients with heart failure?
New finding may hold key to better understand the complexities of neurological disorders

New finding may hold key to better understand the complexities of neurological disorders

image_pdfDownload PDFimage_print

A team of bioengineers at UC San Diego has answered a question that has long puzzled neuroscientists, and may hold a key to better understanding the complexities of neurological disorders: Why are axons, the spindly arms extending from neurons that transmit information from neuron to neuron in the brain, designed the way they are?

Axons are not designed to minimize the use of cell tissue– they wouldn’t be so long and convoluted if that were the case. Conversely, they’re not optimized for speed, as recent studies have shown that axons don’t fire as fast as they physically could, since this would overwhelm the neuron and lead to a loss of network activity.

So what is the role of the geometry of axons in information flow in the brain?

The answer–that axons are designed and optimized to balance the speed that information flows into the neuron relative to the time it takes the neuron to process that information–seems intuitive, but has never been quantified until now.

This underlying principle of neuroscience, published July 11 in Scientific Reports, could revolutionize our understanding of how signal flow in the brain can be measured and perturbed, and could have an equally large impact on artificial neural networks in the field of machine learning.

Refraction Ratio

The specific balance that biological neurons are designed to accommodate is called the refraction ratio: it’s the ratio between the refractory period of a neuron–when the neuron is unable to process incoming signals since its ion channels are resetting after being flooded with sodium– and the signal latency of information traveling down the axon. When that ratio approaches one, there is perfect balance, and the neuron is operating as efficiently as possible.

In the study conducted by first author Francesca Puppo, a postdoctoral researcher in Bioengineering Professor Gabriel Silva’s lab at the Jacobs School of Engineering at UC San Diego, the median refraction ratio value of the nearly 12,000 axonal branches examined was 0.92, quite close to the theoretically predicted perfect balance.

The study used a dataset from the NeuroMorpho database that looked at a type of neuron called basket cells. This data was from rats, but humans have basket cells too. Puppo used the 3D morphological data to reconstruct a graph-based model of the neurons’ axons and axon branches. Then she calculated the conduction velocity along the axons given the diameter at different points along the axonal arborizations, and estimated the refractory period along the axon from soma to synaptic terminals based on data in the literature. The conduction velocity and length of each axon branch were used to calculate the propagation delay, which she compared to the refraction period to calculate the refraction ratio.

Long, short, straight and curvy axons all had a refraction ratio approaching one. This means that when axons grow in a long and curved shape, it’s designed that way by the neuron to slow down the action potential of signals in order to optimize the refraction ratio. When neurons aren’t signaling at this ratio, there is a breakdown in information flow efficiency between cells.

One example of this breakdown in efficiency that Silva and colleagues at the UC San Diego School of Medicine are starting to investigate is in patients with autism spectrum disorder.

“The hypothesis we have is that the refraction ratio deviates from the ideal in neurodevelopmental disorders such as autism,” Silva said. “We think that may be the case for individual neurons, as well as networks of neurons.”

Puppo added that understanding this baseline of optimal function in neurons will allow researchers to better understand how information flow is perturbed in a variety of ways, including other neurological disorders such as schizophrenia, for example, as well as better understanding how drugs affect neuron function, since pharmacological drugs impact the cell’s activity and the way synaptic transmission occurs in networks of neurons.

“It would be interesting to investigate how drug perturbation affects signaling efficiency through computation of the refraction ratio for pairs of neurons in in-vitro networks of neurons before and after exposure to different chemical compounds,” Puppo said. “The detection of a change in the refraction ratio could be helpful in the determination of their neural rescue properties.”

Machine Learning

On the non-biological side, understanding the function of the refraction ratio and the shape of axons has implications in the development of more brain-like artificial neural networks.

Whereas traditional artificial neural networks have many weighted incoming signals with an output that’s a summation of all of these signals, Silva and his lab are developing a new paradigm that adds the element of time to the mix–like the refractory period does in biological systems–so not all incoming signals are calculated in the output.

In geometric spatial-temporal artificial networks they are building, the time a signal takes to reach the node is also a factor in the output, similar to the way the refractory period functions in the human brain. This adds complexity to the system, but makes the learning process richer.

Silva is developing a fundamentally novel machine learning architecture based on these networks as part of the Center for Engineering Natural Intelligence at the Jacobs School of Engineering.

In addition to studying the refraction ratio of people with neurological disorders and applying the concept to artificial neural networks, Puppo said additional further work includes studying varying types of neurons to understand if some have refraction ratios that deviate slightly from 1 to serve a specific purpose in a cell’s dynamics.

Tagged with:

About author

Related Articles