credit: A. Ajifo

Welcome to Brain Bits, where I highlight important or interesting recent news in the world of neuroscience. This week: implanting a compass into the brain, creating an encyclopedia of neurons, discovering how our brains learn so many different things, and more!

A new paper in Current Biology demonstrated that blind rats can navigate just as well as sighted rats using a neuroprosthetic compass connected to their brains. (Non-technical summary here.) Each blind rat wore a digital compass on its head, which told the rat which direction it was facing by sending electrical impulses into its brain. This study not only has obvious implications for potentially improving navigation in blind people, but also shows that the brain has a remarkable capacity to interpret completely new types of information (in this case, geomagnetism), essentially creating a new sense. These days the idea of using neuroprosthetics to create new senses isn’t as crazy as it once seemed. (This Radiolab segment even talks about creating new senses for perceiving weather patterns or stock market prices!)

Dendrite branches of a neuron (credit: JCB)

How do our brains store a lifetime of memories? Neuroscientists believe that learning alters the strength of connections between neurons, and memories are stored in that network of connections. But our brains are constantly learning, and it’s not clear how new memories form without disrupting the old ones. A new Nature paper suggests that individual neurons can store different memories through separate branches of their dendrites, which are the tree-like processes that receive information from other neurons. Researchers trained mice to perform simple motor tasks, such as running on a treadmill, while monitoring their brain activity. Different tasks activated different branches of the same neurons, and this segregation was crucial for learning multiple things: when the mice were manipulated so that different tasks activated the same branches, they weren’t able to learn a second task without disrupting their memory of the first one.

Myelin coats a neuron’s axon, the long process that transmits electrical signals. (credit: Healthwise Inc.)

Many neurons in our brain are coated in a fatty substance called myelin, which dramatically speeds up the electrical signals that they transmit. But other neurons of the same types don’t have myelin, and it’s unknown why they’re denied this perk while their myelinated neighbors get to drive in the fast lane. Now a new study in Nature Neuroscience demonstrates that myelin isn’t sprinkled around randomly; it’s bestowed upon the neurons that are the most active during development. (A second study in the same issue also makes a similar conclusion.) This finding implies that the brain wants to speed up signals from neurons who are contributing lots of information and slow down the neurons who are staying quiet, but it’s not clear how this would really affect brain function. It would be interesting to test whether an animal’s behavior would be altered if you randomly gave out myelin to both active and inactive neurons.

This week’s news reported on two different projects aimed at consolidating vast amounts of information about neurons. One project focuses on the physical structure of neurons, while the second focuses on their electrical properties:

First, the Allen Brain Institute in Seattle announced a large-scale collaborative project called BigNeuron, whose goal is to standardize the way that we classify the shapes of neurons and create a database of all known neuron structures. Neurons can have many different shapes (see below), and their physical structure is closely linked to their function. Scientists have been drawing or taking pictures of neurons’ diverse structures for over a century, but these images are scattered throughout the literature and can’t be found in a single place. In addition to developing new tools for analyzing the structure of neurons, the BigNeuron project intends to catalog all known neuronal structures, creating an encyclopedia of neurons. It’ll be interesting to see how many neuron types they come up with—a potentially contentious issue, as discussed here.

Examples of different types of neurons with different shapes. (credit: R. Stufflebeam and The Mind Project, based on drawings by Ramon y Cajal)

Second, two neuroscientists launched a website called NeuroElectro, which contains a database of information about the electrical properties of over 200 different types of neurons. Much of a neuron’s function is determined by its electrical properties. Scientists have measured these properties for many types of neurons, but these results are dispersed throughout the literature and were not previously available in a centralized location, much like the data on neuronal structure that I mentioned above. NeuroElectro consolidates data from nearly 10,000 published studies, and will be updated as data are extracted from more papers. Users can register to help contribute data and curate the database, leading some to call NeuroElectro a “Wikipedia” for neurons.

Did you see any recent neuroscience news that you’d like to share? Leave a comment below!