SINGLE DOSE OF ANTIDEPRESSANT CHANGES THE BRAIN

A single dose of antidepressant is enough to produce dramatic changes in the functional architecture of the human brain. Brain scans taken of people before and after an acute dose of a commonly prescribed SSRI (serotonin reuptake inhibitor) reveal changes in connectivity within three hours, say researchers who report their observations in the Cell Press journal Current Biology on September 18.

"We were not expecting the SSRI to have such a prominent effect on such a short timescale or for the resulting signal to encompass the entire brain," says Julia Sacher of the Max Planck Institute for Human Cognitive and Brain Sciences.

While SSRIs are among the most widely studied and prescribed form of antidepressants worldwide, it's still not entirely clear how they work. The drugs are believed to change brain connectivity in important ways, but those effects had generally been thought to take place over a period of weeks, not hours.

The new findings show that changes begin to take place right away. Sacher says what they are seeing in medication-free individuals who had never taken antidepressants before may be an early marker of brain reorganization.

Study participants let their minds wander for about 15 minutes in a brain scanner that measures the oxygenation of blood flow in the brain. The researchers characterized three-dimensional images of each individual's brain by measuring the number of connections between small blocks known as voxels (comparable to the pixels in an image) and the change in those connections with a single dose of escitalopram (trade name Lexapro).

Their whole-brain network analysis shows that one dose of the SSRI reduces the level of intrinsic connectivity in most parts of the brain. However, Sacher and her colleagues observed an increase in connectivity within two brain regions, specifically the cerebellum and thalamus.

The researchers say the new findings represent an essential first step toward clinical studies in patients suffering from depression. They also plan to compare the functional connectivity signature of brains in recovery and those of patients who fail to respond after weeks of SSRI treatment.

Understanding the differences between the brains of individuals who respond to SSRIs and those who don't "could help to better predict who will benefit from this kind of antidepressant versus some other form of therapy," Sacher says. "The hope that we have is that ultimately our work will help to guide better treatment decisions and tailor individualized therapy for patients suffering from depression."

SINGLE DOSE NEEDLE FREE EBOLA VACCINE

Scientists have demonstrated for the first time that a single-dose, needleless Ebola vaccine given to primates through their noses and lungs protected them against infection for at least 21 weeks. A vaccine that doesn't require an injection could help prevent passing along infections through unintentional pricks.

They report the results of their study on macaques in the ACS journal Molecular Pharmaceutics.

Maria A. Croyle and colleagues note that in the current Ebola outbreak, which is expected to involve thousands more infections and deaths before it's over, an effective vaccine could help turn the tide. Even better, taking the needle out of the inoculation process could also help prevent the accidental transmission of Ebola, as well as other diseases, such as HIV, that might otherwise spread from unintentional needle pricks and unsafe handling of medical wastes. Other vaccines are currently under development to fight the virus, but they require an injection. Croyle's team tested an adenovirus-based Ebola vaccine using a respiratory delivery route.

The researchers gave a novel formulation of an Ebola vaccine to several macaques then exposed them to the virus more than four months later. All three of the animals that received the vaccine through the nose and via a catheter into their airways did not fall ill. However, since special equipment and training are required for the current respiratory delivery method, the scientists conclude that further work is needed if this formula, or an under-the-tongue version, is to be used eventually in large-scale immunization campaigns.

SINGLE NEURON HUB ORCHESTRATES ACTIVITY OF AN ENTIRE BRAIN CIRCUIT

The idea of mapping the brain is not new. Researchers have known for years that the key to treating, curing, and even preventing brain disorders such as Alzheimer's disease, epilepsy, and traumatic brain injury, is to understand how the brain records, processes, stores, and retrieves information

New Tel Aviv University research published in PLOS Computational Biology makes a major contribution to efforts to navigate the brain. The study, by Prof. Eshel Ben-Jacob and Dr. Paolo Bonifazi of TAU's School of Physics and Astronomy and Sagol School of Neuroscience, and Prof. Alessandro Torcini and Dr. Stefano Luccioli of the Instituto dei Sistemi Complessi, under the auspices of TAU's Joint Italian-Israeli Laboratory on Integrative Network Neuroscience, offers a precise model of the organization of developing neuronal circuits.

In an earlier study of the hippocampi of newborn mice, Dr. Bonifazi discovered that a few "hub neurons" orchestrated the behavior of entire circuits. In the new study, the researchers harnessed cutting-edge technology to reproduce these findings in a computer-simulated model of neuronal circuits. "If we are able to identify the cellular type of hub neurons, we could try to reproduce them in vitro out of stem cells and transplant these into aged or damaged brain circuitries in order to recover functionality," said Dr. Bonifazi.

Flight dynamics and brain neurons

"Imagine that only a few airports in the world are responsible for all flight dynamics on the planet," said Dr. Bonifazi. "We found this to be true of hub neurons in their orchestration of circuits' synchronizations during development. We have reproduced these findings in a new computer model."

According to this model, one stimulated hub neuron impacts an entire circuit dynamic; similarly, just one muted neuron suppresses all coordinated activity of the circuit. "We are contributing to efforts to identify which neurons are more important to specific neuronal circuits," said Dr. Bonifazi. "If we can identify which cells play a major role in controlling circuit dynamics, we know how to communicate with an entire circuit, as in the case of the communication between the brain and prosthetic devices."

Conducting the orchestra of the brain

In the course of their research, the team found that the timely activation of cells is fundamental for the proper operation of hub neurons, which, in turn, orchestrate the entire network dynamic. In other words, a clique of hubs works in a kind of temporally-organized fashion, according to which "everyone has to be active at the right time," according to Dr. Bonifazi.

Coordinated activation impacts the entire network. Just by alternating the timing of the activity of one neuron, researchers were able to affect the operation of a small clique of neurons, and finally that of the entire network.

"Our study fits within framework of the 'complex network theory,' an emerging discipline that explores similar trends and properties among all kinds of networks -- i.e., social networks, biological networks, even power plants," said Dr. Bonifazi. "This theoretical approach offers key insights into many systems, including the neuronal circuit network in our brains."

Parallel to their theoretical study, the researchers are conducting experiments on in vitro cultured systems to better identify electrophysiological and chemical properties of hub neurons. The joint Italy-Israel laboratory is also involved in a European project aimed at linking biological and artificial neuronal circuitries to restore lost brain functions.