- Dr. Ben Clark focuses on a part of the brain responsible for spatial orientation and object recognition as an early indicator of dementia
- unique process maps the brain’s ‘internal compass’
Every time you turn your head one way or another, the nerve cells in your brain, called neurons, keep you oriented in space.
Scientists have clues about how this brain-based compass works. But the nuts and bolts of the system, and its possible role in the way memories form and fade, are still a puzzle that researchers such as Dr. Ben Clark, are trying to solve.
In particular, the University of Lethbridge postdoctoral researcher and Alberta Innovates -- Health Solutions postgraduate fellowship recipient is working to understand if and how the brain circuits that deal with directional information may also impact both memory formation and dementia.
Dauphin, Manitoba-born Clark began looking at the brain’s direction-sensing systems as a graduate student in Jeffrey Taube’s lab at Dartmouth College in New Hampshire.
Now back in Canada and working as a postdoctoral researcher in Dr. Bruce McNaughton’s Lethbridge Brain Dynamics lab at the Canadian Centre for Behavioural Neuroscience (CCBN), Clark, who also holds an Honours Bachelor of Science degree in neuroscience from the University of Lethbridge (2005), is interested in figuring out whether the same sorts of brain maps are also used to commit new information or situations to memory.
If so, he and others speculate that the breakdown of these maps could also contribute to memory-related conditions, such as dementia and Alzheimer’s disease.
The potential links between these two neural functions are complex, Dr. Clark explains, but the idea is that the memories rely, at least in part, on the brain’s ability to determine direction.
In animals, spatial mapping seems to centre on sets of so-called ‘head direction’ neurons, brain cells that are electrically active when an animal’s head is pointing in one direction but not another -- and ‘grid cells,’ which contribute to a broader brain-based map of the surrounding environment.
Together, this brain cell activity produces something of an internal compass for understanding our place in the world around us.
The neurons communicating these direction-dependent signals are spread throughout the brain’s temporal lobes, which are found just behind each ear, Dr. Clark explains.
But past studies suggest that their signals come together in a part of that brain region known as the entorhinal cortex, which also deals with information the brain uses to recognize objects.
There are hints that the entorhinal cortex is among the first parts of the brain to show changes during Alzheimer’s disease too, which is consistent with the notion that object recognition and spatial cues may be crucial to memory.
To explore these potential connections, Dr. Clark plans to follow the activity of grid cells and head direction neurons, those direction-sensitive brain cells, using a system that lets him physically see neurons’ activation.
That’s possible because when neurons fire they turn on specific genes. And with a bit of genetic engineering, researchers can couple the gene activation to the production of proteins that glows fluorescent green or red under certain wavelengths of light.
For the current project, Dr. Clark and his collaborators will use two such genes as a means of tracking spatial mapping and head direction neurons in rats as they encounter new objects or spatial situations, for instance.
With slightly different experimental techniques in other experiments, they also plan to follow the neurons that stretch from the entorhinal cortex into other memory-related parts of the brain.
The researchers have done preliminary experiments to ensure that their fluorescent gene scheme will be able to measure neuron activity. Next, they’re gearing up to use these tools to test normal rats as well as rat models of disease that show some of the symptoms associated with Alzheimer’s disease.
Over the longer term, Dr. Clark explains, researchers intend to create functional maps of the these animal brains during disease, looking not only at the entorhinal cortex but also at other brain areas that are thought to contribute to dementia and Alzheimer’s disease.
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Background information – Researchers
DR. BEN CLARK (photo, left) is funded through the Alberta Innovates -- Health Solutions Postgraduate Fellowship Program. He completed his Honours Bachelor of Science degree in neuroscience at the University of Lethbridge in 2005 and received a PhD in Psychological and Brain Sciences from Dartmouth College in 2011.
He joined the Lethbridge Brain Dynamics group in the summer of 2011 as a postdoctoral researcher, supervised by Bruce McNaughton.
DR. BRUCE MCNAUGHTON (photo, right) was recruited to the Canadian Centre for Behavioural Neuroscience at the University of Lethbridge in 2008, together with a team of about 50 people. Prior to 2008, his research group was based at the University of Arizona.
Alberta Innovates -- Health Solutions, Alberta Innovates -- Techology Futures, and the University of Lethbridge contributed $20 million towards a Polaris Award supporting McNaughton’s research and recruitment to the centre.
The Lethbridge Brain Dynamics group currently includes five principal investigators, along with 55 postdoctoral researchers, graduate students, and staff who carry out research on everything from decision-making and memory to brain aging and addiction.
Background information -- Memory
MEMORY IS A PROCESS, or set of inter-related processes, in which the brain changes in response to events. These changes then result in us being able to repeat a name or phone number (short-term memory), recall a specific event (episodic memory), recite a poem we learned at school (long-term verbal memory) or exercise a learned skill such as riding a bike or skateboarding (procedural memory).
Connections between brain cells, called synapses, are necessary for memories to form. Brain cells take sensory information from our life events and encode them into our long-term memory.
Our brain then consolidates the memories by categorizing them and linking them to similar data. The memories last if we retrieve them from time to time, retracing the initial synapses and strengthening the connections.
Among the important mechanisms that underlie memory are changes to the strength of synapses (the gaps between nerve cells that signals have to cross), the growth of the tiny dendritic spines that grow out of the cells’ branching dendrites, and many chemical changes that strengthen some of the networks of neurons at the expense of others.
These changes occur all over the brain but some areas, such as the tiny hippocampus in the temporal lobe of the brain, are especially important. Damage here can mean a permanent loss of any ability to lay down new memories.
(Information adapted from: http://www.sciencefocus.com and http://www.curiousity.com)
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Story by Andrea Anderson, photos by Trudie Lee. Re-printed with permission from Alberta Innovates -- Health Solutions.
This story appeared in the most recent issue of Health Solutions magazine: http://www.aihealthsolutions.ca/magazine/
For additional information about Alberta Innovates – Health Solutions, please visit their website: http://www.aihealthsolutions.ca/
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