Brain injuries affected thousands of military personnel who served in Iraq and Afghanistan.
Most involved blast injuries and concussions and left those affected with cognitive and behavioural deficits, and significant impairments in short- and long-term memory.
The findings were not unlike those observed following repeated concussions in sports such as football and the far more common neurodegenerative diseases like Alzheimer’s disease, the later stages of fronto-temporal degeneration, Parkinson’s disease and amyotrophic lateral sclerosis.
In the case of soldiers suffering from memory deficits, considerable research and money have been invested to see whether memory loss could be reversed.
One intriguing proposal was to use deep brain stimulation. In this treatment, small electrical stimuli are delivered through electrodes implanted in selected regions of the temporal lobe where memories are initially processed before becoming consolidated elsewhere in the brain through strengthening existing neural connections and developing new connections.
Our modern understanding of the structural and molecular basis of memory came from Eric Kandel, who shared a Nobel Prize in 2000 for working out the structural and molecular underpinnings of memory.
Kandel’s outstanding studies of memory are recounted in his very readable 2008 book, “In Search of Memory.”
Epileptic seizures often begin in the temporal lobe and should they be unresponsive to drugs or if drugs prove intolerable, one option has been to surgically resect the affected anterior (front) part of the temporal lobe, much as Wilder Penfield pioneered many years ago in Montreal.
These days, it’s common practice to implant arrays of electrodes into the suspected temporal lobe before or during the surgery to locate the source of the seizures more precisely.
Those same electrodes also provide a handy means for studying short-term memory because the temporal lobes harbour the hippocampus and dentate gyrus, which are the structures most involved in short-term memory.
They also harbour nerve cells, which serve as the biological equivalents of GPS by providing handy information about our position (so-called place and grid cells). For the latter work, a Nobel Prize was awarded to John O’Keefe, and the wife and husband team of May-Britt Moser and Edvard J. Moser in 2014.
As Kandel pointed years before in the relatively simple nervous system of aplasia (a giant marine snail ideal for research on learning and memory), stimuli delivered shortly after an initial memory tend to consolidate newly formed memories.
Here we’ve come to the heart of the matter.
Why not use deep brain stimulation in the temporal lobe of humans suffering from short-and longer-term memory difficulties to help their brains consolidate memories before they vanish – such as “Where did you put those keys?” or “Where did you park your car in the lot at the mall?”
It’s really a pacemaker for the brain or more specifically a pacemaker for memory that investigators are looking at.
So, maybe those of us who struggle to make and hold onto memories will have an assist soon from technology. It’s not far-fetched but might take a few years before pacemaking for memory becomes a practical tool.
However, it’s a wonderful example of basic science (Kandel and others), clinical scientists, physicians, and a big need coming together to solve an immense problem.
More recently, Rob Reinhart and colleagues from Boston University used weak alternating current stimuli delivered through surface electrodes positioned over the prefrontal cortex to facilitate long-term memories or the inferior parietal lobe to enhance short-term memories.
The stimuli were well-tolerated and probably too weak to stimulate nerve cells directly but probably altered the background excitability of the underlying neocortex. Their preliminary findings were promising because they suggested such weak stimuli could enhance memory.
Perhaps some form of chronic surface stimulation might provide a needed, albeit temporary boost to memory for patients with Alzheimer’s disease. If so, that would be a plus for patients and their caregivers.
Dr. William Brown is a professor of neurology at McMaster University and co-founder of the InfoHealth series at the Niagara-on-the-Lake Public Library.