The Incredible Human GPS

        Ever wonder how a cab driver is able to get you from point A to point “who knows where” without using GPS? Its cause his brain is bigger than yours… well… his hippocampus is. The hippocampus is a region in the brain important for long-term memory and spatial navigation. While it was long thought that talents were innate and had to be nurtured at a young age, researchers studying London cab drivers say that an old dog can learn new tricks. London cab drivers have to learn the layout of over 25, 000 streets through 3-4 years of schooling after which only 25% of aspiring cabbies make it out with a London cab certificate to attest to their ability to find their way through the city’s complexly interconnected web of streets. Through Magnetic Resonance Imaging, researchers have determined that London cab drivers have an increase in volume of the back part or posterior part of their hippocampus, indicating that the adult brain is still capable of changing its structure to meet certain demands. This means that talents are not necessarily innate but can also be acquired through repeated application. That’s right. Practice does make perfect.

        When compared to non-cab drivers or bus drivers, who follow a simple set route, cab drivers have a larger posterior hippocampus, which grows with years of cab driving experience, demonstrating that the posterior portion of the hippocampus is important for spatial representation of highly complex environments. However there is a catch. While the posterior portion of the hippocampus grows larger with driving experience, the anterior or frontal portion becomes smaller than those of bus drivers and non-cab drivers. This decrease in anterior hippocampal volume has been associated with a decrease in anterograde memory performance, that is, while cab drivers were better at spatial representation they were deficient in acquiring and retaining other new types of information such as directing movements in space as indicated by their lower performance in the Rey-Osterrieth test. This means that when cab drivers were shown a complex line figure and asked to draw it from memory, they were able to recall less than than bus drivers or non-cab drivers.

        Cab drivers don't only show that practice makes perfect, they also show that if you don't use it you lose it. Researchers compared the hippocampus of present cab drivers to retired cab drivers and found that the structural changes that occur in full-time taxi drivers are reversed in retired taxi drivers. Furthermore, retired taxi drivers scored less on their ability to navigate around London, however performed better in the Rey-Osterrieth test than full-time cab drivers.

        These observations are a testament to the fact that the adult human brain is not static but is quite dynamic, always adapting to our surrounding environment. This has implications in several fields such as education or rehabilitation of patients with cognitive impairments such as autism or even in Parkinson's disease. Researchers at UCL believe that with the right brain exercises we can strengthen those parts of the brain that are deficient or damaged. So those of you who claim to be "too old" to learn anything new, pick up that crossword puzzle, take that class you've been dying to take, start a new hobby and practice, practice, practice!

                         Michael Tibshirani

                          McGill University

"Parkinson's Disease: Working Towards a Cure": Part 1-- The Basics

This is the first post from a three part series written by Andrew Greene, a graduate student at McGill University studying Parkinson's Disease. 

James Parkinson was a British apothecary-surgeon best known for his medical report entitled "An Essay on the Shaking Palsy." Published in 1817, it was a detailed description of the disorder that would one day be known as Parkinson's disease. The disease can bring on a variety of symptoms, many of which we're only just beginning to appreciate, but the best understood are the movement related effects. Typical symptoms include tremors of the limbs and difficulties performing movements, especially ones that have multiple parts, such as reaching out to a cup, grabbing it, and bringing it to your lips. There is presently no cure for Parkinson's disease, but there are a number of treatments available to at least temporarily alleviate the symptoms, and these will be discussed in detail in part 2.
Despite the fact that Parkinson's disease is primarily a movement disorder, the muscles themselves generally remain healthy. It's actually a part of the brain involved in coordinating movement that has traditionally been said to be most prominently affected by the disease. This part of the brain is called the substantia nigra, which means black substance, referring to its characteristic dark colour compared to surrounding brain regions. The substantia nigra is located near the center of the brain and contains neurons that secrete a chemical called dopamine. Dopamine is a type of neurotransmitter, which are a class of chemicals that neurons emit in order to communicate with each other.
Dopamine is best known for its role in the brain's reward system, in which it's used to provide feelings of pleasure and enjoyment in response to things such as food, sex, and certain drugs. However, dopamine released by the substantia nigra also plays a critical role in modulating the activity of the striatum, a brain region that is essential in planning and coordinating movements. The striatum is the origin of two neural pathways that exert opposite effects on movement. The first of these is the so called direct pathway, which is thought to facilitate and reinforce intended movements. The second is the indirect pathway, which is thought to be responsible for inhibiting unwanted or inappropriate motion. Dopamine released by the substantia nigra helps maintain a balance between these two pathways by increasing the activity of the former and decreasing the activity of the latter.
In Parkinson's disease the dopamine-emitting neurons of the substantia nigra die off, which tips the delicate balance between the direct and indirect pathways. The result is too much activity in the indirect, motion-inhibiting pathway and too little in the direct, motion-facilitating pathway, which ultimately makes it exceedingly difficult for a patient to move. Why dopamine-emitting neurons of the substantia nigra die in Parkinson's disease is not known, though research over the last few decades has gone a long way towards solving the mystery, as we'll see in Part 3. Uncovering the reasons for their death is the first step in learning how to stop these neurons from dying, leading to better treatments and hopefully even a cure.

Stay tuned for Part 2: Current Treatments and Part 3: Towards a Cure. Coming soon!