Breakthrough discovery in spinal cord research

HALIFAX – Scientists at Dalhousie University have made a breakthrough discovery that could one day help spinal cord injury patients and those with neurodegenerative diseases.

The scientists have identified a group of neurons in the spinal cord – called dI3 interneurons – that control the ability of our hands to grasp. If the circuit between those neurons is disrupted, a patient’s ability to grip can be lost or altered.

“We all take for granted how our hand functions and that it functions just right. When that goes wrong, that’s when we notice it,” said Dalhousie neurosurgeon and lead researcher, Dr. Robert Brownstone.

The finding was somewhat serendipitous. Researchers had originally set out to discover whether this particular circuit affected walking and running. However, test mice showed no change in their ability to walk.

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“So it was disappointing at first,” said postdoctoral fellow Tuan Bui.

But researchers found something else: the mice had lost the ability to grasp onto the cage wires.

A subsequent test found that while control mice were able to hang from the top of the cage for several minutes, mice that had this particular circuit disrupted genetically found it impossible to hold on.

“That was kind of one of these, not a Eureka moment, but “That’s funny” moment because that’s not what we were expecting,” said Brownstone, who is also the Canadian Research Chair in spinal cord circuits. “But it was clearly something we had found.”

The researchers’ findings were published Wednesday in the neuroscience journal, Neuron. The study was a collaboration with colleagues from Columbia University.

The next step is to find out how the brain controls this circuit, so that one day patients with spinal cord injuries or neurodegenerative diseases, such as Alzheimer’s disease, can be treated.

“The way the spinal cord controls movement is not well understood,” said Bui.

“And yet it’s something we do on an everyday basis – interact with objects – and so for us to be able to piece out all the different components and just point to a particular class of cells and say, ‘Ah ha, these cells are involved with grip strength.’ I think it will allow us to further down the road fully map out how the spinal cord generates movement.”