14 DAY TRIAL // Striving to understand the way in which neurons transmit information between each other has been a golden prize for biologists for more than half a century. The intricate "signal rate" patterns that occur when the brain is analyzing something or when it's making a decision and elaborating a response has proven to be much more difficult to understand than anyone could have predicted. That's why the latest discovery, made by a team of scientists at the Cold Spring Harbor Laboratory (CSHL), led by Professor Anthony Zador, Ph.D., could prove to be a decisive step forward in understanding how brain cells communicate.
Their research focused on that part of the brain that processes sound sensations, known as the auditory cortex. Once again, unsuspecting mice were used for this experiment. They were conditioned to follow electrical impulses inputted directly into their brain, which guided them in a specific direction. Zador's team discovered that sound stimuli as few as 3 milliseconds apart could make the animals turn the other way. They concluded that it was the lowest interval between two "spikes" in neural activity that the mice's brains could compute.
Past theories regarding neuron data transmissions were based on a "rate" model, which stated that the data to be sent between brain cells was contained within the spiking rates the cells gave off. This new discovery seems to show that the neural code – the term used to describe the way neurons communicate with each other – is actually based on timing, meaning that the information is contained within the patterns of the spikes themselves. The team reached this conclusion after analyzing the way in which the spike patterns were distributed over specific periods of time.
Zador also hinted that specific types of neurons have specific "priority levels" attached to them. In other words, some brain cell classes can make themselves "heard" better than others and the data they transmit reaches its destination before all other electrical impulses. Understanding exactly how this happen is a tremendous task not only for Zador's team, but also for all researchers analyzing the behavior of the brain.
While most of the channel parts of the brain used to communicate with each other have been thoroughly researched and understood, data about basic information transmission between two single neurons remains a mystery. Biology books simply state that the electrical impulse – generated by sodium and potassium atoms that are changing their electrical charge – simply jumps from one brain cell to the other through the synapses binding them.
But considering that several neurons could share the same synapse, it's easy to see why understanding which flow of information has priority and why can be so important. Research in this area could someday help scientists "bypass" parts of the brain that were affected by injuries, thus rerouting the relevant signals through secondary channels. Medical applications for such discoveries would include novel therapies for comatose patients or for people suffering from paralysis.